Acute Motor and Sensory Axonal Neuropathy

MONDO:0020348 Pathograph 24 Show in embeddings browser Guillain-Barre Syndrome Peripheral Neuropathy

Acute motor and sensory axonal neuropathy (AMSAN) is a motor-sensory axonal electrophysiologic and pathologic pattern within Guillain-Barre syndrome (GBS). It is characterized clinically by acute progressive flaccid weakness, reduced reflexes, and sensory involvement, and electrodiagnostically by reduced or absent motor and sensory response amplitudes without a primary demyelinating pattern. In a subset of axonal GBS, especially after Campylobacter jejuni infection, cross-reactive anti-ganglioside antibodies activate complement at vulnerable nodal and axolemmal membranes. Injury can range from reversible nodal conduction failure to irreversible degeneration of motor and sensory axons. AMSAN assignment may change on serial nerve conduction studies, so it should not be treated as a perfectly stable early subtype or as a separate treatment indication.

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Mechanistic Hypotheses

Antiganglioside-complement nodopathy-to-axonopathy continuum

antiganglioside_complement_axonal_injury CANONICAL

Evidence balance 2 support

In the seropositive and especially C. jejuni-associated axonal GBS subset, molecular mimicry generates cross-reactive anti-ganglioside IgG. Antibody binding at nodal and axolemmal sites activates classical complement, producing a continuum from reversible nodal conduction failure to macrophage-associated irreversible motor and sensory axonal degeneration.

Canonical does not mean universal. Ganglioside antibodies are absent in a substantial fraction of GBS, viral and other antecedents remain mechanistically unresolved, and the sensory-axon target in AMSAN is less experimentally developed than the motor-axon arm.

Pathograph links

Campylobacter LOS-Ganglioside Molecular Mimicry -> Cross-Reactive Anti-Ganglioside IgG Response DIRECT LOS-ganglioside mimicry elicits IgG that cross-reacts with neural gangliosides.

Cross-Reactive Anti-Ganglioside IgG Response -> Ganglioside Antibody Binding at Nodal and Axolemmal Membranes DIRECT Circulating anti-ganglioside IgG binds ganglioside-rich vulnerable sites on peripheral axons and motor nerve terminals.

Ganglioside Antibody Binding at Nodal and Axolemmal Membranes -> Classical Complement Activation at Axonal Membranes DIRECT Axon-bound IgG recruits C1q and initiates the classical complement pathway.

Classical Complement Activation at Axonal Membranes -> Reversible Nodal Conduction Failure INDIRECT KNOWN INTERMEDIATES Complement-mediated nodal membrane dysfunction can block conduction before irreversible axonal loss occurs. Intermediates: Nodal and paranodal membrane disruption; Terminal complement complex formation and calcium influx

Classical Complement Activation at Axonal Membranes -> Macrophage Recruitment and Periaxonal Entry INDIRECT KNOWN INTERMEDIATES Complement products promote recruitment of macrophages and other immune cells to injured neural membranes. Intermediates: Complement-fragment signaling and opsonization

Classical Complement Activation at Axonal Membranes -> Motor and Sensory Axonal Degeneration INDIRECT KNOWN INTERMEDIATES Persistent complement-mediated membrane injury can cross the threshold from reversible dysfunction to irreversible axonal degeneration. Intermediates: Terminal complement complex formation; Calcium influx; Calpain and caspase activation

Reversible Nodal Conduction Failure -> Decreased Compound Muscle Action Potential Amplitude DIRECT Failure of motor-axon conduction reduces the evoked compound muscle action potential even when the axon has not yet degenerated.

Motor and Sensory Axonal Degeneration -> Decreased Compound Muscle Action Potential Amplitude DIRECT Loss of functioning motor axons reduces or abolishes compound muscle action potential amplitudes.

Motor and Sensory Axonal Degeneration -> Decreased Sensory Nerve Action Potential Amplitude DIRECT Loss of functioning sensory axons reduces or abolishes sensory nerve action potential amplitudes.

Motor and Sensory Axonal Degeneration -> Limb Weakness DIRECT Motor-axon loss reduces muscle activation and produces acute flaccid limb weakness.

Motor and Sensory Axonal Degeneration -> Areflexia INDIRECT KNOWN INTERMEDIATES Failure of peripheral motor and sensory limbs of the reflex arc reduces or abolishes tendon reflexes. Intermediates: Motor and sensory reflex-arc failure

Motor and Sensory Axonal Degeneration -> Sensory Neuropathy DIRECT Dorsal-root and sensory-nerve axonal loss produces objective sensory dysfunction.

Motor and Sensory Axonal Degeneration -> Paresthesia INDIRECT KNOWN INTERMEDIATES Injured sensory fibers can generate tingling and other abnormal sensations. Intermediates: Abnormal sensory-axon signaling

Motor and Sensory Axonal Degeneration -> Pain INDIRECT KNOWN INTERMEDIATES Sensory-fiber and root injury can produce neuropathic, radicular, and musculoskeletal pain. Intermediates: Sensory-fiber injury and radicular inflammation

Motor and Sensory Axonal Degeneration -> Dysphagia INDIRECT KNOWN INTERMEDIATES Severe cranial motor-nerve involvement can impair swallowing. Intermediates: Bulbar motor-nerve dysfunction

Motor and Sensory Axonal Degeneration -> Respiratory Insufficiency INDIRECT KNOWN INTERMEDIATES Severe motor-axon dysfunction can weaken respiratory muscles and require ventilatory support. Intermediates: Respiratory motor-axon and muscle weakness

Motor and Sensory Axonal Degeneration -> Autonomic Dysfunction INDIRECT KNOWN INTERMEDIATES Involvement of autonomic peripheral fibers can produce cardiovascular, gastrointestinal, and bladder dysfunction. Intermediates: Autonomic peripheral-nerve dysfunction

Show evidence (2 references)

PMID:22507308 SUPPORT Other

"acute motor axonal neuropathy, acute motor and sensory neuropathy and acute sensory neuropathy and possibly also a chronic disorder as multifocal motor neuropathy represent a spectrum of the same immunopathologic process."

This synthesis supports a shared nodal-to-axonal spectrum rather than fully independent mechanisms for AMAN and AMSAN.

DOI:10.1002/ana.410390105 SUPPORT Human Clinical

"represent the most severe end of a spectrum of immune attack directed toward epitopes on the axon."

Direct AMSAN pathology supports the severe-end-of-spectrum interpretation.

Discussions and Knowledge Gaps

Is AMSAN a stable mechanistically distinct subtype, or does it often represent the severe motor-sensory end of a dynamic nodopathy-to-axonopathy spectrum shared with AMAN and other GBS patterns?

INTERPRETATION OPEN interp_amsan_stable_subtype_or_axonal_spectrum

Attached to

pathophysiology#Reversible Nodal Conduction Failure pathophysiology#Motor and Sensory Axonal Degeneration

Fatal pathology supports genuine motor and sensory axonal destruction, but serial NCS shows frequent bidirectional subtype changes and no added value from electrodiagnostic subtyping. Resolving which patients have reversible nodal failure versus fixed sensory and motor axon loss matters more than a single early label.

Proposed experiments

Prospective AMSAN-enriched serial electrophysiology and biomarker study

exp_amsan_serial_ncs_biomarker_trajectory

Enroll early motor-sensory GBS before definitive subtyping; obtain standardized NCS/EMG at baseline, 2-3 weeks, and recovery, with blinded classification by multiple criteria, ganglioside-antibody profiling, complement activity, NfL, and motor, sensory, autonomic, and functional outcomes. Test whether fixed low CMAP/SNAP trajectories separate from reversible nodal-failure trajectories and outperform the initial subtype label for prognosis.

Decision criterion

A stable AMSAN entity is supported if combined motor-sensory axonal trajectories remain reproducible across criteria and time and predict outcomes independently; frequent migration with biomarker-defined nodal recovery supports a continuum model.

Would support

pathophysiology#Reversible Nodal Conduction Failure pathophysiology#Motor and Sensory Axonal Degeneration

Show evidence (2 references)

PMID:41656826 SUPPORT Human Clinical

"the electrodiagnostic subtype changed on serial NCS in 37.8% (Hadden) and 44.7% (Rajabally)."

Frequent reclassification directly motivates the stability question.

DOI:10.1002/ana.410390105 SUPPORT Human Clinical

"represent the most severe end of a spectrum of immune attack directed toward epitopes on the axon."

Human pathology explicitly advances the spectrum interpretation.

What immune targets and effector mechanisms drive clinically compatible AMSAN when standard anti-ganglioside antibodies are absent?

KNOWLEDGE GAP OPEN gap_seronegative_amsan_antigens

Attached to

pathophysiology#Cross-Reactive Anti-Ganglioside IgG Response

Ganglioside antibodies occur in only a subset of GBS, and routine testing has limited clinical value. Treating the canonical GM1/GD1a mechanism as universal would erase seronegative disease and mechanisms following non-C. jejuni antecedents.

Proposed experiments

Unbiased seronegative AMSAN neural-surface antigen discovery

exp_seronegative_amsan_unbiased_antigen_screen

Screen acute serum and CSF from serially confirmed seronegative AMSAN against live human motor-neuron, sensory-neuron, and Schwann-cell nodal cultures, followed by immunoprecipitation-mass spectrometry, antigen validation, complement-deposition assays, and longitudinal titer-outcome analysis with GBS-subtype and healthy controls.

Decision criterion

A candidate is prioritized if disease-phase IgG binds a reproducible neural surface target, deposits complement or disrupts conduction, declines with recovery, and is enriched over control groups.

Would support

pathophysiology#Ganglioside Antibody Binding at Nodal and Axolemmal Membranes

Show evidence (1 reference)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"Whether ganglioside-seronegative patients have other antibodies relevant to GBS is currently unclear."

The primer directly identifies the unresolved antigen problem.

Do current anti-GM1/anti-GD1a motor-axon models reproduce the sensory-axon injury that defines human AMSAN?

HUMAN MODEL MISMATCH OPEN mismatch_motor_only_models_for_sensory_inclusive_amsan

Attached to

pathophysiology#Classical Complement Activation at Axonal Membranes pathophysiology#Motor and Sensory Axonal Degeneration

Existing rabbit, transgenic-mouse, and ex vivo systems convincingly model motor-axon antibody/complement injury. Direct human AMSAN pathology instead shows dorsal as well as ventral root injury. A sensory-inclusive model is needed before subtype-specific mechanism or therapeutic claims are made.

Proposed experiments

Paired human motor- and sensory-neuron nodal injury assay

exp_paired_human_motor_sensory_nodal_injury

Build matched human iPSC-derived motor-neuron and sensory-neuron systems with Schwann-cell myelination and mature nodal domains. Expose both to acute serially confirmed AMSAN IgG with human complement; comparator conditions should include heat-inactivated complement, healthy, AMAN, AIDP, antigen-depleted, and C1q-inhibited controls. Measure antibody/C1q/C3/MAC deposition, conduction, calcium influx, axonal integrity, and sensory-versus-motor susceptibility.

Decision criterion

A sensory-inclusive model is established if AMSAN IgG causes reproducible complement-dependent injury in both compartments, whereas AMAN IgG remains motor-predominant and antigen depletion or C1q blockade rescues injury.

Would support

pathophysiology#Classical Complement Activation at Axonal Membranes pathophysiology#Motor and Sensory Axonal Degeneration

Show evidence (2 references)

PMID:26936605 SUPPORT Model Organism

"new in vivo transgenic mouse model of AMAN"

The model is explicitly AMAN rather than AMSAN.

DOI:10.1002/ana.410390105 SUPPORT Human Clinical

"wallerian-like degeneration of fibers in the ventral and dorsal roots"

Human AMSAN pathology requires a model capable of both motor and sensory injury.

Should poor predicted prognosis or initial non-response prompt routine corticosteroids, a second IVIG course, or immediate plasma exchange followed by IVIG?

INTERPRETATION RESOLVED resolved_nonbeneficial_routine_escalation

Attached to

disease#Acute Motor and Sensory Axonal Neuropathy

These regimens can be mistaken for positive treatment options if represented as ordinary treatment nodes. Current guideline and randomized evidence do not support routine use for poor prognosis or initial non-response.

Posed 2026-07-18T00:35:23Z Resolved 2026-07-18T00:35:23Z

Resolution: Do not represent these regimens as routine beneficial AMSAN treatments. True treatment-related fluctuation after stabilization or improvement is a separate scenario in which specialist-guided re-treatment may be considered.

Show evidence (3 references)

PMID:37814552 SUPPORT Other

"recommends against using oral corticosteroids, and weakly recommends against using IV corticosteroids"

The guideline directly recommends against corticosteroid therapy.

PMID:33743237 SUPPORT Human Clinical

"a second intravenous immunoglobulin course should not be considered for treatment of Guillain-Barre syndrome because of a poor prognosis."

The randomized SID-GBS trial found no benefit and more serious adverse events.

PMID:9014908 SUPPORT Human Clinical

"The combination of PE with IVIg did not confer a significant advantage."

The randomized comparison found no significant advantage for the immediate combination.

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Pathophysiology

Campylobacter LOS-Ganglioside Molecular Mimicry

In a biologically defined subset of axonal GBS, sialylated C. jejuni lipooligosaccharides resemble peripheral-nerve gangliosides. The mimicry can initiate an antibody response that recognizes both bacterial carbohydrate and neural ganglioside. This mechanism is not asserted for every AMSAN case.

Antiganglioside-complement nodopathy-to-axonopathy continuum

Antigen processing and presentation GO:0019882

Downstream

Cross-Reactive Anti-Ganglioside IgG Response LOS-ganglioside mimicry elicits IgG that cross-reacts with neural gangliosides.

Show evidence (2 references)

PMID:15277677 SUPPORT Model Organism

"On sensitization with C. jejuni lipooligosaccharide, rabbits developed anti-GM1 IgG antibody and flaccid limb weakness."

Active immunization provides experimental causal evidence for the LOS-to-anti-GM1 molecular-mimicry step, although the model is motor-predominant.

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"preceding Campylobacter jejuni infection, molecular mimicry causes a cross-reactive antibody response to nerve gangliosides."

The primer synthesizes the established C. jejuni mechanism in GBS; it is applied only to the relevant AMSAN subset.

Cross-Reactive Anti-Ganglioside IgG Response

Activated B-cell and plasma-cell responses produce IgG against gangliosides such as GM1, GM1b, and GD1a. These antibodies occur in some, but not all, patients with axonal GBS. A small human study found the same antibody profile in AMSAN and AMAN, supporting a shared immune spectrum rather than a uniquely AMSAN-specific marker.

Antiganglioside-complement nodopathy-to-axonopathy continuum

B cell CL:0000236

Immunoglobulin production GO:0002377 ↑ INCREASED

Downstream

Ganglioside Antibody Binding at Nodal and Axolemmal Membranes Circulating anti-ganglioside IgG binds ganglioside-rich vulnerable sites on peripheral axons and motor nerve terminals.

Show evidence (2 references)

PMID:10526194 SUPPORT Human Clinical

"The patients with AMSAN had anti-GM1, anti-GM1b, and anti-GD1a IgG antibodies"

This is direct AMSAN serologic evidence, limited by the small historical series and not a sensitivity estimate.

DOI:10.1186/s43161-024-00258-8 SUPPORT Other

"specific autoantibodies, such as anti-GM1 and anti-GQ1b, are associated with distinct subtypes of GBS"

The systematic review supports antibody-associated GBS heterogeneity but does not establish a universal or AMSAN-specific diagnostic marker.

Ganglioside Antibody Binding at Nodal and Axolemmal Membranes

Anti-ganglioside IgG binds the nodal axolemma and nerve-terminal membranes. Antigen density and ganglioside complexes influence binding, which helps explain why antibody presence alone does not predict the exact clinical distribution of injury.

Antiganglioside-complement nodopathy-to-axonopathy continuum

Motor neuron CL:0000100 Sensory neuron CL:0000101

Node of Ranvier GO:0033268 Axolemma GO:0030673

Experimental models

Anti-GD1a/complement ex vivo motor nerve-terminal injury model OTHER Anti-GD1a antibody deposition on presynaptic motor axons.

Downstream

Classical Complement Activation at Axonal Membranes Axon-bound IgG recruits C1q and initiates the classical complement pathway.

Show evidence (1 reference)

PMID:26936605 SUPPORT Model Organism

"complement-fixing anti-ganglioside antibodies that directly bind and injure the axon at sites of vulnerability such as nodes of Ranvier and nerve terminals."

This establishes vulnerable axonal binding sites in an AMAN model; sensory axon targeting in AMSAN remains unmodeled.

Classical Complement Activation at Axonal Membranes

C1q-initiated classical complement activation deposits complement products at nodal, paranodal, and nerve-terminal membranes. Terminal-complement pores, calcium influx, and downstream protease activation can produce early functional failure and, if injury is not reversed, structural axonal loss.

Antiganglioside-complement nodopathy-to-axonopathy continuum

Motor neuron CL:0000100 Sensory neuron CL:0000101

Classical complement activation GO:0006958 ↑ INCREASED

Node of Ranvier GO:0033268 Axolemma GO:0030673

Downstream

Reversible Nodal Conduction Failure Complement-mediated nodal membrane dysfunction can block conduction before irreversible axonal loss occurs.

Macrophage Recruitment and Periaxonal Entry Complement products promote recruitment of macrophages and other immune cells to injured neural membranes.

Motor and Sensory Axonal Degeneration Persistent complement-mediated membrane injury can cross the threshold from reversible dysfunction to irreversible axonal degeneration.

Show evidence (2 references)

PMID:26936605 SUPPORT Model Organism

"Anti-C1q monoclonal antibody treatment attenuated complement cascade activation and deposition"

Targeted C1q inhibition provides intervention evidence for classical complement activation in acute motor-axonal injury, with incomplete AMSAN fidelity.

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"Complement activation at these sites causes initial peripheral nerve dysfunction followed by structural injury"

The primer synthesizes complement as the link from antibody binding to functional and structural nerve injury across GBS.

Reversible Nodal Conduction Failure

Immune disruption of nodal and paranodal excitability can transiently block conduction without the temporal dispersion expected from remyelination and without established Wallerian degeneration. Serial studies are required to distinguish recovery of nodal function from fixed axonal loss.

Antiganglioside-complement nodopathy-to-axonopathy continuum

Motor neuron CL:0000100

Transmission of nerve impulse GO:0019226 ↓ DECREASED

Node of Ranvier GO:0033268

Experimental models

Anti-GD1a/complement ex vivo motor nerve-terminal injury model OTHER Complement-dependent blockade of motor nerve-terminal function.

Downstream

Decreased Compound Muscle Action Potential Amplitude Failure of motor-axon conduction reduces the evoked compound muscle action potential even when the axon has not yet degenerated.

Show evidence (1 reference)

PMID:22480600 SUPPORT Other

"transient conduction block/slowing in intermediate and distal nerve segments, mimicking demyelination but without the development of abnormal temporal dispersion, named reversible conduction failure"

The electrodiagnostic review defines reversible conduction failure in axonal GBS; the direct examples are primarily AMAN rather than AMSAN.

Macrophage Recruitment and Periaxonal Entry

Macrophages accumulate around injured myelinated axons and can enter the periaxonal space. Human AMSAN autopsy establishes this localization, but the relative injurious versus debris-clearing role and timing remain uncertain.

Macrophage CL:0000235

Macrophage chemotaxis GO:0048246 ↑ INCREASED

Show evidence (1 reference)

DOI:10.1002/ana.410390105 SUPPORT Human Clinical

"All 3 had numerous macrophages in the periaxonal space of myelinated internodes"

Fatal human AMSAN autopsies directly localize macrophages around axons; the tiny, severity-selected series limits generalization.

Motor and Sensory Axonal Degeneration

Irreversible AMSAN injury is dominated by Wallerian-like degeneration and loss of motor and sensory fibers in ventral and dorsal roots and peripheral nerves. This acute pattern is not assumed to be length-dependent, and primary demyelination is not required.

Antiganglioside-complement nodopathy-to-axonopathy continuum

Motor neuron CL:0000100 Sensory neuron CL:0000101

Downstream

Decreased Compound Muscle Action Potential Amplitude Loss of functioning motor axons reduces or abolishes compound muscle action potential amplitudes.

Decreased Sensory Nerve Action Potential Amplitude Loss of functioning sensory axons reduces or abolishes sensory nerve action potential amplitudes.

Limb Weakness Motor-axon loss reduces muscle activation and produces acute flaccid limb weakness.

Areflexia Failure of peripheral motor and sensory limbs of the reflex arc reduces or abolishes tendon reflexes.

Sensory Neuropathy Dorsal-root and sensory-nerve axonal loss produces objective sensory dysfunction.

Paresthesia Injured sensory fibers can generate tingling and other abnormal sensations.

Pain Sensory-fiber and root injury can produce neuropathic, radicular, and musculoskeletal pain.

Dysphagia Severe cranial motor-nerve involvement can impair swallowing.

Respiratory Insufficiency Severe motor-axon dysfunction can weaken respiratory muscles and require ventilatory support.

Autonomic Dysfunction Involvement of autonomic peripheral fibers can produce cardiovascular, gastrointestinal, and bladder dysfunction.

Show evidence (2 references)

DOI:10.1002/ana.410390105 SUPPORT Human Clinical

"predominantly axonal lesions of both motor and sensory fibers, even in the early stages of the disease"

This is direct human AMSAN pathology, although it derives from four fatal cases and therefore overrepresents severe disease.

DOI:10.1002/ana.410390105 SUPPORT Human Clinical

"ongoing wallerian-like degeneration of fibers in the ventral and dorsal roots and in the peripheral nerves, with only minimal demyelination"

The autopsy series distinguishes combined motor-sensory axonal loss from a primarily demyelinating lesion.

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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

Digestive 1

Dysphagia HP:0002015

Show evidence (1 reference)

DOI:10.3389/fneur.2023.1227505 SUPPORT Human Clinical

"dysarthria, dysphagia, bilateral facial paralysis, facial diplegia"

This case documents dysphagia during AMSAN progression; it is illustrative rather than frequency evidence.

Limbs 1

Limb Weakness Limb muscle weakness HP:0003690

Course: PROGRESSIVE

Show evidence (1 reference)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"progressive flaccid limb paresis and areflexia."

This is the hallmark motor-sensory GBS phenotype and therefore applies to AMSAN, without supplying an AMSAN-specific frequency.

Musculoskeletal 1

Respiratory Insufficiency Respiratory insufficiency due to muscle weakness HP:0002747

Show evidence (1 reference)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"The most severely affected patients also develop respiratory failure and autonomic dysfunction"

GBS-wide evidence supports the severe complication; no AMSAN-specific frequency is asserted.

Nervous System 4

Areflexia HP:0001284

Show evidence (1 reference)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"progressive flaccid limb paresis and areflexia."

Areflexia is a defining GBS-wide clinical feature relevant to AMSAN.

Sensory Neuropathy HP:0000763

Show evidence (1 reference)

DOI:10.1002/ana.410390105 SUPPORT Human Clinical

"axonal lesions of both motor and sensory fibers"

Direct human AMSAN autopsy confirms sensory-fiber involvement, with the limitation of a small fatal-case series.

Paresthesia HP:0003401

Show evidence (1 reference)

DOI:10.3389/fneur.2023.1227505 SUPPORT Human Clinical

"weakness and paraesthesia in both her legs and arms for 4 days"

A single AMSAN case illustrates paresthesia but does not establish its frequency.

Autonomic Dysfunction Abnormality of the autonomic nervous system HP:0002270

Show evidence (1 reference)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"respiratory failure and autonomic dysfunction"

The current GBS primer supports dysautonomia in severe disease; the applicability is GBS-wide rather than AMSAN-specific.

Constitutional 1

Pain HP:0012531

Show evidence (1 reference)

PMID:39687605 SUPPORT Human Clinical

"Pain is a serious manifestation in both the acute and chronic stages of Guillain-Barre syndrome"

This prospective GBS cohort supports pain and reports an association with axonal GBS, but does not give an AMSAN-specific rate.

Other 2

Decreased Compound Muscle Action Potential Amplitude HP:0033383

Show evidence (1 reference)

DOI:10.1111/jns.12625 SUPPORT Other

"axonal neuropathies are simply diagnosed by reduced amplitude of motor and sensory nerve action potentials with normal or slightly slow conduction velocity."

The conventional motor-amplitude pattern supports the finding, while the review and serial GBS data caution against over-simple subtype inference.

Decreased Sensory Nerve Action Potential Amplitude Decreased amplitude of sensory action potentials HP:0007078

Show evidence (1 reference)

DOI:10.1111/jns.12625 SUPPORT Other

"axonal neuropathies are simply diagnosed by reduced amplitude of motor and sensory nerve action potentials with normal or slightly slow conduction velocity."

Reduced sensory amplitudes are part of the conventional axonal pattern; AMSAN classification still requires clinical context and serial testing.

💊

Medical Actions

Intravenous Immunoglobulin

Category: Therapeutic Action: Intravenous Immunoglobulin Therapy NCIT:C121331

Agent: Human immunoglobulin G NCIT:C80829

IVIG is one of two established immune treatments for GBS. The guideline regimen is 0.4 g/kg daily for five days, generally started within two weeks of weakness onset in a patient unable to walk unaided; selected patients may be treated at two to four weeks. Evidence and recommendations are GBS-wide, not AMSAN-specific.

Target Phenotypes: Limb muscle weakness HP:0003690

Show evidence (1 reference)

PMID:37814552 SUPPORT Other

"TF recommends intravenous immunoglobulin (IVIg) 0.4 g/kg for 5 days"

The guideline establishes the regimen for non-ambulatory GBS. No randomized AMSAN-specific efficacy evidence was identified.

Plasma Exchange

Category: Therapeutic Action: Plasmapheresis NCIT:C15304

Plasma exchange is an established alternative first-line immune treatment for GBS. The guideline regimen is 12-15 L in four to five exchanges over one to two weeks, generally within four weeks of weakness onset when the patient cannot walk unaided. It is not routine rescue immediately after IVIG.

Target Phenotypes: Limb muscle weakness HP:0003690

Show evidence (1 reference)

PMID:37814552 SUPPORT Other

"a course of plasma exchange (PE) 12-15 L in four to five exchanges over 1-2 weeks"

The guideline establishes the standard GBS regimen; no randomized AMSAN-specific treatment comparison was identified.

Respiratory, Swallowing, and Autonomic Monitoring

Category: Monitoring Action: Pulmonary function testing Ontology label: Pulmonary Function Test NCIT:C38081

All hospitalized patients require repeated respiratory assessment because dyspnea can be absent despite declining vital capacity. Monitoring also includes cough and swallow safety, heart rate, blood pressure, rhythm, bowel and bladder function, strength, and GBS disability. Rapid deterioration, bulbar weakness, dysautonomia, or adverse mEGRIS should lower the threshold for intensive-care transfer.

Show evidence (2 references)

PMID:31541214 SUPPORT Other

"Respiratory function should be monitored in all patients"

Consensus guidance supports proactive respiratory monitoring across GBS, including AMSAN.

PMID:31541214 SUPPORT Other

"patients should be monitored for swallowing and coughing difficulties."

Bulbar monitoring is part of GBS supportive care and is relevant to severe AMSAN.

Mechanical Ventilation

Category: Therapeutic Action: Artificial respiration Ontology label: Mechanical Ventilation NCIT:C70909

Invasive ventilation is supportive therapy for respiratory failure. It does not modify the immune attack, so respiratory monitoring and timely airway planning remain essential.

Target Phenotypes: Respiratory insufficiency due to muscle weakness HP:0002747

Show evidence (1 reference)

DOI:10.1007/s12028-023-01707-3 SUPPORT Other

"10-30% require mechanical ventilation during the acute phase of the disease."

The GBS-wide guideline supports ventilation as a common severe-disease requirement without assigning this rate to AMSAN.

Multidisciplinary Rehabilitation

Category: Therapeutic Action: Rehabilitation NCIT:C15315

Rehabilitation should begin during hospitalization and continue after discharge as needed. Physical and occupational therapy, graded mobility and strengthening, positioning and contracture prevention, speech/swallow care, respiratory therapy, assistive devices, and psychosocial support are tailored to weakness, sensory loss, fatigue, pain, and bulbar or respiratory deficits.

Target Phenotypes: Limb muscle weakness HP:0003690 Sensory neuropathy HP:0000763 Dysphagia HP:0002015

Show evidence (1 reference)

PMID:31541214 SUPPORT Other

"Start rehabilitation programme early"

Consensus guidance supports multidisciplinary rehabilitation; controlled AMSAN-specific rehabilitation evidence is not available.

Pain Management

Category: Therapeutic Action: Pain management Ontology label: Supportive Care NCIT:C15747

Neuropathic, radicular, and nociceptive pain should be assessed repeatedly and treated while accounting for respiratory and autonomic vulnerability. The guideline weakly supports gabapentinoids, tricyclic antidepressants, or carbamazepine; drug choice and dose require individualized safety review.

Target Phenotypes: Pain HP:0012531

Show evidence (1 reference)

PMID:37814552 SUPPORT Other

"weakly recommends gabapentinoids, tricyclic antidepressants or carbamazepine for treatment of pain"

This is a weak GBS-wide recommendation and not an AMSAN-specific trial result.

🌍

Environmental Factors

Campylobacter jejuni infection

Antecedent C. jejuni enteritis is the best-defined trigger for the ganglioside-mimicry mechanism and is associated with motor and axonal GBS patterns. GBS-wide risk estimates must not be read as AMSAN-specific risk.

Show evidence (2 references)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"patients with C. jejuni infection have anti-GM1 and anti-GD1a antibodies and are susceptible to developing motor and axonal forms of GBS"

The primer connects the antecedent to axonal GBS but does not isolate an AMSAN-specific effect size.

DOI:10.1002/ana.410390105 SUPPORT Human Clinical

"High titers of antibodies recognizing C. jejuni, consistent with recent infection, were found in the 2 patients tested."

Direct AMSAN pathology cases had serologic evidence of recent infection, but only two selected fatal cases were tested.

Mechanism Target:

TRIGGERS Campylobacter LOS-Ganglioside Molecular Mimicry — Antecedent enteritis supplies the sialylated lipooligosaccharide this node is built around, with the anti-GM1 and anti-GD1a response as the named intervening step. Both evidence items keep the partial grade this entry already assigned them, because neither isolates an effect size for this axonal subtype as opposed to the syndrome at large.

Show evidence (2 references)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"patients with C. jejuni infection have anti-GM1 and anti-GD1a antibodies and are susceptible to developing motor and axonal forms of GBS"

Connects the antecedent infection to anti-GM1 and anti-GD1a antibodies and to motor and axonal forms, which is this node's mimicry route.

DOI:10.1002/ana.410390105 SUPPORT Human Clinical

"High titers of antibodies recognizing C. jejuni, consistent with recent infection, were found in the 2 patients tested."

Autopsy-confirmed cases of this subtype carried serology for recent C. jejuni infection, though only two selected fatal cases were tested.

SARS-CoV-2 infection

AMSAN has been reported after SARS-CoV-2 infection. Current evidence here is a case-level temporal association and does not establish a causal trigger or population risk.

Show evidence (1 reference)

DOI:10.3389/fneur.2023.1227505 SUPPORT Human Clinical

"A nasopharyngeal swab for SARS-CoV-2 returned positive."

A single AMSAN case establishes co-occurrence and temporal context only.

🔬

Biochemical Markers

Albuminocytologic Dissociation (Supportive when present)

Context: Elevated CSF protein with a normal or near-normal white-cell count supports GBS but neither confirms the diagnosis nor determines the AMSAN subtype. A normal protein level early in the illness does not exclude GBS.

Show evidence (2 references)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"albumino-cytological dissociation, in which CSF protein levels are raised (>0.45 g/l) with a normal white cell count"

The primer defines the supportive CSF pattern across GBS.

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"patients can have normal CSF protein levels in the first week of disease onset, which does not exclude the diagnosis of GBS"

This prevents early normal CSF protein from being used to exclude AMSAN.

Anti-GM1, Anti-GM1b, and Anti-GD1a IgG (Associated in a subset)

Context: These antibodies support a shared AMAN/AMSAN immune spectrum in some patients but are not required, are not sufficiently sensitive to establish AMSAN, and should not replace serial electrodiagnostic assessment.

Show evidence (1 reference)

PMID:10526194 SUPPORT Human Clinical

"The patients with AMSAN had anti-GM1, anti-GM1b, and anti-GD1a IgG antibodies"

The small human AMSAN series directly supports association, not diagnostic sensitivity or universal presence.

Neurofilament Light Chain (Higher levels associated with poorer GBS outcome)

Context: Serum or plasma NfL reflects neuroaxonal injury and is an emerging prognostic/pharmacodynamic biomarker in GBS. It has not been validated as an AMSAN diagnostic test.

Show evidence (1 reference)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"high levels of neurofilament light chain (NfL)"

The primer lists high NfL among GBS poor-prognosis associations; this is not AMSAN-specific validation.

🔬

Diagnosis

Clinical GBS Syndrome Assessment

Establish the clinical syndrome first: progressive weakness of arms and legs, reduced or absent reflexes, and progression no longer than four weeks, with compatible sensory, cranial, autonomic, respiratory, pain, and antecedent-infection features. AMSAN is not diagnosed by a biomarker alone.

Diagnostic procedure NCIT:C18020

Results: A compatible acute motor-sensory GBS syndrome; atypical findings trigger evaluation for mimics.

Show evidence (2 references)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"Progressive weakness of arms and legs"

The 2024 primer reproduces the guideline's required motor-sensory GBS features; AMSAN classification is a subsequent electrophysiologic step.

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"Absent or decreased tendon reflexes in affected limbs"

Reduced reflexes are a required clinical feature in the guideline-based motor-sensory GBS criteria.

Serial Nerve Conduction Studies and Electromyography

NCS/EMG supports poly(radiculo)neuropathy and the motor-sensory axonal pattern: reduced CMAP and SNAP amplitudes without primary demyelinating criteria. Early studies may be normal or equivocal. Repeat testing is appropriate, and a single early subtype label should not be treated as immutable or as a treatment selector.

Nerve conduction study NCIT:C88502

Results: Reproducible motor and sensory axonal abnormalities; classification may change on serial studies.

Show evidence (2 references)

PMID:41656826 SUPPORT Human Clinical

"the electrodiagnostic subtype changed on serial NCS in 37.8% (Hadden) and 44.7% (Rajabally)."

The 469-patient serial-NCS analysis quantifies substantial early subtype instability.

PMID:41656826 SUPPORT Human Clinical

"If these early NCS are non-diagnostic, repeating the study should be considered. Electrodiagnostic subtyping offers no additional value."

The study supports prompt NCS, repeat testing when needed, and restraint in assigning independent prognostic or treatment value to the subtype label.

Cerebrospinal Fluid Analysis

CSF cell count and protein help support GBS and identify mimics. Elevated protein with a normal cell count is supportive but may be absent early; marked pleocytosis argues for infectious, malignant, or inflammatory alternatives. CSF cannot determine AMSAN.

Cerebrospinal fluid analysis NCIT:C173272

Results: Albuminocytologic dissociation may support GBS; early normal protein does not exclude it, and pleocytosis requires explanation.

Show evidence (2 references)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"increased CSF protein levels were found in <50% of patients at 1 day and in >80% at >1 week after onset of weakness"

The time dependence shows why CSF protein cannot confirm or exclude early GBS and does not subtype AMSAN.

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"CSF pleocytosis (>50 cells/microl) in general is atypical and should alert clinicians to consider other differential diagnoses"

Marked pleocytosis should redirect the workup toward mimics.

Anti-Ganglioside Antibody Testing as a Limited Adjunct

Anti-GM1, anti-GM1b, or anti-GD1a IgG can support the biological context in selected cases or research but is neither required nor sufficiently sensitive for AMSAN diagnosis. Negative testing does not exclude AMSAN, and routine testing has limited value in typical motor-sensory GBS.

Serology testing NCIT:C25294

Results: A positive result may support an axonal GBS immune profile; a negative result is nondiagnostic.

Show evidence (1 reference)

PMID:37814552 SUPPORT Other

"testing for anti-ganglioside antibodies is of limited clinical value in most patients with typical motor-sensory GBS"

The guideline directly limits routine diagnostic use in the clinical pattern that includes AMSAN.

📈

Progression

Acute progressive phase

Duration: Usually less than 14; by definition no more than 28 days

Weakness progresses rapidly. The timing is GBS-wide evidence rather than an AMSAN-specific natural-history estimate.

Show evidence (2 references)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"initial acute and progressive phase of <4 weeks"

The current GBS primer defines the acute progressive phase; AMSAN-specific timing has not been established independently.

PMID:31541214 SUPPORT Other

"most patients with GBS reach their maximum disability within 2 weeks."

Consensus guidance supports the usual early nadir while remaining GBS-wide evidence.

Plateau phase

Duration: Variable

The plateau follows the progressive phase. Continued progression beyond four weeks questions typical GBS, and deterioration after eight weeks should prompt reconsideration as acute-onset CIDP.

Show evidence (2 references)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"followed by a plateau phase and recovery phase of weeks to years"

The primer describes the usual GBS sequence; the duration is variable and not specific to AMSAN.

PMID:37814552 SUPPORT Other

"acute-onset chronic inflammatory demyelinating polyradiculoneuropathy (A-CIDP) should be considered if progression continues after 8 weeks from onset"

The guideline identifies prolonged progression as a reason to reconsider the diagnosis rather than extend the AMSAN label indefinitely.

Recovery phase

Duration: Weeks to years

Recovery is heterogeneous. Reversible nodal failure can improve faster than fixed axonal loss, whereas extensive axonal degeneration can leave prolonged weakness, sensory loss, pain, and fatigue. GBS-wide prognostic tools such as mEGOS and mEGRIS are preferred over assuming prognosis from the AMSAN label.

Show evidence (1 reference)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"the rate of progression and recovery varies considerably between patients."

This supports variable recovery and cautions against a uniform AMSAN-specific prognosis.

🌍

Epidemiology

AMSAN fraction in a Mexican single-center adult GBS cohort

8.6–8.6 percent of electrodiagnostically assessed GBS cases

This is a cohort-specific subtype fraction, not population prevalence. The study was single-center and classification was based on one criteria set.

Show evidence (1 reference)

PMID:32674942 SUPPORT Human Clinical

"acute motor and sensory axonal neuropathy (AMSAN) 8,6%."

The cohort reports an AMSAN case fraction among adults with GBS; it cannot be generalized as prevalence.

AMSAN fraction in a northern India GBS cohort

4.6–4.6 percent of consecutive GBS cases

This is a cohort-specific subtype fraction, not population prevalence. Repeat NCS was performed only when the initial study was normal.

Show evidence (1 reference)

PMID:24456386 SUPPORT Human Clinical

"15 (4.6%) AMSAN"

The study reports 15 AMSAN classifications among 328 GBS patients in one regional cohort.

🔀

Differential Diagnoses

Conditions with similar clinical presentations that must be differentiated from Acute Motor and Sensory Axonal Neuropathy:

Acute Motor Axonal Neuropathy Not Yet Curated MONDO:0020349

Overlapping Features AMAN is the motor-only axonal GBS pattern and shares anti-GM1/GD1a biology with AMSAN. Preserved sensory examination and sensory nerve action potentials favor AMAN, while reproducible sensory abnormalities favor AMSAN.

Distinguishing Features

Sensory loss and reduced sensory responses are absent in the motor-only pattern.
Serial NCS is required because early classifications can change.

Show evidence (1 reference)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"Sensory loss is also present in the predominant motor-sensory form but absent in the motor form."

This directly states the clinical sensory distinction between motor-only and motor-sensory GBS patterns.

Acute Inflammatory Demyelinating Polyradiculoneuropathy Not Yet Curated MONDO:0020347

Overlapping Features AIDP is the primary demyelinating GBS pattern. Demyelinating slowing, temporal dispersion, prolonged distal latencies, and conduction block with evolution distinct from reversible nodal failure favor AIDP over AMSAN.

Distinguishing Features

Primary demyelinating rather than low-amplitude motor-sensory axonal pattern.
Serial studies help separate remyelinating block from reversible nodal failure.

Show evidence (1 reference)

PMID:22480600 SUPPORT Other

"Serial electrophysiological studies are mandatory for proper diagnosis of GBS subtypes"

The review explains why longitudinal electrodiagnosis is necessary to distinguish demyelinating and axonal patterns.

Acute-Onset Chronic Inflammatory Demyelinating Polyradiculoneuropathy MONDO:0006702

Overlapping Features A-CIDP can resemble GBS initially but becomes more likely with progression or relapse beyond the expected monophasic window.

Distinguishing Features

Continued progression or deterioration after eight weeks.
Three or more treatment-related fluctuations or a chronic relapsing course.

Show evidence (1 reference)

PMID:37814552 SUPPORT Other

"acute-onset chronic inflammatory demyelinating polyradiculoneuropathy (A-CIDP) should be considered if progression continues after 8 weeks from onset"

The guideline gives the key temporal discriminator.

Critical Illness Polyneuropathy or Myopathy Not Yet Curated MONDO:0001957

Overlapping Features Critical-illness neuropathy/myopathy produces weakness and an axonal NCS pattern during prolonged severe illness or ventilation and can confound an ICU diagnosis of AMSAN.

Distinguishing Features

Begins in the setting of prolonged critical illness or ventilation.
EMG may show myopathic features; sensory studies help separate pure myopathy.

Show evidence (1 reference)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"Prolonged illness or ventilation NCS: axonal neuropathy with or without myopathic features on EMG"

The GBS differential table states the context and electrodiagnostic discriminator.

Acute Porphyria MONDO:0008294

Overlapping Features Acute hepatic porphyria can cause an acute motor-predominant axonal neuropathy with autonomic and psychiatric symptoms that resembles GBS.

Distinguishing Features

Abdominal pain, psychiatric symptoms, dysautonomia, or family history.
Elevated urinary porphobilinogen during an attack.

Show evidence (1 reference)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"Family history, concomitant psychiatric symptoms and abdominal pain"

The primer lists the clinical clues that distinguish porphyria from GBS.

Transverse Myelitis or Other Spinal Cord Disease MONDO:0021553

Overlapping Features Acute spinal cord inflammation can cause rapidly progressive limb weakness and sensory symptoms but localizes to the central nervous system.

Distinguishing Features

A sensory level, brisk reflexes, extensor plantar responses, or sphincter-predominant onset.
Spinal MRI shows an intramedullary lesion.

Show evidence (1 reference)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"Transverse myelitis Sensory level, brisk reflexes MRI spine: hyperintense lesion"

The GBS differential table supplies the localization and imaging clues.

Botulism MONDO:0005498

Overlapping Features Botulism can progress rapidly with weakness and dysautonomia but is a presynaptic neuromuscular-junction disorder rather than an axonal polyradiculoneuropathy.

Distinguishing Features

Pupillary abnormalities and descending rather than ascending paralysis.
Incremental response on rapid repetitive nerve stimulation and toxin detection.

Show evidence (1 reference)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"Rapid progression, pupillary abnormalities, dysautonomia, descending paralysis"

The table identifies the characteristic botulism pattern.

Thiamine Deficiency Neuropathy

Overlapping Features Severe nutritional thiamine deficiency can cause an acute axonal neuropathy that resembles AMSAN.

Distinguishing Features

Malnutrition, hyperemesis, alcohol exposure, or Wernicke encephalopathy.
Abnormal thiamine indices and an axonal NCS pattern without the typical GBS context.

Show evidence (1 reference)

DOI:10.1038/s41572-024-00580-4 SUPPORT Other

"Precipitating factors (for example, hyperemesis gravidarum, alcoholism, nutritional deficiency)"

The primer identifies the exposure context that separates thiamine deficiency from immune-mediated GBS.

🔬

Clinical Trials

NCT04752566 PHASE_III COMPLETED

Completed randomized placebo-controlled Phase 3 trial of eculizumab added to IVIG in severe GBS. The published primary endpoint was not achieved. The study did not report AMSAN-specific efficacy and does not establish eculizumab as standard GBS or AMSAN therapy.

Target Phenotypes: Limb muscle weakness HP:0003690

Show evidence (2 references)

clinicaltrials:NCT04752566 SUPPORT Human Clinical

"This is a Phase 3, prospective, multicenter, placebo controlled, double blind, randomized study to investigate the efficacy and safety of eculizumab in participants with severe GBS"

The registry supports the trial design; the population was severe GBS and not AMSAN-specific.

DOI:10.1111/jns.12646 SUPPORT Human Clinical

"Primary endpoint was not achieved (hazard ratio, 0.9; 95% CI, 0.45-1.97; p = .89)."

The published negative primary endpoint prevents interpreting complement biology alone as proof of clinical efficacy.

NCT04701164 PHASE_III COMPLETED

Completed randomized double-blind placebo-controlled Phase 3 study of the anti-C1q antibody ANX005 (tanruprubart) in recent-onset GBS. The registry reports 242 participants and no posted results as of the current review. It was not restricted to AMSAN.

Target Phenotypes: Limb muscle weakness HP:0003690

Show evidence (1 reference)

clinicaltrials:NCT04701164 SUPPORT Human Clinical

"This study is intended to evaluate the efficacy and safety of ANX005 administered by intravenous (IV) infusion to participants recently diagnosed with Guillain-Barré Syndrome (GBS)."

The registry supports the intervention and GBS population but not an AMSAN-specific effect or a result claim.

NCT07020819 PHASE_III RECRUITING

FORWARD is an open-label Phase 3 study of a single tanruprubart (ANX005) dose in adult and pediatric recent-onset GBS, measuring pharmacokinetics, pharmacodynamics, early efficacy, and safety. It is ongoing, GBS-wide, and cannot yet establish efficacy for AMSAN.

Target Phenotypes: Limb muscle weakness HP:0003690

Show evidence (1 reference)

clinicaltrials:NCT07020819 SUPPORT Human Clinical

"The goal of this open label study is to measure pharmacokinetics, pharmacodynamics, early efficacy, and safety of tanruprubart in adult and pediatric participants, in the United States, Canada, and Europe."

The registry establishes the prospective study and objectives, not an efficacy result.

🧫

Experimental Models

Anti-GD1a/complement ex vivo motor nerve-terminal injury model OTHER

Nerve-muscle preparations from mice overexpressing GD1a are exposed to anti-GD1a monoclonal antibodies and complement. The preparation demonstrates antibody/complement deposition, ultrastructural injury, and motor-terminal conduction block while sparing postsynaptic membranes. It is a mechanistic motor-axon assay rather than a sensory-inclusive AMSAN model.

Organism

House mouse NCBITaxon:10090

Culture

Ex vivo nerve-muscle preparation

Publication

PMID:15716397

Pathograph links

Ganglioside Antibody Binding at Nodal and Axolemmal Membranes Anti-GD1a antibody deposition on presynaptic motor axons.

Show evidence (1 reference)

PMID:15716397 SUPPORT In Vitro

"Dense antibody and complement deposits were observed only over presynaptic motor axons"

The ex vivo finding directly supports the modeled binding step but not sensory-axon injury.

Reversible Nodal Conduction Failure Complement-dependent blockade of motor nerve-terminal function.

Show evidence (1 reference)

PMID:15716397 SUPPORT In Vitro

"electrophysiological blockade of motor nerve terminal function."

The preparation measures functional motor-terminal blockade but is not a full in vivo AMSAN phenotype.

Findings

Antigen density controls susceptibility to anti-GD1a antibody/complement injury at motor nerve terminals.

"demonstrating the central role of membrane antigen density in modulating both immune tolerance to GD1a and axonal susceptibility"

Show evidence (1 reference)

PMID:15716397 SUPPORT In Vitro

"severe ultrastructural damage and electrophysiological blockade of motor nerve terminal function."

The model recapitulates complement-dependent motor-terminal injury but not combined motor-sensory AMSAN.

🐁

Animal Models

Oryctolagus cuniculus Active-immunization axonal GBS model

Rabbits sensitized with bovine brain ganglioside mixture or purified GM1 developed anti-GM1 IgG, acute monophasic flaccid weakness, and Wallerian-like peripheral-nerve degeneration without lymphocytic infiltration or demyelination. This models motor-predominant axonal GBS and does not validate sensory-inclusive AMSAN.

Species

Oryctolagus cuniculus

Show evidence (1 reference)

PMID:11409422 SUPPORT Model Organism

"Pathological findings for the peripheral nerves showed predominant Wallerian-like degeneration, with neither lymphocytic infiltration nor demyelination."

The rabbit model reproduces acute axonal injury but does not demonstrate sensory-axon disease equivalent to AMSAN.

Oryctolagus cuniculus Campylobacter LOS molecular-mimicry model

Rabbits immunized with ganglioside-mimicking C. jejuni LOS developed anti-GM1 IgG, flaccid weakness, and GBS-like peripheral-nerve pathology. This provides causal molecular-mimicry evidence but is not a validated AMSAN model.

Species

Oryctolagus cuniculus

Show evidence (1 reference)

PMID:15277677 SUPPORT Model Organism

"On sensitization with C. jejuni lipooligosaccharide, rabbits developed anti-GM1 IgG antibody and flaccid limb weakness."

The experiment directly links LOS mimicry to antibody and weakness, with motor-predominant rather than AMSAN fidelity.

Neuron-restricted complex ganglioside expression Mus musculus Anti-GM1 complement-mediated AMAN model

A transgenic mouse system restricts complex ganglioside expression to neurons, permitting anti-GM1 targeting of axons. Anti-C1q treatment reduces complement deposition, immune-cell recruitment, axonal injury, and respiratory dysfunction. The model is explicitly AMAN and omits the sensory injury that defines AMSAN.

Species

Mus musculus

Genotype

Neuron-restricted complex ganglioside expression

Show evidence (1 reference)

PMID:26936605 SUPPORT Model Organism

"Anti-C1q monoclonal antibody treatment attenuated complement cascade activation and deposition, reduced immune cell recruitment and axonal injury"

The model gives causal complement evidence but is motor-only and therefore an incomplete proxy for AMSAN.

{ }

Source YAML

click to show

name: Acute Motor and Sensory Axonal Neuropathy
creation_date: "2026-05-07T23:29:25Z"
categories:
- Autoimmune Disease
- Peripheral Neuropathy
- Rare Disease
- Neurologic Disease
parents:
- Guillain-Barre Syndrome
- Peripheral Neuropathy
disease_term:
  preferred_term: Acute motor and sensory axonal neuropathy
  term:
    id: MONDO:0020348
    label: acute motor and sensory axonal neuropathy
description: >-
  Acute motor and sensory axonal neuropathy (AMSAN) is a motor-sensory axonal
  electrophysiologic and pathologic pattern within Guillain-Barre syndrome
  (GBS). It is characterized clinically by acute progressive flaccid weakness,
  reduced reflexes, and sensory involvement, and electrodiagnostically by
  reduced or absent motor and sensory response amplitudes without a primary
  demyelinating pattern. In a subset of axonal GBS, especially after
  Campylobacter jejuni infection, cross-reactive anti-ganglioside antibodies
  activate complement at vulnerable nodal and axolemmal membranes. Injury can
  range from reversible nodal conduction failure to irreversible degeneration
  of motor and sensory axons. AMSAN assignment may change on serial nerve
  conduction studies, so it should not be treated as a perfectly stable early
  subtype or as a separate treatment indication.
synonyms:
- Acute motor-sensory axonal polyneuropathy
- AMSAN
- Acute motor-sensory axonal Guillain-Barre syndrome

progression:
- phase: Acute progressive phase
  duration_days: Usually less than 14; by definition no more than 28
  notes: >-
    Weakness progresses rapidly. The timing is GBS-wide evidence rather than an
    AMSAN-specific natural-history estimate.
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      initial acute and progressive phase of <4 weeks
    explanation: >-
      The current GBS primer defines the acute progressive phase; AMSAN-specific
      timing has not been established independently.
  - reference: PMID:31541214
    reference_title: "Diagnosis and management of Guillain-Barré syndrome in ten steps."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      most patients with GBS reach their maximum disability within 2 weeks.
    explanation: >-
      Consensus guidance supports the usual early nadir while remaining
      GBS-wide evidence.
- phase: Plateau phase
  duration: Variable
  notes: >-
    The plateau follows the progressive phase. Continued progression beyond four
    weeks questions typical GBS, and deterioration after eight weeks should
    prompt reconsideration as acute-onset CIDP.
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      followed by a plateau phase and recovery phase of weeks to years
    explanation: >-
      The primer describes the usual GBS sequence; the duration is variable and
      not specific to AMSAN.
  - reference: PMID:37814552
    reference_title: "European Academy of Neurology/Peripheral Nerve Society Guideline on diagnosis and treatment of Guillain-Barré syndrome."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      acute-onset chronic inflammatory demyelinating polyradiculoneuropathy
      (A-CIDP) should be considered if progression continues after 8 weeks from
      onset
    explanation: >-
      The guideline identifies prolonged progression as a reason to reconsider
      the diagnosis rather than extend the AMSAN label indefinitely.
- phase: Recovery phase
  duration: Weeks to years
  notes: >-
    Recovery is heterogeneous. Reversible nodal failure can improve faster than
    fixed axonal loss, whereas extensive axonal degeneration can leave prolonged
    weakness, sensory loss, pain, and fatigue. GBS-wide prognostic tools such as
    mEGOS and mEGRIS are preferred over assuming prognosis from the AMSAN label.
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      the rate of progression and recovery varies considerably between patients.
    explanation: >-
      This supports variable recovery and cautions against a uniform
      AMSAN-specific prognosis.

pathophysiology:
- name: Campylobacter LOS-Ganglioside Molecular Mimicry
  role: trigger
  conforms_to: "molecular_mimicry_autoimmunity#Infection-Associated Cross-Reactive Antigen Exposure"
  description: >-
    In a biologically defined subset of axonal GBS, sialylated C. jejuni
    lipooligosaccharides resemble peripheral-nerve gangliosides. The mimicry can
    initiate an antibody response that recognizes both bacterial carbohydrate
    and neural ganglioside. This mechanism is not asserted for every AMSAN case.
  biological_processes:
  - preferred_term: Antigen processing and presentation
    term:
      id: GO:0019882
      label: antigen processing and presentation
  evidence:
  - reference: PMID:15277677
    reference_title: Carbohydrate mimicry between human ganglioside GM1 and Campylobacter jejuni lipooligosaccharide causes Guillain-Barre syndrome.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      On sensitization with C. jejuni lipooligosaccharide, rabbits developed
      anti-GM1 IgG antibody and flaccid limb weakness.
    explanation: >-
      Active immunization provides experimental causal evidence for the
      LOS-to-anti-GM1 molecular-mimicry step, although the model is motor-predominant.
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      preceding Campylobacter jejuni infection, molecular mimicry causes a
      cross-reactive antibody response to nerve gangliosides.
    explanation: >-
      The primer synthesizes the established C. jejuni mechanism in GBS; it is
      applied only to the relevant AMSAN subset.
  downstream:
  - target: Cross-Reactive Anti-Ganglioside IgG Response
    causal_link_type: DIRECT
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      LOS-ganglioside mimicry elicits IgG that cross-reacts with neural
      gangliosides.
    evidence:
    - reference: PMID:15277677
      reference_title: Carbohydrate mimicry between human ganglioside GM1 and Campylobacter jejuni lipooligosaccharide causes Guillain-Barre syndrome.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        On sensitization with C. jejuni lipooligosaccharide, rabbits developed
        anti-GM1 IgG antibody
      explanation: >-
        The intervention directly links bacterial LOS exposure to anti-GM1 IgG
        production in vivo.

- name: Cross-Reactive Anti-Ganglioside IgG Response
  role: central_effector
  conforms_to: "molecular_mimicry_autoimmunity#Cross-Reactive Autoreactive Lymphocyte Activation"
  description: >-
    Activated B-cell and plasma-cell responses produce IgG against gangliosides
    such as GM1, GM1b, and GD1a. These antibodies occur in some, but not all,
    patients with axonal GBS. A small human study found the same antibody profile
    in AMSAN and AMAN, supporting a shared immune spectrum rather than a uniquely
    AMSAN-specific marker.
  cell_types:
  - preferred_term: B cell
    term:
      id: CL:0000236
      label: B cell
  biological_processes:
  - preferred_term: Immunoglobulin production
    term:
      id: GO:0002377
      label: immunoglobulin production
    modifier: INCREASED
  evidence:
  - reference: PMID:10526194
    reference_title: Acute motor axonal neuropathy and acute motor-sensory axonal neuropathy share a common immunological profile.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The patients with AMSAN had anti-GM1, anti-GM1b, and anti-GD1a IgG
      antibodies
    explanation: >-
      This is direct AMSAN serologic evidence, limited by the small historical
      series and not a sensitivity estimate.
  - reference: DOI:10.1186/s43161-024-00258-8
    reference_title: "Autoimmune mechanisms in Guillain-Barré syndrome subtypes: a systematic review"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      specific autoantibodies, such as anti-GM1 and anti-GQ1b, are associated
      with distinct subtypes of GBS
    explanation: >-
      The systematic review supports antibody-associated GBS heterogeneity but
      does not establish a universal or AMSAN-specific diagnostic marker.
  downstream:
  - target: Ganglioside Antibody Binding at Nodal and Axolemmal Membranes
    causal_link_type: DIRECT
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      Circulating anti-ganglioside IgG binds ganglioside-rich vulnerable sites
      on peripheral axons and motor nerve terminals.
    evidence:
    - reference: PMID:15716397
      reference_title: Overexpression of GD1a ganglioside sensitizes motor nerve terminals to anti-GD1a antibody-mediated injury in a model of acute motor axonal neuropathy.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        Dense antibody and complement deposits were observed only over
        presynaptic motor axons
      explanation: >-
        The ex vivo model directly demonstrates antibody deposition on axonal
        membranes but models motor terminals rather than sensory-inclusive AMSAN.

- name: Ganglioside Antibody Binding at Nodal and Axolemmal Membranes
  role: effector
  description: >-
    Anti-ganglioside IgG binds the nodal axolemma and nerve-terminal membranes.
    Antigen density and ganglioside complexes influence binding, which helps
    explain why antibody presence alone does not predict the exact clinical
    distribution of injury.
  cell_types:
  - preferred_term: Motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  - preferred_term: Sensory neuron
    term:
      id: CL:0000101
      label: sensory neuron
  cellular_components:
  - preferred_term: Node of Ranvier
    term:
      id: GO:0033268
      label: node of Ranvier
  - preferred_term: Axolemma
    term:
      id: GO:0030673
      label: axolemma
  evidence:
  - reference: PMID:26936605
    reference_title: C1q-targeted inhibition of the classical complement pathway prevents injury in a novel mouse model of acute motor axonal neuropathy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      complement-fixing anti-ganglioside antibodies that directly bind and
      injure the axon at sites of vulnerability such as nodes of Ranvier and
      nerve terminals.
    explanation: >-
      This establishes vulnerable axonal binding sites in an AMAN model; sensory
      axon targeting in AMSAN remains unmodeled.
  downstream:
  - target: Classical Complement Activation at Axonal Membranes
    causal_link_type: DIRECT
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      Axon-bound IgG recruits C1q and initiates the classical complement pathway.
    evidence:
    - reference: PMID:15716397
      reference_title: Overexpression of GD1a ganglioside sensitizes motor nerve terminals to anti-GD1a antibody-mediated injury in a model of acute motor axonal neuropathy.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        Dense antibody and complement deposits were observed only over
        presynaptic motor axons
      explanation: >-
        Co-localized antibody and complement deposition directly supports the
        binding-to-complement edge in a motor-terminal preparation.

- name: Classical Complement Activation at Axonal Membranes
  role: effector
  conforms_to: "molecular_mimicry_autoimmunity#Autoreactive Effector-Mediated Tissue Injury"
  description: >-
    C1q-initiated classical complement activation deposits complement products
    at nodal, paranodal, and nerve-terminal membranes. Terminal-complement pores,
    calcium influx, and downstream protease activation can produce early
    functional failure and, if injury is not reversed, structural axonal loss.
  biological_processes:
  - preferred_term: Classical complement activation
    term:
      id: GO:0006958
      label: complement activation, classical pathway
    modifier: INCREASED
  cell_types:
  - preferred_term: Motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  - preferred_term: Sensory neuron
    term:
      id: CL:0000101
      label: sensory neuron
  cellular_components:
  - preferred_term: Node of Ranvier
    term:
      id: GO:0033268
      label: node of Ranvier
  - preferred_term: Axolemma
    term:
      id: GO:0030673
      label: axolemma
  evidence:
  - reference: PMID:26936605
    reference_title: C1q-targeted inhibition of the classical complement pathway prevents injury in a novel mouse model of acute motor axonal neuropathy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Anti-C1q monoclonal antibody treatment attenuated complement cascade
      activation and deposition
    explanation: >-
      Targeted C1q inhibition provides intervention evidence for classical
      complement activation in acute motor-axonal injury, with incomplete AMSAN
      fidelity.
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Complement activation at these sites causes initial peripheral nerve
      dysfunction followed by structural injury
    explanation: >-
      The primer synthesizes complement as the link from antibody binding to
      functional and structural nerve injury across GBS.
  downstream:
  - target: Reversible Nodal Conduction Failure
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Nodal and paranodal membrane disruption
    - Terminal complement complex formation and calcium influx
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      Complement-mediated nodal membrane dysfunction can block conduction before
      irreversible axonal loss occurs.
    evidence:
    - reference: PMID:22507308
      reference_title: A common mechanism and a new categorization for anti-ganglioside antibody-mediated neuropathies.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        complement mediated dysfunction and disruption of the nodes of Ranvier
        which causes a pathophysiological continuum from early reversible
        conduction failure to axonal degeneration.
      explanation: >-
        The review explicitly links complement-mediated nodal disruption to the
        reversible-conduction-failure end of the axonal GBS continuum.
  - target: Macrophage Recruitment and Periaxonal Entry
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Complement-fragment signaling and opsonization
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      Complement products promote recruitment of macrophages and other immune
      cells to injured neural membranes.
    evidence:
    - reference: PMID:26936605
      reference_title: C1q-targeted inhibition of the classical complement pathway prevents injury in a novel mouse model of acute motor axonal neuropathy.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        attenuated complement cascade activation and deposition, reduced immune
        cell recruitment and axonal injury
      explanation: >-
        C1q blockade reduced both complement deposition and immune-cell
        recruitment, supporting an indirect complement-to-recruitment link in a
        motor-axonal model.
  - target: Motor and Sensory Axonal Degeneration
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Terminal complement complex formation
    - Calcium influx
    - Calpain and caspase activation
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      Persistent complement-mediated membrane injury can cross the threshold
      from reversible dysfunction to irreversible axonal degeneration.
    evidence:
    - reference: PMID:22507308
      reference_title: A common mechanism and a new categorization for anti-ganglioside antibody-mediated neuropathies.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        a pathophysiological continuum from early reversible conduction failure
        to axonal degeneration.
      explanation: >-
        This synthesis explicitly places axonal degeneration downstream of the
        complement-mediated nodal process.

- name: Reversible Nodal Conduction Failure
  role: effector
  description: >-
    Immune disruption of nodal and paranodal excitability can transiently block
    conduction without the temporal dispersion expected from remyelination and
    without established Wallerian degeneration. Serial studies are required to
    distinguish recovery of nodal function from fixed axonal loss.
  cell_types:
  - preferred_term: Motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  biological_processes:
  - preferred_term: Transmission of nerve impulse
    term:
      id: GO:0019226
      label: transmission of nerve impulse
    modifier: DECREASED
  cellular_components:
  - preferred_term: Node of Ranvier
    term:
      id: GO:0033268
      label: node of Ranvier
  evidence:
  - reference: PMID:22480600
    reference_title: "Electrodiagnostic criteria for Guillain-Barrè syndrome: a critical revision and the need for an update."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      transient conduction block/slowing in intermediate and distal nerve
      segments, mimicking demyelination but without the development of abnormal
      temporal dispersion, named reversible conduction failure
    explanation: >-
      The electrodiagnostic review defines reversible conduction failure in
      axonal GBS; the direct examples are primarily AMAN rather than AMSAN.
  downstream:
  - target: Decreased Compound Muscle Action Potential Amplitude
    causal_link_type: DIRECT
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      Failure of motor-axon conduction reduces the evoked compound muscle action
      potential even when the axon has not yet degenerated.
    evidence:
    - reference: PMID:22480600
      reference_title: "Electrodiagnostic criteria for Guillain-Barrè syndrome: a critical revision and the need for an update."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        transient conduction block/slowing in intermediate and distal nerve
        segments
      explanation: >-
        Conduction block provides a functional route to a reduced motor response;
        amplitude is not separately quantified in this review excerpt.

- name: Macrophage Recruitment and Periaxonal Entry
  role: effector
  description: >-
    Macrophages accumulate around injured myelinated axons and can enter the
    periaxonal space. Human AMSAN autopsy establishes this localization, but the
    relative injurious versus debris-clearing role and timing remain uncertain.
  biological_processes:
  - preferred_term: Macrophage chemotaxis
    term:
      id: GO:0048246
      label: macrophage chemotaxis
    modifier: INCREASED
  cell_types:
  - preferred_term: Macrophage
    term:
      id: CL:0000235
      label: macrophage
  evidence:
  - reference: DOI:10.1002/ana.410390105
    reference_title: "Pathology of the motor‐sensory axonal Guillain‐Barré syndrome"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All 3 had numerous macrophages in the periaxonal space of myelinated
      internodes
    explanation: >-
      Fatal human AMSAN autopsies directly localize macrophages around axons;
      the tiny, severity-selected series limits generalization.

- name: Motor and Sensory Axonal Degeneration
  role: central_effector
  description: >-
    Irreversible AMSAN injury is dominated by Wallerian-like degeneration and
    loss of motor and sensory fibers in ventral and dorsal roots and peripheral
    nerves. This acute pattern is not assumed to be length-dependent, and
    primary demyelination is not required.
  cell_types:
  - preferred_term: Motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  - preferred_term: Sensory neuron
    term:
      id: CL:0000101
      label: sensory neuron
  evidence:
  - reference: DOI:10.1002/ana.410390105
    reference_title: "Pathology of the motor‐sensory axonal Guillain‐Barré syndrome"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      predominantly axonal lesions of both motor and sensory fibers, even in the
      early stages of the disease
    explanation: >-
      This is direct human AMSAN pathology, although it derives from four fatal
      cases and therefore overrepresents severe disease.
  - reference: DOI:10.1002/ana.410390105
    reference_title: "Pathology of the motor‐sensory axonal Guillain‐Barré syndrome"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      ongoing wallerian-like degeneration of fibers in the ventral and dorsal
      roots and in the peripheral nerves, with only minimal demyelination
    explanation: >-
      The autopsy series distinguishes combined motor-sensory axonal loss from a
      primarily demyelinating lesion.
  downstream:
  - target: Decreased Compound Muscle Action Potential Amplitude
    causal_link_type: DIRECT
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      Loss of functioning motor axons reduces or abolishes compound muscle action
      potential amplitudes.
    evidence:
    - reference: DOI:10.1111/jns.12625
      reference_title: "Conduction slowing, conduction block and temporal dispersion in demyelinating, dysmyelinating and axonal neuropathies: Electrophysiology meets pathology"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        axonal neuropathies are simply diagnosed by reduced amplitude of motor
        and sensory nerve action potentials with normal or slightly slow
        conduction velocity.
      explanation: >-
        The review states the conventional axonal-amplitude heuristic while
        cautioning that electrophysiology-pathology relationships are more
        complex; serial GBS studies remain necessary.
  - target: Decreased Sensory Nerve Action Potential Amplitude
    causal_link_type: DIRECT
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      Loss of functioning sensory axons reduces or abolishes sensory nerve action
      potential amplitudes.
    evidence:
    - reference: DOI:10.1111/jns.12625
      reference_title: "Conduction slowing, conduction block and temporal dispersion in demyelinating, dysmyelinating and axonal neuropathies: Electrophysiology meets pathology"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        axonal neuropathies are simply diagnosed by reduced amplitude of motor
        and sensory nerve action potentials with normal or slightly slow
        conduction velocity.
      explanation: >-
        The conventional amplitude pattern is relevant to AMSAN, but the review
        warns against treating it as a simple one-to-one pathology rule.
  - target: Limb Weakness
    causal_link_type: DIRECT
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      Motor-axon loss reduces muscle activation and produces acute flaccid limb
      weakness.
    evidence:
    - reference: PMID:11409422
      reference_title: "Animal model of axonal Guillain-Barré syndrome induced by sensitization with GM1 ganglioside."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        flaccid limb weakness of acute onset
      explanation: >-
        The rabbit model links acute axonal injury to flaccid weakness but does
        not reproduce the sensory component of AMSAN.
  - target: Areflexia
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Motor and sensory reflex-arc failure
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      Failure of peripheral motor and sensory limbs of the reflex arc reduces or
      abolishes tendon reflexes.
    evidence:
    - reference: DOI:10.1038/s41572-024-00580-4
      reference_title: "Guillain–Barré syndrome"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        progressive flaccid limb paresis and areflexia.
      explanation: >-
        The motor-sensory GBS primer links peripheral nerve dysfunction with the
        hallmark weakness-areflexia phenotype; evidence is not AMSAN-frequency data.
  - target: Sensory Neuropathy
    causal_link_type: DIRECT
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      Dorsal-root and sensory-nerve axonal loss produces objective sensory
      dysfunction.
    evidence:
    - reference: DOI:10.1002/ana.410390105
      reference_title: "Pathology of the motor‐sensory axonal Guillain‐Barré syndrome"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        axonal lesions of both motor and sensory fibers
      explanation: >-
        Direct AMSAN autopsy evidence establishes sensory-fiber as well as
        motor-fiber injury.
  - target: Paresthesia
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Abnormal sensory-axon signaling
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      Injured sensory fibers can generate tingling and other abnormal sensations.
    evidence:
    - reference: DOI:10.3389/fneur.2023.1227505
      reference_title: "Acute motor-sensory axonal polyneuropathy variant of Guillain-Barré syndrome with a thalamic lesion and COVID-19: a case report and discussion on mechanism"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        weakness and paraesthesia in both her legs and arms for 4 days
      explanation: >-
        A single AMSAN case directly illustrates paresthesia but cannot establish
        frequency or mechanism by itself.
  - target: Pain
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Sensory-fiber injury and radicular inflammation
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      Sensory-fiber and root injury can produce neuropathic, radicular, and
      musculoskeletal pain.
    evidence:
    - reference: PMID:39687605
      reference_title: "Pain determinants and quality of life in Guillain-Barre syndrome: a prospective cohort study."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Pain is a serious manifestation in both the acute and chronic stages of
        Guillain-Barre syndrome
      explanation: >-
        The prospective cohort supports pain across GBS and reports association
        with axonal GBS, but does not isolate AMSAN.
  - target: Dysphagia
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Bulbar motor-nerve dysfunction
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      Severe cranial motor-nerve involvement can impair swallowing.
    evidence:
    - reference: DOI:10.3389/fneur.2023.1227505
      reference_title: "Acute motor-sensory axonal polyneuropathy variant of Guillain-Barré syndrome with a thalamic lesion and COVID-19: a case report and discussion on mechanism"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        dysarthria, dysphagia, bilateral facial paralysis, facial diplegia
      explanation: >-
        This AMSAN case documents bulbar and cranial progression but is
        anecdotal and cannot define frequency.
  - target: Respiratory Insufficiency
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Respiratory motor-axon and muscle weakness
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      Severe motor-axon dysfunction can weaken respiratory muscles and require
      ventilatory support.
    evidence:
    - reference: DOI:10.1038/s41572-024-00580-4
      reference_title: "Guillain–Barré syndrome"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        The most severely affected patients also develop respiratory failure and
        autonomic dysfunction
      explanation: >-
        This is GBS-wide severe-disease evidence rather than an AMSAN-specific
        respiratory-risk estimate.
  - target: Autonomic Dysfunction
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Autonomic peripheral-nerve dysfunction
    hypothesis_groups:
    - antiganglioside_complement_axonal_injury
    description: >-
      Involvement of autonomic peripheral fibers can produce cardiovascular,
      gastrointestinal, and bladder dysfunction.
    evidence:
    - reference: DOI:10.1038/s41572-024-00580-4
      reference_title: "Guillain–Barré syndrome"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        respiratory failure and autonomic dysfunction
      explanation: >-
        The primer supports autonomic dysfunction in severe GBS; the exact
        AMSAN frequency is unknown.

mechanistic_hypotheses:
- hypothesis_group_id: antiganglioside_complement_axonal_injury
  hypothesis_label: Antiganglioside-complement nodopathy-to-axonopathy continuum
  status: CANONICAL
  description: >-
    In the seropositive and especially C. jejuni-associated axonal GBS subset,
    molecular mimicry generates cross-reactive anti-ganglioside IgG. Antibody
    binding at nodal and axolemmal sites activates classical complement,
    producing a continuum from reversible nodal conduction failure to
    macrophage-associated irreversible motor and sensory axonal degeneration.
  evidence:
  - reference: PMID:22507308
    reference_title: A common mechanism and a new categorization for anti-ganglioside antibody-mediated neuropathies.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      acute motor axonal neuropathy, acute motor and sensory neuropathy and acute
      sensory neuropathy and possibly also a chronic disorder as multifocal motor
      neuropathy represent a spectrum of the same immunopathologic process.
    explanation: >-
      This synthesis supports a shared nodal-to-axonal spectrum rather than
      fully independent mechanisms for AMAN and AMSAN.
  - reference: DOI:10.1002/ana.410390105
    reference_title: "Pathology of the motor‐sensory axonal Guillain‐Barré syndrome"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      represent the most severe end of a spectrum of immune attack directed
      toward epitopes on the axon.
    explanation: >-
      Direct AMSAN pathology supports the severe-end-of-spectrum interpretation.
  notes: >-
    Canonical does not mean universal. Ganglioside antibodies are absent in a
    substantial fraction of GBS, viral and other antecedents remain
    mechanistically unresolved, and the sensory-axon target in AMSAN is less
    experimentally developed than the motor-axon arm.

phenotypes:
- name: Decreased Compound Muscle Action Potential Amplitude
  description: >-
    Motor nerve conduction studies show reduced or absent compound muscle action
    potential amplitudes. Serial testing is needed because reversible conduction
    failure and fixed motor-axon loss can initially appear similar.
  phenotype_term:
    preferred_term: Decreased compound muscle action potential amplitude
    term:
      id: HP:0033383
      label: Decreased compound muscle action potential amplitude
  electrophysiology:
    electrophysiology_modality: NERVE_CONDUCTION_STUDY
  evidence:
  - reference: DOI:10.1111/jns.12625
    reference_title: "Conduction slowing, conduction block and temporal dispersion in demyelinating, dysmyelinating and axonal neuropathies: Electrophysiology meets pathology"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      axonal neuropathies are simply diagnosed by reduced amplitude of motor and
      sensory nerve action potentials with normal or slightly slow conduction
      velocity.
    explanation: >-
      The conventional motor-amplitude pattern supports the finding, while the
      review and serial GBS data caution against over-simple subtype inference.
- name: Decreased Sensory Nerve Action Potential Amplitude
  description: >-
    Sensory nerve conduction studies show reduced or absent sensory nerve action
    potential amplitudes, distinguishing a motor-sensory pattern from motor-only
    AMAN when the finding is reproducible and not explained by another neuropathy.
  phenotype_term:
    preferred_term: Decreased amplitude of sensory action potentials
    term:
      id: HP:0007078
      label: Decreased amplitude of sensory action potentials
  electrophysiology:
    electrophysiology_modality: NERVE_CONDUCTION_STUDY
  evidence:
  - reference: DOI:10.1111/jns.12625
    reference_title: "Conduction slowing, conduction block and temporal dispersion in demyelinating, dysmyelinating and axonal neuropathies: Electrophysiology meets pathology"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      axonal neuropathies are simply diagnosed by reduced amplitude of motor and
      sensory nerve action potentials with normal or slightly slow conduction
      velocity.
    explanation: >-
      Reduced sensory amplitudes are part of the conventional axonal pattern;
      AMSAN classification still requires clinical context and serial testing.
- name: Limb Weakness
  description: >-
    Acute, usually symmetric, progressive flaccid weakness affects the legs and
    arms and may progress to inability to walk or complete paralysis.
  phenotype_term:
    preferred_term: Limb muscle weakness
    term:
      id: HP:0003690
      label: Limb muscle weakness
    clinical_course: PROGRESSIVE
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      progressive flaccid limb paresis and areflexia.
    explanation: >-
      This is the hallmark motor-sensory GBS phenotype and therefore applies to
      AMSAN, without supplying an AMSAN-specific frequency.
- name: Areflexia
  description: >-
    Tendon reflexes are reduced or absent in affected limbs because the
    peripheral reflex arc is impaired.
  phenotype_term:
    preferred_term: Areflexia
    term:
      id: HP:0001284
      label: Areflexia
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      progressive flaccid limb paresis and areflexia.
    explanation: >-
      Areflexia is a defining GBS-wide clinical feature relevant to AMSAN.
- name: Sensory Neuropathy
  description: >-
    Objective sensory loss and abnormal sensory responses reflect involvement of
    sensory roots and peripheral sensory axons.
  phenotype_term:
    preferred_term: Sensory neuropathy
    term:
      id: HP:0000763
      label: Sensory neuropathy
  evidence:
  - reference: DOI:10.1002/ana.410390105
    reference_title: "Pathology of the motor‐sensory axonal Guillain‐Barré syndrome"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      axonal lesions of both motor and sensory fibers
    explanation: >-
      Direct human AMSAN autopsy confirms sensory-fiber involvement, with the
      limitation of a small fatal-case series.
- name: Paresthesia
  description: >-
    Tingling or other abnormal sensations can accompany weakness, often early in
    the illness.
  phenotype_term:
    preferred_term: Paresthesia
    term:
      id: HP:0003401
      label: Paresthesia
  evidence:
  - reference: DOI:10.3389/fneur.2023.1227505
    reference_title: "Acute motor-sensory axonal polyneuropathy variant of Guillain-Barré syndrome with a thalamic lesion and COVID-19: a case report and discussion on mechanism"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      weakness and paraesthesia in both her legs and arms for 4 days
    explanation: >-
      A single AMSAN case illustrates paresthesia but does not establish its
      frequency.
- name: Pain
  description: >-
    Radicular, neuropathic, and musculoskeletal pain can occur during the acute
    illness and may persist into recovery.
  phenotype_term:
    preferred_term: Pain
    term:
      id: HP:0012531
      label: Pain
  evidence:
  - reference: PMID:39687605
    reference_title: "Pain determinants and quality of life in Guillain-Barre syndrome: a prospective cohort study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Pain is a serious manifestation in both the acute and chronic stages of
      Guillain-Barre syndrome
    explanation: >-
      This prospective GBS cohort supports pain and reports an association with
      axonal GBS, but does not give an AMSAN-specific rate.
- name: Dysphagia
  description: >-
    Bulbar and cranial motor involvement can impair swallowing and increase
    aspiration risk.
  phenotype_term:
    preferred_term: Dysphagia
    term:
      id: HP:0002015
      label: Dysphagia
  evidence:
  - reference: DOI:10.3389/fneur.2023.1227505
    reference_title: "Acute motor-sensory axonal polyneuropathy variant of Guillain-Barré syndrome with a thalamic lesion and COVID-19: a case report and discussion on mechanism"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      dysarthria, dysphagia, bilateral facial paralysis, facial diplegia
    explanation: >-
      This case documents dysphagia during AMSAN progression; it is illustrative
      rather than frequency evidence.
- name: Respiratory Insufficiency
  description: >-
    Severe motor weakness can involve respiratory muscles and require invasive
    ventilation even before prominent dyspnea is reported.
  phenotype_term:
    preferred_term: Respiratory insufficiency due to muscle weakness
    term:
      id: HP:0002747
      label: Respiratory insufficiency due to muscle weakness
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The most severely affected patients also develop respiratory failure and
      autonomic dysfunction
    explanation: >-
      GBS-wide evidence supports the severe complication; no AMSAN-specific
      frequency is asserted.
- name: Autonomic Dysfunction
  description: >-
    Dysautonomia can manifest as heart-rate or blood-pressure instability,
    gastrointestinal dysmotility, or bladder dysfunction.
  phenotype_term:
    preferred_term: Abnormality of the autonomic nervous system
    term:
      id: HP:0002270
      label: Abnormality of the autonomic nervous system
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      respiratory failure and autonomic dysfunction
    explanation: >-
      The current GBS primer supports dysautonomia in severe disease; the
      applicability is GBS-wide rather than AMSAN-specific.

biochemical:
- name: Albuminocytologic Dissociation
  presence: Supportive when present
  context: >-
    Elevated CSF protein with a normal or near-normal white-cell count supports
    GBS but neither confirms the diagnosis nor determines the AMSAN subtype. A
    normal protein level early in the illness does not exclude GBS.
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      albumino-cytological dissociation, in which CSF protein levels are raised
      (>0.45 g/l) with a normal white cell count
    explanation: >-
      The primer defines the supportive CSF pattern across GBS.
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      patients can have normal CSF protein levels in the first week of disease
      onset, which does not exclude the diagnosis of GBS
    explanation: >-
      This prevents early normal CSF protein from being used to exclude AMSAN.
- name: Anti-GM1, Anti-GM1b, and Anti-GD1a IgG
  presence: Associated in a subset
  context: >-
    These antibodies support a shared AMAN/AMSAN immune spectrum in some
    patients but are not required, are not sufficiently sensitive to establish
    AMSAN, and should not replace serial electrodiagnostic assessment.
  evidence:
  - reference: PMID:10526194
    reference_title: Acute motor axonal neuropathy and acute motor-sensory axonal neuropathy share a common immunological profile.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The patients with AMSAN had anti-GM1, anti-GM1b, and anti-GD1a IgG
      antibodies
    explanation: >-
      The small human AMSAN series directly supports association, not diagnostic
      sensitivity or universal presence.
- name: Neurofilament Light Chain
  presence: Higher levels associated with poorer GBS outcome
  context: >-
    Serum or plasma NfL reflects neuroaxonal injury and is an emerging
    prognostic/pharmacodynamic biomarker in GBS. It has not been validated as an
    AMSAN diagnostic test.
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      high levels of neurofilament light chain (NfL)
    explanation: >-
      The primer lists high NfL among GBS poor-prognosis associations; this is
      not AMSAN-specific validation.

environmental:
- name: Campylobacter jejuni infection
  influences_mechanisms:
  - target: Campylobacter LOS-Ganglioside Molecular Mimicry
    environmental_effect: TRIGGERS
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Antecedent enteritis supplies the sialylated lipooligosaccharide this
      node is built around, with the anti-GM1 and anti-GD1a response as the
      named intervening step. Both evidence items keep the partial grade this
      entry already assigned them, because neither isolates an effect size for
      this axonal subtype as opposed to the syndrome at large.
    evidence:
    - reference: DOI:10.1038/s41572-024-00580-4
      reference_title: "Guillain–Barré syndrome"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "patients with C. jejuni infection have anti-GM1 and anti-GD1a antibodies and are susceptible to developing motor and axonal forms of GBS"
      explanation: >-
        Connects the antecedent infection to anti-GM1 and anti-GD1a antibodies
        and to motor and axonal forms, which is this node's mimicry route.
    - reference: DOI:10.1002/ana.410390105
      reference_title: "Pathology of the motor‐sensory axonal Guillain‐Barré syndrome"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "High titers of antibodies recognizing C. jejuni, consistent with recent infection, were found in the 2 patients tested."
      explanation: >-
        Autopsy-confirmed cases of this subtype carried serology for recent C.
        jejuni infection, though only two selected fatal cases were tested.
  presence: Established antecedent for an axonal GBS subset
  description: >-
    Antecedent C. jejuni enteritis is the best-defined trigger for the
    ganglioside-mimicry mechanism and is associated with motor and axonal GBS
    patterns. GBS-wide risk estimates must not be read as AMSAN-specific risk.
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      patients with C. jejuni infection have anti-GM1 and anti-GD1a antibodies
      and are susceptible to developing motor and axonal forms of GBS
    explanation: >-
      The primer connects the antecedent to axonal GBS but does not isolate an
      AMSAN-specific effect size.
  - reference: DOI:10.1002/ana.410390105
    reference_title: "Pathology of the motor‐sensory axonal Guillain‐Barré syndrome"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      High titers of antibodies recognizing C. jejuni, consistent with recent
      infection, were found in the 2 patients tested.
    explanation: >-
      Direct AMSAN pathology cases had serologic evidence of recent infection,
      but only two selected fatal cases were tested.
- name: SARS-CoV-2 infection
  presence: Reported temporal antecedent
  description: >-
    AMSAN has been reported after SARS-CoV-2 infection. Current evidence here is
    a case-level temporal association and does not establish a causal trigger or
    population risk.
  evidence:
  - reference: DOI:10.3389/fneur.2023.1227505
    reference_title: "Acute motor-sensory axonal polyneuropathy variant of Guillain-Barré syndrome with a thalamic lesion and COVID-19: a case report and discussion on mechanism"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A nasopharyngeal swab for SARS-CoV-2 returned positive.
    explanation: >-
      A single AMSAN case establishes co-occurrence and temporal context only.

epidemiology:
- name: AMSAN fraction in a Mexican single-center adult GBS cohort
  minimum_value: 8.6
  maximum_value: 8.6
  unit: percent of electrodiagnostically assessed GBS cases
  notes: >-
    This is a cohort-specific subtype fraction, not population prevalence. The
    study was single-center and classification was based on one criteria set.
  evidence:
  - reference: PMID:32674942
    reference_title: "Electrophysiological subtypes and associated prognosis factors of Mexican adults diagnosed with Guillain-Barré syndrome, a single center experience."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      acute motor and sensory axonal neuropathy (AMSAN) 8,6%.
    explanation: >-
      The cohort reports an AMSAN case fraction among adults with GBS; it cannot
      be generalized as prevalence.
- name: AMSAN fraction in a northern India GBS cohort
  minimum_value: 4.6
  maximum_value: 4.6
  unit: percent of consecutive GBS cases
  notes: >-
    This is a cohort-specific subtype fraction, not population prevalence.
    Repeat NCS was performed only when the initial study was normal.
  evidence:
  - reference: PMID:24456386
    reference_title: "Guillain-Barré syndrome: subtypes and predictors of outcome from India."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      15 (4.6%) AMSAN
    explanation: >-
      The study reports 15 AMSAN classifications among 328 GBS patients in one
      regional cohort.

diagnosis:
- name: Clinical GBS Syndrome Assessment
  description: >-
    Establish the clinical syndrome first: progressive weakness of arms and
    legs, reduced or absent reflexes, and progression no longer than four weeks,
    with compatible sensory, cranial, autonomic, respiratory, pain, and
    antecedent-infection features. AMSAN is not diagnosed by a biomarker alone.
  diagnosis_term:
    preferred_term: Diagnostic procedure
    term:
      id: NCIT:C18020
      label: Diagnostic Procedure
  results: >-
    A compatible acute motor-sensory GBS syndrome; atypical findings trigger
    evaluation for mimics.
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Progressive weakness of arms and legs
    explanation: >-
      The 2024 primer reproduces the guideline's required motor-sensory GBS
      features; AMSAN classification is a subsequent electrophysiologic step.
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Absent or decreased tendon reflexes in affected limbs
    explanation: >-
      Reduced reflexes are a required clinical feature in the guideline-based
      motor-sensory GBS criteria.
- name: Serial Nerve Conduction Studies and Electromyography
  description: >-
    NCS/EMG supports poly(radiculo)neuropathy and the motor-sensory axonal
    pattern: reduced CMAP and SNAP amplitudes without primary demyelinating
    criteria. Early studies may be normal or equivocal. Repeat testing is
    appropriate, and a single early subtype label should not be treated as
    immutable or as a treatment selector.
  diagnosis_term:
    preferred_term: Nerve conduction study
    term:
      id: NCIT:C88502
      label: Nerve Conduction Velocity Test
  results: >-
    Reproducible motor and sensory axonal abnormalities; classification may
    change on serial studies.
  evidence:
  - reference: PMID:41656826
    reference_title: "Dynamics of Nerve Conduction Studies in Patients With Guillain-Barré Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the electrodiagnostic subtype changed on serial NCS in 37.8% (Hadden) and
      44.7% (Rajabally).
    explanation: >-
      The 469-patient serial-NCS analysis quantifies substantial early subtype
      instability.
  - reference: PMID:41656826
    reference_title: "Dynamics of Nerve Conduction Studies in Patients With Guillain-Barré Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      If these early NCS are non-diagnostic, repeating the study should be
      considered. Electrodiagnostic subtyping offers no additional value.
    explanation: >-
      The study supports prompt NCS, repeat testing when needed, and restraint in
      assigning independent prognostic or treatment value to the subtype label.
- name: Cerebrospinal Fluid Analysis
  description: >-
    CSF cell count and protein help support GBS and identify mimics. Elevated
    protein with a normal cell count is supportive but may be absent early;
    marked pleocytosis argues for infectious, malignant, or inflammatory
    alternatives. CSF cannot determine AMSAN.
  diagnosis_term:
    preferred_term: Cerebrospinal fluid analysis
    term:
      id: NCIT:C173272
      label: CSF Analysis
  results: >-
    Albuminocytologic dissociation may support GBS; early normal protein does not
    exclude it, and pleocytosis requires explanation.
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      increased CSF protein levels were found in <50% of patients at 1 day and
      in >80% at >1 week after onset of weakness
    explanation: >-
      The time dependence shows why CSF protein cannot confirm or exclude early
      GBS and does not subtype AMSAN.
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      CSF pleocytosis (>50 cells/microl) in general is atypical and should alert
      clinicians to consider other differential diagnoses
    explanation: >-
      Marked pleocytosis should redirect the workup toward mimics.
- name: Anti-Ganglioside Antibody Testing as a Limited Adjunct
  description: >-
    Anti-GM1, anti-GM1b, or anti-GD1a IgG can support the biological context in
    selected cases or research but is neither required nor sufficiently
    sensitive for AMSAN diagnosis. Negative testing does not exclude AMSAN, and
    routine testing has limited value in typical motor-sensory GBS.
  diagnosis_term:
    preferred_term: Serology testing
    term:
      id: NCIT:C25294
      label: Laboratory Procedure
  results: >-
    A positive result may support an axonal GBS immune profile; a negative result
    is nondiagnostic.
  evidence:
  - reference: PMID:37814552
    reference_title: "European Academy of Neurology/Peripheral Nerve Society Guideline on diagnosis and treatment of Guillain-Barré syndrome."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      testing for anti-ganglioside antibodies is of limited clinical value in
      most patients with typical motor-sensory GBS
    explanation: >-
      The guideline directly limits routine diagnostic use in the clinical
      pattern that includes AMSAN.

differential_diagnoses:
- name: Acute Motor Axonal Neuropathy
  description: >-
    AMAN is the motor-only axonal GBS pattern and shares anti-GM1/GD1a biology
    with AMSAN. Preserved sensory examination and sensory nerve action
    potentials favor AMAN, while reproducible sensory abnormalities favor AMSAN.
  disease_term:
    preferred_term: acute motor axonal neuropathy
    term:
      id: MONDO:0020349
      label: acute motor axonal neuropathy
  distinguishing_features:
  - Sensory loss and reduced sensory responses are absent in the motor-only pattern.
  - Serial NCS is required because early classifications can change.
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Sensory loss is also present in the predominant motor-sensory form but
      absent in the motor form.
    explanation: >-
      This directly states the clinical sensory distinction between motor-only
      and motor-sensory GBS patterns.
- name: Acute Inflammatory Demyelinating Polyradiculoneuropathy
  description: >-
    AIDP is the primary demyelinating GBS pattern. Demyelinating slowing,
    temporal dispersion, prolonged distal latencies, and conduction block with
    evolution distinct from reversible nodal failure favor AIDP over AMSAN.
  disease_term:
    preferred_term: acute inflammatory demyelinating polyradiculoneuropathy
    term:
      id: MONDO:0020347
      label: acute inflammatory demyelinating polyradiculoneuropathy
  distinguishing_features:
  - Primary demyelinating rather than low-amplitude motor-sensory axonal pattern.
  - Serial studies help separate remyelinating block from reversible nodal failure.
  evidence:
  - reference: PMID:22480600
    reference_title: "Electrodiagnostic criteria for Guillain-Barrè syndrome: a critical revision and the need for an update."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Serial electrophysiological studies are mandatory for proper diagnosis of
      GBS subtypes
    explanation: >-
      The review explains why longitudinal electrodiagnosis is necessary to
      distinguish demyelinating and axonal patterns.
- name: Acute-Onset Chronic Inflammatory Demyelinating Polyradiculoneuropathy
  description: >-
    A-CIDP can resemble GBS initially but becomes more likely with progression
    or relapse beyond the expected monophasic window.
  disease_term:
    preferred_term: chronic inflammatory demyelinating polyradiculoneuropathy
    term:
      id: MONDO:0006702
      label: chronic inflammatory demyelinating polyradiculoneuropathy
  distinguishing_features:
  - Continued progression or deterioration after eight weeks.
  - Three or more treatment-related fluctuations or a chronic relapsing course.
  evidence:
  - reference: PMID:37814552
    reference_title: "European Academy of Neurology/Peripheral Nerve Society Guideline on diagnosis and treatment of Guillain-Barré syndrome."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      acute-onset chronic inflammatory demyelinating polyradiculoneuropathy
      (A-CIDP) should be considered if progression continues after 8 weeks from
      onset
    explanation: >-
      The guideline gives the key temporal discriminator.
- name: Critical Illness Polyneuropathy or Myopathy
  description: >-
    Critical-illness neuropathy/myopathy produces weakness and an axonal NCS
    pattern during prolonged severe illness or ventilation and can confound an
    ICU diagnosis of AMSAN.
  disease_term:
    preferred_term: critical illness polyneuropathy
    term:
      id: MONDO:0001957
      label: critical illness polyneuropathy
  distinguishing_features:
  - Begins in the setting of prolonged critical illness or ventilation.
  - EMG may show myopathic features; sensory studies help separate pure myopathy.
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Prolonged illness or ventilation NCS: axonal neuropathy with or without
      myopathic features on EMG
    explanation: >-
      The GBS differential table states the context and electrodiagnostic
      discriminator.
- name: Acute Porphyria
  description: >-
    Acute hepatic porphyria can cause an acute motor-predominant axonal
    neuropathy with autonomic and psychiatric symptoms that resembles GBS.
  disease_term:
    preferred_term: acute intermittent porphyria
    term:
      id: MONDO:0008294
      label: acute intermittent porphyria
  distinguishing_features:
  - Abdominal pain, psychiatric symptoms, dysautonomia, or family history.
  - Elevated urinary porphobilinogen during an attack.
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Family history, concomitant psychiatric symptoms and abdominal pain
    explanation: >-
      The primer lists the clinical clues that distinguish porphyria from GBS.
- name: Transverse Myelitis or Other Spinal Cord Disease
  description: >-
    Acute spinal cord inflammation can cause rapidly progressive limb weakness
    and sensory symptoms but localizes to the central nervous system.
  disease_term:
    preferred_term: transverse myelitis
    term:
      id: MONDO:0021553
      label: transverse myelitis
  distinguishing_features:
  - A sensory level, brisk reflexes, extensor plantar responses, or sphincter-predominant onset.
  - Spinal MRI shows an intramedullary lesion.
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Transverse myelitis Sensory level, brisk reflexes MRI spine: hyperintense
      lesion
    explanation: >-
      The GBS differential table supplies the localization and imaging clues.
- name: Botulism
  description: >-
    Botulism can progress rapidly with weakness and dysautonomia but is a
    presynaptic neuromuscular-junction disorder rather than an axonal
    polyradiculoneuropathy.
  disease_term:
    preferred_term: botulism
    term:
      id: MONDO:0005498
      label: botulism
  distinguishing_features:
  - Pupillary abnormalities and descending rather than ascending paralysis.
  - Incremental response on rapid repetitive nerve stimulation and toxin detection.
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Rapid progression, pupillary abnormalities, dysautonomia, descending
      paralysis
    explanation: >-
      The table identifies the characteristic botulism pattern.
- name: Thiamine Deficiency Neuropathy
  description: >-
    Severe nutritional thiamine deficiency can cause an acute axonal neuropathy
    that resembles AMSAN.
  distinguishing_features:
  - Malnutrition, hyperemesis, alcohol exposure, or Wernicke encephalopathy.
  - Abnormal thiamine indices and an axonal NCS pattern without the typical GBS context.
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Precipitating factors (for example, hyperemesis gravidarum, alcoholism,
      nutritional deficiency)
    explanation: >-
      The primer identifies the exposure context that separates thiamine
      deficiency from immune-mediated GBS.

treatments:
- name: Intravenous Immunoglobulin
  action_category: THERAPEUTIC
  description: >-
    IVIG is one of two established immune treatments for GBS. The guideline
    regimen is 0.4 g/kg daily for five days, generally started within two weeks
    of weakness onset in a patient unable to walk unaided; selected patients may
    be treated at two to four weeks. Evidence and recommendations are GBS-wide,
    not AMSAN-specific.
  treatment_term:
    preferred_term: Intravenous Immunoglobulin Therapy
    term:
      id: NCIT:C121331
      label: Intravenous Immunoglobulin Therapy
    therapeutic_agent:
    - preferred_term: Human immunoglobulin G
      term:
        id: NCIT:C80829
        label: Human Immunoglobulin G
  target_phenotypes:
  - preferred_term: Limb muscle weakness
    term:
      id: HP:0003690
      label: Limb muscle weakness
  evidence:
  - reference: PMID:37814552
    reference_title: "European Academy of Neurology/Peripheral Nerve Society Guideline on diagnosis and treatment of Guillain-Barré syndrome."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      TF recommends intravenous immunoglobulin (IVIg) 0.4 g/kg for 5 days
    explanation: >-
      The guideline establishes the regimen for non-ambulatory GBS. No
      randomized AMSAN-specific efficacy evidence was identified.
  notes: >-
    IVIG and plasma exchange are alternatives rather than a routine immediate
    sequence. Poor predicted prognosis alone is not an indication for a second
    IVIG course. A true treatment-related fluctuation after initial stabilization
    or improvement is a separate clinical situation requiring specialist review.
- name: Plasma Exchange
  action_category: THERAPEUTIC
  description: >-
    Plasma exchange is an established alternative first-line immune treatment
    for GBS. The guideline regimen is 12-15 L in four to five exchanges over one
    to two weeks, generally within four weeks of weakness onset when the patient
    cannot walk unaided. It is not routine rescue immediately after IVIG.
  treatment_term:
    preferred_term: Plasmapheresis
    term:
      id: NCIT:C15304
      label: Plasmapheresis
  target_phenotypes:
  - preferred_term: Limb muscle weakness
    term:
      id: HP:0003690
      label: Limb muscle weakness
  evidence:
  - reference: PMID:37814552
    reference_title: "European Academy of Neurology/Peripheral Nerve Society Guideline on diagnosis and treatment of Guillain-Barré syndrome."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      a course of plasma exchange (PE) 12-15 L in four to five exchanges over
      1-2 weeks
    explanation: >-
      The guideline establishes the standard GBS regimen; no randomized
      AMSAN-specific treatment comparison was identified.
  notes: >-
    Treatment choice between IVIG and plasma exchange depends on timing,
    contraindications, access, and clinical context. Immediate PE followed by
    IVIG does not improve outcome over either treatment alone.
- name: Respiratory, Swallowing, and Autonomic Monitoring
  action_category: MONITORING
  description: >-
    All hospitalized patients require repeated respiratory assessment because
    dyspnea can be absent despite declining vital capacity. Monitoring also
    includes cough and swallow safety, heart rate, blood pressure, rhythm, bowel
    and bladder function, strength, and GBS disability. Rapid deterioration,
    bulbar weakness, dysautonomia, or adverse mEGRIS should lower the threshold
    for intensive-care transfer.
  treatment_term:
    preferred_term: Pulmonary function testing
    term:
      id: NCIT:C38081
      label: Pulmonary Function Test
  evidence:
  - reference: PMID:31541214
    reference_title: "Diagnosis and management of Guillain-Barré syndrome in ten steps."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Respiratory function should be monitored in all patients
    explanation: >-
      Consensus guidance supports proactive respiratory monitoring across GBS,
      including AMSAN.
  - reference: PMID:31541214
    reference_title: "Diagnosis and management of Guillain-Barré syndrome in ten steps."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      patients should be monitored for swallowing and coughing difficulties.
    explanation: >-
      Bulbar monitoring is part of GBS supportive care and is relevant to severe
      AMSAN.
  notes: >-
    Standard inpatient prevention also addresses aspiration, venous thrombosis,
    pressure injury, infection, corneal injury in facial weakness, contracture,
    nutrition, communication, and psychological distress.
- name: Mechanical Ventilation
  action_category: THERAPEUTIC
  description: >-
    Invasive ventilation is supportive therapy for respiratory failure. It does
    not modify the immune attack, so respiratory monitoring and timely airway
    planning remain essential.
  treatment_term:
    preferred_term: Artificial respiration
    term:
      id: NCIT:C70909
      label: Mechanical Ventilation
  target_phenotypes:
  - preferred_term: Respiratory insufficiency due to muscle weakness
    term:
      id: HP:0002747
      label: Respiratory insufficiency due to muscle weakness
  evidence:
  - reference: DOI:10.1007/s12028-023-01707-3
    reference_title: "Guidelines for Neuroprognostication in Adults with Guillain–Barré Syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      10-30% require mechanical ventilation during the acute phase of the disease.
    explanation: >-
      The GBS-wide guideline supports ventilation as a common severe-disease
      requirement without assigning this rate to AMSAN.
- name: Multidisciplinary Rehabilitation
  action_category: THERAPEUTIC
  description: >-
    Rehabilitation should begin during hospitalization and continue after
    discharge as needed. Physical and occupational therapy, graded mobility and
    strengthening, positioning and contracture prevention, speech/swallow care,
    respiratory therapy, assistive devices, and psychosocial support are tailored
    to weakness, sensory loss, fatigue, pain, and bulbar or respiratory deficits.
  treatment_term:
    preferred_term: Rehabilitation
    term:
      id: NCIT:C15315
      label: Rehabilitation
  target_phenotypes:
  - preferred_term: Limb muscle weakness
    term:
      id: HP:0003690
      label: Limb muscle weakness
  - preferred_term: Sensory neuropathy
    term:
      id: HP:0000763
      label: Sensory neuropathy
  - preferred_term: Dysphagia
    term:
      id: HP:0002015
      label: Dysphagia
  evidence:
  - reference: PMID:31541214
    reference_title: "Diagnosis and management of Guillain-Barré syndrome in ten steps."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Start rehabilitation programme early
    explanation: >-
      Consensus guidance supports multidisciplinary rehabilitation; controlled
      AMSAN-specific rehabilitation evidence is not available.
- name: Pain Management
  action_category: THERAPEUTIC
  description: >-
    Neuropathic, radicular, and nociceptive pain should be assessed repeatedly
    and treated while accounting for respiratory and autonomic vulnerability.
    The guideline weakly supports gabapentinoids, tricyclic antidepressants, or
    carbamazepine; drug choice and dose require individualized safety review.
  treatment_term:
    preferred_term: Pain management
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Pain
    term:
      id: HP:0012531
      label: Pain
  evidence:
  - reference: PMID:37814552
    reference_title: "European Academy of Neurology/Peripheral Nerve Society Guideline on diagnosis and treatment of Guillain-Barré syndrome."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      weakly recommends gabapentinoids, tricyclic antidepressants or
      carbamazepine for treatment of pain
    explanation: >-
      This is a weak GBS-wide recommendation and not an AMSAN-specific trial
      result.

clinical_trials:
- name: NCT04752566
  phase: PHASE_III
  status: COMPLETED
  description: >-
    Completed randomized placebo-controlled Phase 3 trial of eculizumab added to
    IVIG in severe GBS. The published primary endpoint was not achieved. The
    study did not report AMSAN-specific efficacy and does not establish
    eculizumab as standard GBS or AMSAN therapy.
  target_phenotypes:
  - preferred_term: Limb muscle weakness
    term:
      id: HP:0003690
      label: Limb muscle weakness
  evidence:
  - reference: clinicaltrials:NCT04752566
    reference_title: "A Phase 3, Prospective, Multicenter, Double Blind, Randomized, Placebo Controlled Study to Evaluate the Efficacy and Safety of Eculizumab in Patients With Guillain-Barré Syndrome (GBS)"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This is a Phase 3, prospective, multicenter, placebo controlled, double
      blind, randomized study to investigate the efficacy and safety of
      eculizumab in participants with severe GBS
    explanation: >-
      The registry supports the trial design; the population was severe GBS and
      not AMSAN-specific.
  - reference: DOI:10.1111/jns.12646
    reference_title: "Efficacy and safety of eculizumab in Guillain‐Barré syndrome: A phase 3, multicenter, double‐blind, randomized, placebo‐controlled clinical trial"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Primary endpoint was not achieved (hazard ratio, 0.9; 95% CI,
      0.45-1.97; p = .89).
    explanation: >-
      The published negative primary endpoint prevents interpreting complement
      biology alone as proof of clinical efficacy.
  notes: >-
    ClinicalTrials.gov status and posted results were checked on 2026-07-17.
- name: NCT04701164
  phase: PHASE_III
  status: COMPLETED
  description: >-
    Completed randomized double-blind placebo-controlled Phase 3 study of the
    anti-C1q antibody ANX005 (tanruprubart) in recent-onset GBS. The registry
    reports 242 participants and no posted results as of the current review.
    It was not restricted to AMSAN.
  target_phenotypes:
  - preferred_term: Limb muscle weakness
    term:
      id: HP:0003690
      label: Limb muscle weakness
  evidence:
  - reference: clinicaltrials:NCT04701164
    reference_title: "A Randomized, Double-blind, Placebo-controlled Phase 3 Study to Evaluate the Efficacy, Safety, Pharmacokinetics, and Pharmacodynamics of ANX005 in Subjects With Guillain-Barré Syndrome"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This study is intended to evaluate the efficacy and safety of ANX005
      administered by intravenous (IV) infusion to participants recently
      diagnosed with Guillain-Barré Syndrome (GBS).
    explanation: >-
      The registry supports the intervention and GBS population but not an
      AMSAN-specific effect or a result claim.
  notes: >-
    ClinicalTrials.gov listed the study as completed, actual enrollment 242,
    with no registry results posted when checked on 2026-07-17. Conference and
    sponsor reports are not substituted here for a complete peer-reviewed Phase
    3 report.
- name: NCT07020819
  phase: PHASE_III
  status: RECRUITING
  description: >-
    FORWARD is an open-label Phase 3 study of a single tanruprubart (ANX005) dose
    in adult and pediatric recent-onset GBS, measuring pharmacokinetics,
    pharmacodynamics, early efficacy, and safety. It is ongoing, GBS-wide, and
    cannot yet establish efficacy for AMSAN.
  target_phenotypes:
  - preferred_term: Limb muscle weakness
    term:
      id: HP:0003690
      label: Limb muscle weakness
  evidence:
  - reference: clinicaltrials:NCT07020819
    reference_title: "An Open-Label Study to Evaluate the Pharmacokinetics, Pharmacodynamics, Efficacy, and Safety of a Single Dose of Tanruprubart (Also Commonly Known as ANX005) in Participants With Guillain-Barré Syndrome (GBS) (FORWARD Study)"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The goal of this open label study is to measure pharmacokinetics,
      pharmacodynamics, early efficacy, and safety of tanruprubart in adult and
      pediatric participants, in the United States, Canada, and Europe.
    explanation: >-
      The registry establishes the prospective study and objectives, not an
      efficacy result.
  notes: >-
    ClinicalTrials.gov listed the trial as recruiting when checked on
    2026-07-17. Tanruprubart remains investigational; this entry is not a
    treatment recommendation.

animal_models:
- species: Oryctolagus cuniculus
  category: Active-immunization axonal GBS model
  description: >-
    Rabbits sensitized with bovine brain ganglioside mixture or purified GM1
    developed anti-GM1 IgG, acute monophasic flaccid weakness, and
    Wallerian-like peripheral-nerve degeneration without lymphocytic infiltration
    or demyelination. This models motor-predominant axonal GBS and does not
    validate sensory-inclusive AMSAN.
  associated_phenotypes:
  - Acute flaccid limb weakness
  - Wallerian-like peripheral axonal degeneration
  evidence:
  - reference: PMID:11409422
    reference_title: "Animal model of axonal Guillain-Barré syndrome induced by sensitization with GM1 ganglioside."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Pathological findings for the peripheral nerves showed predominant
      Wallerian-like degeneration, with neither lymphocytic infiltration nor
      demyelination.
    explanation: >-
      The rabbit model reproduces acute axonal injury but does not demonstrate
      sensory-axon disease equivalent to AMSAN.
- species: Oryctolagus cuniculus
  category: Campylobacter LOS molecular-mimicry model
  description: >-
    Rabbits immunized with ganglioside-mimicking C. jejuni LOS developed
    anti-GM1 IgG, flaccid weakness, and GBS-like peripheral-nerve pathology.
    This provides causal molecular-mimicry evidence but is not a validated AMSAN
    model.
  associated_phenotypes:
  - Acute flaccid limb weakness
  - Peripheral nerve injury
  evidence:
  - reference: PMID:15277677
    reference_title: Carbohydrate mimicry between human ganglioside GM1 and Campylobacter jejuni lipooligosaccharide causes Guillain-Barre syndrome.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      On sensitization with C. jejuni lipooligosaccharide, rabbits developed
      anti-GM1 IgG antibody and flaccid limb weakness.
    explanation: >-
      The experiment directly links LOS mimicry to antibody and weakness, with
      motor-predominant rather than AMSAN fidelity.
- species: Mus musculus
  genotype: Neuron-restricted complex ganglioside expression
  category: Anti-GM1 complement-mediated AMAN model
  description: >-
    A transgenic mouse system restricts complex ganglioside expression to
    neurons, permitting anti-GM1 targeting of axons. Anti-C1q treatment reduces
    complement deposition, immune-cell recruitment, axonal injury, and
    respiratory dysfunction. The model is explicitly AMAN and omits the sensory
    injury that defines AMSAN.
  associated_phenotypes:
  - Motor axonal injury
  - Respiratory dysfunction
  evidence:
  - reference: PMID:26936605
    reference_title: C1q-targeted inhibition of the classical complement pathway prevents injury in a novel mouse model of acute motor axonal neuropathy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Anti-C1q monoclonal antibody treatment attenuated complement cascade
      activation and deposition, reduced immune cell recruitment and axonal
      injury
    explanation: >-
      The model gives causal complement evidence but is motor-only and therefore
      an incomplete proxy for AMSAN.

experimental_models:
- name: Anti-GD1a/complement ex vivo motor nerve-terminal injury model
  description: >-
    Nerve-muscle preparations from mice overexpressing GD1a are exposed to
    anti-GD1a monoclonal antibodies and complement. The preparation demonstrates
    antibody/complement deposition, ultrastructural injury, and motor-terminal
    conduction block while sparing postsynaptic membranes. It is a mechanistic
    motor-axon assay rather than a sensory-inclusive AMSAN model.
  experimental_model_type: OTHER
  organism:
    preferred_term: House mouse
    term:
      id: NCBITaxon:10090
      label: Mus musculus
  cell_types:
  - preferred_term: Motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  - preferred_term: Schwann cell
    term:
      id: CL:0002573
      label: Schwann cell
  conditions:
  - GD1a overexpression in neural membranes
  - Anti-GD1a monoclonal antibody exposure with complement
  culture_system: Ex vivo nerve-muscle preparation
  publication: PMID:15716397
  modeled_mechanisms:
  - target: Ganglioside Antibody Binding at Nodal and Axolemmal Membranes
    description: Anti-GD1a antibody deposition on presynaptic motor axons.
    evidence:
    - reference: PMID:15716397
      reference_title: Overexpression of GD1a ganglioside sensitizes motor nerve terminals to anti-GD1a antibody-mediated injury in a model of acute motor axonal neuropathy.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        Dense antibody and complement deposits were observed only over
        presynaptic motor axons
      explanation: >-
        The ex vivo finding directly supports the modeled binding step but not
        sensory-axon injury.
  - target: Reversible Nodal Conduction Failure
    description: Complement-dependent blockade of motor nerve-terminal function.
    evidence:
    - reference: PMID:15716397
      reference_title: Overexpression of GD1a ganglioside sensitizes motor nerve terminals to anti-GD1a antibody-mediated injury in a model of acute motor axonal neuropathy.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        electrophysiological blockade of motor nerve terminal function.
      explanation: >-
        The preparation measures functional motor-terminal blockade but is not a
        full in vivo AMSAN phenotype.
  findings:
  - statement: >-
      Antigen density controls susceptibility to anti-GD1a antibody/complement
      injury at motor nerve terminals.
    supporting_text: >-
      demonstrating the central role of membrane antigen density in modulating
      both immune tolerance to GD1a and axonal susceptibility
  evidence:
  - reference: PMID:15716397
    reference_title: Overexpression of GD1a ganglioside sensitizes motor nerve terminals to anti-GD1a antibody-mediated injury in a model of acute motor axonal neuropathy.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      severe ultrastructural damage and electrophysiological blockade of motor
      nerve terminal function.
    explanation: >-
      The model recapitulates complement-dependent motor-terminal injury but not
      combined motor-sensory AMSAN.

discussions:
- discussion_id: interp_amsan_stable_subtype_or_axonal_spectrum
  prompt: >-
    Is AMSAN a stable mechanistically distinct subtype, or does it often
    represent the severe motor-sensory end of a dynamic nodopathy-to-axonopathy
    spectrum shared with AMAN and other GBS patterns?
  kind: INTERPRETATION
  status: OPEN
  attaches_to:
  - pathophysiology#Reversible Nodal Conduction Failure
  - pathophysiology#Motor and Sensory Axonal Degeneration
  rationale: >-
    Fatal pathology supports genuine motor and sensory axonal destruction, but
    serial NCS shows frequent bidirectional subtype changes and no added value
    from electrodiagnostic subtyping. Resolving which patients have reversible
    nodal failure versus fixed sensory and motor axon loss matters more than a
    single early label.
  evidence:
  - reference: PMID:41656826
    reference_title: "Dynamics of Nerve Conduction Studies in Patients With Guillain-Barré Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the electrodiagnostic subtype changed on serial NCS in 37.8% (Hadden) and
      44.7% (Rajabally).
    explanation: >-
      Frequent reclassification directly motivates the stability question.
  - reference: DOI:10.1002/ana.410390105
    reference_title: "Pathology of the motor‐sensory axonal Guillain‐Barré syndrome"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      represent the most severe end of a spectrum of immune attack directed
      toward epitopes on the axon.
    explanation: >-
      Human pathology explicitly advances the spectrum interpretation.
  proposed_experiments:
  - experiment_id: exp_amsan_serial_ncs_biomarker_trajectory
    name: Prospective AMSAN-enriched serial electrophysiology and biomarker study
    description: >-
      Enroll early motor-sensory GBS before definitive subtyping; obtain
      standardized NCS/EMG at baseline, 2-3 weeks, and recovery, with blinded
      classification by multiple criteria, ganglioside-antibody profiling,
      complement activity, NfL, and motor, sensory, autonomic, and functional
      outcomes. Test whether fixed low CMAP/SNAP trajectories separate from
      reversible nodal-failure trajectories and outperform the initial subtype
      label for prognosis.
    decision_criterion: >-
      A stable AMSAN entity is supported if combined motor-sensory axonal
      trajectories remain reproducible across criteria and time and predict
      outcomes independently; frequent migration with biomarker-defined nodal
      recovery supports a continuum model.
    would_support:
    - pathophysiology#Reversible Nodal Conduction Failure
    - pathophysiology#Motor and Sensory Axonal Degeneration
- discussion_id: gap_seronegative_amsan_antigens
  prompt: >-
    What immune targets and effector mechanisms drive clinically compatible
    AMSAN when standard anti-ganglioside antibodies are absent?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Cross-Reactive Anti-Ganglioside IgG Response
  rationale: >-
    Ganglioside antibodies occur in only a subset of GBS, and routine testing has
    limited clinical value. Treating the canonical GM1/GD1a mechanism as
    universal would erase seronegative disease and mechanisms following non-C.
    jejuni antecedents.
  evidence:
  - reference: DOI:10.1038/s41572-024-00580-4
    reference_title: "Guillain–Barré syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Whether ganglioside-seronegative patients have other antibodies relevant
      to GBS is currently unclear.
    explanation: >-
      The primer directly identifies the unresolved antigen problem.
  proposed_experiments:
  - experiment_id: exp_seronegative_amsan_unbiased_antigen_screen
    name: Unbiased seronegative AMSAN neural-surface antigen discovery
    description: >-
      Screen acute serum and CSF from serially confirmed seronegative AMSAN
      against live human motor-neuron, sensory-neuron, and Schwann-cell nodal
      cultures, followed by immunoprecipitation-mass spectrometry, antigen
      validation, complement-deposition assays, and longitudinal titer-outcome
      analysis with GBS-subtype and healthy controls.
    decision_criterion: >-
      A candidate is prioritized if disease-phase IgG binds a reproducible neural
      surface target, deposits complement or disrupts conduction, declines with
      recovery, and is enriched over control groups.
    would_support:
    - pathophysiology#Ganglioside Antibody Binding at Nodal and Axolemmal Membranes
- discussion_id: mismatch_motor_only_models_for_sensory_inclusive_amsan
  prompt: >-
    Do current anti-GM1/anti-GD1a motor-axon models reproduce the sensory-axon
    injury that defines human AMSAN?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Classical Complement Activation at Axonal Membranes
  - pathophysiology#Motor and Sensory Axonal Degeneration
  rationale: >-
    Existing rabbit, transgenic-mouse, and ex vivo systems convincingly model
    motor-axon antibody/complement injury. Direct human AMSAN pathology instead
    shows dorsal as well as ventral root injury. A sensory-inclusive model is
    needed before subtype-specific mechanism or therapeutic claims are made.
  evidence:
  - reference: PMID:26936605
    reference_title: C1q-targeted inhibition of the classical complement pathway prevents injury in a novel mouse model of acute motor axonal neuropathy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      new in vivo transgenic mouse model of AMAN
    explanation: >-
      The model is explicitly AMAN rather than AMSAN.
  - reference: DOI:10.1002/ana.410390105
    reference_title: "Pathology of the motor‐sensory axonal Guillain‐Barré syndrome"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      wallerian-like degeneration of fibers in the ventral and dorsal roots
    explanation: >-
      Human AMSAN pathology requires a model capable of both motor and sensory
      injury.
  proposed_experiments:
  - experiment_id: exp_paired_human_motor_sensory_nodal_injury
    name: Paired human motor- and sensory-neuron nodal injury assay
    description: >-
      Build matched human iPSC-derived motor-neuron and sensory-neuron systems
      with Schwann-cell myelination and mature nodal domains. Expose both to
      acute serially confirmed AMSAN IgG with human complement; comparator
      conditions should include heat-inactivated complement, healthy, AMAN,
      AIDP, antigen-depleted, and C1q-inhibited controls. Measure
      antibody/C1q/C3/MAC deposition, conduction,
      calcium influx, axonal integrity, and sensory-versus-motor susceptibility.
    decision_criterion: >-
      A sensory-inclusive model is established if AMSAN IgG causes reproducible
      complement-dependent injury in both compartments, whereas AMAN IgG remains
      motor-predominant and antigen depletion or C1q blockade rescues injury.
    would_support:
    - pathophysiology#Classical Complement Activation at Axonal Membranes
    - pathophysiology#Motor and Sensory Axonal Degeneration
- discussion_id: resolved_nonbeneficial_routine_escalation
  prompt: >-
    Should poor predicted prognosis or initial non-response prompt routine
    corticosteroids, a second IVIG course, or immediate plasma exchange followed
    by IVIG?
  kind: INTERPRETATION
  status: RESOLVED
  attaches_to:
  - disease#Acute Motor and Sensory Axonal Neuropathy
  rationale: >-
    These regimens can be mistaken for positive treatment options if represented
    as ordinary treatment nodes. Current guideline and randomized evidence do
    not support routine use for poor prognosis or initial non-response.
  evidence:
  - reference: PMID:37814552
    reference_title: "European Academy of Neurology/Peripheral Nerve Society Guideline on diagnosis and treatment of Guillain-Barré syndrome."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      recommends against using oral corticosteroids, and weakly recommends
      against using IV corticosteroids
    explanation: >-
      The guideline directly recommends against corticosteroid therapy.
  - reference: PMID:33743237
    reference_title: "Second intravenous immunoglobulin dose in patients with Guillain-Barré syndrome with poor prognosis (SID-GBS): a double-blind, randomised, placebo-controlled trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      a second intravenous immunoglobulin course should not be considered for
      treatment of Guillain-Barre syndrome because of a poor prognosis.
    explanation: >-
      The randomized SID-GBS trial found no benefit and more serious adverse
      events.
  - reference: PMID:9014908
    reference_title: "Randomised trial of plasma exchange, intravenous immunoglobulin, and combined treatments in Guillain-Barré syndrome. Plasma Exchange/Sandoglobulin Guillain-Barré Syndrome Trial Group."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The combination of PE with IVIg did not confer a significant advantage.
    explanation: >-
      The randomized comparison found no significant advantage for the immediate
      combination.
  posed_date: "2026-07-18T00:35:23Z"
  resolved_date: "2026-07-18T00:35:23Z"
  resolution_note: >-
    Do not represent these regimens as routine beneficial AMSAN treatments.
    True treatment-related fluctuation after stabilization or improvement is a
    separate scenario in which specialist-guided re-treatment may be considered.

notes: >-
  AMSAN is an acquired immune-mediated GBS pattern; no dummy negative genetic
  assertion is included. No AMSAN-specific population prevalence, randomized
  treatment trial, validated sensory-inclusive animal model, or stable early
  electrodiagnostic boundary was identified. Most management, progression,
  prognosis, and complication evidence is therefore explicitly marked as
  GBS-wide PARTIAL evidence. Review articles and guidelines are classified as
  OTHER; primary patient cohorts, pathology, and trials as HUMAN_CLINICAL;
  whole-animal experiments as MODEL_ORGANISM; and the ex vivo nerve-muscle assay
  as IN_VITRO.

references:
- reference: DOI:10.1038/s41572-024-00580-4
  title: "Guillain–Barré syndrome"
  findings:
  - statement: >-
      Current synthesis of GBS mechanism, clinical criteria, differential
      diagnosis, course, prognostic factors, and management.
- reference: PMID:37814552
  title: European Academy of Neurology/Peripheral Nerve Society Guideline on diagnosis and treatment of Guillain-Barré syndrome.
  findings:
  - statement: >-
      Defines current diagnostic support, limited antiganglioside testing value,
      IVIG/PE regimens, negative treatment recommendations, and prognostic tools.
- reference: PMID:31541214
  title: Diagnosis and management of Guillain-Barré syndrome in ten steps.
  findings:
  - statement: >-
      Provides practical guidance for serial testing, monitoring, complications,
      and rehabilitation.
- reference: DOI:10.1007/s12028-023-01707-3
  title: Guidelines for Neuroprognostication in Adults with Guillain–Barré Syndrome
  findings:
  - statement: >-
      Synthesizes respiratory-support frequency and evidence-based limits on
      early long-term neuroprognostication in adults with GBS.
- reference: PMID:41656826
  title: Dynamics of Nerve Conduction Studies in Patients With Guillain-Barré Syndrome.
  findings:
  - statement: >-
      Serial NCS in 469 patients showed frequent subtype changes and supports
      repeat testing when early studies are nondiagnostic.
- reference: PMID:22480600
  title: "Electrodiagnostic criteria for Guillain-Barrè syndrome: a critical revision and the need for an update."
  findings:
  - statement: >-
      Distinguishes reversible nodal conduction failure from demyelinating block
      and fixed axonal loss.
- reference: DOI:10.1111/jns.12625
  title: "Conduction slowing, conduction block and temporal dispersion in demyelinating, dysmyelinating and axonal neuropathies: Electrophysiology meets pathology"
  findings:
  - statement: >-
      Reviews the amplitude and conduction patterns used to relate axonal and
      demyelinating electrophysiology to pathology.
- reference: DOI:10.1186/s43161-024-00258-8
  title: "Autoimmune mechanisms in Guillain-Barré syndrome subtypes: a systematic review"
  findings:
  - statement: >-
      Synthesizes autoantibody and immune-mechanism evidence across GBS subtypes
      while identifying major residual research gaps.
- reference: PMID:22507308
  title: A common mechanism and a new categorization for anti-ganglioside antibody-mediated neuropathies.
  findings:
  - statement: >-
      Frames antiganglioside neuropathies as a nodal-to-axonal continuum.
- reference: DOI:10.1002/ana.410390105
  title: "Pathology of the motor‐sensory axonal Guillain‐Barré syndrome"
  findings:
  - statement: >-
      Four fatal human cases showed motor and sensory Wallerian-like axonal
      degeneration, little demyelination, and periaxonal macrophages.
- reference: PMID:10526194
  title: Acute motor axonal neuropathy and acute motor-sensory axonal neuropathy share a common immunological profile.
  findings:
  - statement: >-
      A small human series found anti-GM1, anti-GM1b, and anti-GD1a IgG in AMSAN.
- reference: PMID:15277677
  title: Carbohydrate mimicry between human ganglioside GM1 and Campylobacter jejuni lipooligosaccharide causes Guillain-Barre syndrome.
  findings:
  - statement: >-
      C. jejuni LOS immunization induced anti-GM1 IgG, weakness, and GBS-like
      pathology in rabbits.
- reference: PMID:11409422
  title: Animal model of axonal Guillain-Barré syndrome induced by sensitization with GM1 ganglioside.
  findings:
  - statement: >-
      GM1-sensitized rabbits developed acute flaccid weakness and Wallerian-like
      axonal degeneration without primary demyelination.
- reference: PMID:15716397
  title: Overexpression of GD1a ganglioside sensitizes motor nerve terminals to anti-GD1a antibody-mediated injury in a model of acute motor axonal neuropathy.
  findings:
  - statement: >-
      Anti-GD1a plus complement produced motor-terminal deposition, structural
      damage, and functional block ex vivo.
- reference: PMID:26936605
  title: C1q-targeted inhibition of the classical complement pathway prevents injury in a novel mouse model of acute motor axonal neuropathy.
  findings:
  - statement: >-
      Anti-C1q reduced complement deposition, immune recruitment, axonal injury,
      and respiratory dysfunction in motor-axonal mouse models.
- reference: PMID:40000167
  title: Results From a Phase 1 Study Evaluating the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, and Efficacy of ANX005, a C1q Inhibitor, in Patients With Guillain-Barré Syndrome.
  findings:
  - statement: >-
      Phase 1 ANX005 data showed C1q inhibition and lower NfL with exploratory
      clinical outcomes, requiring larger confirmatory study.
- reference: DOI:10.1111/jns.12646
  title: "Efficacy and safety of eculizumab in Guillain‐Barré syndrome: A phase 3, multicenter, double‐blind, randomized, placebo‐controlled clinical trial"
  findings:
  - statement: >-
      The eculizumab Phase 3 primary endpoint was not achieved.
- reference: clinicaltrials:NCT04752566
  title: A Phase 3, Prospective, Multicenter, Double Blind, Randomized, Placebo Controlled Study to Evaluate the Efficacy and Safety of Eculizumab in Patients With Guillain-Barré Syndrome (GBS)
  findings:
  - statement: Completed severe-GBS eculizumab trial with posted results.
- reference: clinicaltrials:NCT04701164
  title: A Randomized, Double-blind, Placebo-controlled Phase 3 Study to Evaluate the Efficacy, Safety, Pharmacokinetics, and Pharmacodynamics of ANX005 in Subjects With Guillain-Barré Syndrome
  findings:
  - statement: Completed 242-participant anti-C1q Phase 3 trial without posted registry results at review.
- reference: clinicaltrials:NCT07020819
  title: An Open-Label Study to Evaluate the Pharmacokinetics, Pharmacodynamics, Efficacy, and Safety of a Single Dose of Tanruprubart (Also Commonly Known as ANX005) in Participants With Guillain-Barré Syndrome (GBS) (FORWARD Study)
  findings:
  - statement: Recruiting open-label Phase 3 tanruprubart pharmacology, early-efficacy, and safety study.
- reference: PMID:33743237
  title: "Second intravenous immunoglobulin dose in patients with Guillain-Barré syndrome with poor prognosis (SID-GBS): a double-blind, randomised, placebo-controlled trial."
  findings:
  - statement: A second IVIG course for poor prognosis did not improve outcome and increased serious adverse events.
- reference: PMID:9014908
  title: Randomised trial of plasma exchange, intravenous immunoglobulin, and combined treatments in Guillain-Barré syndrome. Plasma Exchange/Sandoglobulin Guillain-Barré Syndrome Trial Group.
  findings:
  - statement: Immediate combined PE and IVIG had no significant advantage over either treatment alone.
- reference: PMID:32674942
  title: Electrophysiological subtypes and associated prognosis factors of Mexican adults diagnosed with Guillain-Barré syndrome, a single center experience.
  findings:
  - statement: AMSAN represented 8.6 percent of this single-center adult GBS cohort.
- reference: PMID:24456386
  title: "Guillain-Barré syndrome: subtypes and predictors of outcome from India."
  findings:
  - statement: AMSAN represented 4.6 percent of this northern India GBS cohort.
- reference: PMID:39687605
  title: "Pain determinants and quality of life in Guillain-Barre syndrome: a prospective cohort study."
  findings:
  - statement: A prospective GBS cohort documented frequent acute and chronic pain and an association with axonal GBS.
- reference: DOI:10.3389/fneur.2023.1227505
  title: "Acute motor-sensory axonal polyneuropathy variant of Guillain-Barré syndrome with a thalamic lesion and COVID-19: a case report and discussion on mechanism"
  findings:
  - statement: A single AMSAN case illustrates weakness, paresthesia, areflexia, later bulbar/autonomic findings, and temporal SARS-CoV-2 association.

📚

References & Deep Research

References

DOI:10.1038/s41572-024-00580-4

Guillain–Barré syndrome

1 finding

Current synthesis of GBS mechanism, clinical criteria, differential diagnosis, course, prognostic factors, and management.

PMID:37814552

European Academy of Neurology/Peripheral Nerve Society Guideline on diagnosis and treatment of Guillain-Barré syndrome.

1 finding

Defines current diagnostic support, limited antiganglioside testing value, IVIG/PE regimens, negative treatment recommendations, and prognostic tools.

PMID:31541214

Diagnosis and management of Guillain-Barré syndrome in ten steps.

1 finding

Provides practical guidance for serial testing, monitoring, complications, and rehabilitation.

DOI:10.1007/s12028-023-01707-3

Guidelines for Neuroprognostication in Adults with Guillain–Barré Syndrome

1 finding

Synthesizes respiratory-support frequency and evidence-based limits on early long-term neuroprognostication in adults with GBS.

PMID:41656826

Dynamics of Nerve Conduction Studies in Patients With Guillain-Barré Syndrome.

1 finding

Serial NCS in 469 patients showed frequent subtype changes and supports repeat testing when early studies are nondiagnostic.

PMID:22480600

Electrodiagnostic criteria for Guillain-Barrè syndrome: a critical revision and the need for an update.

1 finding

Distinguishes reversible nodal conduction failure from demyelinating block and fixed axonal loss.

DOI:10.1111/jns.12625

Conduction slowing, conduction block and temporal dispersion in demyelinating, dysmyelinating and axonal neuropathies: Electrophysiology meets pathology

1 finding

Reviews the amplitude and conduction patterns used to relate axonal and demyelinating electrophysiology to pathology.

DOI:10.1186/s43161-024-00258-8

Autoimmune mechanisms in Guillain-Barré syndrome subtypes: a systematic review

1 finding

Synthesizes autoantibody and immune-mechanism evidence across GBS subtypes while identifying major residual research gaps.

PMID:22507308

A common mechanism and a new categorization for anti-ganglioside antibody-mediated neuropathies.

1 finding

Frames antiganglioside neuropathies as a nodal-to-axonal continuum.

DOI:10.1002/ana.410390105

Pathology of the motor‐sensory axonal Guillain‐Barré syndrome

1 finding

Four fatal human cases showed motor and sensory Wallerian-like axonal degeneration, little demyelination, and periaxonal macrophages.

PMID:10526194

Acute motor axonal neuropathy and acute motor-sensory axonal neuropathy share a common immunological profile.

1 finding

A small human series found anti-GM1, anti-GM1b, and anti-GD1a IgG in AMSAN.

PMID:15277677

Carbohydrate mimicry between human ganglioside GM1 and Campylobacter jejuni lipooligosaccharide causes Guillain-Barre syndrome.

1 finding

C. jejuni LOS immunization induced anti-GM1 IgG, weakness, and GBS-like pathology in rabbits.

PMID:11409422

Animal model of axonal Guillain-Barré syndrome induced by sensitization with GM1 ganglioside.

1 finding

GM1-sensitized rabbits developed acute flaccid weakness and Wallerian-like axonal degeneration without primary demyelination.

PMID:15716397

Overexpression of GD1a ganglioside sensitizes motor nerve terminals to anti-GD1a antibody-mediated injury in a model of acute motor axonal neuropathy.

1 finding

Anti-GD1a plus complement produced motor-terminal deposition, structural damage, and functional block ex vivo.

PMID:26936605

C1q-targeted inhibition of the classical complement pathway prevents injury in a novel mouse model of acute motor axonal neuropathy.

1 finding

Anti-C1q reduced complement deposition, immune recruitment, axonal injury, and respiratory dysfunction in motor-axonal mouse models.

PMID:40000167

Results From a Phase 1 Study Evaluating the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, and Efficacy of ANX005, a C1q Inhibitor, in Patients With Guillain-Barré Syndrome.

1 finding

Phase 1 ANX005 data showed C1q inhibition and lower NfL with exploratory clinical outcomes, requiring larger confirmatory study.

DOI:10.1111/jns.12646

Efficacy and safety of eculizumab in Guillain‐Barré syndrome: A phase 3, multicenter, double‐blind, randomized, placebo‐controlled clinical trial

1 finding

The eculizumab Phase 3 primary endpoint was not achieved.

clinicaltrials:NCT04752566

A Phase 3, Prospective, Multicenter, Double Blind, Randomized, Placebo Controlled Study to Evaluate the Efficacy and Safety of Eculizumab in Patients With Guillain-Barré Syndrome (GBS)

1 finding

Completed severe-GBS eculizumab trial with posted results.

clinicaltrials:NCT04701164

A Randomized, Double-blind, Placebo-controlled Phase 3 Study to Evaluate the Efficacy, Safety, Pharmacokinetics, and Pharmacodynamics of ANX005 in Subjects With Guillain-Barré Syndrome

1 finding

Completed 242-participant anti-C1q Phase 3 trial without posted registry results at review.

clinicaltrials:NCT07020819

An Open-Label Study to Evaluate the Pharmacokinetics, Pharmacodynamics, Efficacy, and Safety of a Single Dose of Tanruprubart (Also Commonly Known as ANX005) in Participants With Guillain-Barré Syndrome (GBS) (FORWARD Study)

1 finding

Recruiting open-label Phase 3 tanruprubart pharmacology, early-efficacy, and safety study.

PMID:33743237

Second intravenous immunoglobulin dose in patients with Guillain-Barré syndrome with poor prognosis (SID-GBS): a double-blind, randomised, placebo-controlled trial.

1 finding

A second IVIG course for poor prognosis did not improve outcome and increased serious adverse events.

PMID:9014908

Randomised trial of plasma exchange, intravenous immunoglobulin, and combined treatments in Guillain-Barré syndrome. Plasma Exchange/Sandoglobulin Guillain-Barré Syndrome Trial Group.

1 finding

Immediate combined PE and IVIG had no significant advantage over either treatment alone.

PMID:32674942

Electrophysiological subtypes and associated prognosis factors of Mexican adults diagnosed with Guillain-Barré syndrome, a single center experience.

1 finding

AMSAN represented 8.6 percent of this single-center adult GBS cohort.

PMID:24456386

Guillain-Barré syndrome: subtypes and predictors of outcome from India.

1 finding

AMSAN represented 4.6 percent of this northern India GBS cohort.

PMID:39687605

Pain determinants and quality of life in Guillain-Barre syndrome: a prospective cohort study.

1 finding

A prospective GBS cohort documented frequent acute and chronic pain and an association with axonal GBS.

DOI:10.3389/fneur.2023.1227505

Acute motor-sensory axonal polyneuropathy variant of Guillain-Barré syndrome with a thalamic lesion and COVID-19: a case report and discussion on mechanism

1 finding

A single AMSAN case illustrates weakness, paresthesia, areflexia, later bulbar/autonomic findings, and temporal SARS-CoV-2 association.

Deep Research

Falcon ▸

Acute Motor and Sensory Axonal Neuropathy (AMSAN) — Comprehensive Disease Characteristics Report

Edison Scientific Literature 27 citations 2026-05-07T19:42:51.902600

Acute Motor and Sensory Axonal Neuropathy (AMSAN) — Comprehensive Disease Characteristics Report

Target disease: Acute motor and sensory axonal neuropathy (AMSAN) (autoimmune; acute post-infectious immune-mediated peripheral neuropathy; axonal Guillain–Barré syndrome (GBS) variant). (shang2021axonalvariantsof pages 1-2)

High-level definition (current understanding): AMSAN is an axonal form of GBS with acute involvement of motor and sensory axons, typically presenting with rapidly progressive limb weakness plus sensory loss/paresthesia and areflexia/hyporeflexia, often after an infectious trigger. (shang2021axonalvariantsof pages 1-2, leonhard2024guillain–barrésyndrome pages 1-3)

Key abstract-quoted definition (GBS umbrella): Nature Reviews Disease Primers (published 2024-12-19) states: “Guillain–Barré syndrome (GBS) is a rare immune-mediated polyradiculoneuropathy” and notes that “Diagnosis is based on clinical features, supported by cerebrospinal fluid analysis and nerve conduction studies.” (leonhard2024guillain–barrésyndrome pages 1-3)

1. Disease Information

1.1 Overview

AMSAN is a GBS subtype within “axonal variants” (primarily AMAN and AMSAN). AMSAN differs from AMAN by having prominent sensory axonal involvement in addition to motor axonal injury. (shang2021axonalvariantsof pages 1-2)

1.2 Key identifiers / ontology mappings (availability in retrieved sources)

The retrieved literature focused on GBS and axonal variants but did not provide a specific MONDO ID or Orphanet code for AMSAN.

ICD (from real-world claims-based definitions for GBS): - GBS was defined using ICD-9 357.0 and ICD-10 G61.0, G65.0 in a US prescribing-patterns study. (stino2024intravenousimmunoglobulinand pages 1-2)

MeSH / MONDO / Orphanet / OMIM: not explicitly stated in the retrieved texts; thus not reliably reportable here.

1.3 Synonyms / alternative names

“Acute motor-sensory axonal polyneuropathy” (used as a synonym in case literature). (geng2023acutemotorsensoryaxonal pages 3-5)
“Axonal Guillain–Barré syndrome” (umbrella term encompassing AMAN/AMSAN). (umar2024complexneurologicalsequelae pages 4-6, shang2021axonalvariantsof pages 1-2)

1.4 Evidence source type

Most disease-level statements here are derived from aggregated disease resources and reviews (e.g., Nature Reviews Disease Primers; axonal GBS update review; Campylobacter–ganglioside review), supplemented by human clinical case reports illustrating AMSAN phenotypes/triggers and treatment response. (leonhard2024guillain–barrésyndrome pages 1-3, shang2021axonalvariantsof pages 1-2, latov2022campylobacterjejuniinfection pages 1-2, geng2023acutemotorsensoryaxonal pages 3-5)

2. Etiology

2.1 Primary causal factors (mechanistic etiology)

Post-infectious autoimmunity via molecular mimicry is the leading paradigm for axonal GBS/AMSAN, particularly in Campylobacter jejuni–associated disease. (shang2021axonalvariantsof pages 1-2, latov2022campylobacterjejuniinfection pages 1-2, leonhard2024guillain–barrésyndrome pages 1-3)

Abstract quote (Campylobacter–GBS link; published 2022-10-28): Latov writes: “Preceding infection with Campylobacter jejuni (Cj) occurs in approximately 30% of patients with Guillain–Barre syndrome (GBS), and the risk of GBS following Cj infection is increased by 77 to 100-fold. GBS is most often of the axonal subtype and is thought to be mediated by IgG antibodies to peripheral nerve gangliosides … induced by molecular mimicry.” (latov2022campylobacterjejuniinfection pages 1-2)

2.2 Risk factors

Infectious triggers (human clinical + epidemiologic evidence): - Campylobacter jejuni enteritis: strong epidemiologic association and mechanistic evidence via ganglioside mimicry. (latov2022campylobacterjejuniinfection pages 1-2, leonhard2024guillain–barrésyndrome pages 1-3) - Viral and other infectious triggers reported for axonal variants include Zika and other pathogens in review summaries; case literature also reports post–COVID-19 AMSAN. (shang2021axonalvariantsof pages 1-2, geng2023acutemotorsensoryaxonal pages 3-5)

Timing after diarrheal illness: in C. jejuni–associated GBS, neurological symptoms “usually begin at 10 days to 3 weeks after the onset of diarrhea.” (latov2022campylobacterjejuniinfection pages 1-2)

COVID-19 association (case-level, mechanistic hypotheses): AMSAN has been described following SARS-CoV-2 infection, with proposed mechanisms including molecular mimicry and hyperinflammatory para-infectious immune injury; anti-ganglioside antibodies may be absent in some cases. (geng2023acutemotorsensoryaxonal pages 3-5, geng2023acutemotorsensoryaxonal pages 5-6)

2.3 Protective factors

No specific protective genetic variants, environmental protective factors, or proven preventive interventions for AMSAN were identified in the retrieved sources.

2.4 Gene–environment interactions

The retrieved sources emphasize infection-triggered autoimmunity and mention “host genetic predisposition” as an important research direction in GBS broadly, but do not provide validated AMSAN-specific gene–environment interaction loci. (shang2021axonalvariantsof pages 1-2)

3. Phenotypes (clinical features)

3.1 Core phenotype spectrum (suggested HPO terms)

AMSAN typically includes: - Acute/subacute limb weakness (often symmetric), progressing over days (HP:0001324 Muscle weakness; HP:0003674 Motor delay/impairment not specific; consider HP:0003323 Progressive muscular weakness). - Areflexia/hyporeflexia (HP:0001284 Areflexia). (leonhard2024guillain–barrésyndrome pages 1-3) - Sensory symptoms (paresthesia, sensory loss) (HP:0003401 Paresthesia; HP:0000763 Sensory neuropathy). (leonhard2024guillain–barrésyndrome pages 1-3, geng2023acutemotorsensoryaxonal pages 3-5) - Pain (HP:0012531 Pain). (leonhard2024guillain–barrésyndrome pages 1-3) - Cranial nerve involvement may occur in severe GBS phenotypes (facial palsy, bulbar weakness) (HP:0001343 Facial palsy; HP:0002493 Dysphagia). (leonhard2024guillain–barrésyndrome pages 1-3) - Autonomic dysfunction in severe cases (HP:0001278 Orthostatic hypotension; HP:0002013 Vomiting; broader: dysautonomia). (busl2023guidelinesforneuroprognostication pages 1-3, umar2024complexneurologicalsequelae pages 4-6) - Respiratory failure / need for ventilation in severe cases (HP:0002878 Respiratory failure; HP:0002094 Dyspnea). (leonhard2024guillain–barrésyndrome pages 1-3)

3.2 Onset and progression

GBS (including AMSAN) is characterized by rapid progression with a typical nadir within weeks. Neurocritical Care guidelines note symptoms reach maximum “within 2–4 weeks.” (busl2023guidelinesforneuroprognostication pages 1-3)

3.3 Frequency among affected individuals (data availability)

Phenotype frequencies are best described for GBS overall rather than AMSAN specifically in the retrieved sources: - “Around 20% of patients may develop weakness in all four limbs … and respiratory failure requiring mechanical ventilation.” (leonhard2024guillain–barrésyndrome pages 1-3)

3.4 Quality-of-life impact

Nature Reviews Disease Primers emphasizes residual disability: “~20% of patients who received treatment are unable to walk after 6 months.” (leonhard2024guillain–barrésyndrome pages 1-3)

4. Genetic/Molecular Information

4.1 Causal genes

AMSAN is not a monogenic disorder in standard clinical framing; the retrieved sources do not identify causal genes or OMIM disease entries specific to AMSAN. (leonhard2024guillain–barrésyndrome pages 1-3, shang2021axonalvariantsof pages 1-2)

4.2 Key molecular targets (autoantigens)

Gangliosides on peripheral nerves are key immune targets in axonal GBS/AMSAN: - Anti-ganglioside antibodies reported in association with AMSAN include anti-GM1, anti-GM1b, anti-GD1a. (shang2021axonalvariantsof pages 6-7)

4.3 Pathogenic “variants” (not applicable)

Pathogenic DNA variants are not established as causal for AMSAN in the provided evidence.

4.4 Epigenetics / chromosomal abnormalities

Not established for AMSAN in the retrieved sources.

5. Environmental Information

5.1 Infectious agents (key environmental triggers)

Campylobacter jejuni is the best-supported trigger for axonal GBS/AMSAN. (latov2022campylobacterjejuniinfection pages 1-2, leonhard2024guillain–barrésyndrome pages 1-3)
SARS-CoV-2 has been associated with AMSAN in case literature, with immune-mediated mechanisms proposed. (geng2023acutemotorsensoryaxonal pages 3-5, geng2023acutemotorsensoryaxonal pages 5-6)

5.2 Lifestyle/occupational factors

No AMSAN-specific lifestyle protective/risk factors were established in the retrieved sources.

6. Mechanism / Pathophysiology

6.1 Causal chain (upstream → downstream)

Upstream trigger: infection (especially C. jejuni; also viral triggers). (latov2022campylobacterjejuniinfection pages 1-2, leonhard2024guillain–barrésyndrome pages 1-3)

Immune priming via molecular mimicry: bacterial lipooligosaccharides mimic peripheral nerve gangliosides, producing cross-reactive antibodies. Nature Reviews Disease Primers explicitly summarizes: “For example, in patients with preceding Campylobacter jejuni infection, molecular mimicry causes a cross-reactive antibody response to nerve gangliosides.” (leonhard2024guillain–barrésyndrome pages 1-3)

Effector injury: anti-ganglioside antibodies activate complement at nodes/paranodes and axolemma, causing conduction failure and structural axonal injury/degeneration (axonal variants). (leonhard2024guillain–barrésyndrome pages 5-7, latov2022campylobacterjejuniinfection pages 2-4)

Downstream clinical manifestations: reduced compound muscle action potentials (CMAPs), sensory nerve action potential (SNAP) abnormalities, weakness + sensory loss, and in severe cases bulbar/respiratory/autonomic failure. (geng2023acutemotorsensoryaxonal pages 3-5, leonhard2024guillain–barrésyndrome pages 1-3)

6.2 Immune system involvement

Axonal variants are associated with anti-ganglioside antibodies and complement-dependent mechanisms; Latov describes that GBS axonal subtype is “thought to be mediated by IgG antibodies to peripheral nerve gangliosides” cross-reactive with C. jejuni components. (latov2022campylobacterjejuniinfection pages 1-2)

6.3 Suggested GO biological process terms (mechanism-oriented)

GO:0006956 complement activation
GO:0006955 immune response
GO:0002250 adaptive immune response
GO:0042113 B cell activation
GO:0007166 cell surface receptor signaling pathway (broad)

6.4 Suggested Cell Ontology terms (CL)

CL:0000945 B cell
CL:0000084 T cell
CL:0000235 macrophage
CL:0000584 Schwann cell (peripheral glia; mechanistic relevance to peripheral nerves broadly)

6.5 Molecular profiling / biomarkers (availability)

The retrieved sources highlight a lack of specific biomarkers for GBS broadly (including axonal variants). (leonhard2024guillain–barrésyndrome pages 1-3)

7. Anatomical Structures Affected

7.1 Organ/system level

Peripheral nervous system (peripheral nerves and roots; polyradiculoneuropathy). (leonhard2024guillain–barrésyndrome pages 1-3)

7.2 Tissue/cell level (suggested UBERON terms)

UBERON:0000010 peripheral nerve
UBERON:0001021 spinal nerve root

7.3 Subcellular (suggested GO Cellular Component)

GO:0033267 axon part
GO:0043209 myelin sheath (even in “axonal” variants, nerve architecture is involved)
GO:0030054 cell junction (node/paranode microdomains; mechanistic target region) (leonhard2024guillain–barrésyndrome pages 5-7)

8. Temporal Development

8.1 Onset pattern

Acute onset with rapid progression; nadir typically within 2–4 weeks in GBS overall. (busl2023guidelinesforneuroprognostication pages 1-3)

8.2 Course

Typically monophasic: Nature Reviews Disease Primers states “GBS is usually a monophasic disease.” (leonhard2024guillain–barrésyndrome pages 1-3)

9. Inheritance and Population

9.1 Epidemiology

Data are primarily for GBS overall; AMSAN-specific incidence is not provided in the retrieved evidence.

GBS annual global incidence “1–2 per 100,000 persons per year.” (leonhard2024guillain–barrésyndrome pages 1-3)
Axonal-variants review provides a similar range: 0.81–1.89 per 100,000/year. (shang2021axonalvariantsof pages 1-2)
Sex/age: males affected ~1.5× more than females; risk rises ~20% per decade of age. (leonhard2024guillain–barrésyndrome pages 1-3)

9.2 Population differences (axonal variants)

Axonal variants (including AMSAN) are discussed as having geographic variability, with higher representation in some regions (review-level). (restrepojimenez2018theimmunotherapyof pages 46-47)

10. Diagnostics

10.1 Diagnostic approach (real-world implementation)

GBS diagnosis is “based on clinical features, supported by cerebrospinal fluid analysis and nerve conduction studies.” (leonhard2024guillain–barrésyndrome pages 1-3)

CSF: - Axonal-variants review: CSF albuminocytologic dissociation is a hallmark “detectable in almost 90%,” with CSF albumin rising from week 2 and present in ~70% by the end of week 2. (shang2021axonalvariantsof pages 1-2)

Electrophysiology (NCS/EMG): - Axonal variants: early studies can be misleading; decreased CMAP amplitudes and reversible conduction failure/block can appear early; electrophysiology “more reliable” at 3–6 weeks than at 1–2 weeks. (shang2021axonalvariantsof pages 1-2) - Nature Reviews Disease Primers emphasizes heterogeneity: mixed axonal–demyelinating or even normal NCS can occur, limiting strict NCS-only subclassification. (leonhard2024guillain–barrésyndrome pages 4-5)

Serology (supportive, not required for all): Anti-ganglioside antibodies support axonal subtype classification (anti-GM1/anti-GD1a and related), but seronegative axonal cases exist. (shang2021axonalvariantsof pages 6-7, geng2023acutemotorsensoryaxonal pages 5-6)

10.2 Differential diagnosis (high-level)

Acute onset CIDP (A-CIDP) is clinically challenging and can lead to reclassification; this carries therapeutic implications. (stino2024intravenousimmunoglobulinand pages 1-2)

11. Outcome / Prognosis

11.1 Key outcome statistics (GBS overall)

Nature Reviews Disease Primers reports: “~20% of patients who received treatment are unable to walk after 6 months and ~5% die as a consequence of GBS.” (leonhard2024guillain–barrésyndrome pages 1-3)

Neurocritical Care neuroprognostication guidelines provide ICU-relevant statistics: - “10–30% require mechanical ventilation during the acute phase.” (busl2023guidelinesforneuroprognostication pages 1-3) - Mortality “range between 1 and 13%,” with “mortality rates up to 20%” among ventilated patients. (busl2023guidelinesforneuroprognostication pages 1-3)

11.2 Prognostic tools / expert consensus

Busl et al. recommend: - EGRIS (Erasmus GBS Respiratory Insufficiency Score) for predicting ventilation, and - EGOS / modified EGOS for predicting independent ambulation at 3 months and beyond. (busl2023guidelinesforneuroprognostication pages 1-3)

12. Treatment

12.1 Standard of care

Only proven effective disease-modifying treatments for GBS (including AMSAN) remain: - Intravenous immunoglobulin (IVIg) - Plasma exchange (PE/PLEX) (leonhard2024guillain–barrésyndrome pages 1-3)

Nature Reviews Disease Primers (2024) abstract quote: “Effective treatments include plasma exchange and intravenous immunoglobulins.” (leonhard2024guillain–barrésyndrome pages 1-3)

12.2 Treatment strategy and common pitfalls (guidelines + evidence)

A US real-world analysis emphasizes trials showing no benefit from: - Repeat IVIG dosing and - PLEX followed by IVIG (combination therapy) in non-responders. (stino2024intravenousimmunoglobulinand pages 1-2)

Abstract quote (real-world utilization; published 2024-09): Stino et al. state: “Randomized controlled trials show that repeat IVIG dosing and … combination therapy have no additional therapeutic benefit in Guillain-Barre Syndrome (GBS) non-responders.” (stino2024intravenousimmunoglobulinand pages 1-2)

12.3 Recent developments (2023–2024) — complement inhibition (eculizumab)

A key 2024 development is a phase 3 randomized trial of eculizumab (C5 inhibitor) added to IVIg in severe GBS.

Abstract quote (published 2024-07; J Peripher Nerv Syst): “This study evaluated the efficacy and safety of eculizumab add-on therapy to IVIg … in patients with severe GBS.” (kuwabara2024efficacyandsafety pages 1-2)

Results: - Primary endpoint not met (time to Hughes FG ≤1): HR 0.9, 95% CI 0.45–1.97; p = 0.89. (kuwabara2024efficacyandsafety pages 1-2) - Strong target engagement: serum free C5 reduced by 99.99% at 1 hour postdose and sustained to week 5. (kuwabara2024efficacyandsafety pages 1-2)

12.4 MAXO (Medical Action Ontology) suggestions

MAXO:0000412 intravenous immunoglobulin therapy
MAXO:0000756 therapeutic plasma exchange
MAXO:0000610 mechanical ventilation (for respiratory failure)
MAXO:0000571 physical therapy / rehabilitation (supportive)

13. Prevention

No established primary-prevention intervention is specific to AMSAN beyond prevention/management of infectious triggers at the population level.

Vaccine-associated GBS (broader context): The retrieved evidence supports ongoing pharmacovigilance and risk assessment for GBS after vaccination, but does not provide AMSAN-specific prevention guidance. (shang2021axonalvariantsof pages 1-2)

14. Other Species / Natural Disease

Direct naturally occurring AMSAN analogs in non-human species were not identified in the retrieved sources.

15. Model Organisms

Experimental autoimmune neuritis and anti-ganglioside models (mechanistic relevance): Latov reports animal models in which rabbits immunized with GM1 or C. jejuni LPS develop acute axonal neuropathy with anti-GM1 antibodies, supporting the antibody-mediated mechanism relevant to axonal GBS/AMSAN. (latov2022campylobacterjejuniinfection pages 2-4)

2023–2024 “latest research” highlights (prioritized)

2024 authoritative synthesis: Nature Reviews Disease Primers (Leonhard et al.; 2024-12-19) consolidates contemporary consensus on GBS triggers, diagnosis (CSF + NCS), treatment (IVIg/PE), and residual disability (20% non-ambulant at 6 months; ~5% mortality). (leonhard2024guillain–barrésyndrome pages 1-3)
2024 mechanism-directed therapy trial: Phase 3 add-on eculizumab to IVIg did not improve functional recovery despite robust complement suppression, suggesting complement blockade alone is insufficient or that patient selection/timing remain unresolved. (kuwabara2024efficacyandsafety pages 1-2)
2024 real-world implementation gap: A US claims-based cohort (2001–2018) found repeat IVIG use (39.7%) and combination therapy (6.1%) persisted, despite RCT evidence against these approaches in non-responders; diagnostic reclassification to CIDP occurred in 32%. (stino2024intravenousimmunoglobulinand pages 1-2)

Evidence summary table

Domain	Evidence summary	Key quantitative stats (with values)	Primary source (first author, year, journal)	URL	Context citation ID
Definition	AMSAN is an axonal Guillain-Barré syndrome (GBS) subtype characterized by acute motor and sensory axonal involvement; axonal GBS variants include AMAN and AMSAN. GBS is an acute, immune-mediated polyradiculoneuropathy with rapidly progressive weakness and sensory deficits.	Global GBS incidence: 1–2/100,000/year; males affected ~1.5× more often; risk rises ~20% per decade of age.	Leonhard, 2024, Nature Reviews Disease Primers	https://doi.org/10.1038/s41572-024-00580-4	(leonhard2024guillain–barrésyndrome pages 1-3, shang2021axonalvariantsof pages 1-2)
Triggers	AMSAN is usually post-infectious, with Campylobacter jejuni the best-supported trigger; COVID-19, chikungunya, and other infections have also been reported as antecedents in axonal GBS/AMSAN cases. Molecular mimicry between microbial glycans and nerve gangliosides is the leading mechanism.	Preceding C. jejuni in ~30% of GBS; GBS risk after C. jejuni infection increased 77–100-fold; neurologic symptoms usually begin 10 days to 3 weeks after diarrhea.	Latov, 2022, Microorganisms	https://doi.org/10.3390/microorganisms10112139	(latov2022campylobacterjejuniinfection pages 1-2, latov2022campylobacterjejuniinfection pages 2-4, geng2023acutemotorsensoryaxonal pages 3-5)
Autoantibodies	Axonal GBS including AMSAN is associated most often with anti-ganglioside antibodies, particularly anti-GM1, anti-GM1b, and anti-GD1a. Antibodies are often IgG1/IgG3 subclasses and can cross-react with C. jejuni lipooligosaccharides.	Anti-ganglioside antibodies reported in 41–85% of GBS following C. jejuni infection.	Shang, 2021, Journal of Neurology	https://doi.org/10.1007/s00415-020-09742-2	(shang2021axonalvariantsof pages 6-7, latov2022campylobacterjejuniinfection pages 2-4, latov2022campylobacterjejuniinfection pages 1-2)
Pathophysiology	The best-supported causal chain is infection → molecular mimicry → anti-ganglioside antibody generation → complement activation at nodes/paranodes/axolemma → conduction failure and axonal degeneration. Pathology in axonal GBS shows antibody/complement deposition on axolemma and macrophage-associated axonal injury.	Serum C5 in the eculizumab phase 3 trial was reduced by 99.99% 1 hour post-dose and remained suppressed through week 5, showing effective target engagement.	Latov, 2022, Microorganisms	https://doi.org/10.3390/microorganisms10112139	(latov2022campylobacterjejuniinfection pages 2-4, leonhard2024guillain–barrésyndrome pages 5-7, kuwabara2024efficacyandsafety pages 1-2)
Diagnostics	Diagnosis is primarily clinical and supported by CSF and electrophysiology. For axonal variants, serial NCS/EMG are important because early studies may show reduced CMAPs, reversible conduction failure/block, or equivocal findings; CSF albuminocytologic dissociation is common but may lag.	CSF albuminocytologic dissociation in almost 90%; CSF protein elevated in ~70% by end of week 2; electrophysiology more reliable at 3–6 weeks than 1–2 weeks.	Shang, 2021, Journal of Neurology	https://doi.org/10.1007/s00415-020-09742-2	(shang2021axonalvariantsof pages 1-2, busl2023guidelinesforneuroprognostication pages 1-3, leonhard2024guillain–barrésyndrome pages 1-3)
Prognosis	Axonal GBS/AMSAN generally has a more severe course and slower recovery than demyelinating GBS. Across GBS, respiratory failure, bulbar weakness, and severe nadir disability are major poor prognostic features; EGOS and EGRIS are used for outcome and ventilation risk prediction.	10–30% require mechanical ventilation; ~20% of treated GBS patients cannot walk at 6 months; ~5% die; mortality can reach up to 20% among ventilated patients.	Busl, 2023, Neurocritical Care	https://doi.org/10.1007/s12028-023-01707-3	(busl2023guidelinesforneuroprognostication pages 1-3, leonhard2024guillain–barrésyndrome pages 1-3, umar2024complexneurologicalsequelae pages 4-6)
Treatment	Standard evidence-based treatment remains IVIG or plasma exchange; combination therapy and repeat IVIG do not add benefit and can increase adverse events. Supportive ICU care and rehabilitation remain essential, especially in severe axonal cases.	Median time to walk without aid: 51 days with IVIG, 49 days with plasma exchange, 40 days with combined treatment in older trial data; repeat IVIG used in 39.7% and combination therapy in 6.1% of a US real-world cohort before newer evidence/guidelines.	Kuwabara, 2024, Journal of the Peripheral Nervous System	https://doi.org/10.1111/jns.12646	(kuwabara2024efficacyandsafety pages 1-2, stino2024intravenousimmunoglobulinand pages 1-2)
Recent developments 2023-2024	Recent work emphasized 2023 EAN/PNS guideline-based care and mechanism-directed therapy. A 2024 phase 3 trial of eculizumab added to IVIG in severe GBS did not meet its primary endpoint despite strong complement suppression and acceptable safety.	Phase 3 eculizumab trial enrolled 57 participants (37 eculizumab, 20 placebo); primary endpoint HR 0.9, 95% CI 0.45–1.97, p=.89.	Kuwabara, 2024, Journal of the Peripheral Nervous System	https://doi.org/10.1111/jns.12646	(kuwabara2024efficacyandsafety pages 1-2, freiha2026guillainbarrésyndromeprogress pages 7-9)
Real-world implementation	Real-world US prescribing data show persistent use of non-recommended repeat IVIG and some IVIG/PLEX combination therapy, suggesting a gap between evidence/guidelines and practice. Diagnostic reclassification from GBS to CIDP also occurs frequently in claims-based care pathways.	US cohort n=2325; repeat IVIG 39.7%; combination therapy 6.1%; later reclassified to CIDP 32.0%.	Stino, 2024, Muscle & Nerve	https://doi.org/10.1002/mus.28265	(stino2024intravenousimmunoglobulinand pages 1-2)

Table: This table condenses the most supported AMSAN findings from the available context into disease knowledge base fields. It highlights what is known specifically for axonal GBS/AMSAN and where evidence comes from broader GBS literature used to inform AMSAN care.

Limitations of this report (evidence availability constraints)

AMSAN-specific ontology identifiers (MONDO, Orphanet, OMIM, MeSH term strings) were not available in the retrieved full-text excerpts and therefore are not asserted here.
Many epidemiologic and prognosis statistics are reported at the GBS umbrella level; AMSAN-specific incidence, subtype-specific mortality, and antibody-frequency distributions require additional targeted cohort studies not captured in the retrieved evidence subset.

References

(shang2021axonalvariantsof pages 1-2): Pei Shang, Mingqin Zhu, Ying Wang, Xiang-yu Zheng, Xiujuan Wu, Jie Zhu, Jiachun Feng, and Hong-Liang Zhang. Axonal variants of guillain–barré syndrome: an update. Journal of Neurology, pages 1-18, Mar 2021. URL: https://doi.org/10.1007/s00415-020-09742-2, doi:10.1007/s00415-020-09742-2. This article has 93 citations and is from a domain leading peer-reviewed journal.
(leonhard2024guillain–barrésyndrome pages 1-3): Sonja E. Leonhard, Nowshin Papri, Luis Querol, Simon Rinaldi, Nortina Shahrizaila, and Bart C. Jacobs. Guillain–barré syndrome. Nature Reviews Disease Primers, Dec 2024. URL: https://doi.org/10.1038/s41572-024-00580-4, doi:10.1038/s41572-024-00580-4. This article has 48 citations.
(stino2024intravenousimmunoglobulinand pages 1-2): Amro M. Stino, Evan L. Reynolds, Maya Watanabe, and Brian C. Callaghan. Intravenous immunoglobulin and plasma exchange prescribing patterns for guillain‐barre syndrome in the united states—2001 to 2018. Muscle & Nerve, 70:1192-1199, Sep 2024. URL: https://doi.org/10.1002/mus.28265, doi:10.1002/mus.28265. This article has 3 citations and is from a peer-reviewed journal.
(geng2023acutemotorsensoryaxonal pages 3-5): Na Geng, Pengfei Wang, and Yong Zhang. Acute motor-sensory axonal polyneuropathy variant of guillain-barré syndrome with a thalamic lesion and covid-19: a case report and discussion on mechanism. Frontiers in Neurology, Sep 2023. URL: https://doi.org/10.3389/fneur.2023.1227505, doi:10.3389/fneur.2023.1227505. This article has 6 citations and is from a peer-reviewed journal.
(umar2024complexneurologicalsequelae pages 4-6): Anam Umar, Amber E Faquih, Bilal Jawed, and Muhammad Bilal. Complex neurological sequelae: axonal guillain-barré syndrome post covid-19 in a young patient. Cureus, Aug 2024. URL: https://doi.org/10.7759/cureus.67213, doi:10.7759/cureus.67213. This article has 0 citations.
(latov2022campylobacterjejuniinfection pages 1-2): Norman Latov. Campylobacter jejuni infection, anti-ganglioside antibodies, and neuropathy. Microorganisms, 10:2139, Oct 2022. URL: https://doi.org/10.3390/microorganisms10112139, doi:10.3390/microorganisms10112139. This article has 25 citations.
(geng2023acutemotorsensoryaxonal pages 5-6): Na Geng, Pengfei Wang, and Yong Zhang. Acute motor-sensory axonal polyneuropathy variant of guillain-barré syndrome with a thalamic lesion and covid-19: a case report and discussion on mechanism. Frontiers in Neurology, Sep 2023. URL: https://doi.org/10.3389/fneur.2023.1227505, doi:10.3389/fneur.2023.1227505. This article has 6 citations and is from a peer-reviewed journal.
(busl2023guidelinesforneuroprognostication pages 1-3): Katharina M. Busl, Herbert Fried, Susanne Muehlschlegel, Katja E. Wartenberg, Venkatakrishna Rajajee, Sheila A. Alexander, Claire J. Creutzfeldt, Gabriel V. Fontaine, Sara E. Hocker, David Y. Hwang, Keri S. Kim, Dominik Madzar, Dea Mahanes, Shraddha Mainali, Juergen Meixensberger, Oliver W. Sakowitz, Panayiotis N. Varelas, Thomas Westermaier, and Christian Weimar. Guidelines for neuroprognostication in adults with guillain–barré syndrome. Neurocritical Care, 38:564-583, Mar 2023. URL: https://doi.org/10.1007/s12028-023-01707-3, doi:10.1007/s12028-023-01707-3. This article has 52 citations and is from a peer-reviewed journal.
(shang2021axonalvariantsof pages 6-7): Pei Shang, Mingqin Zhu, Ying Wang, Xiang-yu Zheng, Xiujuan Wu, Jie Zhu, Jiachun Feng, and Hong-Liang Zhang. Axonal variants of guillain–barré syndrome: an update. Journal of Neurology, pages 1-18, Mar 2021. URL: https://doi.org/10.1007/s00415-020-09742-2, doi:10.1007/s00415-020-09742-2. This article has 93 citations and is from a domain leading peer-reviewed journal.
(leonhard2024guillain–barrésyndrome pages 5-7): Sonja E. Leonhard, Nowshin Papri, Luis Querol, Simon Rinaldi, Nortina Shahrizaila, and Bart C. Jacobs. Guillain–barré syndrome. Nature Reviews Disease Primers, Dec 2024. URL: https://doi.org/10.1038/s41572-024-00580-4, doi:10.1038/s41572-024-00580-4. This article has 48 citations.
(latov2022campylobacterjejuniinfection pages 2-4): Norman Latov. Campylobacter jejuni infection, anti-ganglioside antibodies, and neuropathy. Microorganisms, 10:2139, Oct 2022. URL: https://doi.org/10.3390/microorganisms10112139, doi:10.3390/microorganisms10112139. This article has 25 citations.
(restrepojimenez2018theimmunotherapyof pages 46-47): Paula Restrepo-Jiménez, Yhojan Rodríguez, Paulina González, Christopher Chang, M. Eric Gershwin, and Juan-Manuel Anaya. The immunotherapy of guillain-barré syndrome. Expert Opinion on Biological Therapy, 18:619-631, May 2018. URL: https://doi.org/10.1080/14712598.2018.1468885, doi:10.1080/14712598.2018.1468885. This article has 26 citations and is from a peer-reviewed journal.
(leonhard2024guillain–barrésyndrome pages 4-5): Sonja E. Leonhard, Nowshin Papri, Luis Querol, Simon Rinaldi, Nortina Shahrizaila, and Bart C. Jacobs. Guillain–barré syndrome. Nature Reviews Disease Primers, Dec 2024. URL: https://doi.org/10.1038/s41572-024-00580-4, doi:10.1038/s41572-024-00580-4. This article has 48 citations.
(kuwabara2024efficacyandsafety pages 1-2): Satoshi Kuwabara, Susumu Kusunoki, Motoi Kuwahara, Yoshihisa Yamano, Yoichiro Nishida, Hirokazu Ishida, Tomoyuki Kasuya, Erik Kupperman, Qun Lin, Glen Frick, and Sonoko Misawa. Efficacy and safety of eculizumab in guillain‐barré syndrome: a phase 3, multicenter, double‐blind, randomized, placebo‐controlled clinical trial. Journal of the Peripheral Nervous System, 29:339-349, Jul 2024. URL: https://doi.org/10.1111/jns.12646, doi:10.1111/jns.12646. This article has 29 citations and is from a peer-reviewed journal.
(freiha2026guillainbarrésyndromeprogress pages 7-9): Joumana Freiha, Young Gi Min, Chinar Osman, and Yusuf Rajabally. Guillain-barré syndrome: progress in diagnosis, biomarkers, neuroimaging and management. ImmunoTargets and Therapy, Volume 15:1-13, Apr 2026. URL: https://doi.org/10.2147/itt.s390161, doi:10.2147/itt.s390161. This article has 0 citations.

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Mechanistic Hypotheses

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Medical Actions

Environmental Factors

Biochemical Markers

Diagnosis

Progression

Epidemiology

Differential Diagnoses

Clinical Trials

Experimental Models

Animal Models

Source YAML

References & Deep Research

References

Deep Research

Acute Motor and Sensory Axonal Neuropathy (AMSAN) — Comprehensive Disease Characteristics Report

1. Disease Information

1.1 Overview

1.2 Key identifiers / ontology mappings (availability in retrieved sources)

1.3 Synonyms / alternative names

1.4 Evidence source type

2. Etiology

2.1 Primary causal factors (mechanistic etiology)

2.2 Risk factors

2.3 Protective factors

2.4 Gene–environment interactions

3. Phenotypes (clinical features)

3.1 Core phenotype spectrum (suggested HPO terms)

3.2 Onset and progression

3.3 Frequency among affected individuals (data availability)

3.4 Quality-of-life impact

4. Genetic/Molecular Information

4.1 Causal genes

4.2 Key molecular targets (autoantigens)

4.3 Pathogenic “variants” (not applicable)

4.4 Epigenetics / chromosomal abnormalities

5. Environmental Information

5.1 Infectious agents (key environmental triggers)

5.2 Lifestyle/occupational factors

6. Mechanism / Pathophysiology

6.1 Causal chain (upstream → downstream)

6.2 Immune system involvement

6.3 Suggested GO biological process terms (mechanism-oriented)

6.4 Suggested Cell Ontology terms (CL)

6.5 Molecular profiling / biomarkers (availability)

7. Anatomical Structures Affected

7.1 Organ/system level

7.2 Tissue/cell level (suggested UBERON terms)

7.3 Subcellular (suggested GO Cellular Component)

8. Temporal Development

8.1 Onset pattern

8.2 Course

9. Inheritance and Population

9.1 Epidemiology

9.2 Population differences (axonal variants)

10. Diagnostics

10.1 Diagnostic approach (real-world implementation)

10.2 Differential diagnosis (high-level)

11. Outcome / Prognosis

11.1 Key outcome statistics (GBS overall)

11.2 Prognostic tools / expert consensus

12. Treatment

12.1 Standard of care

12.2 Treatment strategy and common pitfalls (guidelines + evidence)

12.3 Recent developments (2023–2024) — complement inhibition (eculizumab)

12.4 MAXO (Medical Action Ontology) suggestions

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

2023–2024 “latest research” highlights (prioritized)

Evidence summary table

Limitations of this report (evidence availability constraints)