Bell's palsy

Complex MONDO:0005665 Pathograph 12 Neurological Disorder Peripheral Neuropathy

Bell's palsy is an acute idiopathic peripheral facial neuropathy causing sudden unilateral weakness of the muscles of facial expression. The leading mechanistic model invokes post-viral inflammatory edema of cranial nerve VII at the geniculate ganglion and within the narrow facial canal, producing transient compression, conduction block, and facial muscle dysfunction.

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Inheritance

Pathophysiology

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Histopathology

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Subtypes

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Models

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Classifications

Harrison's Chapter

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Mappings

MONDO

MONDO:0005665 Bell's palsy

Primary MONDO disease identifier for this Bell's palsy entry.

ICD-10-CM

ICD10CM:G51.0 Bell's palsy

Bell's palsy is represented directly by ICD-10-CM code G51.0.

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Definitions

1

Clinical syndrome definition for Bell's palsy

Bell's palsy is acute unilateral peripheral facial weakness or paralysis of unknown cause that develops over hours to two days.

CASE_DEFINITION General clinical framing of acute idiopathic peripheral facial palsy

Show evidence (2 references)

PMID:39939082 SUPPORT Human Clinical

"Bell's palsy is acute weakness of the facial muscles associated with compression of cranial nerve VII."

This directly supports the standard clinical definition of Bell's palsy as acute cranial-nerve-VII-mediated facial weakness.

PMID:36397921 SUPPORT Human Clinical

"Bell's palsy, also known as "acute facial palsy of unknown cause", is a common cranial neuropathy leading to facial muscle paresis or complete paralysis characteristically on one side, occurring suddenly and may progress over 48 hours."

This supports the idiopathic acute cranial-neuropathy framing and typical time course.

📚

References

12

PMID:33602968

A meta-analysis uncovers the first sequence variant conferring risk of Bell's palsy.

No top-level findings curated for this source.

PMID:35160337

Comparison of Medical and Surgical Treatment in Severe Bell's Palsy.

No top-level findings curated for this source.

PMID:33088514

New onset of Bell's palsy in a patient with West Nile Encephalitis.

No top-level findings curated for this source.

PMID:36397921

Bell's Palsy: A Review.

No top-level findings curated for this source.

PMID:39939082

Bell's Palsy.

No top-level findings curated for this source.

PMID:27689547

Steroid/Antiviral for the treatment of Bell's palsy: Double blind randomized clinical trial.

No top-level findings curated for this source.

PMID:37752723

Psychosocial functioning in patients with altered facial expression: a scoping review in five neurological diseases.

No top-level findings curated for this source.

PMID:38517799

Treatment Approaches for Altered Facial Expression: A Systematic Review in Facioscapulohumeral Muscular Dystrophy and Other Neurological Diseases.

No top-level findings curated for this source.

PMID:40255708

Cheilitis Granulomatosa: A Case Report of a Sarcoid Mimic.

No top-level findings curated for this source.

PMID:31124964

Increased risk of Bell palsy in patient with migraine: A longitudinal follow-up study.

No top-level findings curated for this source.

PMID:34640384

Clinical Prognostic Factors Associated with Good Outcomes in Pediatric Bell's Palsy.

No top-level findings curated for this source.

PMID:40299566

Exploring the Role of Inflammation and Metabolites in Bell's Palsy and Potential Treatment Strategies.

No top-level findings curated for this source.

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Pathophysiology

5

Putative post-viral immune activation in the geniculate ganglion

Bell's palsy is widely modeled as a post-viral inflammatory neuropathy in which latent viral reactivation or other infection-related immune activation triggers inflammation around cranial nerve VII, particularly at the geniculate ganglion.

peripheral nervous system neuron link Schwann cell link

response to virus link inflammatory response link

geniculate ganglion link facial nerve link

Show evidence (2 references)

PMID:33602968 PARTIAL Human Clinical

"While the pathogenesis remains unknown, previous studies have implicated post-viral inflammation and resulting compression of the facial nerve."

This supports post-viral inflammation as a leading but not definitively proven Bell's palsy mechanism.

PMID:33088514 PARTIAL Human Clinical

"Even though the underlying pathophysiology remains elusive, Bell's palsy is thought to result due to virus-mediated inflammation resulting in swelling of the CN VII and its compression at the geniculate ganglion."

This supports the commonly proposed geniculate-ganglion-centered viral inflammatory mechanism while making clear that it remains inferential.

JAK-STAT-associated inflammatory signaling and immune-cell recruitment

Emerging systems-biology analyses implicate inflammatory protein networks, immune-cell traits, and JAK-STAT-associated signaling as candidate amplifiers of local facial-nerve inflammation in Bell's palsy.

JAK-STAT cascade link inflammatory response link

Show evidence (1 reference)

PMID:40299566 PARTIAL Computational

"Our study identifies causal relationships between inflammatory proteins, metabolites, immune cells, and Bell's palsy, highlighting that the JAK/STAT signaling pathway may be a potentially critical target for intervention in Bell's palsy, and that its modulation may provide new directions and..."

This computational Mendelian-randomization and network-analysis study supports JAK/STAT-centered inflammatory signaling as a plausible mechanistic contributor, but not yet a definitive established pathway in human Bell's palsy.

Facial nerve edema within the facial canal

Inflammatory swelling of the facial nerve develops within the rigid Fallopian canal, a confined anatomic space that limits expansion and promotes secondary entrapment injury.

Schwann cell link

inflammatory response link

facial nerve link

Show evidence (1 reference)

PMID:33088514 SUPPORT Human Clinical

"Bell's palsy is thought to result due to virus-mediated inflammation resulting in swelling of the CN VII and its compression at the geniculate ganglion."

This directly supports facial nerve swelling as a central mechanistic event in Bell's palsy.

Intracanalicular compression and conduction block of cranial nerve VII

Entrapment of the swollen facial nerve impairs neural conduction and produces acute lower motor neuron facial dysfunction.

peripheral nervous system neuron link

facial nerve link

Show evidence (1 reference)

PMID:39939082 SUPPORT Human Clinical

"Bell's palsy is acute weakness of the facial muscles associated with compression of cranial nerve VII."

This supports nerve compression as the mechanism linking facial nerve pathology to weakness of facial musculature.

Incomplete recovery with aberrant reinnervation

A minority of patients have incomplete recovery after the acute episode, with residual weakness or aberrant facial motor reinnervation leading to synkinesis.

peripheral nervous system neuron link

facial nerve link

Show evidence (2 references)

PMID:36397921 SUPPORT Human Clinical

"But there is always a risk of residual paresis after treatment or recovery, which may require medical help."

This supports persistent motor dysfunction in a subset of patients after the acute episode.

PMID:39939082 SUPPORT Human Clinical

"Oral corticosteroids improve recovery rates and antiviral medications reduce synkinesis."

This supports synkinesis as a recognized downstream sequela relevant to treatment decisions.

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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

5

Head and Neck 3

Facial weakness OBLIGATE Weakness of facial musculature (HP:0030319)

Show evidence (1 reference)

PMID:36397921 SUPPORT Human Clinical

"Bell's palsy, also known as "acute facial palsy of unknown cause", is a common cranial neuropathy leading to facial muscle paresis or complete paralysis characteristically on one side, occurring suddenly and may progress over 48 hours."

This directly supports acute unilateral peripheral facial weakness as the core phenotype of Bell's palsy.

Lagophthalmos FREQUENT Lagophthalmos (HP:0030001)

Show evidence (1 reference)

PMID:33088514 SUPPORT Human Clinical

"Bell's palsy is an idiopathic facial nerve paralysis which often presents with unilateral facial weakness commonly characterized by an inability to close the eye, disappearance of the nasolabial fold, and eyebrow drooping at the affected corner of the mouth."

This supports incomplete eye closure as a common acute manifestation of Bell's palsy.

Abnormal taste sensation OCCASIONAL Abnormality of taste sensation (HP:0000223)

Show evidence (1 reference)

PMID:33088514 SUPPORT Human Clinical

"There may also be decreased tearing, hyperacusis, and/or loss of taste sensation on the anterior two thirds of the tongue."

This supports abnormal taste sensation as a recognized Bell's palsy phenotype.

Nervous System 2

Hyperacusis OCCASIONAL Hyperacusis (HP:0010780)

Show evidence (1 reference)

PMID:33088514 SUPPORT Human Clinical

"There may also be decreased tearing, hyperacusis, and/or loss of taste sensation on the anterior two thirds of the tongue."

This supports hyperacusis as a recognized though non-universal clinical manifestation.

Facial synkinesis OCCASIONAL Facial synkinesis (HP:0034979)

Show evidence (1 reference)

PMID:39939082 SUPPORT Human Clinical

"Oral corticosteroids improve recovery rates and antiviral medications reduce synkinesis."

This supports facial synkinesis as a recognized sequela important enough to be targeted therapeutically.

🧬

Genetic Associations

1

Common susceptibility locus at 6p21.1 (Risk Factor)

Show evidence (1 reference)

PMID:33602968 SUPPORT Human Clinical

"Here, we report findings from a meta-analysis of genome-wide association studies uncovering the first unequivocal association with Bell's palsy (rs9357446-A; P = 6.79 × 10-23, OR = 1.23; Ncases = 4714, Ncontrols = 1,011,520)."

This supports a reproducible common-genetic susceptibility signal for Bell's palsy.

💊

Treatments

4

Oral corticosteroids

Action: pharmacotherapy MAXO:0000058

Early oral corticosteroid therapy is first-line treatment for new-onset Bell's palsy and improves the chance of complete recovery.

Show evidence (1 reference)

PMID:39939082 SUPPORT Human Clinical

"Oral corticosteroids improve recovery rates and antiviral medications reduce synkinesis."

This supports oral corticosteroids as the central evidence-backed acute therapy for Bell's palsy.

Adjunctive antiviral therapy

Action: pharmacotherapy MAXO:0000058

Antiviral therapy is sometimes added to corticosteroids, particularly in more severe acute Bell's palsy, with evidence suggesting improved recovery or reduced synkinesis in selected patients.

Mechanism Target:

Putative post-viral immune activation in the geniculate ganglion

Show evidence (1 reference)

PMID:27689547 SUPPORT Human Clinical

"The combination of steroid and antiviral treatment increases the possibility of recovery in moderately severe to complete acute Bell's palsy."

This supports antiviral therapy as a treatment strategy directed at the putative infection-linked inflammatory component of Bell's palsy.

Show evidence (2 references)

PMID:27689547 SUPPORT Human Clinical

"The combination of steroid and antiviral treatment increases the possibility of recovery in moderately severe to complete acute Bell's palsy."

This randomized trial supports benefit from adding antiviral therapy in moderate-to-severe acute Bell's palsy.

PMID:39939082 SUPPORT Human Clinical

"Oral corticosteroids improve recovery rates and antiviral medications reduce synkinesis."

This supports a role for antivirals in reducing sequelae such as synkinesis.

Facial physical therapy

Action: physical therapy MAXO:0000011

Facial neuromuscular retraining and related physical therapy approaches can help patients with persistent weakness, asymmetry, or functional sequelae after the acute phase.

Show evidence (1 reference)

PMID:39939082 SUPPORT Human Clinical

"Physical therapy and Botox injections can help patients with persistent symptoms."

This supports physical therapy as a symptomatic treatment for persistent Bell's palsy deficits.

Botulinum toxin type A therapy

Action: botulinum toxin type A therapy MAXO:0009016

Botulinum toxin injections can be used in patients with persistent facial synkinesis or troublesome asymmetry after incomplete recovery.

Target Phenotypes: facial synkinesis ↗

Show evidence (1 reference)

PMID:39939082 SUPPORT Human Clinical

"Physical therapy and Botox injections can help patients with persistent symptoms."

This supports botulinum toxin treatment for persistent Bell's palsy sequelae such as synkinesis and asymmetry.

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Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from Bell's palsy:

Stroke Not Yet Curated MONDO:0005098

Overlapping Features Acute facial weakness from stroke can mimic Bell's palsy, but Bell's palsy produces a peripheral facial weakness pattern and is diagnosed only after alternative causes are excluded.

Distinguishing Features

Bell's palsy causes peripheral facial weakness, whereas stroke more often produces a central pattern with relative forehead sparing.
Bell's palsy is diagnosed clinically only after excluding other causes of facial weakness such as stroke.

Show evidence (1 reference)

PMID:39939082 SUPPORT Human Clinical

"Diagnosis is based on a thorough history and physical examination, with careful attention to exclude other causes of facial weakness, such as stroke or Lyme disease."

This directly supports stroke as an important alternative diagnosis that must be excluded.

Lyme disease MONDO:0019632

Overlapping Features Lyme neuroborreliosis can present with acute facial palsy and should be considered in the appropriate epidemiologic setting.

Distinguishing Features

Lyme disease is suggested by tick exposure, compatible geography, systemic symptoms, or other evidence of Borrelia infection.
Bell's palsy remains idiopathic after focused evaluation and exclusion of alternative infectious causes.

Show evidence (1 reference)

PMID:39939082 SUPPORT Human Clinical

"Diagnosis is based on a thorough history and physical examination, with careful attention to exclude other causes of facial weakness, such as stroke or Lyme disease."

This directly supports Lyme disease as a clinically important differential diagnosis for Bell's palsy.

Melkersson-Rosenthal syndrome MONDO:0007969

Overlapping Features Melkersson-Rosenthal syndrome can include facial paralysis, but it is distinguished by recurrent disease together with lip or facial edema and a fissured tongue.

Distinguishing Features

Melkersson-Rosenthal syndrome includes additional recurrent orofacial edema and fissured tongue rather than isolated acute idiopathic facial weakness.
Bell's palsy is typically an isolated acute peripheral facial palsy without the classic granulomatous syndrome features.

Show evidence (1 reference)

PMID:40255708 SUPPORT Human Clinical

"CG can occur as an isolated condition or as part of Melkersson-Rosenthal syndrome, which also includes facial paralysis and a fissured tongue."

This supports Melkersson-Rosenthal syndrome as a facial-paralysis differential distinguished by additional syndrome-defining features.

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Related Datasets

1

A meta-analysis uncovers the first sequence variant conferring risk of Bell's palsy DOI:10.1038/s41598-021-82736-w

Bell's palsy genome-wide association meta-analysis spanning four cohorts, used to identify the first robust common susceptibility locus for the disorder.

human GWAS n=1016234

Conditions: Bell's palsy facial paralysis genetics

PMID:33602968

The study combines four cohorts from Iceland, the UK, Denmark, and Finland to define Bell's palsy genetic susceptibility.

Show evidence (1 reference)

PMID:33602968 SUPPORT Human Clinical

"Here, we report findings from a meta-analysis of genome-wide association studies uncovering the first unequivocal association with Bell's palsy (rs9357446-A; P = 6.79 × 10-23, OR = 1.23; Ncases = 4714, Ncontrols = 1,011,520)."

This supports the cohort size and GWAS design of a major Bell's palsy genetics dataset.

🔬

Clinical Trials

2

NCT03508440 PHASE_II COMPLETED

Completed interventional phase 2/3 study testing whether intratympanic dexamethasone injections added to standard oral steroid treatment improve recovery in acute moderate-to-severe Bell's palsy.

Target Phenotypes: acute unilateral peripheral facial weakness ↗

Show evidence (1 reference)

clinicaltrials:NCT03508440 SUPPORT Human Clinical

"There are indications that the use of intratympanic injections, in addition to the oral steroids, will speed up the recovery rate of the facial nerve paralysis, as well as improve the complete recovery of the facial nerve paralysis."

This ClinicalTrials.gov record supports a Bell's palsy trial evaluating adjunct intratympanic steroid therapy to improve recovery.

NCT05846217 NOT_APPLICABLE COMPLETED

Completed randomized controlled trial evaluating photobiomodulation with Multiwave Locked System laser therapy for Bell's palsy persisting longer than 8 weeks.

Target Phenotypes: acute unilateral peripheral facial weakness ↗

Show evidence (1 reference)

clinicaltrials:NCT05846217 SUPPORT Human Clinical

"OBJECTIVE: To determine whether photobiomodulation therapy by class IV Multiwave Locked System laser treatment could relieve symptoms in patients with Bell's palsy with a duration of greater than 8 weeks."

This ClinicalTrials.gov record supports an interventional trial for persistent Bell's palsy symptoms using photobiomodulation therapy.

{ }

Source YAML

click to show

name: Bell's palsy
creation_date: "2026-03-18T15:33:50Z"
updated_date: "2026-03-18T17:46:50Z"
category: Complex
categories:
  - Neurological Disease
  - Cranial Neuropathy
description: >-
  Bell's palsy is an acute idiopathic peripheral facial neuropathy causing
  sudden unilateral weakness of the muscles of facial expression. The leading
  mechanistic model invokes post-viral inflammatory edema of cranial nerve VII
  at the geniculate ganglion and within the narrow facial canal, producing
  transient compression, conduction block, and facial muscle dysfunction.
disease_term:
  preferred_term: Bell's palsy
  term:
    id: MONDO:0005665
    label: Bell's palsy
synonyms:
  - idiopathic peripheral facial palsy
  - idiopathic facial nerve palsy
definitions:
  - name: Clinical syndrome definition for Bell's palsy
    definition_type: CASE_DEFINITION
    description: >-
      Bell's palsy is acute unilateral peripheral facial weakness or paralysis
      of unknown cause that develops over hours to two days.
    scope: General clinical framing of acute idiopathic peripheral facial palsy
    evidence:
      - reference: PMID:39939082
        reference_title: "Bell's Palsy."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Bell's palsy is acute weakness of the facial muscles associated with compression of cranial nerve VII."
        explanation: This directly supports the standard clinical definition of Bell's palsy as acute cranial-nerve-VII-mediated facial weakness.
      - reference: PMID:36397921
        reference_title: "Bell's Palsy: A Review."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Bell's palsy, also known as \"acute facial palsy of unknown cause\", is a common cranial neuropathy leading to facial muscle paresis or complete paralysis characteristically on one side, occurring suddenly and may progress over 48 hours."
        explanation: This supports the idiopathic acute cranial-neuropathy framing and typical time course.
mappings:
  icd10cm_mappings:
    - term:
        id: ICD10CM:G51.0
        label: Bell's palsy
      mapping_predicate: skos:exactMatch
      mapping_source: ICD-10-CM
      mapping_justification: Bell's palsy is represented directly by ICD-10-CM code G51.0.
  mondo_mappings:
    - term:
        id: MONDO:0005665
        label: Bell's palsy
      mapping_predicate: skos:exactMatch
      mapping_source: MONDO
      mapping_justification: Primary MONDO disease identifier for this Bell's palsy entry.
classifications:
  harrisons_chapter:
    - classification_value: nervous system disorder
      evidence:
        - reference: PMID:39939082
          reference_title: "Bell's Palsy."
          supports: SUPPORT
          evidence_source: HUMAN_CLINICAL
          snippet: "Bell's palsy is acute weakness of the facial muscles associated with compression of cranial nerve VII."
          explanation: This supports classification of Bell's palsy as a nervous system disorder centered on cranial nerve VII dysfunction.
parents:
  - Neurological Disorder
  - Peripheral Neuropathy
prevalence:
  - subtype: General
    population: General population
    percentage: 20-30 per 100,000 per year
    notes: >-
      Bell's palsy is relatively common among cranial mononeuropathies, with
      modern review literature consistently citing an annual incidence around
      20-30 cases per 100,000 people.
    evidence:
      - reference: PMID:39939082
        reference_title: "Bell's Palsy."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "The annual incidence is 20 to 30 per 100,000."
        explanation: This provides a direct contemporary incidence estimate for Bell's palsy in the general population.
epidemiology:
  - name: Age and clinical risk-factor distribution
    description: >-
      Bell's palsy can occur at any age, but incidence rises with age and is
      increased in people with diabetes, hypertension, obesity, pregnancy, and
      recent upper respiratory tract infection.
    factors:
      - age
      - diabetes
      - hypertension
      - pregnancy
      - obesity
      - upper respiratory tract infection
    evidence:
      - reference: PMID:36397921
        reference_title: "Bell's Palsy: A Review."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Both sexes are equally affected, and though no age is immune, its incidence rises with increasing age."
        explanation: This supports the age distribution of Bell's palsy as a disorder that can occur broadly but becomes more common with increasing age.
      - reference: PMID:36397921
        reference_title: "Bell's Palsy: A Review."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "The risk is high in diabetics, hypertensives, women who are pregnant, obese, and people with upper respiratory tract infections."
        explanation: This supports several commonly cited clinical risk groups and comorbidity associations.
  - name: Migraine-associated risk enrichment
    description: >-
      Population-based longitudinal data suggest that migraine is associated
      with a modestly increased subsequent risk of Bell's palsy, especially in
      adults aged 30 to under 60 years.
    factors:
      - migraine
    evidence:
      - reference: PMID:31124964
        reference_title: "Increased risk of Bell palsy in patient with migraine: A longitudinal follow-up study."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Migraine increased the risk of Bell palsy in the total population."
        explanation: This directly supports migraine as an epidemiologic risk marker associated with later Bell's palsy.
  - name: Recurrence burden
    description: >-
      Recurrence is uncommon but recognized, affecting a minority of patients
      after an initial Bell's palsy episode.
    evidence:
      - reference: PMID:33088514
        reference_title: "New onset of Bell's palsy in a patient with West Nile Encephalitis."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "8% to 12% recurrence rate."
        explanation: This supports recurrence as a real but minority long-term outcome of Bell's palsy without relying on the same case report for general incidence framing.
progression:
  - phase: Acute onset phase
    notes: >-
      Facial weakness typically appears suddenly and progresses to maximal
      deficit over the first 48 hours.
    evidence:
      - reference: PMID:36397921
        reference_title: "Bell's Palsy: A Review."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Bell's palsy, also known as \"acute facial palsy of unknown cause\", is a common cranial neuropathy leading to facial muscle paresis or complete paralysis characteristically on one side, occurring suddenly and may progress over 48 hours."
        explanation: This supports the typical abrupt onset and short early progression window.
  - phase: Recovery and sequelae phase
    notes: >-
      Most patients recover spontaneously, but a minority develop residual
      weakness or synkinesis that persists beyond the acute phase.
    evidence:
      - reference: PMID:36397921
        reference_title: "Bell's Palsy: A Review."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Although the majority of patients recover spontaneously in less than three weeks even if they are not treated. But there is always a risk of residual paresis after treatment or recovery, which may require medical help."
        explanation: This supports the usual favorable recovery trajectory while documenting persistent deficits in a subset of patients.
      - reference: PMID:34640384
        reference_title: "Clinical Prognostic Factors Associated with Good Outcomes in Pediatric Bell's Palsy."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Our results showed that the most important factor influencing the complete recovery of Bell's palsy in children was the lower initial H-B grade at initial presentation."
        explanation: This pediatric cohort supports early clinical severity as an important prognostic determinant of recovery.
pathophysiology:
  - name: Putative post-viral immune activation in the geniculate ganglion
    description: >-
      Bell's palsy is widely modeled as a post-viral inflammatory neuropathy in
      which latent viral reactivation or other infection-related immune
      activation triggers inflammation around cranial nerve VII, particularly at
      the geniculate ganglion.
    evidence:
      - reference: PMID:33602968
        reference_title: "A meta-analysis uncovers the first sequence variant conferring risk of Bell's palsy."
        supports: PARTIAL
        evidence_source: HUMAN_CLINICAL
        snippet: "While the pathogenesis remains unknown, previous studies have implicated post-viral inflammation and resulting compression of the facial nerve."
        explanation: This supports post-viral inflammation as a leading but not definitively proven Bell's palsy mechanism.
      - reference: PMID:33088514
        reference_title: "New onset of Bell's palsy in a patient with West Nile Encephalitis."
        supports: PARTIAL
        evidence_source: HUMAN_CLINICAL
        snippet: "Even though the underlying pathophysiology remains elusive, Bell's palsy is thought to result due to virus-mediated inflammation resulting in swelling of the CN VII and its compression at the geniculate ganglion."
        explanation: This supports the commonly proposed geniculate-ganglion-centered viral inflammatory mechanism while making clear that it remains inferential.
    cell_types:
      - preferred_term: peripheral nervous system neuron
        term:
          id: CL:2000032
          label: peripheral nervous system neuron
      - preferred_term: Schwann cell
        term:
          id: CL:0002573
          label: Schwann cell
    biological_processes:
      - preferred_term: response to virus
        term:
          id: GO:0009615
          label: response to virus
      - preferred_term: inflammatory response
        term:
          id: GO:0006954
          label: inflammatory response
    locations:
      - preferred_term: geniculate ganglion
        term:
          id: UBERON:0001700
          label: geniculate ganglion
      - preferred_term: facial nerve
        term:
          id: UBERON:0001647
          label: facial nerve
    downstream:
      - target: Facial nerve edema within the facial canal
        evidence:
          - reference: PMID:33088514
            reference_title: "New onset of Bell's palsy in a patient with West Nile Encephalitis."
            supports: SUPPORT
            evidence_source: HUMAN_CLINICAL
            snippet: "Bell's palsy is thought to result due to virus-mediated inflammation resulting in swelling of the CN VII and its compression at the geniculate ganglion."
            explanation: This supports inflammatory immune activation as the upstream event leading to facial nerve swelling.
  - name: JAK-STAT-associated inflammatory signaling and immune-cell recruitment
    description: >-
      Emerging systems-biology analyses implicate inflammatory protein
      networks, immune-cell traits, and JAK-STAT-associated signaling as
      candidate amplifiers of local facial-nerve inflammation in Bell's palsy.
    evidence:
      - reference: PMID:40299566
        reference_title: "Exploring the Role of Inflammation and Metabolites in Bell's Palsy and Potential Treatment Strategies."
        supports: PARTIAL
        evidence_source: COMPUTATIONAL
        snippet: "Our study identifies causal relationships between inflammatory proteins, metabolites, immune cells, and Bell's palsy, highlighting that the JAK/STAT signaling pathway may be a potentially critical target for intervention in Bell's palsy, and that its modulation may provide new directions and opportunities for therapeutic strategies and drug discovery for the disease."
        explanation: This computational Mendelian-randomization and network-analysis study supports JAK/STAT-centered inflammatory signaling as a plausible mechanistic contributor, but not yet a definitive established pathway in human Bell's palsy.
    biological_processes:
      - preferred_term: JAK-STAT cascade
        term:
          id: GO:0007259
          label: cell surface receptor signaling pathway via JAK-STAT
      - preferred_term: inflammatory response
        term:
          id: GO:0006954
          label: inflammatory response
    downstream:
      - target: Facial nerve edema within the facial canal
        evidence:
          - reference: PMID:40299566
            reference_title: "Exploring the Role of Inflammation and Metabolites in Bell's Palsy and Potential Treatment Strategies."
            supports: PARTIAL
            evidence_source: COMPUTATIONAL
            snippet: "Our study identifies causal relationships between inflammatory proteins, metabolites, immune cells, and Bell's palsy, highlighting that the JAK/STAT signaling pathway may be a potentially critical target for intervention in Bell's palsy, and that its modulation may provide new directions and opportunities for therapeutic strategies and drug discovery for the disease."
            explanation: This supports inflammatory signaling as a plausible upstream contributor to the local nerve inflammation and edema modeled in Bell's palsy.
  - name: Facial nerve edema within the facial canal
    description: >-
      Inflammatory swelling of the facial nerve develops within the rigid
      Fallopian canal, a confined anatomic space that limits expansion and
      promotes secondary entrapment injury.
    evidence:
      - reference: PMID:33088514
        reference_title: "New onset of Bell's palsy in a patient with West Nile Encephalitis."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Bell's palsy is thought to result due to virus-mediated inflammation resulting in swelling of the CN VII and its compression at the geniculate ganglion."
        explanation: This directly supports facial nerve swelling as a central mechanistic event in Bell's palsy.
    cell_types:
      - preferred_term: Schwann cell
        term:
          id: CL:0002573
          label: Schwann cell
    biological_processes:
      - preferred_term: inflammatory response
        term:
          id: GO:0006954
          label: inflammatory response
    locations:
      - preferred_term: facial nerve
        term:
          id: UBERON:0001647
          label: facial nerve
    downstream:
      - target: Intracanalicular compression and conduction block of cranial nerve VII
        evidence:
          - reference: PMID:33088514
            reference_title: "New onset of Bell's palsy in a patient with West Nile Encephalitis."
            supports: SUPPORT
            evidence_source: HUMAN_CLINICAL
            snippet: "Bell's palsy is thought to result due to virus-mediated inflammation resulting in swelling of the CN VII and its compression at the geniculate ganglion."
            explanation: This supports facial nerve edema as the direct upstream cause of compression-related dysfunction.
  - name: Intracanalicular compression and conduction block of cranial nerve VII
    description: >-
      Entrapment of the swollen facial nerve impairs neural conduction and
      produces acute lower motor neuron facial dysfunction.
    evidence:
      - reference: PMID:39939082
        reference_title: "Bell's Palsy."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Bell's palsy is acute weakness of the facial muscles associated with compression of cranial nerve VII."
        explanation: This supports nerve compression as the mechanism linking facial nerve pathology to weakness of facial musculature.
    cell_types:
      - preferred_term: peripheral nervous system neuron
        term:
          id: CL:2000032
          label: peripheral nervous system neuron
    locations:
      - preferred_term: facial nerve
        term:
          id: UBERON:0001647
          label: facial nerve
    downstream:
      - target: Facial weakness
        evidence:
          - reference: PMID:33088514
            reference_title: "New onset of Bell's palsy in a patient with West Nile Encephalitis."
            supports: SUPPORT
            evidence_source: HUMAN_CLINICAL
            snippet: "Bell's palsy is an idiopathic facial nerve paralysis which often presents with unilateral facial weakness commonly characterized by an inability to close the eye, disappearance of the nasolabial fold, and eyebrow drooping at the affected corner of the mouth."
            explanation: This supports facial nerve conduction failure as the cause of unilateral weakness of facial musculature.
      - target: Lagophthalmos
        evidence:
          - reference: PMID:33088514
            reference_title: "New onset of Bell's palsy in a patient with West Nile Encephalitis."
            supports: SUPPORT
            evidence_source: HUMAN_CLINICAL
            snippet: "Bell's palsy is an idiopathic facial nerve paralysis which often presents with unilateral facial weakness commonly characterized by an inability to close the eye, disappearance of the nasolabial fold, and eyebrow drooping at the affected corner of the mouth."
            explanation: This supports impaired eyelid closure as a downstream consequence of acute facial nerve dysfunction.
      - target: Abnormal taste sensation
        evidence:
          - reference: PMID:33088514
            reference_title: "New onset of Bell's palsy in a patient with West Nile Encephalitis."
            supports: SUPPORT
            evidence_source: HUMAN_CLINICAL
            snippet: "There may also be decreased tearing, hyperacusis, and/or loss of taste sensation on the anterior two thirds of the tongue."
            explanation: This supports disturbed taste sensation as a downstream manifestation of facial nerve involvement.
      - target: Hyperacusis
        evidence:
          - reference: PMID:33088514
            reference_title: "New onset of Bell's palsy in a patient with West Nile Encephalitis."
            supports: SUPPORT
            evidence_source: HUMAN_CLINICAL
            snippet: "There may also be decreased tearing, hyperacusis, and/or loss of taste sensation on the anterior two thirds of the tongue."
            explanation: This supports hyperacusis as a downstream manifestation of facial nerve dysfunction.
  - name: Incomplete recovery with aberrant reinnervation
    description: >-
      A minority of patients have incomplete recovery after the acute episode,
      with residual weakness or aberrant facial motor reinnervation leading to
      synkinesis.
    evidence:
      - reference: PMID:36397921
        reference_title: "Bell's Palsy: A Review."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "But there is always a risk of residual paresis after treatment or recovery, which may require medical help."
        explanation: This supports persistent motor dysfunction in a subset of patients after the acute episode.
      - reference: PMID:39939082
        reference_title: "Bell's Palsy."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Oral corticosteroids improve recovery rates and antiviral medications reduce synkinesis."
        explanation: This supports synkinesis as a recognized downstream sequela relevant to treatment decisions.
    cell_types:
      - preferred_term: peripheral nervous system neuron
        term:
          id: CL:2000032
          label: peripheral nervous system neuron
    locations:
      - preferred_term: facial nerve
        term:
          id: UBERON:0001647
          label: facial nerve
    downstream:
      - target: Facial synkinesis
        evidence:
          - reference: PMID:39939082
            reference_title: "Bell's Palsy."
            supports: SUPPORT
            evidence_source: HUMAN_CLINICAL
            snippet: "Oral corticosteroids improve recovery rates and antiviral medications reduce synkinesis."
            explanation: This supports facial synkinesis as a clinically meaningful sequela of incomplete recovery.
phenotypes:
  - name: Facial weakness
    category: Neurological
    frequency: OBLIGATE
    description: >-
      Acute unilateral lower motor neuron weakness of the muscles of facial
      expression is the defining phenotype of Bell's palsy.
    phenotype_term:
      preferred_term: acute unilateral peripheral facial weakness
      term:
        id: HP:0030319
        label: Weakness of facial musculature
    evidence:
      - reference: PMID:36397921
        reference_title: "Bell's Palsy: A Review."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Bell's palsy, also known as \"acute facial palsy of unknown cause\", is a common cranial neuropathy leading to facial muscle paresis or complete paralysis characteristically on one side, occurring suddenly and may progress over 48 hours."
        explanation: This directly supports acute unilateral peripheral facial weakness as the core phenotype of Bell's palsy.
  - name: Lagophthalmos
    category: Ophthalmologic
    frequency: FREQUENT
    description: >-
      Incomplete eyelid closure is common during the acute phase because of
      facial muscle weakness and creates risk of ocular surface exposure.
    phenotype_term:
      preferred_term: lagophthalmos
      term:
        id: HP:0030001
        label: Lagophthalmos
    evidence:
      - reference: PMID:33088514
        reference_title: "New onset of Bell's palsy in a patient with West Nile Encephalitis."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Bell's palsy is an idiopathic facial nerve paralysis which often presents with unilateral facial weakness commonly characterized by an inability to close the eye, disappearance of the nasolabial fold, and eyebrow drooping at the affected corner of the mouth."
        explanation: This supports incomplete eye closure as a common acute manifestation of Bell's palsy.
  - name: Abnormal taste sensation
    category: Neurological
    frequency: OCCASIONAL
    description: >-
      Bell's palsy can impair taste sensation over the anterior tongue because
      facial nerve dysfunction affects the chorda tympani pathway.
    phenotype_term:
      preferred_term: loss of taste sensation
      term:
        id: HP:0000223
        label: Abnormality of taste sensation
    evidence:
      - reference: PMID:33088514
        reference_title: "New onset of Bell's palsy in a patient with West Nile Encephalitis."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "There may also be decreased tearing, hyperacusis, and/or loss of taste sensation on the anterior two thirds of the tongue."
        explanation: This supports abnormal taste sensation as a recognized Bell's palsy phenotype.
  - name: Hyperacusis
    category: Auditory
    frequency: OCCASIONAL
    description: >-
      Heightened sound sensitivity can occur when facial nerve dysfunction
      impairs stapedius muscle function.
    phenotype_term:
      preferred_term: hyperacusis
      term:
        id: HP:0010780
        label: Hyperacusis
    evidence:
      - reference: PMID:33088514
        reference_title: "New onset of Bell's palsy in a patient with West Nile Encephalitis."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "There may also be decreased tearing, hyperacusis, and/or loss of taste sensation on the anterior two thirds of the tongue."
        explanation: This supports hyperacusis as a recognized though non-universal clinical manifestation.
  - name: Facial synkinesis
    category: Neurological
    frequency: OCCASIONAL
    description: >-
      Some patients develop persistent involuntary linked facial movements as a
      sequela of incomplete recovery and aberrant facial motor reinnervation.
    phenotype_term:
      preferred_term: facial synkinesis
      term:
        id: HP:0034979
        label: Facial synkinesis
    evidence:
      - reference: PMID:39939082
        reference_title: "Bell's Palsy."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Oral corticosteroids improve recovery rates and antiviral medications reduce synkinesis."
        explanation: This supports facial synkinesis as a recognized sequela important enough to be targeted therapeutically.
genetic:
  - name: Common susceptibility locus at 6p21.1
    association: Risk Factor
    notes: >-
      Genome-wide association evidence supports a common Bell's palsy risk
      locus at 6p21.1, but the exact causal gene at the locus remains
      unresolved.
    evidence:
      - reference: PMID:33602968
        reference_title: "A meta-analysis uncovers the first sequence variant conferring risk of Bell's palsy."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Here, we report findings from a meta-analysis of genome-wide association studies uncovering the first unequivocal association with Bell's palsy (rs9357446-A; P = 6.79 × 10-23, OR = 1.23; Ncases = 4714, Ncontrols = 1,011,520)."
        explanation: This supports a reproducible common-genetic susceptibility signal for Bell's palsy.
diagnosis:
  - name: Clinical history and neurologic physical examination
    description: >-
      Diagnosis is primarily clinical and is based on focused history and
      physical examination demonstrating acute unilateral peripheral facial
      weakness while excluding alternative causes such as stroke or Lyme
      disease.
    diagnosis_term:
      preferred_term: physical examination
      term:
        id: MAXO:0000527
        label: physical examination
    evidence:
      - reference: PMID:39939082
        reference_title: "Bell's Palsy."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Diagnosis is based on a thorough history and physical examination, with careful attention to exclude other causes of facial weakness, such as stroke or Lyme disease."
        explanation: This directly supports diagnosis by focused clinical evaluation and exclusion of key mimics.
  - name: Electromyography in severe or persistent cases
    description: >-
      Electromyography can help assess severity and recovery potential in
      patients with severe Bell's palsy or prolonged deficits.
    diagnosis_term:
      preferred_term: electromyography procedure
      term:
        id: MAXO:0035091
        label: electromyography procedure
    evidence:
      - reference: clinicaltrials:NCT02328079
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "EMG was done for facial muscles of both sides beside measuring facial nerve excitability to determine the excitation threshold by recording the minimum electrical stimulus required to produce visible muscle contraction."
        explanation: This supports use of EMG as part of structured evaluation in acute Bell's palsy studies.
  - name: Nerve conduction study for prognostic assessment
    description: >-
      Nerve conduction testing can be used to quantify facial nerve dysfunction
      and identify patients at higher risk for poor recovery.
    diagnosis_term:
      preferred_term: nerve conduction study
      term:
        id: MAXO:0035059
        label: nerve conduction study
    evidence:
      - reference: clinicaltrials:NCT02328079
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Nerve conduction study of facial nerves of both sides using concentric needle electrode."
        explanation: This supports nerve conduction study as an electrophysiologic assessment method used in Bell's palsy prognosis studies.
treatments:
  - name: Oral corticosteroids
    description: >-
      Early oral corticosteroid therapy is first-line treatment for new-onset
      Bell's palsy and improves the chance of complete recovery.
    treatment_term:
      preferred_term: pharmacotherapy
      term:
        id: MAXO:0000058
        label: pharmacotherapy
      qualifiers:
        - predicate:
            preferred_term: route of administration
            term:
              id: NCIT:C38114
              label: Route of Administration
          value:
            preferred_term: oral route of administration
            term:
              id: NCIT:C38288
              label: Oral Route of Administration
        - predicate:
            preferred_term: therapeutic agent
            term:
              id: NCIT:C2259
              label: Pharmacologic Substance
          value:
            preferred_term: prednisone
            term:
              id: CHEBI:8382
              label: prednisone
    evidence:
      - reference: PMID:39939082
        reference_title: "Bell's Palsy."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Oral corticosteroids improve recovery rates and antiviral medications reduce synkinesis."
        explanation: This supports oral corticosteroids as the central evidence-backed acute therapy for Bell's palsy.
  - name: Adjunctive antiviral therapy
    description: >-
      Antiviral therapy is sometimes added to corticosteroids, particularly in
      more severe acute Bell's palsy, with evidence suggesting improved
      recovery or reduced synkinesis in selected patients.
    treatment_term:
      preferred_term: pharmacotherapy
      term:
        id: MAXO:0000058
        label: pharmacotherapy
      qualifiers:
        - predicate:
            preferred_term: route of administration
            term:
              id: NCIT:C38114
              label: Route of Administration
          value:
            preferred_term: oral route of administration
            term:
              id: NCIT:C38288
              label: Oral Route of Administration
        - predicate:
            preferred_term: therapeutic agent
            term:
              id: NCIT:C2259
              label: Pharmacologic Substance
          value:
            preferred_term: acyclovir
            term:
              id: CHEBI:2453
              label: acyclovir
    target_mechanisms:
      - target: Putative post-viral immune activation in the geniculate ganglion
        evidence:
          - reference: PMID:27689547
            reference_title: "Steroid/Antiviral for the treatment of Bell's palsy: Double blind randomized clinical trial."
            supports: SUPPORT
            evidence_source: HUMAN_CLINICAL
            snippet: "The combination of steroid and antiviral treatment increases the possibility of recovery in moderately severe to complete acute Bell's palsy."
            explanation: This supports antiviral therapy as a treatment strategy directed at the putative infection-linked inflammatory component of Bell's palsy.
    evidence:
      - reference: PMID:27689547
        reference_title: "Steroid/Antiviral for the treatment of Bell's palsy: Double blind randomized clinical trial."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "The combination of steroid and antiviral treatment increases the possibility of recovery in moderately severe to complete acute Bell's palsy."
        explanation: This randomized trial supports benefit from adding antiviral therapy in moderate-to-severe acute Bell's palsy.
      - reference: PMID:39939082
        reference_title: "Bell's Palsy."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Oral corticosteroids improve recovery rates and antiviral medications reduce synkinesis."
        explanation: This supports a role for antivirals in reducing sequelae such as synkinesis.
  - name: Facial physical therapy
    description: >-
      Facial neuromuscular retraining and related physical therapy approaches
      can help patients with persistent weakness, asymmetry, or functional
      sequelae after the acute phase.
    treatment_term:
      preferred_term: physical therapy
      term:
        id: MAXO:0000011
        label: physical therapy
    evidence:
      - reference: PMID:39939082
        reference_title: "Bell's Palsy."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Physical therapy and Botox injections can help patients with persistent symptoms."
        explanation: This supports physical therapy as a symptomatic treatment for persistent Bell's palsy deficits.
  - name: Botulinum toxin type A therapy
    description: >-
      Botulinum toxin injections can be used in patients with persistent facial
      synkinesis or troublesome asymmetry after incomplete recovery.
    treatment_term:
      preferred_term: botulinum toxin type A therapy
      term:
        id: MAXO:0009016
        label: botulinum toxin type A therapy
    target_phenotypes:
      - preferred_term: facial synkinesis
        term:
          id: HP:0034979
          label: Facial synkinesis
    evidence:
      - reference: PMID:39939082
        reference_title: "Bell's Palsy."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Physical therapy and Botox injections can help patients with persistent symptoms."
        explanation: This supports botulinum toxin treatment for persistent Bell's palsy sequelae such as synkinesis and asymmetry.
differential_diagnoses:
  - name: Stroke
    disease_term:
      preferred_term: stroke disorder
      term:
        id: MONDO:0005098
        label: stroke disorder
    description: >-
      Acute facial weakness from stroke can mimic Bell's palsy, but Bell's
      palsy produces a peripheral facial weakness pattern and is diagnosed only
      after alternative causes are excluded.
    distinguishing_features:
      - Bell's palsy causes peripheral facial weakness, whereas stroke more often produces a central pattern with relative forehead sparing.
      - Bell's palsy is diagnosed clinically only after excluding other causes of facial weakness such as stroke.
    evidence:
      - reference: PMID:39939082
        reference_title: "Bell's Palsy."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Diagnosis is based on a thorough history and physical examination, with careful attention to exclude other causes of facial weakness, such as stroke or Lyme disease."
        explanation: This directly supports stroke as an important alternative diagnosis that must be excluded.
  - name: Lyme disease
    disease_term:
      preferred_term: Lyme disease
      term:
        id: MONDO:0019632
        label: Lyme disease
    description: >-
      Lyme neuroborreliosis can present with acute facial palsy and should be
      considered in the appropriate epidemiologic setting.
    distinguishing_features:
      - Lyme disease is suggested by tick exposure, compatible geography, systemic symptoms, or other evidence of Borrelia infection.
      - Bell's palsy remains idiopathic after focused evaluation and exclusion of alternative infectious causes.
    evidence:
      - reference: PMID:39939082
        reference_title: "Bell's Palsy."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Diagnosis is based on a thorough history and physical examination, with careful attention to exclude other causes of facial weakness, such as stroke or Lyme disease."
        explanation: This directly supports Lyme disease as a clinically important differential diagnosis for Bell's palsy.
  - name: Melkersson-Rosenthal syndrome
    disease_term:
      preferred_term: Melkersson-Rosenthal syndrome
      term:
        id: MONDO:0007969
        label: Melkersson-Rosenthal syndrome
    description: >-
      Melkersson-Rosenthal syndrome can include facial paralysis, but it is
      distinguished by recurrent disease together with lip or facial edema and a
      fissured tongue.
    distinguishing_features:
      - Melkersson-Rosenthal syndrome includes additional recurrent orofacial edema and fissured tongue rather than isolated acute idiopathic facial weakness.
      - Bell's palsy is typically an isolated acute peripheral facial palsy without the classic granulomatous syndrome features.
    evidence:
      - reference: PMID:40255708
        reference_title: "Cheilitis Granulomatosa: A Case Report of a Sarcoid Mimic."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "CG can occur as an isolated condition or as part of Melkersson-Rosenthal syndrome, which also includes facial paralysis and a fissured tongue."
        explanation: This supports Melkersson-Rosenthal syndrome as a facial-paralysis differential distinguished by additional syndrome-defining features.
clinical_trials:
  - name: NCT03508440
    phase: PHASE_II
    status: COMPLETED
    description: >-
      Completed interventional phase 2/3 study testing whether intratympanic
      dexamethasone injections added to standard oral steroid treatment improve
      recovery in acute moderate-to-severe Bell's palsy.
    target_phenotypes:
      - preferred_term: acute unilateral peripheral facial weakness
        term:
          id: HP:0030319
          label: Weakness of facial musculature
    evidence:
      - reference: clinicaltrials:NCT03508440
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "There are indications that the use of intratympanic injections, in addition to the oral steroids, will speed up the recovery rate of the facial nerve paralysis, as well as improve the complete recovery of the facial nerve paralysis."
        explanation: This ClinicalTrials.gov record supports a Bell's palsy trial evaluating adjunct intratympanic steroid therapy to improve recovery.
    notes: >-
      Current ClinicalTrials.gov metadata lists this as a completed phase 2/3
      trial; the schema stores a single phase value, so this entry uses
      PHASE_II and notes the combined designation.
  - name: NCT05846217
    phase: NOT_APPLICABLE
    status: COMPLETED
    description: >-
      Completed randomized controlled trial evaluating photobiomodulation with
      Multiwave Locked System laser therapy for Bell's palsy persisting longer
      than 8 weeks.
    target_phenotypes:
      - preferred_term: acute unilateral peripheral facial weakness
        term:
          id: HP:0030319
          label: Weakness of facial musculature
    evidence:
      - reference: clinicaltrials:NCT05846217
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "OBJECTIVE: To determine whether photobiomodulation therapy by class IV Multiwave Locked System laser treatment could relieve symptoms in patients with Bell's palsy with a duration of greater than 8 weeks."
        explanation: This ClinicalTrials.gov record supports an interventional trial for persistent Bell's palsy symptoms using photobiomodulation therapy.
references:
  - reference: PMID:33602968
    title: "A meta-analysis uncovers the first sequence variant conferring risk of Bell's palsy."
    findings: []
  - reference: PMID:35160337
    title: "Comparison of Medical and Surgical Treatment in Severe Bell's Palsy."
    findings: []
  - reference: PMID:33088514
    title: "New onset of Bell's palsy in a patient with West Nile Encephalitis."
    findings: []
  - reference: PMID:36397921
    title: "Bell's Palsy: A Review."
    findings: []
  - reference: PMID:39939082
    title: "Bell's Palsy."
    findings: []
  - reference: PMID:27689547
    title: "Steroid/Antiviral for the treatment of Bell's palsy: Double blind randomized clinical trial."
    findings: []
  - reference: PMID:37752723
    title: "Psychosocial functioning in patients with altered facial expression: a scoping review in five neurological diseases."
    findings: []
  - reference: PMID:38517799
    title: "Treatment Approaches for Altered Facial Expression: A Systematic Review in Facioscapulohumeral Muscular Dystrophy and Other Neurological Diseases."
    findings: []
  - reference: PMID:40255708
    title: "Cheilitis Granulomatosa: A Case Report of a Sarcoid Mimic."
    findings: []
  - reference: PMID:31124964
    title: "Increased risk of Bell palsy in patient with migraine: A longitudinal follow-up study."
    findings: []
  - reference: PMID:34640384
    title: "Clinical Prognostic Factors Associated with Good Outcomes in Pediatric Bell's Palsy."
    findings: []
  - reference: PMID:40299566
    title: "Exploring the Role of Inflammation and Metabolites in Bell's Palsy and Potential Treatment Strategies."
    findings: []
datasets:
  - accession: DOI:10.1038/s41598-021-82736-w
    title: A meta-analysis uncovers the first sequence variant conferring risk of Bell's palsy
    description: >-
      Bell's palsy genome-wide association meta-analysis spanning four cohorts,
      used to identify the first robust common susceptibility locus for the
      disorder.
    organism:
      preferred_term: human
      term:
        id: NCBITaxon:9606
        label: Homo sapiens
    data_type: GWAS
    sample_count: 1016234
    conditions:
      - Bell's palsy
      - facial paralysis genetics
    publication: PMID:33602968
    evidence:
      - reference: PMID:33602968
        reference_title: "A meta-analysis uncovers the first sequence variant conferring risk of Bell's palsy."
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: "Here, we report findings from a meta-analysis of genome-wide association studies uncovering the first unequivocal association with Bell's palsy (rs9357446-A; P = 6.79 × 10-23, OR = 1.23; Ncases = 4714, Ncontrols = 1,011,520)."
        explanation: This supports the cohort size and GWAS design of a major Bell's palsy genetics dataset.
    notes: >-
      The study combines four cohorts from Iceland, the UK, Denmark, and
      Finland to define Bell's palsy genetic susceptibility.