| Test/modality | What it assesses | Key findings (numbers/ORs/%) | Interpretation/role | Source (URL/date) |
|---|---|---|---|---|
| Cerebrospinal fluid (CSF) analysis | Pleocytosis, protein elevation, hypoglycorrhachia, oligoclonal bands | ESO guideline: hyperproteinorrachia and pleocytosis "do not have evidence supporting their use as diagnostic tools." In Utah cohort (n=44), secondary CNS vasculitis had more low CSF glucose (41.2% vs 8.7%, P=0.02) and unique OCBs (63.6% vs 0, P<0.01); normal CSF can occur. In Kharal 2024, each +1 CSF WBC/µL increased odds of PACNS vs ICAD by 47% (OR 1.47, 95% CI 1.04–2.07). (pqac-00000000, pqac-00000002, pqac-00000014) | Supportive but nonspecific; useful for differential diagnosis and, with imaging/clinical context, may increase suspicion for PACNS, but cannot confirm or exclude it alone. | ESO guideline: https://doi.org/10.1177/23969873231190431 (Oct 2023); Hoshina et al.: https://doi.org/10.1177/19418744231223283 (Dec 2024); Kharal et al.: https://doi.org/10.1212/cpj.0000000000200321 (Aug 2024) |
| Conventional brain MRI | Parenchymal injury patterns: infarcts, hemorrhage, white-matter lesions, enhancement, edema | ESO guideline: no neuroimaging pattern is specific for PACNS. Utah cohort: MRI abnormal in all cases (100%). D’Aniello 2024: DWI abnormalities matched vessel-wall enhancement territories in 77%. Agarwal 2024 biopsy-proven PCNSV series (n=56): parenchymal enhancement in 96.3% (52/54). (pqac-00000000, pqac-00000002, pqac-00000010, pqac-00000011) | Core first-line test to detect CNS injury and guide biopsy/imaging correlation, but findings are not pathognomonic. | ESO guideline: https://doi.org/10.1177/23969873231190431 (Oct 2023); Hoshina et al.: https://doi.org/10.1177/19418744231223283 (Dec 2024); D’Aniello et al.: https://doi.org/10.3390/diagnostics14090927 (Apr 2024); Agarwal et al.: https://doi.org/10.1038/s41598-024-55222-2 (Feb 2024) |
| Diffusion-weighted imaging (DWI) | Acute/subacute ischemic injury and lesion-territory correlation | D’Aniello 2024: DWI alterations corresponded to vessel-wall enhancement in 77% of patients. (pqac-00000010) | May reflect downstream ischemia/hypoperfusion or microembolization in territories of inflamed vessels; useful adjunct to vessel-wall imaging. | https://doi.org/10.3390/diagnostics14090927 (Apr 2024) |
| Digital subtraction angiography (DSA) / vascular imaging | Vessel caliber abnormalities, beading, stenosis/occlusion; medium/large-vessel disease | ESO guideline: non-invasive vascular imaging should be interpreted cautiously because of limited validation and different sensitivities vs DSA/histopathology. Utah cohort: vasculitic changes on vessel imaging in 33/44 (75%); 12 showed large–middle vessel and 21 middle–small vessel patterns. Agarwal 2024: venous-phase pseudophlebitic abnormalities/venulitis in 95%, but few arterial stenoses/occlusions in biopsy-proven small-vessel PCNSV. (pqac-00000000, pqac-00000002, pqac-00000011) | Helpful particularly for larger-vessel PACNS, but sensitivity is limited for small-vessel disease; a negative study does not exclude PACNS. | ESO guideline: https://doi.org/10.1177/23969873231190431 (Oct 2023); Hoshina et al.: https://doi.org/10.1177/19418744231223283 (Dec 2024); Agarwal et al.: https://doi.org/10.1038/s41598-024-55222-2 (Feb 2024) |
| High-resolution vessel-wall MRI (VW-MRI/VWI) | Arterial wall thickening and enhancement pattern (concentric vs eccentric; intense vs mild; vessel distribution) | D’Aniello 2024 (n=14): enhancement in 13/14; intense in 84.6%; concentric in 92.3%; anterior circulation in 69.2%, posterior 15.4%, both 15.4%; middle cerebral artery involved in 69.2%. Kharal 2024: C/E ratio >1 (OR 115.00), concentricity ≥50% (OR 55.00), irregularity <50% (OR 55.00) predicted PACNS vs ICAD. Authors note smooth, concentric, diffuse thickening/enhancement is typical, whereas eccentric/focal patterns suggest ICAD. (pqac-00000010, pqac-00000013, pqac-00000014) | Promising adjunct for differentiating inflammatory vasculopathy from atherosclerotic disease and for mapping affected territories; still not fully validated as a stand-alone diagnostic test. | D’Aniello et al.: https://doi.org/10.3390/diagnostics14090927 (Apr 2024); Kharal et al.: https://doi.org/10.1212/cpj.0000000000200321 (Aug 2024) |
| Susceptibility-weighted imaging (SWI) / GRE | Microhemorrhages, macrohemorrhages, hemorrhagic burden | Agarwal 2024 biopsy-proven PCNSV series: SWI hemorrhages in 96.4% (54/56); SWI described as five times more sensitive than T2* for hemorrhage detection; microbleeds may persist despite steroid treatment. D’Aniello dataset also reported SWI microbleeds in some PCNSV patients. (pqac-00000011, pqac-00000009) | Particularly valuable in small-vessel PCNSV where microhemorrhages are common; may be a useful minor diagnostic clue in the right clinical setting. | Agarwal et al.: https://doi.org/10.1038/s41598-024-55222-2 (Feb 2024); D’Aniello et al.: https://doi.org/10.3390/diagnostics14090927 (Apr 2024) |
| Contrast-enhanced T1-weighted MRI | Parenchymal, perivascular, leptomeningeal, pachymeningeal enhancement | Agarwal 2024: parenchymal enhancement in 96.3% (52/54); dot-linear pattern 87%, nodular 61.1%, perivascular 25.9%, patchy 16.7%; leptomeningeal enhancement 20.8%; pachymeningeal enhancement 7.6%. (pqac-00000011) | High-yield adjunct in biopsy-proven PCNSV; dot-linear/perivascular enhancement patterns may raise suspicion for PCNSV, especially with hemorrhagic SWI findings. | https://doi.org/10.1038/s41598-024-55222-2 (Feb 2024) |
| Clinical + CSF + quantitative VWMRI model | Composite diagnostic discrimination between PACNS and intracranial atherosclerotic disease (ICAD) | Kharal 2024 (n=59): encephalopathy OR 7.60 (95% CI 1.07–54.09), seizure OR 23.00 (1.77–298.45), headache significant in sensitivity analysis; CSF WBC OR 1.47 per 1 cell/µL; VWMRI metrics had strongest associations (C/E ratio >1 OR 115.00; concentricity ≥50% OR 55.00; irregularity <50% OR 55.00). (pqac-00000014) | Suggests PACNS diagnosis is strengthened by integrating syndrome features, inflammatory CSF, and vessel-wall geometry rather than relying on a single test. | https://doi.org/10.1212/cpj.0000000000200321 (Aug 2024) |
| Brain biopsy / histopathology | Direct confirmation of vasculitis and subtype/pattern (lymphocytic, granulomatous, necrotizing; exclusion of mimics) | ESO guideline and D’Aniello 2024: biopsy is the gold standard / required for definite PCNSV. D’Aniello notes biopsy can be nondiagnostic in up to 50% of cases. Hoshina 2024: PACNS biopsy positive in 7/10; inflammatory CAA 4/4. Agarwal 2024: 80 biopsies performed, 56/80 positive (70%) for PCNSV. (pqac-00000000, pqac-00000010, pqac-00000002, pqac-00000011) | Reference standard for definite diagnosis, especially crucial in small-vessel disease and tumor-like or mimic-rich presentations; false negatives remain an important limitation. | ESO guideline: https://doi.org/10.1177/23969873231190431 (Oct 2023); D’Aniello et al.: https://doi.org/10.3390/diagnostics14090927 (Apr 2024); Hoshina et al.: https://doi.org/10.1177/19418744231223283 (Dec 2024); Agarwal et al.: https://doi.org/10.1038/s41598-024-55222-2 (Feb 2024) |


*Table: This table summarizes the main 2023-2024 diagnostic tests used in CNS vasculitis/PACNS and the most relevant quantitative findings from recent guideline, cohort, and imaging studies. It is useful for comparing what each modality measures, how strongly it supports diagnosis, and where its limitations lie.*