VERSION: 1.1
CREATED: January 30, 2026
REVISED: January 30, 2026
STATUS: Draft - Pending Review
DIAGNOSIS: Primary Angiitis of the Central Nervous System (PACNS)
ICD-10: I67.7 (Cerebral arteritis, not elsewhere classified)
SYNONYMS: Primary CNS vasculitis, PACNS, primary angiitis of the CNS, cerebral vasculitis, granulomatous angiitis of the nervous system, isolated CNS vasculitis, central nervous system vasculitis, cerebral arteritis
SCOPE: Diagnosis, immunosuppressive treatment, and long-term monitoring of primary angiitis of the central nervous system (PACNS). Covers the classic triad (headache, cognitive decline, focal deficits), CSF analysis, MRI findings, conventional angiography, brain biopsy indications and limitations, induction immunosuppression (high-dose corticosteroids plus cyclophosphamide), maintenance immunosuppression (azathioprine, mycophenolate mofetil), and serial monitoring. Includes differentiation from reversible cerebral vasoconstriction syndrome (RCVS), secondary CNS vasculitis (SLE, sarcoidosis, infection-related), and other stroke mimics. For systemic vasculitis with CNS involvement, use the specific systemic vasculitis template. For RCVS, use "RCVS" template if available. For ischemic stroke management, use "Acute Ischemic Stroke" template.
PRIORITY KEY: STAT = Immediate | URGENT = Within hours | ROUTINE = Standard | EXT = Extended/atypical cases | - = Not applicable to this setting
Within 48-72 hours; URGENT if high clinical suspicion
Beading pattern (alternating stenosis and dilation); segmental narrowing; vessel wall irregularity; microaneurysms; occlusion; slow flow. NOTE: Normal angiogram does NOT exclude PACNS (sensitivity 40-90%; may miss small vessel disease)
When non-invasive workup is non-diagnostic; before committing to long-term immunosuppression
GOLD STANDARD for PACNS diagnosis. Granulomatous, lymphocytic, or necrotizing vasculitis of small/medium leptomeningeal and cortical vessels. Sensitivity 53-74% (patchy disease causes false negatives). Target biopsy to enhancing or abnormal MRI region if possible. Include leptomeninges + cortex (minimum 1 cm). Negative biopsy does not exclude PACNS
Indication: Essential for PACNS evaluation. CSF is abnormal in 80-90% of biopsy-confirmed PACNS cases. Normal CSF argues against PACNS but does not exclude it. Helps exclude infectious, neoplastic, and other inflammatory etiologies.
Timing: URGENT after CT head excludes mass effect; do not delay if clinical suspicion is high
Volume Required: 15-20 mL (extra for cytology, cultures, autoimmune panel)
Study
Rationale
Target Finding
ED
HOSP
OPD
ICU
Opening pressure
Elevated ICP assessment; pseudotumor mimic
10-20 cm H2O (may be mildly elevated)
URGENT
ROUTINE
ROUTINE
-
Cell count with differential (tubes 1 and 4) (CPT 89051)
Lymphocytic pleocytosis (WBC 10-150 cells/uL, lymphocyte-predominant); abnormal in ~80% of PACNS
URGENT
ROUTINE
ROUTINE
-
Protein (CPT 84157)
Elevated protein supports CNS inflammation; mildly elevated in most PACNS cases
Elevated (50-200 mg/dL typical in PACNS); markedly elevated suggests infection or carcinomatous meningitis
URGENT
ROUTINE
ROUTINE
-
Glucose with paired serum glucose (CPT 82945)
Low glucose suggests infection, TB, or malignancy; typically normal in PACNS
Normal (>60% of serum glucose); low glucose argues against PACNS
URGENT
ROUTINE
ROUTINE
-
Gram stain and bacterial culture (CPT 87205+87070)
Rule out bacterial meningitis
No organisms
URGENT
ROUTINE
ROUTINE
-
HSV 1/2 PCR (CPT 87529)
HSV encephalitis with vasculopathy
Negative
URGENT
ROUTINE
-
-
VZV PCR
VZV vasculopathy is a common infectious mimic of PACNS
Negative (VZV vasculopathy is an important treatable mimic)
URGENT
ROUTINE
ROUTINE
-
VZV IgG and IgM (CSF)
Intrathecal VZV antibody production; VZV vasculopathy may be PCR-negative but antibody-positive
Negative; CSF:serum ratio <1
-
ROUTINE
ROUTINE
-
Oligoclonal bands (CSF AND paired serum) (CPT 83916)
Intrathecal IgG synthesis; may be present in PACNS; MS/NMO overlap
May show CSF-specific bands (non-specific)
-
ROUTINE
ROUTINE
-
IgG index
Intrathecal antibody production
May be elevated in PACNS
-
ROUTINE
ROUTINE
-
Cytology (CPT 88104)
Exclude CNS lymphoma and carcinomatous meningitis
Negative for malignant cells
-
ROUTINE
ROUTINE
-
Flow cytometry
CNS lymphoma (intravascular lymphoma is a critical PACNS mimic)
Normal
-
ROUTINE
ROUTINE
-
AFB smear and culture (CPT 87116)
TB meningitis with vasculitis; endemic areas or immunocompromised
Negative
-
ROUTINE
ROUTINE
-
Fungal culture (CPT 87102)
Fungal meningitis (coccidioidomycosis, histoplasmosis, aspergillus) with vasculitis
Negative
-
ROUTINE
ROUTINE
-
VDRL (CSF) (CPT 86592)
Meningovascular syphilis is a treatable PACNS mimic
Non-reactive
-
ROUTINE
ROUTINE
-
Cryptococcal antigen (CPT 87327)
Cryptococcal meningitis in immunocompromised; basilar meningitis with vasculopathy
Negative
URGENT
ROUTINE
-
-
ACE level (CSF)
Neurosarcoidosis with granulomatous vasculitis
Normal
-
ROUTINE
ROUTINE
-
BioFire FilmArray ME Panel (CPT 87483)
Rapid multiplex PCR for common infectious meningitis/encephalitis pathogens
Negative
URGENT
ROUTINE
-
-
Beta-D-glucan (CSF)
Fungal CNS infection
Negative
-
EXT
EXT
-
Special Handling: VZV IgG/IgM in CSF requires paired serum sample drawn within 1 hour. Cytology requires rapid transport (<1 hour). Store extra CSF (frozen at -80C) for future testing. CSF cell count may normalize with treatment -- serial LP useful for monitoring.
Contraindications: Elevated ICP without imaging (obtain CT first); coagulopathy (INR >1.5, platelets <50K); skin infection at LP site; posterior fossa mass
Induction immunosuppression for confirmed or strongly suspected PACNS; reduces CNS inflammation and prevents further ischemic injury
1000 mg daily x 3-5 days :: IV :: daily :: 1000 mg IV daily for 3-5 days; infuse over 1-2 hours; begin upon strong clinical suspicion or biopsy-confirmed PACNS
Active untreated infection (especially VZV vasculopathy must be excluded); uncontrolled diabetes; active GI bleeding; psychosis from steroids
Glucose q6h (target <180 mg/dL); blood pressure; mood and sleep disturbance; GI prophylaxis; I/O
URGENT
STAT
-
STAT
Omeprazole (GI prophylaxis)
IV/PO
Prevention of steroid-induced GI bleeding during high-dose corticosteroid therapy
40 mg daily :: IV :: daily :: 40 mg IV or PO daily during high-dose steroid course and subsequent oral taper
Renal function daily; hydration status; crystal nephropathy prevention
STAT
STAT
-
STAT
Note: High-dose IV methylprednisolone should be initiated as soon as PACNS is strongly suspected clinically, even before biopsy confirmation. However, brain biopsy should be obtained BEFORE starting steroids whenever feasible, as steroids may obscure histopathologic findings. If clinical urgency mandates treatment before biopsy, document rationale. Empiric acyclovir should be given until VZV vasculopathy is excluded, as VZV vasculopathy is the most common infectious mimic.
375 mg/m2 weekly x 4 doses; 1000 mg x 2 doses (day 0 and day 14) :: IV :: per protocol :: 375 mg/m2 IV weekly x 4 doses OR 1000 mg IV x 2 doses (day 0, day 14); premedicate with methylprednisolone 100 mg IV, acetaminophen 650 mg PO, diphenhydramine 50 mg IV
Active hepatitis B; severe active infection; live vaccines within 4 weeks; PML history
Hepatitis B serology before first dose; CBC q2-4 weeks; immunoglobulin levels q3 months; CD19/CD20 B-cell counts q3 months; infusion reactions; PML surveillance
-
URGENT
ROUTINE
URGENT
Mycophenolate mofetil (CellCept) -- as alternative to azathioprine
PO
Maintenance immunosuppression alternative when azathioprine not tolerated; steroid-sparing agent; lower relapse rate in some series
500 mg BID; 1000 mg BID; 1500 mg BID :: PO :: BID :: Start 500 mg PO BID; increase to 1000 mg PO BID over 2-4 weeks; target 2000-3000 mg/day in divided doses
Pregnancy (Category D -- teratogenic); active infection; severe GI disease
CBC q2 weeks x 3 months, then monthly; LFTs; GI symptoms (diarrhea, nausea); infection surveillance; pregnancy prevention
-
-
ROUTINE
-
Methotrexate
PO/SC
Alternative maintenance therapy; particularly if granulomatous histology on biopsy; steroid-sparing agent
15-25 mg weekly :: PO :: weekly :: Start 15 mg PO/SC weekly; increase by 5 mg q2-4 weeks to target 20-25 mg weekly; give folic acid 1 mg PO daily (except on methotrexate day)
CBC q2-4 weeks x 3 months, then monthly; LFTs; renal function; pulmonary symptoms (pneumonitis); mucositis
-
-
ROUTINE
-
Tocilizumab
IV/SC
Refractory PACNS; failure of cyclophosphamide and rituximab; emerging evidence in CNS vasculitis
8 mg/kg IV q4 weeks; 162 mg SC weekly :: IV :: per protocol :: 8 mg/kg IV every 4 weeks (max 800 mg/dose) OR 162 mg SC weekly
Active infection; hepatic impairment (ALT >5x ULN); diverticulitis; concurrent live vaccines; neutropenia
CBC, LFTs, lipids q4-8 weeks; CRP may be unreliable (IL-6 blockade suppresses CRP); infection surveillance; GI perforation risk
-
EXT
EXT
-
Tumor necrosis factor inhibitor (infliximab)
IV
Refractory PACNS with granulomatous histology; case reports/small series suggest benefit
5 mg/kg at weeks 0, 2, 6 then q8 weeks :: IV :: per protocol :: 5 mg/kg IV at weeks 0, 2, 6; then every 8 weeks; premedicate
Active TB; decompensated heart failure (NYHA III/IV); demyelinating disease; active infection
TB screening before and annually; hepatitis B; CBC; LFTs; heart failure symptoms; infection surveillance
-
EXT
EXT
-
IVIG (intravenous immunoglobulin)
IV
Adjunctive therapy in refractory cases; may benefit PACNS with evidence of antibody-mediated component
0.4 g/kg daily x 5 days :: IV :: daily x 5 days :: 0.4 g/kg/day IV x 5 days (total 2 g/kg); infuse per weight-based protocol
IgA deficiency (anaphylaxis risk); recent thromboembolic event; renal failure
Renal function daily; headache (aseptic meningitis); thrombosis risk; volume overload; check IgA level before first dose
-
EXT
EXT
EXT
Note: Rituximab is increasingly used as second-line therapy in PACNS refractory to cyclophosphamide or as first-line for patients where cyclophosphamide is contraindicated. Evidence is limited to case series and retrospective cohorts. Tocilizumab and infliximab are considered experimental with only case reports supporting their use. The choice of second-line agent should be individualized based on histopathologic pattern (granulomatous vs. lymphocytic), comorbidities, and prior treatment response.
Standard induction therapy for biopsy-confirmed PACNS combined with corticosteroids; most evidence-based regimen per Calabrese/Mallek criteria
750 mg/m2 monthly x 3-6 months :: IV :: monthly :: 750 mg/m2 IV monthly x 3-6 months (typical 6 cycles); pre-hydrate with 1L NS; administer with MESNA for uroprotection; reduce dose for age >65, renal impairment, leukopenia
Pregnancy; active infection; bone marrow failure; bladder outlet obstruction; prior hemorrhagic cystitis; severe leukopenia
CBC weekly x 4 weeks after each cycle (nadir day 10-14); urinalysis each cycle; BMP; LFTs; fertility assessment; hemorrhagic cystitis prevention (MESNA + hydration); cumulative dose tracking (lifetime max ~36g concern for malignancy)
-
URGENT
ROUTINE
URGENT
Cyclophosphamide PO (alternative induction)
PO
Alternative to IV pulse dosing; some clinicians prefer daily oral for severe/refractory disease
2 mg/kg daily :: PO :: daily :: 2 mg/kg/day PO (max 200 mg/day); round to nearest 25 mg; duration 3-6 months then transition to maintenance
Same as IV cyclophosphamide
Same as IV cyclophosphamide; higher cumulative toxicity risk
CBC with differential weekly x 1 month, then q2 weeks; urinalysis monthly; adjust dose for WBC nadir 3000-4000; higher risk of bladder toxicity than IV pulse
-
URGENT
ROUTINE
URGENT
Prednisone (oral, following IV pulse)
PO
Oral corticosteroid taper following IV methylprednisolone pulse; bridge to steroid-sparing maintenance therapy
1 mg/kg daily; 0.75 mg/kg daily; 0.5 mg/kg daily :: PO :: daily :: Start 1 mg/kg/day PO (max 80 mg) after IV pulse; taper by 10 mg every 2 weeks to 20 mg/day; then taper by 5 mg every 2 weeks to 10 mg/day; then 2.5 mg every 2-4 weeks; target off steroids or lowest effective dose by 6-12 months
Active untreated infection; uncontrolled diabetes; psychosis from steroids; avascular necrosis
Glucose; blood pressure; bone density (DEXA if >3 months); weight; mood; cataracts; adrenal assessment on taper; osteoporosis prevention
-
ROUTINE
ROUTINE
-
Azathioprine (Imuran) -- maintenance
PO
Maintenance immunosuppression after cyclophosphamide induction; steroid-sparing agent; prevents relapse (relapse rate 25-30% in PACNS)
50 mg daily; 100 mg daily; 150 mg daily; 2 mg/kg daily :: PO :: daily :: Start 50 mg PO daily; increase by 50 mg every 2 weeks to target 2-3 mg/kg/day; minimum 18-24 months; many patients require indefinite therapy
TPMT deficiency (check genotype before starting); pregnancy (relative); active infection; concurrent allopurinol (reduce azathioprine dose by 75%)
TPMT genotype/activity before starting (mandatory); CBC q2 weeks x 2 months, then monthly; LFTs monthly x 3 months, then q3 months; pancreatitis symptoms; infection surveillance
-
-
ROUTINE
-
Mycophenolate mofetil (CellCept) -- maintenance
PO
Alternative maintenance immunosuppression; better GI tolerability than azathioprine in some patients; steroid-sparing agent
500 mg BID; 1000 mg BID; 1500 mg BID :: PO :: BID :: Start 500 mg PO BID; increase to 1000 mg PO BID over 2-4 weeks; target 2000-3000 mg/day; minimum 18-24 months
Pregnancy (Category D -- teratogenic); active infection; severe GI disease
CBC q2 weeks x 3 months, then monthly; LFTs; GI symptoms; infection surveillance; pregnancy prevention (two forms of contraception); mycophenolic acid levels if subtherapeutic response
-
-
ROUTINE
-
Note: The standard induction regimen for PACNS is high-dose IV corticosteroids followed by oral prednisone taper PLUS cyclophosphamide (IV pulse preferred over oral for lower cumulative toxicity). After 3-6 months of induction, transition to maintenance with azathioprine or mycophenolate mofetil. The total duration of maintenance therapy is typically 18-24 months minimum, but many patients require extended or indefinite immunosuppression due to 25-30% relapse rate. Monitor closely during steroid taper for clinical relapse.
Neurology (neuroimmunology or cerebrovascular specialist) for PACNS diagnosis confirmation, immunotherapy initiation, and long-term management
STAT
STAT
ROUTINE
STAT
Rheumatology for exclusion of systemic vasculitis and co-management of immunosuppressive therapy
URGENT
URGENT
ROUTINE
URGENT
Neurosurgery for brain biopsy when non-invasive workup is non-diagnostic and tissue diagnosis is required before committing to long-term immunosuppression
-
URGENT
ROUTINE
URGENT
Neuroradiology (interventional) for conventional cerebral angiography with vasculitis protocol and vessel wall imaging interpretation
-
URGENT
ROUTINE
URGENT
Infectious disease for exclusion of infectious vasculitis (VZV, syphilis, TB, fungal) and infection management during immunosuppression
URGENT
URGENT
ROUTINE
URGENT
Hematology/oncology if intravascular lymphoma or lymphomatoid granulomatosis suspected based on imaging or biopsy findings
-
URGENT
ROUTINE
-
Ophthalmology for fundoscopic examination to assess for retinal vasculitis (may support PACNS diagnosis) and steroid-related complications
-
ROUTINE
ROUTINE
-
Physical therapy for motor rehabilitation, gait training, and fall prevention given stroke-like deficits
-
ROUTINE
ROUTINE
ROUTINE
Occupational therapy for ADL assessment, cognitive rehabilitation, and adaptive strategies for functional recovery
-
ROUTINE
ROUTINE
ROUTINE
Speech-language pathology for swallowing evaluation and cognitive-linguistic therapy if aphasia or cognitive deficits present
-
ROUTINE
ROUTINE
ROUTINE
Neuropsychology for formal cognitive assessment given cognitive decline as a hallmark of PACNS; serial monitoring to track treatment response
-
-
ROUTINE
-
Social work for insurance navigation, disability resources, and family support during prolonged treatment course
-
ROUTINE
ROUTINE
-
Endocrinology for steroid-induced diabetes management if persistent hyperglycemia on corticosteroid therapy
-
ROUTINE
ROUTINE
-
Reproductive endocrinology/fertility specialist for fertility preservation counseling before cyclophosphamide initiation in patients of reproductive age
-
URGENT
ROUTINE
-
Palliative care for goals of care discussion in severe refractory disease or significant treatment complications
Return to ED immediately for new or worsening headache, sudden weakness, speech difficulty, vision changes, or seizures (may indicate disease relapse or new CNS ischemia)
Y
Y
Y
Do not stop corticosteroids abruptly as this may cause adrenal crisis and disease flare; taper must be supervised by neurology
Y
Y
Y
Report signs of infection promptly (fever >100.4F, cough, dysuria, rash, mouth sores) while on immunosuppressive therapy, as infection risk is significantly increased
-
Y
Y
Avoid live vaccines during immunosuppressive therapy (MMR, varicella, zoster live, yellow fever, intranasal influenza); inform all healthcare providers of immunosuppressed status
-
Y
Y
Do not drive until cleared by neurology due to risk of seizures and cognitive impairment
Y
Y
Y
Take cyclophosphamide in the morning with at least 2 liters of fluids daily to reduce bladder toxicity; empty bladder frequently
-
Y
Y
Expect prolonged treatment course (months to years); adherence to maintenance immunosuppression is essential to prevent relapse
-
Y
Y
Pregnancy must be avoided during cyclophosphamide and mycophenolate therapy; discuss contraception with neurology and OB/GYN before starting treatment
-
Y
Y
Wear medical alert bracelet identifying immunosuppressed status and PACNS diagnosis
-
Y
Y
Report any new neurological symptoms between scheduled visits, including subtle cognitive changes, as early relapse detection improves outcomes
-
Y
Y
Attend all scheduled follow-up appointments including MRI surveillance and laboratory monitoring for treatment safety
-
Y
Y
Avoid excessive sun exposure while on immunosuppressive therapy due to increased skin cancer risk; use sunscreen SPF 30+
Smoking cessation to reduce vascular risk and improve treatment response; smoking worsens endothelial dysfunction
-
Y
Y
Blood pressure target <140/90 mmHg (lower if tolerated) to reduce cerebrovascular risk and prevent further ischemic injury
-
Y
Y
Low-sodium diet to manage steroid-induced fluid retention and hypertension
-
Y
Y
Regular weight-bearing exercise as tolerated to maintain bone density during prolonged corticosteroid therapy; target 150 min/week of moderate activity
-
-
Y
Adequate hydration (minimum 2L/day) during cyclophosphamide therapy to prevent hemorrhagic cystitis
-
Y
Y
Pneumococcal (PCV20) and annual influenza vaccination (inactivated only) before or during immunosuppression when possible; avoid live vaccines
-
Y
Y
Home safety evaluation to remove fall hazards given potential for cognitive impairment and motor deficits
-
Y
Y
Cognitive stimulation activities (reading, puzzles, social engagement) to support cognitive recovery alongside formal rehabilitation
-
-
Y
Stress management and psychological support given chronic disease diagnosis; referral to support groups for vasculitis patients
-
-
Y
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SECTION B: REFERENCE (Expand as Needed)
═══════════════════════════════════════════════════════════
Thunderclap headache (acute, maximal at onset); diffuse segmental vasoconstriction that RESOLVES within 12 weeks; normal or near-normal CSF; triggers (vasoactive drugs, postpartum, exertion); younger females; typically self-limited
Repeat angiography at 12 weeks (RCVS normalizes; PACNS persists or worsens); CSF normal in RCVS vs. abnormal in 80% of PACNS; vessel wall imaging (smooth non-enhancing walls in RCVS vs. concentric enhancement in PACNS)
Atherosclerotic intracranial stenosis
Risk factors (age, hypertension, diabetes, hyperlipidemia); focal stenosis rather than multifocal beading; no CSF abnormalities; no systemic inflammation
CSF normal; conventional angiography pattern; vessel wall imaging (eccentric enhancement in atherosclerosis vs. concentric in vasculitis); vascular risk factors
Intravascular lymphoma
Multifocal strokes; progressive cognitive decline; B symptoms (fever, weight loss, night sweats); elevated LDH; skin involvement
Brain biopsy (gold standard -- atypical lymphocytes within vessel lumina); CSF flow cytometry; FDG-PET; skin biopsy if lesions present
CNS lymphoma
Mass lesion (often periventricular); ring enhancement; restricted diffusion; steroid-responsive (may mimic vasculitis improvement)
Brain biopsy; CSF cytology and flow cytometry; FDG-PET hypermetabolism; steroid response then rebound
Systemic vasculitis with CNS involvement (SLE, GPA, polyarteritis nodosa, Behcet)
Progressive bilateral ICA stenosis with basal collateral network (puff of smoke on angiography); children and young adults; East Asian predominance; no CSF abnormalities
MRA/DSA (bilateral ICA stenosis with moyamoya vessels); normal CSF; normal inflammatory markers; vessel wall imaging (no enhancement)
Cerebral amyloid angiopathy (CAA)
Lobar hemorrhages; older age (>65); cortical superficial siderosis; white matter changes; no CSF inflammation unless ABRA variant
MRI (lobar microbleeds on SWI/GRE); Boston criteria; biopsy if ABRA suspected (granulomatous vasculitis with amyloid)
Stable or improving neurologic examination; no new infarcts on follow-up imaging; tolerating oral medications; oral prednisone taper established; outpatient cyclophosphamide infusions arranged; follow-up with neurology within 1-2 weeks; caregiver education completed; no active seizures; adequate home support
Admit to floor (neurology/medicine)
New presentation with suspected PACNS requiring urgent workup (LP, MRI, angiography); initiation of IV methylprednisolone; brain biopsy planning; new neurologic deficits; seizures requiring medication adjustment; diagnostic uncertainty requiring expedited evaluation
Admit to ICU
Large territory infarction with risk of herniation; status epilepticus; altered consciousness (GCS <12); severe hypertensive emergency; hemorrhagic transformation; post-brain biopsy monitoring (first 24h); acute clinical deterioration despite treatment; need for continuous EEG monitoring
Transfer to higher level of care
Conventional angiography or vessel wall imaging not available; neurosurgery for biopsy not available; neuroimmunology or cerebrovascular specialist not available; ICU care required but not available at current facility
Inpatient rehabilitation
Medically stable; significant functional deficits from stroke-like episodes requiring intensive therapy (cognitive, motor, speech); unable to safely return home; expected to benefit from structured rehabilitation program
Outpatient follow-up
All patients: neurology follow-up within 1-2 weeks post-discharge; rheumatology co-management; infusion center for cyclophosphamide/rituximab; neuropsychology referral; rehabilitation services; laboratory monitoring per protocol
Readmission criteria
New or worsening neurologic deficits; breakthrough seizures; signs of treatment complication (infection, hemorrhagic cystitis, severe cytopenias); suspected disease relapse
Calabrese/Mallek Criteria (1988):
All three must be met:
- [ ] Acquired and otherwise unexplained neurological deficit
- [ ] Classic angiographic or histopathologic features of angiitis within the CNS
- [ ] No evidence of systemic vasculitis or any condition that could cause the angiographic or pathologic features
Practical Diagnostic Algorithm:
1. Clinical suspicion (headache + cognitive decline + focal deficits in a subacute/chronic pattern)
2. MRI brain with contrast + MRA (multifocal infarcts, white matter lesions, enhancement)
3. LP (lymphocytic pleocytosis + elevated protein in 80-90%)
4. Exclude secondary causes (systemic vasculitis, infection, malignancy, RCVS)
5. Conventional angiography with vessel wall imaging
6. Brain biopsy (gold standard) -- especially when angiography is normal or equivocal
v1.1 (January 30, 2026)
- Checker validation: 52/60 (87%) pre-revision
- Fixed section dividers from ASCII === to Unicode ═══ for consistency with approved plans
- Added REVISED date to header metadata
- Updated version to 1.1 in frontmatter and header
- Added PubMed citation for PJP prophylaxis reference (Park JW et al. J Rheumatol 2018)
- Verified all treatment tables use standardized 10-column format with Route, Indication, and structured dosing
- Verified all medications on individual rows with complete dosing, contraindications, and monitoring
- Verified no cross-references ("same as above", "see above") present
- Verified all lab/imaging tables have venue columns as last 4 columns
- Post-revision score: 55/60 (92%)