Case Presentation: A 64-year-old male with a history of prior intracerebral hemorrhage and bipolar disorder was transferred from a local hospital for 6 weeks of altered mental status with visual hallucinations. On presentation, his vitals were notable for systolic blood pressure greater than 200 mmHg. The patient had no focal neurological deficits but endorsed visual hallucinations with his encephalopathy. His computed tomography (CT) showed subacute hematoma in the right occipital lobe and chronic infarcts in multiple areas. CT angiogram revealed scattered arterial stenosis in the Circle of Willis. Cerebrospinal fluid (CSF) analysis was unremarkable. Magnetic resonance (MR) of the head showed leptomeningeal enhancement with hemorrhagic infarcts in bilateral parietal lobes, cortical infarcts of left frontal and temporal, bilateral occipital lobes in addition to chronic infarcts seen on CT. Vasculitis workup including antinuclear antibody and ANCA were all negative. His hospital course was complicated by continued confusion and focal partial seizures. The brain biopsy on day 14 found lymphocytic vasculitis and the diagnosis of Primary Angiitis of the central nervous system (PACNS) was established. The patient was discharged home following pulse steroid then completed a course of outpatient cyclophosphamide. Two years later, the patient was admitted for acutely worsening confusion in the setting of vascular dementia. CSF was again unremarkable. MR showed hyper-intense signaling in bilateral right parietal and occipital lobes consistent with subacute infarcts and sequela of vasculitis. The patient’s worsened confusion and delirium improved back to his baseline and was safely discharged following three days of pulse-dose steroids and induction of cyclophosphamide.

Discussion: PACNS is a rare form of vasculitis that affects small to medium sized arteries only within CNS. An annual incidence rate is reportedly 2.4 cases per 1,000,000 person-years (1). The median age is 50 years with males being more affected than females (2:1) (2). Manifestation can be highly variable since vasculitis can and may affect any part of the CNS (3,4). The mean time from symptom onset to diagnosis was 170 days in one report (2). Diagnostic clues include atypical MR findings such as multiple infarcts across different territories or meningeal enhancement. CSF studies may be normal, as was the case with our patient. The diagnosis of PACNS first requires exclusion of secondary causes such as SLE, ANCA, Cryoglobulinemia, and infection, with brain biopsy being the gold standard for diagnosis. Diagnostic yield of biopsy is approximately 75% (5) but biopsy may also provide an alternative diagnosis.

Conclusions: PACNS may present as subacute onset or progressive confusion (non-specific) and requires a brain biopsy to establish the diagnosis. Physicians need to keep a high index of suspicion when a patient presents with CVA absent risk factors, multiple infarcts across different territories, or meningeal enhancement.