Primary Angiitis of the Central Nervous System.

Primary angiitis of the central nervous system (PACNS) is rare but often included in the differential diagnosis for unusual or unexplained neurologic symptoms owing to its array of clinical manifestations. PACNS is not a single entity, but rather an umbrella term for distinct subtypes of disease affecting different parts of the CNS, different sized vessels, and with different histologic and pathologic findings. Although brain biopsy is considered the gold standard test, it is neither highly sensitive nor specific. One must always pursue a workup for mimics of PACNS. Treatment consists of prednisone monotherapy or combination therapy with prednisone and cyclophosphamide.