Focal CNS vasculitis masquerading as new-onset focal aware seizures

Primary angiitis of the central nervous system (PACNS) is an autoimmune disease with myriad presentations in the form of headache, focal neurological deficits, seizures and rapid cognitive decline. Predilection or isolated and recurrent involvement of one hemisphere is rarely described in literature. This leads to low clinical suspicion and often delayed diagnosis of PACNS, if clinical and radiological involvement is focal. We describe the case of a young man presenting with new-onset focal seizures with imaging suggestive of focal involvement and the brain biopsy clinched an early diagnosis. The 1-year follow-up showed clinical and radiological resolution.