Unilateral Relapsing Primary CNS Vasculitis: Description of 3 Cases From a Single-Institutional Cohort of 216 Cases.

OBJECTIVES:To define the frequency and characteristics of patients with unilateral relapsing involvement in a cohort of patients with adult primary CNS vasculitis (PCNSV). METHODS:We retrospectively studied a cohort of 216 patients with PCNSV seen at the Mayo Clinic, Rochester, MN from 1983 to 2022. Twenty-five patients (19.8%) had at least 2 flares. Three of them (1.4%) had unilateral relapsing vasculitis. We described these 3 patients and compared them with the entire cohort of 216 patients. RESULTS:All 3 patients had angiography-negative and biopsy-positive PCNSV with granulomatous-necrotizing and lymphocytic vasculitides and amyloid beta-related angiitis. The main manifestation at diagnosis and during flares was seizures. Unilateral lesions with gadolinium enhancement were the main MRI finding. Spinal fluid examination at diagnosis was normal in 2 patients. All had multiple flares (from 4 to 10) and were treated with long-term high-dose prednisone and numerous traditional immunodepressive drugs, and one received rituximab for steroid resistance. All 3 patients had slight disability with mild cognitive impairment at last follow-up. DISCUSSION:Unilateral relapsing involvement represents a rare subset of PCNSV with peculiar characteristics and can be observed in all neuropathologic patterns.