Rheumatoid Meningitis: Exploring the Broad Differential of Leptomeningeal and Pachymeningeal Enhancement on Brain MRI

Pachymeningeal and leptomeningeal enhancement on contrast-enhanced brain MRI come with broad differentials, including granulomatous disease of infectious or non-infectious etiology, carcinomatosis, and autoimmune disorders such as vasculitis, giant cell arteritis, and IgG-4 related disease. Among them is rheumatoid meningitis, one of the rare manifestations of central nervous system (CNS) involvement in rheumatoid arthritis (RA). Its clinical presentation is nonspecific and grossly overlaps with that of infectious meningitis. Given its vague neurologic symptoms and broad differential of leptomeningeal and pachymeningeal enhancement, rheumatoid meningitis poses a significant diagnostic challenge. In the absence of tissue sampling, a combination of clinical symptoms, serum markers such as rheumatoid factor and complements, and MRI imaging findings is required to arrive at this diagnosis. Rheumatoid meningitis portends high mortality and morbidity, and appropriate immunosuppressive treatment is often delayed in favor of long-term antibiotics. We present a case report on rheumatoid meningitis and corresponding recent literature review including clinical, laboratory, and imaging findings, as well as an exploration of the differentials of pachymeningeal and leptomeningeal enhancement.