Rheumatoid Meningitis Presenting With Paraplegia in the Absence of Arthritis: A Case Report and Literature Review.

Rheumatoid meningitis typically occurs as a late-stage extra-articular central nervous system complication of rheumatoid arthritis (RA); however, its diagnosis can be challenging in the absence of arthritis. A 75-year-old man, without joint pain or stiffness, presented with sudden muscle weakness in both lower limbs. Diffusion-weighted magnetic resonance imaging (MRI) showed hyperintensity along the meninges of the bilateral frontoparietal lobes. He was then diagnosed with rheumatoid meningitis based on the results of the MRI and cerebrospinal fluid (CSF) analysis, which revealed anti-cyclic citrullinated peptide antibody (ACPA) positivity and an increased ACPA index, indicating intrathecal ACPA production. He was then evaluated for uncomplicated RA. Following steroid therapy, his lower limb muscle weakness improved. This case underscores the importance of considering rheumatoid meningitis as a differential diagnosis in patients presenting with acute-onset paraplegia, even in the absence of arthritis. While the differential diagnosis of acute-onset paraplegia typically includes spinal cord lesions, spinal cord disease was deemed unlikely in this case due to the absence of neck or back pain, sensory disturbances, bladder or rectal dysfunction, and abnormal findings on spinal computed tomography. In this case, the inflammation in the subarachnoid space, as detected by MRI, may have stimulated the bilateral cortex at a high convexity level, resulting in paraplegia. Key diagnostic tools in rheumatoid meningitis include diffusion-weighted MRI, which commonly reveals hyperintensity along the meninges, and CSF analysis demonstrating ACPA positivity and an elevated ACPA index.