Rheumatoid Meningitis Mimicking Clinical and Radiological Findings of Subarachnoid Hemorrhage: A Case Report and Review of the Literature.

Rheumatoid meningitis is a rare central neurological complication associated with rheumatoid arthritis. We report an unusual case of rheumatoid meningitis presenting with clinical and radiological findings resembling subarachnoid hemorrhage, with no history of rheumatoid arthritis diagnosis and negative serum rheumatoid factor. A woman in her fifties presented with a severe headache and loss of consciousness. Magnetic resonance imaging suggested subarachnoid hemorrhage involving the interhemispheric fissure and adjacent bilateral cerebral sulci. Cerebral angiography did not reveal any vascular abnormalities, and an initial diagnosis of subarachnoid hemorrhage of unknown etiology was made. Follow-up magnetic resonance imaging failed to identify a source of bleeding, evidence of hematoma resolution, or new vascular lesions. Although she had a family history of rheumatoid arthritis, she had no formal rheumatoid arthritis diagnosis, and serum rheumatoid factor tests were negative. Contrast-enhanced magnetic resonance imaging showed leptomeningeal thickening along the falx cerebri, raising suspicion of an inflammatory condition such as meningitis. Her symptoms progressively worsened, and on day 16, a meningeal biopsy was performed. Histopathological examination confirmed meningitis and subsequent blood tests revealed positive anticyclic citrullinated peptide antibodies. A comprehensive evaluation ultimately led to the diagnosis of rheumatoid meningitis. This case highlights that rheumatoid meningitis can mimic the clinical and imaging findings of subarachnoid hemorrhage, even in patients without a prior rheumatoid arthritis diagnosis or with negative serum rheumatoid factor. Furthermore, rheumatoid meningitis may show progressive deterioration, emphasizing the importance of early meningeal biopsy during the acute phase for accurate diagnosis and improved prognosis. Clinicians should closely monitor changes in clinical and radiological findings and consider early biopsy in such cases.