Persistent meningitis followed by anti-NMDAR encephalitis: case series and literature review (P5-5.002)

Abstract

<h3>Objective:</h3> To report the cases of two patients with persistent meningitis followed by anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis and discuss the pathogenesis of the disease in conjunction with previous reports. <h3>Background:</h3> Although meningeal involvement has been reported in anti-NMDAR encephalitis, reports of persistent meningitis prior to the onset of encephalitis are rare. <h3>Design/Methods:</h3> Case series and literature review. <h3>Results:</h3> We experienced two patients with anti-NMDAR encephalitis preceded by persistent meningitis. Patient 1 presented with protracted fever, and a brain MRI revealed leptomeningitis. Although cerebrospinal fluid (CSF) cell counts spontaneously decreased from 87 to 16 cells/mm³ over 2 weeks without treatment, the symptoms and signs associated with meningitis lasted 60 days. Despite the administration of oral prednisolone, abnormal behavior and speech dysfunction occurred, leading to the diagnosis of encephalitis. After the detection of anti-NMDAR antibodies in CSF, the diagnosis of anti-NMDAR encephalitis was made, which improved after administration of intravenous methylprednisolone and plasmapheresis. Patient 2 had headache and fever for 22 days, and the CSF cell counts declined from 112 to 14 cells/mm³ over 2 weeks without treatment. The emergence of delusion, involuntary movement (tongue protrusion), and decreased level of consciousness prompted the diagnosis of encephalitis. Anti-NMDAR encephalitis was identified after the positive result of anti-NMDAR antibodies in CSF; it was successfully treated with intravenous methylprednisolone and plasmapheresis. In both cases, infectious meningitis was ruled out, suggesting a possible autoimmune mechanism. No tumors, including ovarian teratoma, were found during systemic evaluation. In previous cases, we found two patients with persistent meningitis followed by anti-NMDAR encephalitis. The findings in the four meningitis patients showed prolonged meningitis lasting from 5 to 60 days, and infectious or paraneoplastic meningitis was ruled out. <h3>Conclusions:</h3> Anti-NMDAR encephalitis should be considered a differential diagnosis of long-term persistent nonviral meningitis. <b>Disclosure:</b> Dr. Yamahara has nothing to disclose. Dr. Yoshikura has nothing to disclose. Dr. Kimura has nothing to disclose. Dr. Shimohata has nothing to disclose.