Postoperative Anti-NMDA Receptor Encephalitis Following Resection of an Insular Astrocytoma: A Case Report

Anti-N-methyl-D-aspartate (anti-NMDA) receptor encephalitis is the most common subtype of autoimmune encephalitis, typically associated with ovarian teratomas, but also reported in men and children. We describe an exceptionally rare case of anti-NMDA receptor encephalitis following glioma resection. A 34-year-old man with no prior medical history presented with severe headache and generalized tonic-clonic seizure. Brain MRI suggested a tumor in the right insular region, and surgical resection confirmed a diffuse astrocytoma, WHO grade II. Postoperatively, the patient developed fever, seizures, confusion, and visual symptoms. Initial cerebrospinal fluid analysis suggested viral encephalitis, but repeated testing revealed marked pleocytosis and elevated protein. Autoimmune antibody panel confirmed anti-NMDA receptor antibody, while other antibodies and viral studies were negative. High-dose methylprednisolone and intravenous immunoglobulin therapy resulted in clinical improvement. The patient subsequently received adjuvant chemotherapy with procarbazine and lomustine for glioma, and no recurrence of encephalitis was observed during a 4-year follow-up. This case highlights the diagnostic challenge of distinguishing glioma-related neuropsychiatric symptoms from anti-NMDA receptor encephalitis, and raises the possibility that surgical manipulation may act as a trigger. Early recognition and appropriate immunotherapy remain essential for favorable outcomes. Further studies are needed to clarify the role of chemotherapy in long-term prognosis of tumor-associated anti-NMDA receptor encephalitis.