Anti-NMDAR Encephalitis in a Young Woman: A Case Report of Rapid Neuropsychiatric Decline and Recovery with Early Immunotherapy

Introduction: Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is an autoimmune encephalitis caused by antibodies targeting NMDA receptors in the brain. It often affects young females and presents with psychiatric symptoms, seizures, movement disorders, and cognitive impairment. Early recognition and immunotherapy are essential to prevent long-term neurological sequelae. Presentation: A 17-year-old previously healthy girl presented with a single episode of generalized tonic-clonic seizure, followed by acute behavioral changes within one week. She developed oromotor automatism, speech difficulty, sleep disturbance, and disorientation. Prior to admission, she experienced intermittent fever, runny nose, and headache. On examination, her Glasgow Coma Scale was E4V3M5 with no meningeal signs. Brain MRI was normal, while cerebrospinal fluid (CSF) analysis showed lymphocytic predominance and was positive for anti-NMDAR antibodies. EEG revealed frequent slow-wave activities with possible epileptiform discharges over the bifrontal regions. She was treated with intravenous methylprednisolone (1 g/day for five days) and intravenous immunoglobulin (2 g/kg over five days). Antiepileptic therapy (valproic acid, diazepam, trihexyphenidyl) was continued. The patient’s consciousness and communication improved, and behavioral symptoms subsided. Discussion: This case highlights the importance of considering anti-NMDAR encephalitis in adolescents presenting with seizures and acute psychiatric or cognitive disturbances. Normal MRI findings do not exclude the diagnosis, which relies on CSF antibody testing. Early combined immunotherapy leads to excellent outcomes. Tumor screening, especially for ovarian teratoma, remains a critical component of management.