Purpose or Case Report: Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is an autoimmune disorder of the central nervous system characterized by antibodies targeting NMDA receptors. It primarily affects adolescent and young adult females and frequently coexists with ovarian teratoma. The disease often begins with psychiatric symptoms such as agitation, hallucinations, or affective instability, which may delay proper diagnosis and treatment.
A 16-year-old girl was admitted to a psychiatric ward due to acute behavioral disturbances and depressive symptoms. Four days after admission, she developed impaired consciousness (GCS 9) and focal neurological signs, including right eye divergent strabismus and bilateral Babinski reflex. Cerebrospinal fluid analysis revealed lymphocytic pleocytosis and elevated protein concentration. Anti-NMDAR antibodies were detected in cerebrospinal fluid. MRI showed hyperintense lesions in the occipital lobes. Abdominal ultrasound identified a right ovarian mass; urgent surgical resection confirmed an immature teratoma. The patient received combined immunotherapy including corticosteroids, intravenous immunoglobulins, plasma exchange, and rituximab. Gradual clinical improvement was observed over subsequent weeks.

This case illustrates the complex neuroimmunological interaction between ovarian teratoma and the central nervous system. Psychiatric symptoms were the initial manifestation, delaying recognition of the underlying encephalitis. The presence of anti-NMDAR antibodies in cerebrospinal fluid and identification of ovarian teratoma confirmed the diagnosis. Early tumor resection combined with immunotherapy significantly improves outcomes and reduces neurological sequelae.

Acute-onset psychiatric symptoms in adolescent females should prompt consideration of autoimmune encephalitis, especially in the presence of an ovarian mass. Early detection and multidisciplinary management are crucial for full recovery and prevention of long-term complications.
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