Background: Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is an auto-immune encephalitis with prominent neuropsychiatric manifestations that may be paraneoplastic.
Clinical Description: A teenage girl presented with an acute illness of 4 days with symptoms of generalized weakness of all four limbs, behavioral abnormalities, and a generalized convulsion. On examination, the child was hemodynamically stable and disoriented to time, place, or person. There was the loss of recent memory. The remaining neurological and systemic examination was normal. The differential diagnoses considered were toxic or metabolic encephalopathy, neurological Wilson’s disease, acute intermittent porphyria, autoimmune encephalitis, and neuropsychiatric systemic lupus erythematosus. Investigations were planned for the causes that could not be excluded by history, examination, and baseline investigations. Salient reports were normal brain magnetic resonance imaging (MRI), nonspecific electroencephalogram abnormalities, and absence of pleocytosis and biochemical abnormalities but positive anti?NMDAR antibodies in the cerebrospinal fluid. A right adnexal cystic solid mass was identified in the abdominal ultrasound with the radiological appearance of an ovarian teratoma or germ cell tumor on MRI. Alpha-fetoprotein levels were raised.
Management: The patient underwent right salpingo-oophorectomy. The histopathological diagnosis was an immature ovarian teratoma. The patient received first?line and then second?line immunotherapy (when there was no response), as well as chemotherapy. Signs of improvement appear after 6 weeks, with complete recovery within 6 months.
Conclusion: Pediatric ovarian teratoma-associated anti-NMDAR encephalitis is rare, but neuropsychiatric symptoms should prompt the clinician to think of this diagnosis in girls. Early treatment is associated with a good  prognosis.

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