Anti-NMDA receptor encephalitis secondary to a mature cystic teratoma in a female teenager: A case report

Paraneoplastic encephalitis can occur due to a variety of tumors, the majority of which are rare in the pediatric population. A 15-year-old female patient presented to the emergency department (ED) with altered mental status and four days of unresponsiveness after periods of agitation. Her symptoms of erratic behavior, anger, confusion, difficulty speaking, and visual hallucinations were initially thought to be due to a psychotic episode potentially from a contaminated cannabis vape product. Repeatedly altered neurological workups in the pediatric intensive care unit (PICU) alongside her worsening agitation and lack of resolution that would fit the time frame, cleared these concerns. Additionally, she had symptoms of dysautonomia with oscillating tachycardia and hypertension. These findings prompted an extensive work-up including the Mayo Pediatric Autoimmune Central Nervous System Disorders Panel from CSF (PCDEC). A computed tomography (CT) scan of the chest, abdomen, pelvis was ordered on the 3rd day of hospitalization due to concerns for a paraneoplastic encephalitis. The CT showed a 3.3cm × 3.7cm x 3.9cm left adnexal mass. She was promptly taken to the operating room for a resection of the mass. A laparoscopic total oophorectomy was done without any difficulties. The pathology report was consistent with a mature cystic teratoma. Laboratory results received 10 days later confirmed the diagnosis of anti-NMDA antibody encephalitis. In addition to the operation the patient received high-dose steroids, intravenous immunoglobulin (IVIG), and plasmapheresis. She was ultimately discharged home after 38 days of hospitalization. Ovarian teratomas have the potential to trigger paraneoplastic encephalitis. In patients with suspected paraneoplastic encephalitis who are diagnosed with an ovarian tumor, prompt tumor resection should be performed.