Introduction: Anti-N-methyl-D-aspartate receptor encephalitis is a recently identified paraneoplastic limbic encephalitis. The incidence is still unknown. Approximately 90% of patients are female, and more than 50% are associated with ovarian teratoma. Patients usually present with rapidly progressive neuropsychiatric symptoms, memory deficits, seizures, dyskinesia, autonomic instability, and coma.
Case Report: A 25 year-old nulliparous female presented with one-week history of abnormal behaviour and headache. Initial examinations and investigations including brain computerized tomography (CT) were all inconclusive. She was admitted for further evaluation. Day 3 of admission, she developed signs of autoimmune instability and seizures with gradual decline in GCS, which led to the Intensive Care Unit (ICU) admission. Cerebrospinal fluids (CSF) bacterial and viral cultures, polymerase chain reaction analysis for HSV and tuberculosis showed negative results. The diagnosis of anti-NMDAR encephalitis was made as anti-NMDAR antibodies were positive in both CSF and serum. She was started on plasma exchange and Methylprednisolone followed by Rituximab with episodic intravenous immunoglobulin (IVIG) therapy. Due to a high index of suspicion for teratoma, a pelvic CT scan was performed which showed a 5mm focal fatty lesion within the right ovary, suggestive of a mature teratoma. She underwent laparoscopic right salpingo-oophorectomy. Mature cystic teratoma was confirmed on histological examination. Despite tumour removal, there was no clinical improvement and further imaging failed to prove any evidence of teratoma elsewhere. Given the continuing deterioration in the patient's condition, left saplingo-oophorectomy was performed in expectation of preventing further disease progression. However, the histopathology did not show any teratoma and patient was continued on Cyclophosphamide.
Discussion: Early diagnosis and management with immunotherapy, chemotherapy, surgical resection and ICU support is a critical prognostic factor in anti-NMDAR encephalitis. 75% of patients achieve a full recovery or are left with mild deficits and in 25% of cases, severe residual deficits or death occurs.The literature remains controversial regarding oophorectomy, when no convincing imaging evidence exists, to increase the likelihood of identifying a microscopic teratoma. In our patient, despite early diagnosis and treatment including resection of teratoma, clinical recovery was not achieved. However, in refractory cases recovery may take 2 years or longer and the patient may not always return to their former levels of motor function and cognition. The association ovarian teratoma-anti-NMDAR encephalitis is a potentially fatal pathology occurring in young women. Heightened recognition and diagnosis through confirmation of anti-NMDAR antibodies, appropriate imaging and subsequent tumor removal must be emphasized among gynecologists.