447: Hiding in the Remaining Ovary

Introduction: Anti-N-Methyl-D-Aspartate receptor encephalitis (NMDARE) can present with acute, subacute neuropsychiatric manifestations. Etiologies can be autoimmune, paraneoplastic, or infectious following herpes simplex virus encephalitis. High index of suspicion needs to be maintained to make the accurate and timely diagnosis. We describe a case of NMDARE in a female who had undergone oophorectomy many years back for right complex ovarian cyst, pathology revealed a mature cystic teratoma. She failed conventional treatment and was subsequently found to have a teratoma in the remaining ovary despite negative imaging. Description: 44-year-old female presented with acute onset of altered mental status, hallucinations and seizures. Brain imaging was unrevealing. Her lumbar puncture revealed white blood cell count of 360, 95% lymphocytes, normal glucose and protein. NMDARE antibody came back positive. Patient underwent Computerized Tomography (CT) scan of the abdomen, Magnetic Resonance Imaging (MRI) of the abdomen failed to demonstrate any evidence of teratoma in the remaining ovary. She received high dose intravenous steroids, intravenous immunoglobulin, plasmapheresis without improvement in her neurologic state. She subsequently received Rituximab after failing initial treatment. Her hospital course was complicated by persistent seizures, dyskinetic movements, critical illness myo-neuropathy. Given her lack of neurologic improvement after several weeks and patient having completed her family, prophylactic oophorectomy of the remaining ovary was performed. The pathology came back as teratoma. Patient received a second round of plasmapheresis followed by Cyclophosphamide. Six months later she is interactive, oriented X 4 and following commands. Discussion: This case highlights the importance of having high index of suspicion for teratoma in females presenting with NMDARE. Even though her imaging including CT scan and MRI of the abdomen was unrevealing, oophorectomy led to the diagnosis of teratoma which explains lack of improvement following initial treatment and gradual improvement after oophorectomy. In females presenting with NMDARE with prior history of teratoma, prophylactic oophorectomy should be considered on a case-by-case basis, if there is lack of improvement with conventional treatment.