Multidisciplinary Management of Paraneoplastic Anti-N-Methyl-D-Aspartate Receptor Encephalitis Associated With Ovarian Teratoma: A Case Report.

Anti-N-methyl-D-aspartate (NMDA) receptor encephalitis is a severe autoimmune encephalitis often associated with ovarian teratomas and characterized by a rapidly progressive neuropsychiatric syndrome, seizures, dyskinesias, a decreased level of consciousness, and autonomic instability. Antibodies targeting the GluN1 subunit lead to internalization of synaptic NMDA receptors, a mechanism associated with potential neurological recovery when treatment is initiated in a timely manner. Early recognition and initiation of immunotherapy, together with tumor resection, play a key role in improving patient outcomes. We present the case of a 20-year-old Hispanic woman with subacute neuropsychiatric deterioration and focal seizures beginning in late November 2025, in whom diagnostic evaluation revealed anti-NMDA receptor antibodies and a large ovarian mature cystic teratoma. Due to high clinical suspicion, early surgical resection (<72 hours) and first-line immunotherapy were initiated before antibody confirmation. Following stepwise escalation to plasma exchange, IV immunoglobulin, and second-line therapy with rituximab, the patient demonstrated gradual and sustained neurological recovery after five weeks of inpatient treatment. This case highlights the importance of a multidisciplinary approach in the management of paraneoplastic anti-NMDA receptor encephalitis and supports the safety of ultra-early surgical resection in tumor-associated cases.