case report
She was treated for psychiatric illness. It was anti-NMDA receptor encephalitis.
2026-06-23
She was treated for psychiatric illness. It was anti-NMDA receptor encephalitis.
A psychiatric onset
A 27-year-old woman, who had undergone surgery a year prior for a right ovarian mature cystic teratoma, began to experience a sudden shift in her health. Two months before her eventual admission to a tertiary center, she developed intermittent headaches and hypersomnia. These symptoms soon escalated into disorganized speech and behavioral disturbances.
Because of the nature of her presentation, her condition was initially managed as a primary psychiatric disorder. However, the behavioral disturbances did not improve with psychiatric management. Instead, her condition progressively worsened over several weeks.
Crisis and confusion
The patient eventually developed generalized tonic-clonic seizures and increasing confusion. One week before her referral to a specialist center, her body began to fail; she developed a fever, respiratory distress, and oxygen desaturation. She was admitted to an intensive care unit and required endotracheal intubation.
A head CT performed at a referring hospital suggested she might have a parieto-occipital arteriovenous malformation (AVM). Upon arrival at the tertiary care center, she was in status epilepticus—a seizure lasting approximately 25 minutes—and had a reduced level of consciousness, scoring a 9 on the Glasgow Coma Scale.
The autoimmune discovery
Tests soon revealed that the problem was not a primary mental illness. Cerebrospinal fluid (CSF) analysis demonstrated lymphocytic pleocytosis and tested positive for anti-NMDA receptor antibodies. This confirmed a diagnosis of anti-NMDA receptor encephalitis, an autoimmune condition where the body attacks its own brain receptors, often triggered by a tumor.
While the brain CT angiography confirmed the presence of a small lesion in the right parietal lobe, doctors determined this was an incidental finding and not the cause of her neuropsychiatric deterioration. The real driver was still hidden.
The hidden reservoir
The patient’s history of a "right salpingo-oophorectomy" for a teratoma a year earlier suggested one ovary had been removed. However, a new pelvic ultrasound and a contrast-enhanced abdominal CT revealed a 5.6 x 6.2 x 8.7 cm cystic mass on the left ovary. This was a new mature cystic teratoma containing fat, calcifications, and neural glial tissue.
During an exploratory laparotomy to remove the new mass, surgeons also discovered residual right ovarian tissue from her previous surgery. The original procedure had been an ovarian cystectomy, not a full removal. This meant the patient had been harboring ovarian tissue that acted as a persistent source of immune stimulation, driving the attack on her brain despite aggressive immunotherapy.
Recovery after resection
Once the left ovarian cyst was removed, the patient’s path to recovery finally began. She received high-dose corticosteroids, intravenous immunoglobulin, and rituximab. Although her initial response to steroids had been minimal, her seizures eventually resolved after the surgery and further immunotherapy.
The patient was successfully extubated after two weeks in the hospital. Her psychiatric manifestations progressively diminished, and while her recovery was prolonged, she continued to show improvement during outpatient follow-up.
The medical picture
CSF anti-NMDA receptor antibodies
Positive
CSF mononuclear cells
23 cells/µL
Hemoglobin
8.8 g/dl
Leukocyte count
15,090 /µl
Lactic acid
3.7 mmol/L
Adapted faithfully from the open-access case report: International Journal of Surgery Case Reports (PMC12981796). DOI: 10.1097/RC9.0000000000000292. Read the original at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12981796/.