Objective:

To describe a rare case of anti–N-methyl-D-aspartate receptor (NMDAR) encephalitis associated with bilateral ovarian teratomas of mixed histologic maturity.

Background:

Ovarian teratomas are known triggers of anti-NMDAR encephalitis, but fewer than 10% of girls under 14 have tumors, almost all mature cystic. Immature teratomas with primitive neuroepithelium are rare yet provide direct histopathologic evidence of neural antigenic tissue driving autoimmunity.

Design/Methods:

A previously healthy 14-year-old developed paranoia, agitation, and disorganized speech over one week, initially treated as new-onset psychosis. Neurology was consulted for persistent altered mental status with combative behavior and pacing. Within days, she developed focal status epilepticus with leftward neck version, gaze deviation, and orofacial dyskinesia, requiring intubation. EEG showed focal-to-bilateral tonic–clonic seizures, diffuse slowing, left posterior-quadrant focus, and “extreme delta brush” typical of NMDAR encephalitis. CSF showed elevated protein (147 mg/dL), lymphocytic pleocytosis, and positive NMDAR IgG in serum (1:160) and CSF (1:640). Brain MRI revealed right > left temporal–insular FLAIR hyperintensities. Pelvic MRI identified bilateral cystic–solid ovarian masses. She received IV methylprednisolone, IVIG, cystectomy, and rituximab with gradual recovery. 

Results:

Pathology confirmed a right ovarian grade 3 immature teratoma with extensive neuroepithelium forming rosettes, pseudorosettes, and primitive tubules with high mitotic activity, without surface involvement, and a contralateral mature cystic teratoma (FIGO IA). Paraneoplastic evaluation, including CT chest and tumor markers (AFP, β-hCG, LDH), was negative for metastasis or residual disease. OB-GYN and oncology recommended surveillance with serial markers and imaging. Follow-up MRI showed resolution of right-sided abnormalities and new FLAIR hyperintensities consistent with disease evolution. Serial EEGs normalized, and the patient achieved near-complete neurologic recovery within six weeks after tumor resection and immunotherapy.

Conclusions:

This case highlights the clinicopathologic spectrum of anti-NMDAR encephalitis, showing that ovarian teratomas, both mature and immature, can trigger autoimmune encephalitis in teenagers. Early detection, multidisciplinary care, and detailed histopathologic evaluation are essential for recovery.