# N-Methyl-D-Aspartate (NMDA) Receptor Encephalitis Without Electroencephalogram Abnormalities or Cerebrospinal Fluid Pleocytosis Associated With a Tiny Ovarian Teratoma: A Case Report

## TL;DR

A rare case of NMDA receptor encephalitis is reported in a woman with a tiny ovarian teratoma, despite normal EEG and CSF results.

## Contribution

Highlights the importance of NMDA receptor antibody testing even when typical diagnostic markers are absent.

## Key findings

- NMDA receptor encephalitis was diagnosed in a patient with normal EEG and no CSF pleocytosis.
- A 7 mm ovarian teratoma was identified as the associated tumor.
- The case emphasizes the need for antibody testing in atypical presentations.

## Abstract

N-methyl-D-aspartate (NMDA) receptor encephalitis is one of the autoimmune disorders characterized by neuropsychiatric symptoms, most commonly associated with ovarian teratoma. While detection of NMDA receptor antibody in cerebrospinal fluid (CSF) is the diagnostic standard, it is often limited by a delayed turnaround time. Abnormal electroencephalogram (EEG) findings and pleocytosis in CSF analysis are frequently observed, and computed tomography (CT) can aid in identifying an underlying ovarian teratoma. Here we report the case of a 36-year-old female who presented with acute psychosis, had a normal EEG and no CSF pleocytosis, and was later diagnosed with NMDA receptor encephalitis associated with a 7 mm ovarian teratoma. This case underscores the diagnostic challenges in the setting of a normal EEG and no CSF pleocytosis, which emphasizes the importance of NMDA receptor antibody testing in CSF for accurate diagnosis.