An Unusual Presentation of Anti-NMDA Receptor Antibody Positive Encephalitis: Non-Epileptic Spells and A Splenial Lesion on Brain MRI (P5.394)

Objective: Not applicable Background: A 15-year-old girl with a history of sexual abuse presented with aggressive behavior following three months of non-epileptic spells and behavior changes. Neurological examination revealed superficially bright affect with confusion; a wide-based, unstable gait; high-frequency low-amplitude tremor in all extremities; and micrographia. Witnessed spells were characterized by tremulousness, pelvic thrusting, forced eye closure, and head shaking, with cessation following aggressive alerting. Spells had no electrographic correlate on electroencephalogram, although frontal intermittent rhythmic delta (FIRDA) was noted. Episodes of aggression continued and were unresponsive to high-dose psychiatric medications. Design/Methods: Not applicable Results: Brain MRI demonstrated a T2-hyperintense and diffusion-restricting lesion in the splenium of the corpus callosum. Respiratory viral panel was positive for influenza A and B. The patient was diagnosed with mild encephalitis with reversible splenial lesion (MERS). Repeat imaging demonstrated an enlarged splenial lesion. Intravenous steroids and IVIg were initiated. The patient responded to steroids with improved handwriting, gait, sleep, and mentation. Completion of steroid course was followed by clinical decline, with poor sleep and continued convulsions. These symptoms again improved following additional intravenous steroids. The patient’s cerebrospinal fluid returned positive for NMDA receptor antibodies. She was discharged on a steroid taper and continued on IVIg and immunosuppression. Conclusions: This is an unusual case of NMDA receptor antibody-positive encephalitis (NRE), presenting with non-epileptic spells, without epileptic seizures, and with an evolving lesion in the splenium of the corpus callosum. MERS has been described in pediatric and adult patients and is thought to arise from various etiologies, although not generally associated with NRE. We hypothesize that a mild influenza-mediated encephalitis may have brought our patient to attention prior to development of seizures from NRE. As early treatment improves outcomes, autoimmune encephalitis should be considered as a cause of non-epileptic spells and abnormal behaviors that are unresponsive to psychiatric medications. Study Supported by: not applicable Disclosure: Dr. Christy has nothing to disclose. Dr. Hilde has nothing to disclose. Dr. Marshall has nothing to disclose.