Abstracts

Rationale: Anti-N-methyl-d-aspartate (NMDA) receptor encephalitis is a rare paraneoplastic syndrome characterized by behavioral changes and seizures or status epilepticus. The extreme delta brush (EDB) pattern is considered a characteristic electroencephalographic (EEG) finding that has been associated with poor outcomes. The underlying mechanism and significance of EDB is unclear. An ictal nature has been proposed by some authors. Methods: A 43-year-old female presented with new-onset seizures and behavioral changes. EEG showed nonconvulsive status epilepticus, which was controlled with levetiracetam and lacosamide. Her workup led to the diagnosis of anti-NMDA receptor encephalitis. Screening for malignancy was negative. The patient was treated with high-dose glucocorticosteroids, plasmapheresis, and intravenous immunoglobulin, prior to transfer to a long-term acute care hospital. She presented to our institution with rhythmic myoclonic movements of the head and extremities, facial twitching, and orofacial dyskinetic movements). The rhythmic motor activity persisted despite the addition of phenytoin, valproate, and clobazam. It was only controlled with a continuous infusion of propofol and, more effectively, with ketamine. Empirical salpingo-oophorectomy was performed, revealing an immature left ovarian teratoma. However, no immediate clinical improvement was observed. Attempts to wean anesthetic agents resulted in recurrence of the rhythmic movements. Results: EEG monitoring revealed prolonged runs of generalized 0.5-2 Hz rhythmic delta with superimposed bursts of low-voltage beta activity (consistent with EDB). The pattern was often associated with motoric activity that had a similar frequency. Subtle evolution in the frequency of EDB pattern was paralleled by evolution in the frequency of the rhythmic movements.Due to the positive response to ketamine, a trial of perampanel, a non-selective AMPAreceptor antagonist, was initiated. After 4 hours of persistent rhythmic motor activity, the patient received a loading dose of 36 mg of perampanel. The rhythmic movements started to decrease within 32 minutes of the dose. They completely stopped within 51 minutes and the EDB pattern transiently disappeared. A maintenance dose of 12 mg twice daily allowed sedation to be weaned.  Conclusions: We make the following observations: (1) The synchronicity between the EDB pattern and rhythmic motoric activity suggests a common generator and poses the possibility that the EDB pattern may represent an ictal pattern. (2) In this case, perampanel was more effective than other antiepileptic medications. This could be explained by its unique mechanism of action. Further investigations may help clarify whether it has a specific role in the treatment of patients with anti-NMDA receptor encephalitis. Funding: No funding