Case Report: Triphasic Waves in a 9-Year-Old Girl With Anti-NMDAR Encephalitis

Abstract

Background: Triphasic waves (TWs) are mainly described in association with metabolic encephalopathy, especially hepatic encephalopathy. Now, as different conditions including non-metabolic and structural abnormalities have been reported to be associated with TWs, the presence of TWs becomes a non-specific finding for metabolic encephalopathy.

Case presentation: We report the first case of anti-NMDAR encephalitis in a 9-year-old girl presenting with TWs on EEG. The TWs background EEG lasted for about 12 h on the 40th day of the disease course. No epileptic wave was found during a series of EEG examinations. The child was discharged from the hospital and no neurological sequelae remained after a six-month follow-up.

Conclusions: TWs are not specific to metabolic encephalopathy, but can also occur in children with autoimmune encephalitis. This case achieved a good prognosis after the early initiation of immunotherapy.

Keywords: EEG; anti-NMDAR encephalitis; case report; metabolic encephalopathy; pediatric; triphasic waves.

Figure 1

EEG on day 2 (A), day 8 (B) after PICU admission, and six months after inpatient discharge (C). (A) Day 2, EEG revealed diffuse irregular slow waves. (B) Day 8, EEG showed generalized triphasic waves predominantly in frontal regions. (C) Six months later, EEG demonstrated mild slow background.

Figure 2

Timeline of the clinical course.