A patient presenting with chapeau de gendarme and three phase-ictal EEG pattern: Suggesting a focus in the interhemispheric fissure

Abstract

Introduction

We report a pediatric case of frontal lobe epilepsy with seizures characterized by the “chapeau de gendarme (CdG)” sign and a three phase-ictal scalp EEG (3Ph-EEG) pattern, suggesting a seizure focus in the interhemispheric fissure (IHF) cortex.

Case report

An 8-year-old boy with autism spectrum disorder (ASD) presented with daily episodes of impaired consciousness, staring, and bilateral tonic posturing of the upper limbs, accompanied by stiffening and drooping of both corners of the mouth. These episodes were initially misdiagnosed as behavioral disturbances in patients with ASD. Video-scalp EEG at age 11 revealed a 3Ph-EEG pattern: 1) brief β bursts in the left frontal region; 2) diffuse attenuation; and 3) rhythmic activity evolving from β to δ frequencies over the left fronto-centro-parietal regions. Seizure semiology and EEG findings were consistent with a seizure focus in the anterior IHF cortex, including the cingulate gyrus. Although valproate and levetiracetam were ineffective, lacosamide (LCM) effectively controlled the seizures, and its efficacy was sustained over a 3-year follow-up period.

Discussion

The combination of CdG and 3Ph-EEG patterns may serve as clinical and electrophysiological markers for seizures originating in the frontal IHF cortex. Therefore, LCM may be an effective treatment option for such cases. This case underscores the importance of detailed seizure semiology and EEG interpretation for accurate localization.