Characteristics of Electroencephalogram Changes After Hemispheric Disconnection Surgery in Patients with Drug-Resistant Epilepsy

Objective To retrospectively analyze the characteristics of electroencephalogram (EEG) changes after hemispheric disconnection surgery in patients with drug-resistant epilepsy (DRE) and assess their clinical significance. Methods This study included patients with DRE who underwent treatment at the Epilepsy Center of Jinan Children's Hospital between November 2020 and May 2023. Inclusion criteria comprised: (1) hemispheric disconnection surgery following comprehensive preoperative assessment; (2) long-term video-EEG (VEEG) monitoring conducted preoperatively and at three months, one year, and two years postoperatively; and (3) a minimum postoperative follow-up of two years, with outcomes evaluated using the Engel's classification. To analyze the VEEG characteristics—encompassing background activity, interictal discharges, and ictal patterns—before and after hemispheric disconnection surgery, and to elucidate their clinical significance. Results Among sixteen eligible patients (male-to-female ratio 3:5), the mean age at surgery was three years nine months (from four months to six years and five months ), the postoperative seizure-free rate was 87.5% (n=14). Preoperative and postoperative VEEG analyses revealed: (1) Background activity: The disconnected hemisphere exhibited slow waves or attenuation activity at three–four months postoperatively, with increased attenuation prevalence within the first year and partial improvement thereafter; the non-disconnected hemisphere showed normalized background activity within one year after surgery. (2) Interictal activity: Epileptiform discharges on the disconnected side increased at three–four months postoperatively, frequently accompanied by a burst-suppression pattern (n=9, 56.25%). One year after surgery, discharges increased further, with greater burst-suppression prominence (n=12, 75%); one patient (n=1, 6.25%) exhibited electrographic seizure. Two years after surgery, discharge morphology and frequency stabilized, with resolution or attenuation of burst-suppression in 56.25% (n=9). Contralateral interictal discharges diminished or resolved within the first year after surgery in most cases, though three patients showed persistent increases; At the two-year postoperative follow-up, three patients still exhibited contralateral discharge. (3) Ictal activity: Electroclinical seizures originating from the disconnected hemisphere were recorded in one patient each at three months and one year after surgery, respectively. Among twelve patients exhibiting burst-suppression, no electroclinical seizures were associated with this pattern. (4) No electroclinical seizures arose from the contralateral hemisphere postoperatively among thirteen patients with preoperative contralateral discharges. The impact of postoperative contralateral discharges on prognosis needs to be judged based on long-term follow-up results. Conclusion The VEEG characteristics of the disconnected and contralateral hemisphere in DRE patients evolve dynamically after hemispheric disconnection; The burst-suppression patterns may suggest complete disconnection; The background on the contralateral side of the disconnection can generally be improved, even restored to normal; The contralateral background activity and interictal characteristics of the postoperative VEEG have certain value for prognostic assessment.