Characteristics of electroencephalographic changes after hemispheric disconnection surgery in patients with drug-resistant epilepsy

BACKGROUND: Hemispheric disconnection surgery is a safe and effective therapeutic modality for drug-resistant epilepsy (DRE) secondary to hemispheric or multilobar lesions, while the dynamic evolutionary characteristics of postoperative electroencephalogram (EEG) and its clinical prognostic value remain unclear with no relevant systematic follow-up reports currently available. This study aims to retrospectively analyze EEG changes following hemispheric disconnection surgery in patients with DRE and to assess their clinical significance. METHODS: We enrolled patients with DRE who underwent hemispheric disconnection surgery. EEG data were collected preoperatively and at 3 months, 1 year, and 2 years postoperatively. We analyzed EEG characteristics (including background activity and interictal and ictal patterns) at each time point and evaluated their correlation with prognosis. RESULTS: Sixteen patients met the inclusion criteria; 14 (87.5%) had no seizure recurrence within the 2-year follow-up period. EEG analysis at postoperative time points showed that: (1) The EEG background activity on the ipsilateral side was dominated by slow waves and low-voltage activity. The proportion of low-voltage background activity gradually increased within 1 year, and slow waves became the predominant pattern thereafter. While, the contralateral background activity normalized within 1 year. (2) Epileptiform discharges on the ipsilateral side initially increased then decreased, accompanied by a reversible burst-suppression-like pattern. Epileptiform discharges on the contralateral side gradually decreased and disappeared in most patients (8/11, 72.7%). (3) In this study, seizure recurrence occurred in 2 patients, which was associated with incomplete disconnection and complications. Seizures were subsequently controlled after reoperation. (4) No postoperative EEG features were significantly correlated with prognosis (all P > 0.05). CONCLUSIONS: Following hemispheric disconnection, dynamic alterations are observed in bilateral EEG recordings. A postoperative burst-suppression-like pattern is commonly observed on the ipsilateral side. In this small-sample study, no significant association was found between postoperative EEG characteristics and prognosis.