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Epileptic Disorders

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Epileptiform abnormalities in the disconnected hemisphere are common in seizure-free patients after hemispherectomy Volume 24, issue 5, October 2022

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Tables

Authors
1 The Charles Shor Epilepsy Center, Neurological Institute, Cleveland Clinic, Cleveland, Ohio, USA
2 King Abdulaziz University, Division of Neurology, Department of Medicine, Jeddah, Saudi Arabia
3 Dr. Sulaiman Al Habib Hospital, Division of Neurology, Riyadh, Saudi Arabia
The findings of this study were presented at the 2021 American Epilepsy Society Annual Meeting held in Chicago on December 4th, 2021. Abstract # 1.155.
Correspondence:
Ahsan N. Moosa
The Charles Shor Epilepsy Center, Neurological institute, Cleveland clinic, Cleveland, OH, 44195 USA

Objective

The spectrum of EEG abnormalities in the disconnected hemisphere in seizure-free patients after hemispherectomy has not been well characterized.

Methods

Fifty consecutive patients who were seizure-free following hemispheric disconnection were identified. Data on preoperative clinical, EEG and neuroimaging findings and postoperative EEG findings and antiseizure medication status were collected.

Results

Forty-seven patients (94%) had functional hemispherectomy, and three (6%) had more extensive tissue resection of the posterior quadrant or frontal region along with hemispheric disconnection. Etiologies included: residual effects from vascular lesions including perinatal stroke in 35 patients, Rasmussen encephalitis in six, malformation of cortical development in seven, and Sturge-Weber syndrome in two. Pre-operative EEG showed focal epileptiform discharges in the affected hemisphere in 26 patients and in both hemispheres in 19. Eleven patients had diffuse bisynchronous epileptiform discharges. Postoperative EEGs at six to 12 months after surgery showed slowing and attenuation of physiological rhythms on the operated side in all patients. Thirty-four patients (68%) had epileptiform discharges exclusively from the operated hemisphere, six (12%) had bilateral independent epileptiform discharges, nine (18%) had no epileptiform discharges on either side, and one (2%) had epileptiform discharges from the contralateral hemisphere only. Lateralized periodic discharges from the operated hemisphere were noted in three patients (6%). EEG seizures from the operated hemisphere without clinical signs were noted in four patients (8%). After a median follow-up of three years, 30 patients (60%) were off all antiseizure medications, including 8/9 (89%) patients with no epileptiform discharges, 20/34 (59%) patients with postoperative epileptiform discharges from the operated hemisphere, and 2/7 (28%) patients with contralateral discharges.

Significance

The majority of patients who are seizure-free after disconnective hemispherectomy will continue to show epileptiform discharges in the operated hemisphere. The presence of such discharges should not preclude tapering, nor prompt restarting of antiseizure medication in seizure-free patients.