Abstracts

Rationale: Hemispherectomy has been utilized in intractable epilepsy, for seizure reduction or seizure freedom, and has been shown as most effective for seizure control, optimally for lateralized lesions affecting one hemisphere. The goal of the procedure has been seizure control, while the effect on interictal epileptiform activity has not been well studied. Frequent epileptiform activity such as in ESES (electrical status epilepticus during slow wave sleep), causes significant cognitive dysfunction even in the absence of seizures. In such severe cases, interictal epileptiform activity may also be a potential target for therapeutic intervention; in such case, the benefits of hemispherectomy may potentially extend beyond seizure control, by improving cognition through decreasing interictal spikes in the contralateral hemisphere. Methods: We retrospectively studied consecutive 24 patients with hemispherectomy (anatomical (13) and functional (11), from 1995-2010, through our internal database, which was approved by our institutional review board. All patients had clinical care at Children s Hospital Boston. Clinical data including demographics, interictal and ictal EEG, MRI and pathological data were analyzed. EEG findings including interictal spike distribution and frequency were compared, before and after hemispherectomy. Results: Clinical Data: Age of hemispherectomy ranged from 6 months to 12 years (mean 5.5 /-4.2 years). Pathology was diverse, including structural and functional lesions (malformations of cortical development including cortical dysplasia and hemimegalencephaly (9), perinatal stroke (3), traumatic brain injury (1), auto immune encephalitis (1), viral encephalitis (1) and of unknown etiology (1). All patients had intractable epilepsy failing multiple antiepileptic drugs (mean 2.5 /-1.2 drugs). EEG data: 16 patients had bilateral spikes seen on pre-surgical EEG. 12 out of the 16 patients, including 3 who had ESES, had complete abolition of spikes in the contralateral hemisphere on follow-up EEG (obtained 1-3 months after hemispherectomy). Remaining 4 had no change in the contralateral spikes. None of the patients showed worsening of their spike count, cognitive symptoms, or seizures. All showed improvement in quality of life. Out of the 12 patients who had complete abolition of spikes, 7 had anatomical hemispherectomy and 5 had functional hemispherectomy; thus procedure type did not influence outcome in spike reduction. Conclusions: From our data, we showed that hemispherectomy in intractable epilepsy with spikes in bilateral hemispheres, resulted in complete abolition of spikes in most cases (12 out of 16), regardless of etiology and age at surgery. From our results, we suggest that presence of epileptiform activity in bilateral hemispheres including ESES is not a contraindication for hemispherectomy; in fact, there may be advantages for improving function of the contralateral hemisphere by reducing potential epileptic and epileptiform encephalopathy from the interictal spikes.