THE ROLE OF HEMISPHERECTOMY IN THE TREATMENT OF HOLOHEMISPHERIC HEMIMEGALOENCEPHALY

The role of hemispherectomy in treating holohemispheric hemimegaloence phaly, a unilateral brain malformation, is still not well defined. The authors describe the cases of five infants presenting with intractabl e seizures, progressive neurological deficits, and severe developmenta l delay. Electroencephalography (EEG) showed generalized polyspikes fr om the megaloencephalic hemisphere and progressive slowing on the oppo site side in all children; contralateral seizure spikes occurred in th ree children. Three of the five children underwent hemispherectomy for intractable seizures before 2 years of age, after which the seizures subsided completely in two children and improved remarkably in the thi rd. Preoperative Wada testing proved useful in evaluating pharmacologi cally the effect of hemispherectomy on contralateral polyspikes. Posto perative EEG revealed the absence of polyspikes in the operated hemisp here and decreased slowing on the contralateral side. Psychomotor deve lopment in the surgically treated infants exceeded that of the childre n not undergoing hemispherectomy. Of the two children treated medicall y, one died at 4 years of age in status epilepticus and the other (now 5 years old) has frequent seizures and severe developmental delay. Ba sed on these results, hemispherectomy appears to be a useful procedure for controlling seizures and improving psychomotor development in chi ldren with hemimegaloencephaly involving the entire hemisphere. Surger y in infancy can prevent or minimize seizure foci and encephalopathic changes that may develop in the contralateral hemisphere. Staging the procedure and exercising meticulous hemostasis make surgery relatively safe in infants who otherwise may have significant blood loss associa ted with increased blood flow to the megaloencephalic hemisphere.