Hemispherectomy: the full half of the glass.

Commentary Hemispherectomy was introduced by Walter Dandy in 1928 for removal of a right hemispheric glioma (1) but was pioneered for use in catastrophic epilepsy by McKenzie a decade later (2). The procedure was abandoned for years due to its morbidity and mortality but was repopularized in 1950 by Krynauw, who used it to treat infantile hemiplegia (3). The techniques of hemispherectomy then underwent many changes over the years, with Rasmussen developing the notion of functional hemispherectomy in 1974, which in turn, underwent further modifications with very low mortality rates (4). Hemispherectomy is now a well-established procedure for holohemispheric drug-resistant epilepsies, constituting 20–40% of all pediatric epilepsy surgeries at some centers (5). These epilepsies are often associated with hemimegalencephaly, porencephaly, malformations of cortical development, Sturge–Weber syndrome, infantile hemiplegia, and Rasmussen’s encephalitis. Other etiologies that may be appropriate for hemispherectomy include stroke, trauma, arteriovenous malformations, hemiatrophy, and tuberous sclerosis. Candidates for hemispherectomy typically have hemiparesis and other baseline neurologic deficits that lateralize to the epileptic hemisphere. Furthermore, due to its overall long-term cognitive, behavioral, and psychosocial benefits, this surgery is also recommended in individuals who have retained some functions in the diseased hemisphere, especially when surgery is performed early. Such improvements often outweigh any worsening of motor impairments (6). Additionally, the young brain has remarkable plasticity that facilitates reorganization of eloquent functions. This is exemplified by a child whose baseline language fMRI lateralized to the left, but after left hemispherectomy, the fMRI showed evidence of later reorganization of language functions to the right (7). Moosa et al. studied 186 children who underwent hemispherectomy by a single surgeon (8), with the goal of assessing longitudinal outcome of seizure freedom rates by survival analysis, and predictors of seizure outcome by proportional hazard modeling. They excluded 3 patients due to loss of follow-up and 13 due to emergence of non-epileptic paroxysmal events. Of the remaining 170 patients, 112 (66%) were seizure free after a mean follow-up period of 5.3 (± 3.3) years. Of those who experienced seizure recurrence, 8 patients achieved late remission and 16 achieved more than 90% reduction of seizure frequency, increasing the number of patients achieving major improvement to 136 patients (80%). In addition, the authors mention that the 13 excluded subjects with nonepileptic events also experienced resolution of their habitual seizures. Interestingly, 76 (67%) of the seizure-free subjects were not on antiepileptic medications. Survival analysis found a seizure Longitudinal Seizure Outcome and Prognostic Predictors After Hemispherectomy in 170 Children.