SUMMARYPurpose: To evaluate the seizure control and developmental outcomes after hemispherotomy for refractory epilepsy in childhood and to identify their predictive factors. Methods: We retrospectively studied the clinical courses and outcomes of 52 children with refractory epilepsy who underwent hemispherotomy in the Epilepsy Center Freiburg between 2002 and 2011. Key Findings: Mean age at epilepsy onset was 1.8 years (range 0-8 years) and mean age at surgery was 6.7 years (range 6 months-18 years). The underlying etiology was congenital in 22 (42%) children, acquired in 24 (46%), and progressive in 6 (12%). At final follow-up of 1-9.8 years (mean 3.3), 43 children (83%) were seizure-free. Seizure outcome was not correlated to etiology, with the exception of hemimegalencephaly that was linked to poor seizure control. Presurgical development was impaired in all but one child. Postsurgical development highly correlated with presurgical development. Patients with acquired or progressive etiology, later epilepsy onset, and subsequent later surgery exhibited higher presurgical developmental status that substantially determined postoperative developmental outcome. Improved postsurgical development was determined by acquired etiology and seizure freedom off antiepileptic drugs. Significance: In our study, most of the selected children and adolescents achieved seizure freedom, including those with congenital etiology. Developmental outcomes, however, were superior in patients with acquired etiology and older age at surgery, underscoring that it is never too late to reap the benefits of this procedure in terms of both epilepsy and development.

Our study demonstrates that epilepsy surgery in very young children is safe as well as efficient regarding long-term seizure freedom and antiepileptic drug cessation in selected candidates. Longer epilepsy duration is the only modifiable predictor of impaired adaptive and cognitive development, thus supporting early surgical intervention.