Correlates of intellectual development before and after hemispherotomy: an analysis of 75 children and adolescents

This study describes the intellectual development of 75 children and adolescents who underwent hemispherotomy. Furthermore, we aimed to reveal predicting factors on pre- and postsurgical development with a focus on the role of aetiology. We analysed presurgical and six-month postsurgical developmental and intellectual data of 75 patients (age range: 0.87-19.78 years) and divided them into two groups: a not severely impaired group in which outcome of intellectual functioning was reported based on FSIQ score, and a severely impaired group (not testable by IQ tests) in which intellectual developmental outcome was described based on developmental quotients instead. In the not severely impaired group (n = 31), the preoperative level of intellectual functioning was a strong predictor of postoperative intellectual outcome; for 22/31 (71%) patients, postoperative FSIQ and its subscales were similar to preoperative levels. Improvements were observed for FSIQ in five patients, only for Verbal IQ in one patient and only for Performance IQ in one further patient; significant losses occurred in two patients, only for Performance IQ in both. In the severely impaired group, 30/40 (75%) patients showed further development after surgery, nine (23%) patients had the same results as before surgery, and one (2%) patient showed regression. Longer duration of presurgical epilepsy was related to a marginally lower presurgical developmental level, and good seizure outcome was a predictor of better postoperative development. For all patients, early age at seizure onset and early lesion origin correlated with poorer presurgical intellectual development. Although an entire hemisphere was disconnected, most patients exhibited ongoing development after hemispherotomy or had at least the same preoperative intellectual status; deterioration was rare.