Abstracts

Rationale: Hemispherectomy is a surgical procedure used for the treatment of medically intractable epilepsy in children with severe unilateral cortical disease secondary to malformations of cortical development as well as acquired brain lesions, such as stroke. We describe the outcome after hemispherectomy, comparing patients with brain malformations and patients with acquired brain lesions, who underwent anatomic hemispherectomy (AHE) vs. functional hemispherectomy (FHE). Methods: We describe a retrospective observational study conducted at Children’s Hospital Boston from 1997-2007. Cases were ascertained from a research database of epilepsy surgery patients from the Division of Epilepsy in accordance with the Institutional Review Board. Data were obtained from electronic records and office charts. Outcome after surgery was defined by improvement in seizures (quantity and severity) represented by Engel classification score measured at last follow-up, with a minimum of 12 months. Results: The study population comprised 23 patients. Group1 (n=9) had static acquired lesions, and Group 2 (n= 14) had developmental lesions. Median age at surgery for Group1 was 6.7 years (SD 5.17) and for Group 2 2.77 years (SD 4.01). Outcome related to seizure control was good in both groups (Engel score I for 15, II for two, III for one, IV for five). In Group1, six patients underwent AHE and three underwent FHE; none required a second procedure. In Group 2, six had AHE and seven had FHE; five patients who had had FHE (71.4%) required reoperation to complete the disconnection (Fisher exact test comparing both groups p=0.03). Conclusions: Patients with developmental lesions tend to have hemispherectomy earlier than the patients with acquired lesions, perhaps due to earlier presentation and the intractable nature of their epilepsy. Our study suggests that patients with developmental lesions who undergo FHE often require a second operation to complete their interhemispheric disconnection. This was not the case with patients with acquired lesions undergoing FHE. FHE is sometimes preferred over AHE in the youngest age group of hemipsherectomy candidates since it has lower predicted morbidity. We suspect that our findings reflect the complexity of developmental hemispheric malformations and raise the question of whether there may be abnormal or unexpected interhemipsheric connections that are not being disconnected on the first approach or whether the presence of large developmental malformations might make FHE a more technically challenging procedure in this group of patients. We plan to conduct future studies employing prospective pre- and post-FHE neuroimaging to address the former question.