Anterior callosotomy in the management of intractable epileptic seizures: significance of the extent of resection.

We report our series of twenty consecutive patients who underwent corpus callosotomy for medically intractable epilepsy. The follow-up is 6.7 +/- 0.5 years. Sixteen of 20 patients (80%) had a favourable outcome. Six patients have remained free of major generalized motor seizures, and ten further patients experienced significant sustained reduction in the severity and frequency of the seizures. The type of seizures associated with improved outcome were drop attacks, and generalized tonic-clonic seizures, in 11 of 13 (85%) and 14 of 18 (78%) of the patients, respectively. In order to establish the extent of necessary callosal resection to achieve seizure control, the outcome of patients was correlated with the extent of callosal sectioning on postoperative magnetic resonance imaging. This study confirms that an anterior callosal resection of two-thirds (or 65%) is sufficient to achieve significant improvement in seizure control with an acceptable morbidity in judiciously selected patients with medically intractable epilepsy. Results also suggest that the patient's history and clinical classification of the seizures have prognostic value as selection criteria for patients referred for this operation. In this series, no prognostic value was established for pre-operative electroencephalographic patterns, or neuroimaging findings.