Abstracts

Rationale: To evaluate the surgical outcome in a select group of medically refractory epilepsy patients who have undergone corpus callosotomy combined with subdural EEG electrode placement as the initial step of multistage epilepsy surgery. Methods: A retrospective chart review was undertaken of 14 children (ages 5-18) in whom a corpus callosotomy with subdural bihemispheric EEG electrode placement was performed as the initial step of multistage epilepsy surgery from 2003 to the present. Every patient had medically refractory symptomatic generalized or localization-related epilepsy. All of the patients had tonic and atonic seizures; 3 patients also had complex partial seizures. All of the patients had frequent generalized epileptiform discharges, as well as multifocal independent epileptiform discharges on surface EEG monitoring. All of the patients had either normal MRI scans of the brain (8 out of 14 patients) or bihemispheric abnormalities (6 out of 14 patients). Their surgical outcomes were compared to those of other patients who have undergone more conventional epilepsy surgeries (typically placement of subdural strips and grids without corpus callosotomy) at the same institution and compared to the outcomes of pediatric patients who have undergone corpus callosotomy as reported in the literature. Results: Of the 14 patients who underwent corpus callosotomy and placement of subdural strips and grids, 9 went on to further resection according to the localizing data obtained from invasive EEG monitoring. Mean patient age was 10 years. Duration of invasive monitoring ranged from 3 to 14 days. Follow-up ranged from 3 to 51 months (mean 28.6 months). Complications included wound infection (2), subdural hematoma prompting premature electrode removal (1), epidural fluid accumulation after removal of electrodes requiring evacuation (1), and venous infarct leading to persistent foot-drop (1). There were no cases of major permanent neurological deficit. An Engel outcome score of Class I (patient is seizure-free or has only non-disabling simple partial seizures) was achieved in 6 of the 14 patients (43%), only one of whom did not undergo further resection because no seizures were captured during the period of invasive monitoring. Outcomes were 43% Engel Class I (6 of 14 patients), 43% Class III (6 of 14 patients), and 14% Class IV (2 of 14 patients). 86% of the patients had improvement in quality of life (QOL), as documented on QOL surveys. Conclusions: This patient population presents a treatment challenge often relegated to corpus callosotomy for palliative purposes alone. However, our data show that because a corpus callosotomy slows the spread of abnormal electrical activity between the hemispheres, it may provide an opportunity to gain better localizing data that may lead to further resection of the epileptogenic zone, thereby improving overall seizure outcome in this group generally regarded as having poor surgical prognostic factors.