Abstracts

RATIONALE: Patients with intractable localization related epilepsy of temporal neocortical or extra-temporal origin may have lateralized onsets but of diffuse or multifocal origin. Some will have poor surgical outcome following resective surgery due to inadequate localization of ictal onset zone(s) after conventional intracranial electrode evaluation. We reviewed our pediatric experience with multi-stage epilepsy surgery, defined as intracranial electrode reevaluation immediately after initial resection to allow consideration of further tissue resection in select cases.
METHODS: 12 pediatric patients with medically refractory localization related epilepsy underwent multistage epilepsy surgery between 1996-2001. The database was queried for peri-operative strategy, post operative complications, pathologic diagnosis , and outcome. Outcome was graded on a 1-3 scale: 1=seizure free, 2=reduction in frequency/intensity of seizures, 3=no improvement.
RESULTS: The average age was 7.75 (range .5-14 years). Mean duration of epilepsy was 4.4 years (range .5-10 years). In all cases, seizures were previously lateralized by either non-invasive monitoring or bilateral subdural electrode survey. All patients had ictal analysis after standard subdural electrode placement followed by resection or subpial transection. In 12/12, a second intracranial electrode evaluation was undertaken immediately after initial resection which led to further tissue removal in 9/12. In one case, intracranial electrodes were replaced twice prompting two ablations in addition to the initial procedure. Mean duration of total monitoring was 11.6 days. First invasive monitoring averaged 6.5 days and the second invasive monitoring averaged 4.9 days. In the one isolated case with three invasive analyses, the third monitoring experience was 3 days. Reasons for multiple intracranial reinvestigations included (i) incomplete localization after first invasive analysis (ii) multifocality requiring electrode repositioning and repeat functional mapping (iii) proximity to eloquent cortex, limiting first resection with reinvestigation to determine necessity of extending resection. Complications included pneumonia in one and transient hemiparesis in one. The majority had a pathologic correlate of dysplasia. Mean duration of follow up was 17.8 mos. Outcome grade was: grade 1 (6/12), grade 2 (5/12), grade 3 (1/12).
CONCLUSIONS: Although repeat intracranial investigation performed greater than one year after failed epilepsy surgery has been reported to be a successful methodology, our results indicate the efficacy,utility,and safety of multiple intracranial electrode investigations and surgical reconsiderations within one single hospitalization.