Abstracts

RATIONALE: In the evaluation of patients for epilepsy surgery, noninvasive studies may result in discordant or inadequate localization. Implantation of intracranial electrodes over hypothetical regions of epileptogenicity may not effectively localize an epileptogenic region due to sampling error. Additional electrode implantation may result in a localizing ictal pattern. This study reviews our experience with supplementary intracranial implantation.
METHODS: All patients who underwent intracranial electrode implantation for extraoperative electrocorticography at Henry Ford Hospital between 1993-2000 (n=158) were analyzed. Ten cases were identified in which initial intracranial implantation showed ictal patterns with limited localizing value. These select cases underwent supplementary intracranial implantation, commonly by burr hole craniectomy, during the same hospitalization in an attempt to localize the seizure focus. Both intracranial ictal patterns and clinical onset were reviewed and compared with the initial intracranial investigation.
RESULTS: A more localized ictal pattern was identified with additional electrodes. Earlier EEG ictal onset when compared to initial clinical change,provided sufficient data to confidently identify a focus. Six of the 10 patients had a favorable surgical outcome, while the remaining 4 patients had insufficient improvements in their seizure pattern and were referred for vagus nerve stimulator placement. No infection resulted from supplementary implantation during the same inpatient hospitalization.
CONCLUSIONS: In selected patients, supplementary intracranial implantation may provide additional localizing data and result in a positive surgical outcome.