Abstracts

RATIONALE: Simultaneous implantation of subdural grid and intracerebral depth electrodes is an extension of available techniques for invasive monitoring and seizure localization in epilepsy surgery candidates. We describe this combined approach to invasive epilepsy monitoring, and assess its safety, potential for seizure localization, and influence on surgical outcome. METHODS: We studied all temporal lobectomy patients who had simultaneous intracerebral grid and depth electrodes at the University of Maryland Medical Center. All patients required temporal subdural grids for further localization or language mapping. Our standard practice is to also place ipsilateral depth electrodes in the mesial temporal region through the same craniotomy site. This is intended to allow better seizure localization and to guide surgical resection. We analyzed several issues: 1) surgical complications, 2) numbers of mesial temporal vs. neocortical temporal seizure onsets, and 3) outcomes. RESULTS: There were 56 temporal lobectomy patients who were studied with simultaneous subdural grid and depth electrodes. No operative or post-operative complications were related to the procedure. For 44 patients, adequate information on seizure localization and outcomes at one year or longer were available. Mesial temporal onsets were found in 30 patients (68%). Neocortical temporal seizure onsets occurred in 10 patients (23%). Four patients (9%) had both lateral and mesial or simultaneous onsets. Outcomes were better for patients with mesial temporal onset of seizures. Overall, 33 of 44 patients (73%) had "good" outcomes (Engel Class I or II). Outcome was good in 24 of 30 patients (80%) with mesial onset, 5 of 10 with neocortical (50%), and 3 of 4 (75%) with simultaneous or both lateral and mesial onsets. CONCLUSIONS: Simultaneous subdural grid and depth electrodes is a safe and potentially useful technique for intracranial localization of temporal lobe seizures. Patients with mesial temporal onsets have the best outcomes, but this technique could be useful for better tailoring temporal lobe resections and improving outcomes for other patients as well.