Abstracts

RATIONALE: Invasive monitoring is frequently needed to precisely localize seizure foci. In temporal lobe epilepsy it is sometimes difficult to lateralize seizure origin, or localize origin to lateral versus mesial temporal regions. This specific localization may be particularly important for patients interested in more selective resection for mesial temporal epilepsy, and may require invasive monitoring. We present a modified technique for image-guided, endoscopic placement of an intraventricular electrode array which abuts the amygdalo-hippocampal complex.
METHODS: We selected 8 patients with suspected mesial temporal lobe epilepsy for placement of intraventricular electrodes in conjunction with other invasive monitoring procedures. These patients were evaluated by the Vanderbilt Multidisciplinary Epilepsy Surgery Group. The electrodes were custom-made depth electrode produced by Ad-Tech Medical Instruments. Frameless image guidance and a rigid, neuro-endoscope were used to assist in placing the electrode within the lateral ventricular system. The electrodes were bilateral in all but two patients. In addition to intraventricular electrodes, 7 patients underwent placement of subdural grid or strip electrodes and 4 patients had foramen ovale electrodes. Seven patients had adequate localization in one temporal lobe and had temporal lobe resective surgery. One patient was not offered surgery because of independent occipital foci. The follow-up period ranged from 8 months to 2.5 years.
RESULTS: As a result of information obtained from the invasive monitoring data, we were able to offer surgery to seven patients. Two cases had seizure onset localized and lateralized only with the depth electrodes. In the remaining cases depth electrodes provided data complementing information from other implanted electrodes. All seven operated patients have become seizure-free, but after some postoperative seizures in two. There was one instance of intraparenchymal electrode placement in the first patient, without morbidity. In one instance, one electrode was inadvertently placed into the frontal horn.
CONCLUSIONS: Endoscopically placed temporal horn intraventricular electrodes provide a safe alternative to transcortical depth electrode placement. The technique avoids potential complications associated with multiple depth electrode placements, especially when bilateral amygdalo-hippocampal electrical recordings are desired. In some of our patients the intraventricular depth electrodes provided unique data not seen with subdural strip and foramen ovale electrodes.