Abstracts

Rationale: Intracranial strip, grid, and depth electrodes are utilized during intracranial electroencephalography (iEEG) to maximize the yield of intracranial monitoring and to guide epilepsy surgery. Depth electrodes enable recording of deep anatomical areas. This unique characteristic makes depth electrodes well suited for recording from the opercular cortex within the Sylvian fissure. The goal of this study was to assess the utility and morbidity of superior temporal plane depth electrodes in intracranial electrode monitoring. Methods: A retrospective analysis of all the patients undergoing iEEG monitoring at the University of Iowa Hospitals and Clinics since 2013 was performed. The basic demographic and perioperative information were reviewed. In particular, we identified cases in which depth electrodes were placed within the superior temporal plane and evaluated the utility of these electrodes in management of these patients. Morbidity associated with placement of these electrodes was also reviewed. Results: From January 2013 to April 2016, 48 patients underwent iEEG monitoring, and seizure foci were localized and resection/disconnection procedures performed in 38 patients (79%). For recording within the superior temporal plane, a depth electrode was placed only in the Heschl's gyrus in 18 patients (HGD electrode). A depth electrode was placed only in the planum temporale in four patients (PTD electrode). A combination of the HGD and PTD electrodes were placed in 4 patients. Using the HGD and PTD electrodes, seizure onset was detected in one and three patients, seizure spreading in five and two patients, and subclinical seizures in one and two patients, respectively. Seizure focus resection involved portions of the superior temporal plane due to seizure onset or spreading involving the HGD and PTD electrodes in two and two patients, respectively. Seizure foci were localized to various portions of the temporal lobe in all of the 5 cases of seizure spreading involving the HGD electrodes. Among the two cases where seizures spread to the PTD electrodes, a seizure focus was localized to the mesial temporal lobe in one patient and multiple independent seizure foci were localized to the temporal and extratemporal areas in the other patient. No perioperative complications directly resulting from placement of the electrodes in the superior temporal plane were observed among these patients despite a few other unrelated overall complications. Conclusions: The strategic placement of depth electrodes in iEEG is critical to maximize the yield of the chronic monitoring. Our experience showed that depth electrodes placed within the superior temporal plane in an appropriate patient group can provide useful information in guidance of epilepsy surgery without any additional significant risk of perioperative comorbidities directly due to these electrodes. Funding: None