Authors :
Presenting Author: Akshaya Rathin Sivaji, MD – Epilepsy Center, Neurological Institute, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
Mohamed Ahmed Abdelsabour Hasan, MD – University Hospitals Cleveland Medical Center, Cleveland, OH, USA
Lena Hebermehl, MD – University Hospitals, Cleveland Medical Center
Saeideh Salahizadeh, MD – Epilepsy Center, Neurological Institute, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
Guadalupe Fernandez-Baca Vaca, MD – Epilepsy Center, Neurological Institute, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
Michael D Staudt, MD – Department of Neurological Surgery, Case Western Reserve University School of Medicine, Cleveland, OH, USA
Neel Fotedar, MD – Epilepsy Center, Neurological Institute, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
Rationale:
Stereoelectroencephalography(SEEG) electrode implantation in patients with temporal lobe epilepsy follows a standardized implantation strategy, including extra-temporal electrodes in regions such as the orbitofrontal, cingulate, and insular cortex. However, the necessity of extra-temporal electrodes in cases where phase I evaluation strongly suggests a temporal seizure focus remains unclear. We aim to evaluate the utility of extra-temporal SEEG electrodes in localizing seizure onset zone in patients with a robust phase I hypothesis of temporal or mesial temporal epilepsy.
Methods:
We retrospectively analyzed our epilepsy surgery database and identified patients in whom phase I evaluation localized the epileptogenic zone to either temporal or mesial-temporal region. We included patients with both temporal and extra-temporal SEEG implantation irrespective of surgical status. We assessed the presence of ictal/interictal activity in extra-temporal regions.
Results:
A total of 47 patients were included, of whom 31 had available post-operative follow-up data, while 3 did not undergo surgery. MRI was non-lesional in 30 patients(63.8%). SEEG analysis demonstrated 44 patients(93.6%) had seizures exclusively originating from temporal electrodes, with no ictal activity recorded at the onset in extra-temporal regions. Two patients exhibited non-habitual stimulation-induced seizure from extra-temporal electrodes; however, their spontaneous habitual seizures remained confined to the temporal lobe. One patient had a spontaneous habitual seizure arising from orbitofrontal region.
Regarding inter-ictal activity, 15 patients(31.9%) displayed extra-temporal spikes. However, in all cases temporal interictal discharges were prevalent. Among the 31 patients with available postoperative follow-up, surgical outcomes were favorable, with 27(87.1%) achieving Engel class I outcome at two years post-surgery. At the most recent follow-up, 22 patients(70.1%) remained Engel class I.
Conclusions:
Our findings suggest, patients with strong phase I hypothesis of temporal epilepsy, extra-temporal SEEG electrodes very rarely demonstrate ictal onset. Limiting electrode implantation to the temporal lobe in such cases may improve procedural efficiency and reduce patient burden without compromising diagnostic accuracy. Further studies with larger cohorts are needed to confirm these findings and optimize SEEG implantation.
Funding: None