Presenter(s)
V. Shankar1, H. S. Vangipuram2, S. Ghosh3, S. Paramasivan4, D. Arjundas5, V. R. Anand6, and S. Cholayil7; 1Division of Radiosurgery, Apollo Cancer Centers, Chennai, India, 2Department of Undergradute Education, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India, 3Dept. of Neurosurgery, Apollo Proton Cancer Center, Chennai, India, 4Dept. of Neurosurgery, Apollo Hospitals, Greams Unit, Chennai, India, 5Chief Neurologist, Mercury Hospital, Chennai, India, 6Sai Neuro Hospital, Chennai, India, 7Apollo Cancer Centers, Chennai, India
Purpose/Objective(s):
Management of drug-resistant dominant mesial temporal lobe epilepsy (MTLE) without demonstrable lesions on MRI or FDG-PET remains challenging, as conventional resection carries substantial risk of verbal memory and language impairment. We report our institutional experience integrating stereoelectroencephalography (SEEG) with advanced multimodal imaging to achieve physiology-based localization followed by SEEG-guided stereotactic radiosurgery (SRS) in carefully selected MRI-negative, PET-negative dominant MTLE.
Materials/Methods:
Between 2016 and 2022, eight consecutive patients with drug-resistant focal epilepsy involving the language-dominant mesial temporal lobe and preserved baseline verbal memory (composite scores =75th percentile) were reviewed in a multidisciplinary epilepsy surgery conference and underwent comprehensive presurgical evaluation, including seizure semiology, prolonged video-EEG monitoring, functional language mapping, and structured neuropsychological testing of memory (WMS III/IV, RAVLT/CVLT), global cognition (WAIS IV), language (Boston Naming Test, verbal fluency), and executive function. Non-localizing 3T MRI and FDG-PET were supplemented by SISCOM, electrical source imaging, and MRI–PET fusion to guide SEEG implantation. Epileptogenic zones were defined by concordant spontaneous and stimulation-induced ictal patterns with electroclinical correlation, integrating seizure semiology, electrophysiology, and contact-level SEEG onset biology. Patients demonstrating focal anterior mesial temporal onset without bilateral or temporal-plus network involvement underwent single-fraction SRS (CyberKnife, 20 Gy to the 50% isodose), enabling conformal targeting of SEEG-defined ictal contacts while sparing eloquent cortex. Seizure outcomes were assessed using Engel classification. Median follow-up was 36 months.
Results:
SEEG confirmed focal anterior mesial temporal ictal onset in all patients. At last follow-up, 4 (50%) achieved Engel I, 2 (25%) Engel III, and 2 (25%) Engel IV outcomes, yielding a 75% meaningful response (Engel I–III). Seizure remission evolved over 12–18 months post-SRS. Transient radiation-related edema occurred in all responders and was managed medically without permanent neurological sequelae. Follow-up neuropsychological testing demonstrated preserved proportional verbal memory and language, with six patients (75%) maintaining composite cognitive scores =75th percentile and no clinically significant naming or fluency decline.
Conclusion:
SEEG-guided SRS offers an electrophysiology-anchored, cognition-preserving, minimally invasive treatment strategy for MRI-negative dominant MTLE, achieving durable seizure control with acceptable toxicity. Despite delayed remission and predictable, medically manageable edema, this functional radiosurgical approach may represent a viable alternative for patients in whom resection confers high cognitive risk.
