Efficacy of Frameless Radiosurgical Entorhino-Amygdalohippocampectomy for Pharmacoresistant Medial Temporal Lobe Epilepsy.

PURPOSE/OBJECTIVE(S) Evaluate the efficacy and safety of Linac based surgery in the treatment of pharmaco-resistant epilepsies of mesial temporal lobe origin due to medial temporal sclerosis. MATERIALS/METHODS Retrospective single institution study comprised of 12 MTLE pts. (10 pts. with MT Sclerosis on Dominant side) who underwent SRS between August 2015 to Jan 2019. The epileptogenic substrate was localized using invasive video-EEG monitoring with foramen ovale electrodes, magnetic resonance imaging, metabolic (PET) imaging. All patients underwent detailed neuropsychological testing and the ESI-55 quality-of-life questionnaire. The radiosurgical target included Anterior part of parahippocampal region; entorhinal area adjacent to the collateral sulcus & rhinal sulcus; hippocampus - head & Anterior part and Amygdalofugal part of the amygdaloid complex. Non-coplanar Volumetrically modulated plans or non-isocentric CK plans using variable collimator were generated for prescribed mean dose of 22gy (range: 20-24 Gy), without any dose heterogeneity. Normal structures doses were within acceptable limits. Radiosurgical treatment was performed by using the C-Arm Linac with hexapod robotics (9 pts.) or frameless robotic radiosurgery system with skull tracking (3pts.). A minimum 2-year follow-up period included clinical, neuropsychological, ophthalmic (Visual field charting) & radiologic evaluations. RESULTS Median age at diagnosis is 28 yrs (Range: 17-42yrs). At each 6-month follow-up evaluation, the frequency of seizures was significantly smaller than that at the previous visit. The median seizure frequency of 10.25 the month before treatment was reduced to 0.33 at 2 years after treatment. At 2 years, 67% of the patients (8 of 12) were seizure free - 4 Engel class 1A, 3 Engel class 1B, 1 Engel class 2A responses. The median latent interval from SRS to seizure cessation was 9.5 months (range 6-20 months). One patient was immediately seizure free. The median latency in aura cessation was 14 months (range 9-22 months). Morphological changes, edema, on magnetic resonance imaging were visible at 10 months (median) after SRS (range 7-22 months) in nearly all patients. During the onset period of these radiological changes, three patients experienced headache associated, in two cases, with nausea and vomiting. In these three patients the signs resolved immediately after short course of low doses of steroids. No cases of permanent neurological deficit (except three cases of monosymptomatic visual field deficit), or morbidity, or mortality were observed CONCLUSION: Initial experience of Frameless SRS, as non-invasive technique, for MTLE provides benefits especially in young patients requiring high social skills with dominant lobe involvement in the traditional realms of safety with short- to middle-term efficacy & superior neuropsychological outcomes, similar to published series in GKS studies but with appreciated realms of patient acceptance, comfort and costs. Further long-term follow up is required.