LINAC-based stereotactic radiosurgery targeting the hippocampus in mesial temporal lobe epilepsy: a single-center case series.

BACKGROUND: Epilepsy is a neurological disorder affecting over 50 million people worldwide, with a global incidence of 7.6 per 1,000 individuals. Mesial temporal lobe epilepsy (MTLE) is characterized by recurrent, unprovoked seizures originating in the temporal lobe. The standard surgical treatment is anterior temporal lobectomy; however, many patients are not suitable candidates due to the risk of adverse effects, including significant memory impairment, language deficits, bilateral temporal involvement, or reluctance to undergo resective surgery. This study aimed to evaluate the anticonvulsant effect of linear accelerator (LINAC)-based radiosurgery in patients with drug-resistant unilateral MTLE. METHODS: A prospective, single-center, exploratory pilot case series was conducted from March 1, 2017, to March 1, 2020, at the Hospital de Especialidades, Centro Médico Nacional de Occidente. Patients aged 18-65 years with a confirmed diagnosis of drug-resistant unilateral MTLE were enrolled. The primary outcome was defined as the achievement of complete freedom from disabling seizures (Engel Class I and ILAE Class 1) at 24 months post-radiosurgery. Secondary efficacy outcomes included achieving a ≥ 50% reduction in seizure frequency. The prescribed dose of 22 Gy was normalized to the 50% isodose line at the isocenter, ensuring ≥ 90% target coverage (V100 ≥ 90%) and a dose gradient < 10%, targeting the hippocampal head and anterior body. RESULTS: Seven patients were included. Median seizure frequency decreased from 12 seizures/month at baseline to 3.5 seizures/month at 24 months, corresponding to a median reduction of 75.6%.Longitudinal analysis demonstrated a significant reduction in seizure frequency over time (Friedman χ2 = 14.62, p = 0.006), with significant differences between baseline and all follow-up periods (p = 0.018). No patient achieved seizure freedom. Kaplan-Meier analysis demonstrated that 71.4% of patients maintained a clinically meaningful seizure reduction (≥ 50% from baseline) throughout the 24-month follow-up. Patients with preoperative auras exhibited a median aura reduction of 60%, whereas de novo auras developed in three previously aura-free patients. Adverse events included visual field deficits in three patients (42.8%), psychiatric complications in two (28.6%), and clinically significant memory decline in one patient with pre-existing cognitive impairment. CONCLUSIONS: LINAC-based stereotactic radiosurgery targeting the hippocampal head and anterior body achieved a clinically meaningful reduction in seizure frequency in selected patients with drug-resistant MTLE. However, complete seizure freedom was not achieved, and delayed adverse events were observed. TRIAL REGISTRATION: The study was approved by the ethics committee of the Hospital de Especialidades, Centro Médico Nacional de Occidente (approval number R-2017-1301-57).