Abstracts

Rationale: For focal epilepsy with foci resides in eloquent cortex, electrical cortical stimulation is potentially effective to control seizure and avoid functional deficit caused by surgical resection. Here we report long-term follow-up results in six patients receiving subdural cortical stimulation for drug-resistant focal epilepsy. Methods: All patients received subdural electrocorticography (ECoG) with intra-operative monitoring and post-operative video-EEG recording for one week. Eloquent motor/sensory/language cortexes were identified with functional mapping by direct electrical stimulation method. The patients underwent implantation of either one or two strips of 4-contact subdural electrodes (Resume, Medtronic, Inc., Minneapolis, Minnesota, USA) to cover the possible epileptic foci. Seven days later, an implantable pulse generator was placed infra-clavicular subcutaneously and connected to stimulation electrodes via a lead extension. The cortical stimulation was turned on two weeks later, with initial parameters: bipolar, 1-2 V, 90 s, and 3-5 Hz, cycling or continuous stimulation. The frequency of seizures was compared with baseline data. Results: Two men and four women were included, with age 14-26 years. Etiologies of epilepsy include polymicrogyria for two patients, whereas post-traumatic, post-encephalitis, periventricular heterotopia, and suspected autosomal dominant lateral temporal lobe epilepsy were the etiologies for the remaining four patients. Mean follow-up period was 52.5 months (range 36-72 months). Among the six patients, five patients had an average reduction of 58% (range -3~99%) in seizure frequency after cortical stimulation. The remaining one patient had complex partial status epilepticus at baseline, with an improvement of conscious level and decreased generalized tonic-clonic seizures after cortical stimulation. One patient had post-implantation scalp infection due to allergic reaction to the cable, and needed surgical removal of the implantation system. No other implantation- or stimulation-related side effects occurred. Conclusions: Cortical stimulation of epileptic foci improves seizure control in patients with drug-resistant focal epilepsy of various etiologies. Stimulation of eloquent cortex is well tolerated for most of our patients, without any functional comorbidity. The optimal parameters of stimulation need to be adjusted on an individual basis. Funding: None.