Introduction

One third of patients with focal epilepsy are pharmacoresistant, and only some of them are good candidates for epilepsy surgery. Stimulation of the epileptic focus has been reported to effectively reduce seizure frequency using a new epicranially implanted device (EASEE). So far data have been published for a treatment period of 6 months (Schulze-Bonhage et al., JAMA Neurol 2023, 80:588-596). We here for the first time report long-term treatment efficacy over a period of 24 months of this new treatment approach based on the pooled-analysis of two prospective, multicenter, single-arm trials with the implantable EASEE System (EASEE II and PIMIDES I).

Objectives

To analyze long-term efficacy of epicranial focal cortex stimulation, we here report long-term treatment efficacy over a period of 24 months of this new treatment approach based on the pooled-analysis of two prospective, multicenter, single-arm trials with the implantable EASEE System (EASEE II and PIMIDES I).

Materials ane Methods

In both trials, a total of 33 patients (18 male, 15 female, age 18-75 y, mean age 34.6 y) from seven epilepsy centers in Germany and Belgium were implanted with a neurostimulation system consisting of a pulse generator and a 5-channel electrode array. The system delivers FCS via the stimulation electrode implanted epicranially above the individual epileptic focus region. Outcome data from unblinded stimulation were analyzed based on seizure diaries over a follow-up period of 2 years regarding monthly responder rate (RR: ≥ 50% seizure frequency reduction), monthly seizure frequency (SF), and safety.

Results

81% of patients initially stimulated choose to continue epicranial focus stimulation for a period of 2 years. The responder rate was 41.4 % (95% CI, 23.5%-61.1%; n=29) at 1 year follow-up and 65.4 % at 2 years follow-up (95% CI, 44.3%-82.8%; n=26).

The median monthly seizure frequency decreased from a median baseline of 12/month, to 8/month at 1 year and to 5/month at 1.5 and 2 years follow-up, corresponding to a median seizure frequency reduction by 33% at 12 months follow-up (n=29), and 68% after 18 and 24 months follow-up (n=26).

There were no serious adverse events considered related to the neurostimulation procedure also during the prolonged stimulation period.

Conclusions

Long-term outcomes suggest that epicranial electrical stimulation of the epileptic focus using the EASEE System is a new treatment approach with pharmacoresistant focal epilepsy with maintained efficacy and excellent tolerability also over a two-year-period.