Cognitive safety under epicranial cortex stimulation of the epileptic focus

Epicranial focal cortex stimulation (FCS) is a new CE-certified treatment for pharmacoresistant focal epilepsy. In a multicenter observational trial, we report cognitive tolerability in 11 patients with pharmacoresistant epilepsy undergoing epicranial focal cortex stimulation (eFCS) over the predominant seizure focus (left temporal (N = 4), central (N = 2 right, N = 1 left), left frontal (N = 2), left temporoparietal (N = 1), and left frontoparietal (N = 1)). Extensive cognitive assessment focused on domains represented in the stimulated areas and was compared between baseline and first and last follow-up (after a median 35 months of stimulation). Based on the reliable change index, the majority of patients remained cognitively stable; 3/11 patients showed improvements in more than one cognitive parameter at both follow-up assessments. Isolated task parameters deteriorated exclusively at one time point; no patient revealed consistent worsening. Cognitive changes did not correspond to stimulation site or seizure outcome. Overall, the results from this case study provide preliminary evidence of stable cognitive functioning under focal cortical stimulation even if performed over eloquent brain regions. These findings are limited by the patient sample size and medication changes in part of the patients and need corroboration in larger patient cohorts. PLAIN LANGUAGE SUMMARY: We report on preliminary results of a new brain stimulation treatment for epilepsy that doesn't respond to medication. Over about 3 years, 11 patients showed stable cognitive performance, some even improved, and no patient had lasting declines. These results provide preliminary evidence that the treatment is generally safe for brain function. However, larger studies are needed to confirm these findings.