Abstracts

Rationale: Aim of this study is to investigate cognitive performance before and after implantation of epicranial electrodes and several months of focus stimulation in a multicenter observational trial.


Methods: Patients undergoing epicranial focal cortex stimulation (eFCS) underwent extensive neuropsychological assessments prior to and on average 25±11 months (Median=29 months) after implantation. The applied test battery was adapted to the localization of the stimulation focus (see table 1). Reliable change indices were computed separately for every patient and performance was accordingly classified as either unchanged, improved, or deteriorated at follow-up. Furthermore, seizure outcome at time of follow-up was rated by neurologists.


Results: Fourteen patients (9 from Freiburg, 4 from Marburg, one from Munich) were implanted between 02/2019 and 12/2020. Two patients had to be excluded from the analysis due to technical problems, and suspected diagnosis of an additional neurodegenerative disease, respectively. The following analyses comprise the remaining 12 patients who underwent left temporal (N=4), central (N=3 right, N=1 left), left frontal (N=2), left temporoparietal (N=1) and left frontoparietal (N=1) eFCS (for an overview see table 2).

Most assessed parameters remained unchanged at follow up. Patients receiving left temporal eFCS showed stable or in some cases improved performance in the EpiTrack^®, visuomotor speed, cognitive flexibility, and naming (2 out of 4 patients respectively improved), whereas auditory working memory, and verbal learning improved in one out of 4 patients each (see table 2). After central eFCS, one patient’s visuomotor speed deteriorated (#5, other 3 patients stable), whereas his right-handed and bimanual fine motor speed performance improved at follow-up. Unimanual fine motor speed contralateral to the stimulation (left hand) remained unchanged in all patients with right-sided stimulation. However, one of these patients significantly worsened in a bimanual fine motor task (#6), whereas the other patients showed stable performance. After left frontal stimulation, both patients improved in verbal delayed recall, and one patient (#10) showed better semantic verbal fluency performance at follow-up. However, one patient’s figural fluency performance deteriorated. The single patient with right-sided fronto-parietal eFCS showed decline in visual motor speed as well as in verbal delayed recall performance (otherwise stable), whereas the patient with left temporo-parietal eFCS revealed no decline. Seizure outcome was rated as unchanged in 7 patients, in one patient seizures deteriorated and in 4 patients seizure outcome was reported as improved (in one case the improvement clearly coincided with antiseizure medication (ASM) optimization).

Conclusions: In this clinical observational study, no systematic cognitive deterioration was seen after months of eFCS, in some cases performance even increased. One-third of patients achieved improved seizure control (parallel opimization of ASM was allowed).

Funding: Clinical trials funded by Precisis AG: EASEE II Cl P # CV08-006, PIMIDES I CBP # CV08-017