Long-term effects of vagus nerve stimulation therapy on cognitive functioning in patients with drug-resistant epilepsy.

Abstract

Despite the increasing use of vagus nerve stimulation (VNS) for drug-resistant epilepsy, its impact on cognitive functioning remains insufficiently investigated. We aimed to comprehensively assess changes in cognition after long-term VNS therapy in a prospective sample of adults with epilepsy. Between December 2019 and March 2023, patients scheduled for VNS implantation were invited for neuropsychological assessment, including tests of executive functions, working and short-term memory (recall of a verbal logical story and the Rey-Osterrieth complex figure (ROCF)), and social cognition. Participants were re-evaluated after a year of VNS therapy and the pre- and postoperative scores were compared by means of the Student's t or Wilcoxon's signed rank tests for paired samples. Patients available only after a longer follow-up (more than 24 months) were also re-examined and included in a secondary analysis. The study included 28 PWE (16, 57.1% female, average age 33.7 ± 10.0 years). Twenty-two PWE followed-up at 14.5 ± 4.8 months had worse categorical verbal fluency than preoperatively (t = 2.613, p = 0.016). After including patients with long follow-up (n = 28, 21.6 ± 11.4 months), the group scored better on the delayed recall of the ROCF (17.09 ± 8.84 to 20.65 ± 8.32 points, t(22) = - 2.618, p = 0.016) and the Happé strange stories test (5.0 ± 2.6 to 6.1 ± 2.1 points, t(14) = - 3.281, p = 0.005). No significant changes were observed in other cognitive domains (p > 0.05). We suggest improvements in a task of social cognition and short-term visual memory after longer use of VNS therapy. Such findings should be confirmed in larger trials after controlling for changes in ictal or interictal activity.