20-11-2023 | Vagus Nerve Stimulation | Original Article
Long-term effects of vagus nerve stimulation therapy on cognitive functioning in patients with drug-resistant epilepsy
Published in: Neurological Sciences
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Background
Despite the increasing use of vagus nerve stimulation (VNS) for drug-resistant epilepsy, its impact on cognitive functioning remains insufficiently investigated.
Objective
We aimed to comprehensively assess changes in cognition after long-term VNS therapy in a prospective sample of adults with epilepsy.
Methods
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.
Results
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).
Conclusion
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.