The potential of invasive and non-invasive vagus nerve stimulation to improve verbal memory performance in epilepsy patients.

Cognitive impairment is a common comorbidity in epilepsy, observed in 70–80% of patients1. Therefore, apart from improving seizure control, cognitive impairment should be evaluated and addressed in epilepsy patients in order to improve the patient’s overall functioning and quality of life. There is a lack of controlled clinical trials investigating treatments for cognitive impairment in epilepsy patients.It has been demonstrated that acute vagus nerve stimulation (VNS) improves word recognition memory in epilepsy patients. Transcutaneous auricular vagus nerve stimulation (taVNS) has gained interest as a non-invasive alternative to improve cognition. In this prospective randomized cross-over study, we investigated the effect of both invasive VNS and taVNS on verbal memory performance in 15 patients with drug-resistant epilepsy. This memory paradigm was repeated after 6 weeks of VNS therapy in 2 conditions: VNS ON and VNS OFF (2-period 2-treatment cross-over study design). Acute VNS and taVNS did not improve verbal memory performance. Immediate recall and delayed recognition scores were significantly improved after 6 weeks of VNS treatment irrespective of the acute intervention. We can conclude that the previously described positive effects of invasive VNS on verbal memory performance could not be replicated with invasive VNS and taVNS.