Abstract
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. All patients conducted a word recognition memory paradigm in 3 conditions: VNS ON, VNS OFF and taVNS (3-period 3-treatment cross-over study design). For each condition, patients memorized 21 highlighted words from text paragraphs. Afterwards, the intervention was delivered for 30 s. Immediate recall and delayed recognition scores were obtained for each condition. 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. An improved verbal memory performance was seen after 6 weeks of VNS treatment, suggesting that longer and more repetitive stimulation of the vagal pathway is required to modulate verbal memory performance.Clinical trial registration number: NCT05031208.
Highlights
It has been demonstrated that acute vagus nerve stimulation (VNS) improves word recognition memory in epilepsy patients
The latter is in line with a previous study by our group that could not demonstrate an improvement of verbal memory performance after Transcutaneous auricular vagus nerve stimulation (taVNS) in healthy v olunteers[49]
Five research questions were addressed during the statistical analysis with the following hypotheses: 1. We hypothesized that both acute VNS at moderate stimulation intensity and taVNS at pain threshold stimulation intensity would improve verbal memory performance compared to no stimulation at session 1
Summary
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. The main outcome parameter in clinical studies was the effect on seizures, improvements in quality of life, mood and cognitive functioning have been reported that did not correlate with a reduction in seizure frequency[7,8,9] These findings led to the investigation of VNS as a treatment for drug-resistant d epression[10] (with CE mark in 2001) and cognitive impairment[11]. In 1999, Clark et al demonstrated a significantly enhanced word recognition memory in patients with drug-resistant epilepsy recently implanted with VNS, when stimulation was delivered during the consolidation phase of a memory task. Five research questions were addressed during the statistical analysis with the following hypotheses: 1. We hypothesized that both acute VNS at moderate stimulation intensity and taVNS at pain threshold stimulation intensity would improve verbal memory performance compared to no stimulation at session 1
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