Abstracts

RATIONALE: Animal research and at least one human experimental study indicate that vagus nerve stimulation (VNS) is associated with improved memory. Further, anecdotal reports of patients who have undergone VNS for intractable epilepsy suggest improved cognitive functioning post-operatively. METHODS: We report preliminary neuropsychological data in 10 patients tested pre and post VNS for intractable seizures (time post surgery: mean =17.9 weeks, SD =4.4). Five patients were considered responders with 50% or greater reduction in seizure frequency (n=5), three showed no change in seizure frequency (n=3), and two had seizure frequency of less than 50%. Neuropsychological test scores and self rating scales were analyzed with repeated measures ANOVA and paired t-tests, respectively. RESULTS: No statistically significant change in objective memory testing was observed; however, inspection of mean memory scores suggests mild improvement in total number of words recalled on a verbal list learning test and discriminability on recognition memory testing following VNS. Significant improvements were observed on self-report of depression (p=.03) and self rating of memory (p=.009). Self-ratings of mood and memory were not significantly correlated. DISCUSSION: These findings indicate improvement in mood and subjective memory ratings, consistent with prior studies on VNS and mood as well as anecdotal reports of improved functioning following VNS. The small sample size may have precluded the identification of statistically significant changes on objective memory testing. Given the patient's self-reports of improved memory functioning, larger scale studies on cognition following VNS are warranted. Funded by a grant from Cyberonics, Inc.