Abstracts

RATIONALE: Chronic intermittent left vagal nerve stimulation (VNS) has been shown to be an effective adjunct treatment that suppresses the occurrence of seizures in children. There is evidence for improvements on subjective ratings scales but few studies have utilized quantitative measures to investigate the influence of VNS on cognition, mood, and behavior. A recent study (Hoppe et al ) suggested that VNS does not affect cognitive functioning in adults over time. A similar study in children with Lennox-Gastaut Syndrome (Aldenkamp et al ) showed no significant change across tests measuring mental age, language, attention, cognitive style, behavior, and mood. This study examined a group of children with intractable epilepsy treated with VNS for 12 months with a battery of cognitive and behavioral measures. The goal of this investigation was to better understand the long-term cognitive and behavioral effects of VNS treatment in a cohort of children.
METHODS: Ten children (ages 6 to 18) with intractible epilepsy were examined prior to implantation with the Cyberonics Inc. Vagus Nerve Stimulator on standardized measures assessing cognition and behavior. Six participants were available for examination at 12 months post implantation. The cognitive test battery consisted of three domains that assessed overall intelligence (Wechsler Abbreviated Intelligence Scale), attention (Digit Span/Finger Windows), and learning/memory (California Verbal Learning Test/Visual Learning from WRAML). The behavioral outcome battery consisted of parent ratings on the Behavior Parent Rating Scale (BASC Behavioral Symptoms Composite) and the Vineland Adaptive Rating Scale (Communication, Daily Living Skills, Socializaton, and Adaptive Behavior). The percent change in seizure frequency was also collected. Intergroup comparisons of changes in standardized scores (based on normative data) on the measures were conducted across time intervals utilizing individual Mann Whitney U tests. The relationship between cognitive performance, behavior ratings, and seizure reduction was examined utilizing Spearmans rank correlations.
RESULTS: Five out of six patients experienced a positive seizure reduction at 12 months post implantation. The results of Mann Whitney U tests comparing baseline and 12-month follow up revealed no significant change on the cognitive domains of attention (p=.91), learning/memory (p=.60), and overall intelligence (p=.95). The results from the parent ratings indicated a significant decrease in behavioral symptoms (p=.04). Although no significant changes were noted on the Vineland scales, there was a trend noted for improvement in parent ratings of adaptive skills (p=.10). There were no significant correlations between seizure attenuation and changes in cognitive scores and behavior ratings.
CONCLUSIONS: These findings provide further support for the notion that treatment with VNS does not result in a measureable increase in cognitive functioning. However, it suggests that it is associated with improvement in behavioral functioning and adaptive skills. Our findings confirm beneficial effects of long-term VNS with respect to overall quality of life.