Effects of 6 months of treatment with vagus nerve stimulation on behavior in children with lennox-gastaut syndrome in an open clinical and nonrandomized study
The effect of vagus nerve stimulation (VNS) on behavior outcomes was studied in 16 children with Lennox-Gastaut syndrome. We used the following stimulation parameters: output current, 11 2 to 2 mA; signal frequency, 30 Hz; signal pulse width, 500 microseconds; signal on and off times, 30 seconds on and 3 minutes off. The test battery consisted of cognitive tests measuring mental age, attention, language, psychomotor function, and cognitive style, and quality-of-life measurements assessing independence, behavioral problems, symptoms of pervasive development disorders (PDDs) and mood. The results show relatively small changes in behavioral outcomes concurrently with modest effects on seizure frequency (an average of 26.9% seizure reduction). When baseline and endpoint measurements are compared none of the cognitive measures show any deterioration and three of five cognitive measures show slight positive changes. Among the quality-of-life measures, one measure showed a slight worsening of scores and three showed slight improvement. When the group is divided into subgroups on the basis of treatment effect the most prominent improvements are observed in the group without any effects of VNS on seizure frequency. These patients gained, on average, 9.5 months in mental age and showed more independent behavior, mood improvements and fewer PDD symptoms. This suggests an effect of VNS on behavioral function independent of changes in seizure frequency.