Objectives: The goal of this study was to determine if vagus nerve stimulation (VNS) has any effect on daytime vigilance and perceived sense of well-being.
Methods: Multiple Sleep Latency Tests (MSLTs) were performed and visual reaction times (VRTs) obtained in eight epileptic patients before and during treatment with VNS. Prior to VNS initiation patients' baseline MSLT and VRT scores were recorded. Six months after VNS was initiated, treatment MSLT and VRT scores were obtained. A group of 12 age-matched healthy subjects served as controls. In addition, there was a global evaluation of well-being at baseline and during a follow-up of 6 months.
Results: As expected, patients evaluated both at baseline and during VNS showed more sleepiness than controls. In this group, baseline sleep latencies on the MSLT were significantly shorter, while VRT latencies were significantly longer than those of controls. After 6 months of VNS, MSLT scores in the eight patients did not change significantly with respect to baseline. However, if the single patient treated with relatively high stimulus intensities (1.75 mA) was excluded from the group and only the seven patients treated with low stimulus intensities (<or=1.5 mA) were considered, a significant effect of chronic VNS on MSLT scores could be observed. In fact, the mean sleep latency (MSL) average of the seven subjects significantly improved from 9.9+/-2.5 minutes during baseline to 10.9+/-2.3 minutes after 6 months of VNS (P<0.05). Conversely, the only patient treated with high stimulus intensities showed increased sleepiness, with MSL decreasing from 14.4 to 9.8 minutes. On the other hand, VRT latencies did not significantly change during VNS. Patients considered as a whole had significant improvements on global evaluation scores of quality of life.
Conclusion: VNS at low stimulus intensities promotes daytime vigilance in adult epileptic patients and has a positive effect on quality of life.