Abstracts

Rationale: Vagus nerve stimulation (VNS) has been reported to affect breathing during sleep in children. Obstructive sleep apnea (OSA) is the most significant sleep-related breathing abnormality reported with VNS, but tachypnea and decreased oxygen saturation have also been reported. The purpose of this study was to determine the incidence and degree of sleep-related breathing abnormalities in children with refractory epilepsy who receive vagus nerve stimulation.Methods: This is a retrospective chart review of 12 children with epilepsy (ages 3.3-16 yrs; 10 female) who underwent polysomnography after VNS placement. Polysomnography was performed at the Texas Children s Hospital Sleep Center utilizing Nicolet VicVu equipment. The VNS was turned on during the entire polysomnography. Data were analyzed using descriptive statistics. This study was approved by the Baylor College of Medicine Institutional Review Board.Results: All children had intractable epilepsy and were receiving VNS therapy through the Comprehensive Epilepsy Program at Texas Children s Hospital, Houston, Texas. One patient was not taking any antiepileptic drugs (AED), 2 were taking 1 AED, 6 were taking 2 AEDs, and 3 were taking three AEDs. Seven children had a generalized epilepsy syndrome and five had localization-related epilepsy. The majority of the patients had neurodevelopmental disabilities with 5/12 being non-ambulatory and g-tube fed. The mean BMI was 16.7 (SD 1.86). The VNS generator output current was 1.5 mA in 9 children, 1.75 mA in 2, and 0.5 mA in 1 patient. VNS signal frequency was 30 hertz in 5/12 and 20 hertz in 7/12. The VNS duty cycle had an on-time of 30 seconds for all patients and an off-time of 5 minutes in three patients, 3 minutes in 5 patients, 1.8 minutes in 2 patients, and 1.1 minutes in 2 patients. There was OSA recorded in 5/12 (42%) patients and central sleep apnea recorded in 10/12 (83%) patients. However, the apnea was mild in 9/12 patients (75%), moderate in 1 patient (8%), and severe in 2 patients (17%). The patients who had severe apnea were multiply handicapped and nonambulatory.Conclusions: These findings demonstrate that sleep-related breathing abnormalities may occur in children with refractory epilepsy who receive vagus nerve stimulation. Children at highest risk appear to be those with more severe neurodevelopmental disabilities. Consideration may be given to prescreening these children with polysomnography before proceeding with VNS therapy.