Summary:Purpose: To analyze respiratory alterations and effects on SaO 2 caused by vagus nerve stimulation (VNS) in children with epilepsy.Methods: Polysomnographic recordings, including electroencephalography, thoracoabdominal distention, nasal airflow, SaO 2 , and VNS artifact were evaluated in 10 children with pharmacoresistant epilepsy treated with VNS.Results: Each VNS caused a significant increase in respiratory frequency (p < 0.05) throughout the stimulation period and a decrease in thoracoabdominal-distention amplitude (p < 0.05), especially at the beginning of the stimulation. These respiratory alterations induced a decrease in SaO 2 from 1 to 5%. The effects of VNS on respiration differed significantly between rapid-eyemovement (REM) and non-REM (NREM) sleep states.Conclusions: VNS caused a pronounced change in respiration in children with epilepsy, and this induced a decrease in SaO 2 . It is possible that VNS has a neuroprotective effect, and this possibility calls for further investigation. Key Words: Epilepsy-Vagus nerve stimulation-RespirationNeuroprotection-SaO 2 .Vagus nerve stimulation (VNS), an adjunctive treatment for medication-resistant epilepsy, has been used in Europe since 1994. The antiepileptic effect of VNS was initially found in experiments with animal models (1,2) and has been confirmed in humans (3-5). An average seizure reduction of 44.7% after 6 months was reported (6) for 125 children who had a variety of seizure types. The vagus nerve carries most of the information from viscera to CNS, via various types of fibers (7). These afferents are engaged in physiologic regulation processes, such as those of the digestive and cardiorespiratory systems. An effect of VNS on respiration was first described by Breuer (8). Breuer demonstrated the role of the vagus nerve in shaping the different phases of respiration. Since then, numerous studies have been conducted in animals to elucidate the interaction between VNS afferents and brainstem and pontic respiratory neurons (9). In the Von Euler model, the vagus nerve afferents decrease the inspiratory-off-switch activation threshold, but little attention has been paid to respiratory/VNS interaction. The main discomfort reported by the patients receiving VNS is hoarseness and laryngeal irritation (10). Effects of VNS on respiration were expected, Accepted June 25, 2005. Address correspondence and reprint requests to Dr. B. Zaaimi at GRAMFC Laboratoire de genie biophysique, Laboratoire de neurophysiologie, Faculté de médecine, 3 rue des louvels, 80036 Amiens, France. E-mail : boubker.zaaimi@u-picardie.fr but no major respiratory change due to VNS was detected in one study (11). However, hypopneic-polypneic episodes and hypocapnia were observed in one child (12), and others showed apneas-hypopneas (4,13) or increases in respiratory frequency with hypocapnia (14). VNS influences the interrelated network of respiration, epilepsy, and sleep. Sleep structure is modified by VNS (15,16) and by epilepsy (17,18). Modifications of sleep states are associat...

Vagus nerve stimulation (VNS) is used in pharmaco-resistant epilepsy to decrease the number of seizures. Although it is well known that VNS affects respiration, there are only a few reports concerning an effect of VNS on heart rate or heart rate variability (HRV). We investigated the relationship between respiratory frequency and the high frequency (HF) domain of the discrete Fourier transform (DFT) of the RR interval function during night sleep recordings of ten subjects treated with VNS. Our results show that VNS shifts the frequency of maximal power spectrum density (PSD) in the HF-band, decreases the related PSD and induces a partial cardiorespiratory decoupling.