Vagus nerve stimulator implantation in patients with drug-resistant epilepsy may promote sleep breathing disorders, according to data published in Epilepsia.
Vagus nerve stimulation (VNS) is known to cause side effects related to laryngeal function, and may cause new-onset sleep disordered breathing, however the mechanism by which this occurs is not well-understood.
To assess the relationship, Elena Zambrelli, of the Epilepsy-Sleep Medicine Center at San Paolo Hospital in Milan, Italy, and colleagues evaluated 23 patients (16 female) with drug-resistant epilepsy who were taking antiepileptic polytherapy. All 23 patients underwent out-of-center sleep testing (OCST) before and after VNS implantation. Eighteen patients underwent a post-VNS activation endoscopic laryngeal evaluation between 1 and 10 years post-implantation in order to characterize laryngeal patterns during on and off VNS phases.
Prior to VNS implantation, 83% of patients had a normal respiratory events index (REI), with 17% (4 of 23) affected by obstructive sleep apnea (OSA). After VNS implantation, 57.9% of non-OSA patients presented with new-onset mild to moderate sleep breathing disorders, while two patients with OSA prior to VNS implantation showed REI improvement, and 2 showed worsened OSA. No statistically significant difference was found between demographics and VNS parameters between groups with increased REI and OSA after VNS implantation and the other group, however there was a difference in the distribution of laryngeal patterns with or without left vocal cord adduction (LVCA).
Fifteen of 18 patients showed LVCA during VNS activation upon laryngeal examination. All patients with new onset/worsening OSA who underwent laryngeal examination showed LVCA during the VNA “on” phase. Four of 15 patients with LVCA did not develop OSA.
The study results indicate a pivotal role for laryngeal motility alterations in VNS-induced OSA, supporting the need for routine investigation of sleep respiratory and laryngeal motility patterns both before and after VNS implantation.
The authors encourage collaboration between neurologists and otolaryngologists in order to provide comprehensive VNS patient management to best monitor VNS settings, seizure control, and patient quality of life.