Endoscopic laryngeal patterns in vagus nerve stimulation therapy for drug-resistant epilepsy

Abstract

In 30% of patients with epilepsy seizure control cannot be achieved with medications. When medical therapy is not effective, and epilepsy surgery cannot be performed, vagus nerve stimulator (VNS) implantation is a therapeutic option. Laryngeal patterns in vagus nerve stimulation have not been extensively studied yet. The objective was to evaluate laryngeal patterns in a cohort of patients affected by drug-resistant epilepsy after implantation and activation of a vagus nerve stimulation therapy device. 14 consecutive patients underwent a systematic otolaryngologic examination between 6 months and 5 years after implantation and activation of a vagus nerve stimulation therapy device. All patients underwent fiberoptic endoscopic evaluation, which was recorded on a portable device allowing a convenient slow-motion analysis of laryngeal patterns. All recordings were blindly evaluated by two of the authors. We observed three different laryngeal patterns. Four patients showed left vocal cord palsy at the baseline and during vagus nerve stimulation; seven showed left vocal cord palsy at the baseline and left vocal cord adduction during vagus nerve stimulation; and three patients showed a symmetric pattern at the baseline and constant left vocal cord adduction during vagus nerve stimulation. These laryngeal findings are here described for the first time in the literature and can be only partially explained by existing knowledge of laryngeal muscles and vagus nerve physiology. This might represent a new starting point for studies concerning laryngeal physiology and phonation, while the vagus nerve stimulation therapy could act as a new and ethical experimental model for human laryngeal physiology.

Laryngeal motility alteration: A missing link between sleep apnea and vagus nerve stimulation for epilepsy

“…Overall effects on the larynx are still a matter of debate. Our preliminary study may have shed some light on the pathophysiology; however, ongoing electrophysiologic studies will help deeper understanding …”

“…VNS is known to cause side effects related to laryngeal function . VNS may also cause a new‐onset SBD or an increase in apneic events during stimulation.…”

“…11 VNS is known to cause side effects related to laryngeal function. 9 VNS may also cause a new-onset SBD or an increase in apneic events during stimulation. Literature has proposed diverse hypotheses for a cause-effect relationship between VNS and SBD and the obstructive etiology is supported by some.…”

“…Our preliminary study may have shed some light on the pathophysiology; however, ongoing electrophysiologic studies will help deeper understanding. 9 Our study analyzed a wide range of parameters comparing the subjects with increased REI and OSA to those with stable or decreased REI. Our data fail to report any significant differences in the examined parameters in the two groups, therefore suggesting that the examined parameters do not influence the LVCA.…”

“…The mechanisms by which VNS can induce SBD are not clearly understood. A possible explanation is based on the effects on laryngeal muscles related to VNS . The aim of this study is to evaluate the prevalence of SBD and laryngeal functional obstruction after VNS implantation in order to ascertain the correlation between these two clinical issues.…”