The cranial nerves IX and X emerge from medulla oblongata and have motor, sensory, and parasympathetic functions. Some of these are amenable to neurophysiological assessment. It is often hard to separate the individual contribution of each nerve; in fact, some of the techniques are indeed a composite functional measure of both nerves. The main methods are the evaluation of the swallowing function (combined IX and X), laryngeal electromyogram (predominant motor vagal function), and heart rate variability (predominant parasympathetic vagal function). This review describes, therefore, the techniques that best evaluate the major symptoms presented in IX and X cranial nerve disturbance: dysphagia, dysphonia, and autonomic parasympathetic dysfunction.
Neurophysiology Unit, Department of Neurology, University of Campinas (UNICAMP), São Paulo, Brazil.
Address correspondence and reprint requests to Marcondes C. França, PhD, Department of Neurology, University of Campinas e UNICAMP, Rua Tessália Vieira de Camargo, 126, Cidade Universitaria “Zeferino Vaz”, Campinas, São Paulo 13083-887, Brazil; e-mail: firstname.lastname@example.org.
The authors have no funding or conflicts of interest to disclose.
A. R. M. Martinez and M. P. Martins contributed equally for this work.