Electrophysiological Changes on Laryngeal Motor Neuropathways Cause Voice Disorders for Postradiotherapy Patients with Nasopharyngeal Carcinoma

Abstract

ObjectiveThis study explored electrophysiological changes in the laryngeal motor neuropathway and determined whether lesions in the laryngeal motor cortex (LMC) and its descending tract contribute to voice deterioration and peripheral nerve palsy in patients with nasopharyngeal carcinoma (NPC) post-radiotherapy (RT). Study DesignsProspective cohort study MethodsTwenty-two patients with NPC at 2 to 4 years post-RT (8 female and 14 male), 22 patients with NPC at 8 to 10 years post-RT (8 female and 14 male), and 22 healthy individuals (9 female and 13 male) were selected to test their magnetic evoked potentials (MEP), motor nerve conduction (MNC), and voice quality using transcranial magnetic stimulation (TMS), laryngeal electromyography (LEMG), and the XION DiVAS acoustic analysis software. Three groups were matched according to approximate age. Multiple comparisons were performed among the three groups. ResultsThe voice quality of post-RT patients with NPC deteriorated compared to that of healthy individuals. Bilateral LMC and their corticonuclear tracts to the bilateral ambiguous nuclei of post-RT patients with NPC were impaired according to multi-group comparisons of MEP amplitudes, latencies, and resting motor thresholds (RMT). The vagus and recurrent laryngeal nerves (RLN) of post-RT patients with NPC were impaired according to multi-group comparisons of the amplitude and latencies of the compound muscle action potential (CMAP) and latencies of f-waves. ConclusionsThe voice quality of patients with NPC deteriorated after RT. The pathogenesis of post-RT voice deterioration may involve radiation-induced injuries to the vagus, RLN, and bilateral LMC. Furthermore, radiation-induced injuries to the bilateral LMC may contribute to vagus and RLN palsies. These findings support the use of transcranial approaches to treating voice disorders and peripheral nerve palsies in post-RT patients with NPC.