Hypoglossal Nerve Stimulation and Airway Changes under Fluoroscopy

Abstract

Objective: Characterize the changes in tongue base position, the anteroposterior dimension of the retropalatal and retrolingual airway spaces, and the hyoid bone during hypoglossal nerve stimulation in OSA subjects under general anesthesia.

Method: Twenty-four subjects underwent implantation of the Apnex Medical Hypoglossal Nerve Stimulation (HGNS) system, with cross-table fluoroscopy imaging during hypoglossal nerve stimulation under general anesthesia. Standardized measurements determined changes in tongue base position, the retrolingual and retropalatal airways, and the hyoid bone. Airway changes were compared with subject’s C3 vertebral width.

Results: During hypoglossal nerve stimulation, all subjects demonstrated anterior displacement of the tongue base. The resulting anteroposterior retrolingual airway opening was at least one-third the width of the C3 vertebral body in all subjects, with a mean ratio of 0.61 ± 0.15. Opening of the retropalatal airway with stimulation occurred in 74% (14/19) of subjects; in 5 cases the fluoroscopy videos did not permit adequate visualization of the retropalatal region. There was a wide variation in the change of hyoid bone position during stimulation.

Conclusion: Hypoglossal nerve stimulation created anterior tongue base displacement and an increase in the anteroposterior retrolingual airway dimensions in all subjects. Opening of the retropalatal airway occurred in the majority of subjects. Further study is warranted to evaluate 3-dimensional airway changes and the mechanisms of action, especially for the retropalatal airway.