Direct hypoglossal nerve stimulation in obstructive sleep apnea

Objectives: To determine the motor responses resulting from direct electrical stimulation of the hypoglossal (HG) nerve and to correlate these responses to changes in upper airway patency during sleep. Design: The motor effects of direct electrical stimulation of the main trunk of the HG nerve and the branch that supplies the genioglossus muscle during anesthesia and wakefulness were assessed visually. Responses in airflow during sleep to HG nerve stimulation were assessed with standard polysomnographic techniques. Setting: University medical center. Patients: Fifteen patients undergoing a surgical procedure that involved the neck that exposed the HG nerve and 5 volunteer patients with obstructive sleep apnea constituted the study population. Interventions: The main trunk (n=3) and genioglossus branch (n=2) of the HG nerve were stimulated electrically with a half-cuff tripolar electrode. Results: Stimulation of the branch of the HG nerve that innervates the genioglossus muscle caused protrusion and contralateral deviation of the tongue. Stimulation of the main trunk of the HG nerve caused slight ipsilateral deviation and retrusion of the tongue. The arousal threshold for stimulation exceeded the motor recruitment threshold by 0.8±0.4 V. Inspiratory airflow increased in all patients by 184.5±61.7 mL/s (mean±SD; P=.02, analysis of variance) with stimulation. Conclusion: Direct HG nerve stimulation below the arousal threshold can improve airflow in patients with obstructive sleep apnea.