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Open Access Research

Corticomotor control of the genioglossus in awake OSAS patients: a transcranial magnetic stimulation study

Frédéric Sériès12*, Wei Wang13 and Thomas Similowski24

Author Affiliations

1 Centre de recherche, Hôpital Laval, Institut universitaire de cardiologie et de pneumologie de l'Université Laval, Quebec City, Quebec, Canada

2 UPMC Université Paris 6 Pierre et Marie Curie, EA 2397, Paris, France

3 The 1st Affiliated Hospital of China Medical University, Shen Yang City, Liao Ning Province, PR China

4 Assistance Publique – Hôpitaux de Paris, Groupe Hospitalier Pitié-Salpêtrière, Service de Pneumologie et Réanimation, Paris, France

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Respiratory Research 2009, 10:74  doi:10.1186/1465-9921-10-74

Published: 13 August 2009

Abstract

Background

Upper airway collapse does not occur during wake in obstructive sleep apnea patients. This points to wake-related compensatory mechanisms, and possibly to a modified corticomotor control of upper airway dilator muscles. The objectives of the study were to characterize the responsiveness of the genioglossus to transcranial magnetic stimulation during respiratory and non-respiratory facilitatory maneuvers in obstructive sleep apnea patients, and to compare it to the responsiveness of the diaphragm, with reference to normal controls.

Methods

Motor evoked potentials of the genioglossus and of the diaphragm, with the corresponding motor thresholds, were recorded in response to transcranial magnetic stimulation applied during expiration, inspiration and during maximal tongue protraction in 13 sleep apnea patients and 8 normal controls.

Main Results

In the sleep apnea patients: 1) combined genioglossus and diaphragm responses occurred more frequently than in controls (P < 0.0001); 2) the amplitude of the genioglossus response increased during inspiratory maneuvers (not observed in controls); 3) the latency of the genioglossus response decreased during tongue protraction (not observed in controls). A significant negative correlation was found between the latency of the genioglossus response and the apnea-hypopnea index; 4) the difference in diaphragm and genioglossus cortico-motor responses during tongue protraction and inspiratory loading differed between sleep apnea and controls.

Conclusion

Sleep apnea patients and control subjects differ in the response pattern of the genioglossus and of the diaphragm to facilitatory maneuvers, some of the differences being related to the frequency of sleep-related events.