MRI study of pharyngeal airway changes during stimulation of the hypoglossal nerve
branches in rats.
Brennick, Michael J., Theodore P. Trouard, Arthur F. Gmitro, and Ralph F. Fregosi.
1Center for Sleep and Respiratory Neurobiology, University of Pennsylvania,
Philadelphia, Pennsylvania 19104; 2Department of Radiology, University of Arizona
85721«hyphen»5067; and 3Department of Physiology, University of Arizona, Tucson,
AZ 85721«hyphen»0093
APStracts 8:0019A, 2001.
The medial branch (Med) of the hypoglossal nerve innervates the tongue protrudor
muscles, which promote pharyngeal patency, whereas the lateral branch (Lat) innervates
tongue retractor muscles. Our previous finding that pharyngeal airflow increased during
either selective Med stimulation or whole hypoglossal nerve (WHL) stimulation
(coactivation of protrudor and retractor muscles) led us to examine how WHL, Med, or
Lat stimulation affected tongue movements and nasopharyngeal (NP) and oropharyngeal
(OP) airway volume. Electrical stimulation of either WHL, Med, or Lat nerves was
performed in anesthetized, tracheotomized rats while magnetic resonance images of the
NP and OP were acquired (slice thickness 0.5 mm, in-plane resolution 0.25 mm). NP and
OP volume was greater during WHL and Med stimulation vs. no stimulation (P < 0.05).
Ventral tongue depression (measured in the midsagittal images) and OP volume were
greater during Med stimulation than during WHL stimulation (P < 0.05). Lat
stimulation did not alter NP volume (P = 0.39). Our finding that either WHL or Med
stimulation dilates the NP and OP airways sheds new light on the control of pharyngeal
airway caliber by extrinsic tongue muscles and may lead to new treatments for patients
with obstructive sleep apnea.
Received 26 May 2000; accepted in final form 16 November 2000
APS Manuscript Number A0527-0.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 29 January 2001