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


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.


CONCLUSIONS
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.
Sériès
Frédéric
F
Centre de recherche, Hôpital Laval, Institut universitaire de cardiologie et de pneumologie de l'Université Laval, Quebec City, Quebec, Canada. frederic.series@med.ulaval.ca
Wang
Wei
W
Similowski
Thomas
T
D000328:Adult; D003964:Diaphragm / Q000503:physiopathology*; D005246:Feedback; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009119:Muscle Contraction; D015656:Respiratory Mechanics; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*; D014059:Tongue / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D014851:Wakefulness
Am Rev Respir Dis. 1989 Sep;140(3):724-8
2782743
Intern Med. 1998 Feb;37(2):134-40
9550592
J Physiol. 2007 Nov 15;585(Pt 1):135-46
17916615
J Physiol. 2005 Apr 15;564(Pt 2):549-62
15695240
Electroencephalogr Clin Neurophysiol. 1998 Apr;109(2):114-8
9741801
Eur J Neurosci. 2004 Jun;19(11):3099-104
15182318
J Appl Physiol (1985). 2003 Feb;94(2):453-61
12391044
Am J Respir Crit Care Med. 1997 Sep;156(3 Pt 1):867-73
9310006
Thorax. 2007 Oct;62(10):861-7
17412778
Eur Respir J. 1996 Jun;9(6):1224-31
8804942
Respir Physiol Neurobiol. 2006 Dec;154(3):406-18
16406377
Am J Respir Crit Care Med. 1999 May;159(5 Pt 1):1551-5
10228125
J Appl Physiol Respir Environ Exerc Physiol. 1980 Oct;49(4):638-42
6777347
J Clin Invest. 1992 May;89(5):1571-9
1569196
FASEB J. 1996 Jun;10(8):897-904
8666167
Respir Physiol Neurobiol. 2002 Apr;130(2):161-8
12380006
J Physiol. 1971 Jun;215(2):557-75
4336048
Am J Respir Crit Care Med. 2001 Dec 1;164(11):2025-30
11739130
J Sleep Res. 2004 Mar;13(1):31-6
14996032
Electroencephalogr Clin Neurophysiol. 1997 Feb;105(1):15-23
9118834
J Appl Physiol (1985). 2004 Sep;97(3):902-12
15133007
J Appl Physiol (1985). 2003 Jul;95(1):26-34
12639850
Exp Physiol. 2007 Jul;92(4):739-47
17412750
J Sleep Res. 2004 Jun;13(2):159-63
15175096
J Appl Physiol (1985). 1990 Aug;69(2):443-50
2228853
Neuroscience. 2002;110(4):711-22
11934478
Respir Physiol. 1999 Sep 15;117(2-3):85-95
10563437
Exp Physiol. 1991 Mar;76(2):159-200
2059424
J Appl Physiol (1985). 1985 Apr;58(4):1378-82
3988690
J Appl Physiol (1985). 2003 Oct;95(4):1453-9
12832431
Am J Respir Crit Care Med. 1996 Dec;154(6 Pt 1):1771-7
8970369
J Clin Invest. 1995 Jan;95(1):20-5
7814616
BMC Physiol. 2006 Jul 29;6:7
16875504