Received February 28, 2007
Revised March 12, 2007
Accepted after revision March 29, 2007
Interaction between genioglossus and diaphragm responses
to transcranial magnetic stimulation in awake humans
Wei Wang 1,
Thomas Similowski 2,
Frédéric Sériès 3*
1 1st Affiliated Hospital of China Medical University
2 Université Paris VI Pierre et Marie Curie
3 Hôpital Laval
* To whom correspondence should be addressed. E-mail: frederic.series{at}med.ulaval.ca.
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Abstract |
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Background. The modulation of upper airway dilator and
respiratory muscles activities plays a key role in the
regulation of ventilation but little is known about the
link between their neuromuscular activation processes in
vivo. This study was aimed at investigating genioglossus
and diaphragm responses to transcranial magnetic
stimulation applied in different facilitatory
conditions.
Methods. Amplitude and latency of motor evoked potential
responses, the stimulation intensity threshold leading
to a motor response (motor threshold) were recorded with
stimulation applied at vertex and antero-lateral area in
13 awake normal subjects. Stimuli were applied during
inspiration with and without resistance, expiration with
and without maximal tongue protrusion and during deep
inspiration.
Results. In each stimulation location and condition, no
diaphragmatic response was obtained without previous
genioglossus activity (diaphragmatic and genioglossus
responses latencies during expiration: 18.1±2.9 ms and
6.3±2.6 ms respectively, Mean±SD, P<0.01).
Genioglossus motor evoked potential amplitude, latency
and motor threshold were significantly modified with
tongue protrusion with a maximal effect observed for
stimulation in the antero-lateral area. Deep inspiration
was associated with a significant facilitatory effect on
both genioglossus and diaphragm motor responses. The
facilitatory effects of respiratory and non-respiratory
maneuvers were also observed during focal stimulation
where isolated genioglossus responses were observed.
Genioglossus and diaphragm differed in their motor
threshold both at baseline and following facilitatory
maneuvers.
Key Words:
Airway, Cortex, Pharynx
