Neurogenic changes in the upper airway of patients with obstructive sleep apnea.
BACKGROUND
Controversy persists regarding the presence and importance of hypoglossal nerve dysfunction in obstructive sleep apnea (OSA).


OBJECTIVE
We assessed quantitative parameters related to motor unit potential (MUP) morphology derived from electromyographic (EMG) signals in patients with OSA versus control subjects and hypothesized that signs of neurogenic remodeling would be present in the patients with OSA.


METHODS
Participants underwent diagnostic sleep studies to obtain apnea-hypopnea indices. Muscle activity was detected with 50-mm concentric needle electrodes. The concentric needle was positioned at more than 10 independent sites per subject, after the local anatomy of the upper airway musculature was examined by ultrasonography. All activity was quantified with subjects awake, during supine eupneic breathing while wearing a nasal mask connected to a pneumotachograph. Genioglossus EMG signals were analyzed offline by automated software (DQEMG), which extracted motor unit potential trains (MUPTs) contributed by individual motor units from the composite EMG signals. Quantitative measurements of MUP templates, including duration, peak-to-peak amplitude, area, area-to-amplitude ratio, and size index, were compared between the untreated patients with OSA and healthy control subjects.


RESULTS
A total of 1,655 MUPTs from patients with OSA (n = 17; AHI, 55 ± 6/h) and control subjects (n = 14; AHI, 4 ± 1/h) were extracted from the genioglossus muscle EMG signals. MUP peak-to-peak amplitudes in the patients with OSA were not different compared with the control subjects (397.5 ± 9.0 vs. 382.5 ± 10.0 μV). However, the MUPs of the patients with OSA were longer in duration (11.5 ± 0.1 vs. 10.3 ± 0.1 ms; P < 0.001) and had a larger size index (4.09 ± 0.02 vs. 3.92 ± 0.02; P < 0.001) compared with control subjects.


CONCLUSIONS
These results confirm and quantify the extent and existence of structural neural remodeling in OSA.
Sleep Disorders Program, Division of Sleep Medicine, Brigham and Women’s Hospital, Boston, Massachusetts, USA. j.saboisky@neura.edu.au
Julian P
JP
Saboisky
Daniel W
DW
Stashuk
Andrew
A
Hamilton-Wright
Andrea L
AL
Carusona
Lisa M
LM
Campana
John
J
Trinder
Danny J
DJ
Eckert
Amy S
AS
Jordan
David G
DG
McSharry
David P
DP
White
Sanjeev
S
Nandedkar
William S
WS
David
Atul
A
Malhotra
D000200:Action Potentials; D000328:Adult; D056151:Airway Remodeling; D016022:Case-Control Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D007002:Hypoglossal Nerve / Q000503:physiopathology*; D008297:Male; D009046:Motor Neurons / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation* / Q000503:physiopathology; D055495:Neurogenesis; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*; D014059:Tongue / Q000503:physiopathology