Inhomogeneous neuromuscular injury of the genioglossus muscle in subjects with obstructive sleep apnea.

PURPOSE: Muscle injury exists in the upper airway in subjects with obstructive sleep apnea (OSA). However, whether this injury is homogeneous remains unclear. The objective of this study was to measure neuromuscular changes in the anterior and posterior genioglossus muscle (GG) in subjects with OSA using motor unit potentials (MUPs). METHODS: Male subjects underwent diagnostic sleep studies to obtain apnea/hypopnea index (AHI) and lowest oxygen saturation (LSAT) data. MUPs of the anterior and posterior GG were recorded. Mean values and outliers of MUP parameters were analyzed. RESULTS: Seventeen subjects with severe OSA (AHI, 72.3 ± 16.7 events/h) and nine control subjects (AHI, 3.7 ± 0.4 events/h) were enrolled in this study. In the control group, the MUP values of amplitude, duration, area, area/amplitude, and size index did not differ significantly between the posterior and anterior GG. In the OSA group, these values were significantly higher in the posterior than anterior GG (amplitude: P = 0.011; duration: P = 0.007; area: P = 0.008; size index: P = 0.033). Posterior GG values were greater in the OSA group than in the control group, whereas anterior values were similar. A larger proportion of subjects with OSA had outlying values for the posterior GG than anterior GG (52.9 vs. 11.8%; P < 0.05). No significant correlation between MUP parameters and body mass index, AHI, or LSAT was observed in the OSA group. CONCLUSIONS: Chronic neuromuscular injury in subjects with OSA was more severe in the posterior than in the anterior GG.