QUANTITATIVE MAGNETIC-RESONANCE-IMAGING OF UPPER AIRWAY MUSCULATURE IN AN ANIMAL-MODEL OF SLEEP-APNEA

Electromyographic studies of patients with sleep apnea and of the Engl ish bulldog, an animal model of sleep apnea, indicate that there is in creased activity of the airway dilator muscles. The muscles, when biop sied, show both adaptation and muscle injury. In this study we have ut ilized quantitative magnetic resonance imaging to characterize changes in the upper airway musculature of the bulldog in vivo. The imaging p rocedure utilized provided a quantitative measurement of the T-2 relax ation times of airway muscles (geniohyoid, sternohyoid, sternothyroid, thyropharyngeus, and hyopharyngeus) and nonairway muscles spatially l ocalized to submillimeter-resolution levels. Quantitative differences between the medians and distributions of T-2 relaxation times of airwa y vs. nonairway muscles were demonstrated. These differences were rela ted to the degree of sleep-disordered breathing. The changes observed are compatible with the hypothesis that there is both increased edema and fibrosis in upper airway muscles in sleep apnea.