Sleep magnetic resonance imaging as a new diagnostic method in obstructive sleep apnea syndrome.

OBJECTIVES/HYPOTHESIS: Although precise localization of obstruction sites in the upper airway during sleep is essential in subjects with obstructive sleep apnea syndrome (OSAS), no gold standard diagnostic method has been established. This study aimed to evaluate the dynamic collapse inside the upper airway by using cine magnetic resonance imaging (MRI), also called sleep MRI.

STUDY DESIGN

Cross-sectional study with retrospective data.

METHODS

The changes in the transverse and anteroposterior diameters of the retrolingual airway were studied during a respiratory cycle in 35 snoring subjects. The collapsibility of the airway was calculated by using axial images, and the actual obstruction sites were also identified by using sagittal images.

RESULTS

Airway collapse occurred in the retropalatal area in 13 (37.1%) of 35 subjects and in both the retropalatal and retrolingual regions in 20 subjects (57.1%). The respiratory disturbance index (RDI) and supine RDI were higher and the minimal oxygen saturation during sleep (MinSaO₂) value was lower in subjects with both retropalatal and retrolingual obstruction than in those with only retropalatal obstruction. Airway collapse analyzed by using axial images was classified into four subgroups: patent group (five of 35, 14.2%), anteroposterior collapse group (one of 35, 2.9%), transverse collapse group (14 of 35, 40%) and circumferential collapse group (15 of 35, 42.9%). Supine RDI, MinSaO₂, and age were significantly different between these four groups. In addition, anteroposterior, transverse, and circumferential collapses correlated well with MinSaO₂. Significant correlation was also found between RDI/supine RDI and transverse collapse.

CONCLUSIONS

Sleep MRI is a valuable method for evaluating dynamic obstruction during sleep and may be helpful in selecting the appropriate treatment approaches.