Sleep magnetic resonance imaging with electroencephalogram in obstructive sleep apnea syndrome.

OBJECTIVE To evaluate the mechanism and level of upper airway obstruction in obstructive sleep apnea (OSA) patients during natural sleep, together with synchronous electroencephalogram and respiratory events registration at 3-Tesla magnetic resonance imaging (MRI) platform with high spatial and temporal resolution. STUDY DESIGN A prospective cohort study of 20 randomly selected OSA patients. METHODS Fifteen of 20 patients were able to complete spontaneous sleep during MRI. While asleep, dynamic MR images of pharynx were obtained in the midline sagittal view. During the scan, nasal and oral airflow, thoracoabdominal wall effort, and electroencephalogram were synchronously recorded. The physiologic data were retrospectively scored to identify periods of apneas and synchronized with dynamic MR images. RESULTS In all 15 patients, the site of complete airway obstruction occurred at the retropalatal space. We noticed different positions of the soft palate during apneic events. In seven of 15 patients (47%), the soft palate was attached to the tongue base and moved backward, compressing the airway. In five of 15 patients (33%), the soft palate was detached from the tongue base and solely moved backward, compressing the airway. In three patients (20%), we recorded both mechanisms of complete airway obstruction. In cases with attached soft palate to the tongue base, we noticed significant narrowing of the retrolingual space during apneic events. CONCLUSION We describe a novel mechanism of obstruction dependent on the position of soft palate. This mechanism might play an important role in selecting candidates for surgery or treatment with hypoglossal nerve stimulation. LEVEL OF EVIDENCE 2b.