Magnetic resonance imaging of the upper airway in obstructive sleep apnea

To define the role and reliability of MR imaging of the oropharynx during wakefulness in the evaluation of patients with Obstructive Sleep Apnoea Syndrome.

During a 33-month period, 28 patients with clinical diagnosis of Obstructive Sleep Apnoea Syndrome (OSAS) were evaluated with Magnetic Resonance imaging. MR imaging was performed during wakefulness by T1-, DP- and T2-weighted sequences in the sagittal and axial plane. The morphological and quantitative data of the imaging, the majority of which were obtained from the relevant Literature (minimal pharyngeal cross-sectional area and its location and shape, increase of adipose tissue of the neck, tongue swelling, posterior dislocation of the tongue, soft and hard palate length, geniohyoid muscle length, evaluation of oral floor lowering), were subsequently compared with clinical-instrumental parameters (Body Mass Index, apnoea/hypopnoea index, hematocrit, arterial oxygen partial pressure, average nocturnal oxyhemoglobin saturation and sleeping-time percentage with oxygen saturation lower than 90%), to assess correlations.

The minimal pharyngeal cross-area is significantly positively correlated with the arterial oxygen partial pressure and with the average nocturnal oxyhemoglobin saturation and is inversely correlated with the apnoea/hypopnoea index and with the sleeping-time percentage with oxygen saturation lower than 90%; the inverse correlation with the Body Mass Index is less marked. Furthermore, the minimal pharyngeal cross-sectional area is correlated with its shape on the axial section. Increase of the adipose tissue of the neck is significantly correlated with the Body Mass Index, with a low nocturnal oxygen saturation, with a high percentage of sleeping time with oxygen saturation lower than 90%, and with the axial-section shape of the minimal pharyngeal area. An inverse correlation between the soft palate length and the arterial oxygen partial pressure was observed. Oral floor lowering is significantly inversely correlated with the minimal area only if the minimal area is located at the tongue base level and is directly correlated with the Body Mass Index as well as with the apnoea/hypopnoea index. The remaining MR findings appear to be independent parameters that may worsen the syndrome when associated with other parameters.

In patients with a clinical diagnosis of OSAS, MR imaging performed during wakefulness can provide reliable information on the causes, severity and site/s of oropharyngeal obstruction with important consequences on therapeutic decisions.