Magnetic resonance imaging in simple snoring and obstructive sleep apnea-hypopnea syndrome

Obstructive Sleep Apnea-Hypopnea Syndrome (OSAHS) is a condition characterised by periodic cessation of breathing during sleep, associated with Upper Air-Digestive Ways (UADW) morphologic abnormalities that can be detected, in awake patients, by using various imaging techniques. The purpose of this study is to determine the usefulness of MR imaging and new original morphometrical measurements that we are proposing in patients with Sleep Obstructive Breathing Disordered (SOBD).

We studied 70 patients (52 with OSAHS and 18 snoring without OSAHS) using 1.5T and 0.5T MR imagers with neck and head coils and T1-DP-T2-weighted SE sequences. During the procedure, the patients were awake and with tidal breathing. We also evaluated sagittal pharyngeal diameters at different levels; the length and maximum width of soft palate; the distance between the hyoid bone and the C2C3-Me line (ideally joining the geometrical centre of the C2-C3 intervertebral space to the lower point of mandibular symphysis) measured on the perpendicular; the angle resulting from the longitudinal axis of the cervical spine and the epiglottis axis (alpha); the slope angle of the tongue -- resulting from the longitudinal axis of the cervical spine and the longitudinal axis of the tongue (beta). We used sagittal, coronal and axial sections of the head and neck.

In OSAHS patients, pharynx calibre medium sizes were reduced compared with simple snoring patients. Only in OSAHS patients (not in simple snorers without OSAHS) we observed: 16 patients with narrowing sites = or <3 mm. On axial images we observed three different narrowing patterns: rounded, with greater anterior-posterior axis; with greater axis in lateral direction. In OSAHS patients we also observed, on average, increase of the distance between the hyoid bone (Hmr point) and the line C2C3-Me; increase in the angle resulting between cervical rachis and epiglottis (alpha); reduction of sloping angle of the tongue (beta).

MR imaging, together with the morphometrical measurements we are proposing, is useful to evaluate UADW in SOBD. In particular, we noted that increase of the distance between the hyoid bone (Hmr point) and the line C2C3-Me (due to lowering of the hyoid bone), increase in the angle resulting between the cervical rachis and the epiglottis (alpha) and the reduction of the sloping angle of the tongue (beta), are highly specific and sensitive indexes in OSAHS. There are different levels and findings of narrowing in OSAHS and their identification is very important for a surgical approach: the uvulo-palato-pharyngoplasty (UPPP) has a higher success rate in patients with obstruction at retro-palatopharynx site, but it is associated with no (or poor) results in hypopharyngeal obstruction.