UPPER AIRWAY AND SOFT-TISSUE ANATOMY IN NORMAL SUBJECTS AND PATIENTS WITH SLEEP-DISORDERED BREATHING - SIGNIFICANCE OF THE LATERAL PHARYNGEAL WALLS

The geometry and caliber of the upper airway in apneic patients differ s from those in normal subjects. The apneic airway is smaller and is n arrowed laterally. Examination of the soft tissue structures surroundi ng the upper airway can lead to an understanding of these apneic airwa y dimensional changes. Magnetic resonance imaging was utilized to stud y the upper airway and surrounding soft tissue structures in 21 normal subjects, 21 snorer/mild apneic subjects, and 26 patients with obstru ctive sleep apnea. The major findings of this investigation in the 68 subjects were as follows: (1) minimum airway area was significantly sm aller in apneic compared with normal subjects and occurred in the retr opalatal region; (2) airway narrowing in apneic patients was predomina ntly in the lateral dimension; there was no significant difference in the anterior-posterior (AP) airway dimension between subject groups; a nd (3) distance between the rami of the mandible was equal between sub ject groups, and thus the narrowing of the lateral dimension was not e xplained by differences in bony structure; (4) lateral airway narrowin g was explained predominantly by larger lateral pharyngeal walls in ap neic patients (the parapharyngeal fat pads were not closer together as one would expect if the airway walls were compressed by fat); and (5) fat pad size at the level of the minimum airway was not greater in ap neic than normal subjects. At the minimum airway area, thickness of th e lateral pharyngeal muscular walls rather than enlargement of the par apharyngeal fat pads was the predominant anatomic factor causing airwa y narrowing in apneic subjects.