Cranial base and airway morphology in adult malays with obstructive sleep apnoea

Obstructive sleep apnoea (OSA) has been described as a public health problem comparable to smoking in its impacts upon society.

To compare the differences in cranial base and airway morphology in Malay adults with and without OSA using finite element analysis (FEM).

Lateral skull radiographs of 38 adult Malays aged 18-60 years were divided into two groups of 19 (13 male, 6 female). The first group consisted of 19 patients with OSA, defined as an apnoea-hypopnea index > 5/hr of sleep, diagnosed with overnight polysomnography. The second group consisted of 19 healthy, non-OSA control subjects. For each lateral skull radiograph 27 homologous landmarks, which encompassed the naso-oropharyngeal airway, were digitised using MorphoStudio software. The mean OSA and control 2D airway configurations were computed and subjected to t-tests and FEM.

The mean 2D OSA airway was statistically different from the mean control airway (p < 0.01). Inter-landmark analysis revealed that the cranial base saddle angle was more acute in the OSA group (153.9 degrees +/- 3.4) compared to the control group (158.3 degrees +/- 2.5; p < 0.01). In addition, using pseudo-coloured FEM a relative 58 per cent decrease in nasopharyngeal airway area was found above and behind the soft palate. As well, a 32 per cent decrease in oropharyngeal airway area was located behind the base of the tongue, with a 23 per cent decrease in hypopharyngeal area near the level of the hyoid bone. In contrast, a 96 per cent increase in area associated with downward displacement of the hyoid bone was detected.

Functional airway impairments associated with OSA can be quantified and localised in Malay patients, and are predominantly associated with the morphology of the posterior regions of the cranial base.