UPPER AIRWAY MORPHOLOGY IN PATIENTS WITH IDIOPATHIC OBSTRUCTIVE SLEEP-APNEA

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Abstract
Fundamental to the pathogenesis of obstructive sleep apnea (OSA) is the interaction of physiologic and anatomic alterations of the upper airway. However, many patients with OSA have no identifiable abnormality of the upper airway, and they have been termed idiopathic. To find a structural deviation in upper airway anatomy, acoustic echography and cephalometric roentgenograms were performed in 9 male patients with OSA, and no clinical evidence of upper airway abnormality. Mean cross-sectional area of the pharynx by acoustic reflection was less in these patients (3.7 .+-. 0.8 cm2) than in subjects in a control group (5.3 .+-. 0.6 cm2) (P < 0.001). Mean glottic cross-sectional area was less in the patient group (1.5 .+-. 0.5 cm2) than in the control group (2.7 .+-. 0.5) (P < 0.001). There was a significant correlation between the number of apneas per sleep hour and pharyngeal cross-sectional area (r = 0.87, P < 0.01). Cephalometric analysis indicated that the patients had smaller mandibles by a mean of 5.4 .+-. 6.6 mm (P < 0.05). The overall posterior displacement of the mandibular symphysis, which is representative of the skeletal support of the anterior pharyngeal wall and is dependent on both mandibular size and position, was highly significant (6.4 .+-. 4.7 mm) (P < 0.01). There was a significant correlation between the number of apnea episodes per sleep hour and the total posterior displacement (r = 0.67, P < 0.05). Patients with so-called idiopathic OSA may have an anatomic predisposition to the development of upper airway occlusion that may not be detectable on clinical examination.