Understanding the anatomic basis for obstructive sleep apnea syndrome in adolescents

Abstract

Rationale: Structural risk factors for obstructive sleep apnea syndrome (OSAS) in adolescents have not been well characterized. Because many adolescents with OSAS are obese, we hypothesized that the anatomic OSAS risk factors would be more similar to those in adults than those in children.

Objectives: To investigate the anatomic risk factors in adolescents with OSAS compared with obese and lean control subjects using magnetic resonance imaging (MRI).

Methods: Three groups of adolescents (age range: 12-16 yr) underwent MRI: obese individuals with OSAS (n = 49), obese control subjects (n = 38), and lean control subjects (n = 50).

Measurements and main results: We studied 137 subjects and found that (1) obese adolescents with OSAS had increased adenotonsillar tissue compared with obese and lean control subjects; (2) obese OSAS adolescents had a smaller nasopharyngeal airway than control subjects; (3) the size of other upper airway soft tissue structures (volume of the tongue, parapharyngeal fat pads, lateral walls, and soft palate) was similar between subjects with OSAS and obese control subjects; (4) although there were no major craniofacial abnormalities in most of the adolescents with OSAS, the ratio of soft tissue to craniofacial space surrounding the airway was increased; and (5) there were sex differences in the pattern of lymphoid proliferation.

Conclusions: Increased size of the pharyngeal lymphoid tissue, rather than enlargement of the upper airway soft tissue structures, is the primary anatomic risk factor for OSAS in obese adolescents. These results are important for clinical decision making and suggest that adenotonsillectomy should be considered as the initial treatment for OSAS in obese adolescents, a group that has poor continuous positive airway pressure adherence and difficulty in achieving weight loss.

Keywords: MRI; adenoid; adolescents; obstructive sleep apnea syndrome; tonsils.

Figures

Figure 1.

(A) Anatomic definitions of the upper airway regions on a midsagittal magnetic resonance (MR) image are demonstrated: nasopharyngeal (from level of skull base to level of hard palate), retropalatal (from level of hard palate to caudal margin of soft palate), and retroglossal (from caudal margin of soft palate to base of tongue). (B) Upper airway segmented into three regions on a midsagittal MR slice. Red = nasopharyngeal airway; green = retropalatal airway; yellow = retroglossal airway. The participant was a lean control with an apnea–hypopnea index of 0.12/h and a body mass index z-score of −0.86.

Figure 2.

Magnetic resonance imaging analysis of upper airway soft tissue structures. (A) Upper airway anatomy on a sagittal magnetic resonance (MR) image. (B) Upper airway anatomy on an axial MR image. (C) Three-dimensional reconstruction of upper airway soft tissue structures using Amira software. White = mandible; pink = soft palate; yellow = parapharyngeal fat pads; green = lateral pharyngeal walls; red = genioglossus; purple = pterygoid muscles; gray = airway. Images show the same participant as in Figure 1.

Figure 3.

Magnetic resonance imaging analysis highlighting the upper airway lymphoid tissue. (A) Axial T2-weighted magnetic resonance (MR) image with palatine tonsil tissue segmentation (orange). (B) Axial T2-weighted MR image with adenoid tissue segmentation (blue). (C) Three-dimensional reconstruction of adenoid (blue) and tonsils (orange/rust). White = mandible; pink = soft palate; red = genioglossus; gray = airway. Images show the same participant as in Figure 1.

Figure 4.

Midsagittal magnetic resonance image showing anatomic landmarks and outline of the combined nasopharyngeal and oropharyngeal craniofacial structure. Top panel depicts anatomic landmarks and segmentation of the nasopharyngeal portion of the craniofacial structure. Middle panel shows anatomic landmarks and segmentation of the oropharyngeal portion of the craniofacial structure. Bottom panel depicts the combined craniofacial structure outlined in red. Images show the same participant as in Figure 1.

Figure 5.

Upper airway anatomy shown in three participants, all girls. (Left) Lean control participant with an apnea–hypopnea index (AHI) of 0.0/h. (Middle) Obese control participant with AHI of 0.3/h. (Right) Obese participant with obstructive sleep apnea syndrome (OSAS) with an AHI of 9.0/h. The adolescent with OSAS had larger adenotonsillar tissue, total soft tissue, and lateral wall volumes, as well as a smaller nasopharyngeal airway, than the obese and lean control subjects.

Figure 6.

Bar graphs showing differences in adenoid volume, tonsil volume, nasopharyngeal airway volume, total soft tissue volume, craniofacial space, and ratio of total soft tissue to craniofacial space (TST:CF) in the three participant groups and separated into boys and girls. LC = lean control subjects; OC = obese control subjects; OSAS = obstructive sleep apnea syndrome.