State-Dependent Biomechanical Behavior of Oropharyngeal Structures in Apneic and Control Subjects: A Proof-of-Concept Study.

Rationale: Apneic individuals have reduced airway caliber during sleep. The biomechanical changes in upper airway anatomy contributing to this airway narrowing are largely unknown. Objectives: We sought to investigate the state-dependent (wake vs. sleep) biomechanical behavior of the upper airway soft-tissue and craniofacial structures. Methods: Upper airway magnetic resonance imaging was performed in 15 sleep-deprived control subjects (apnea-hypopnea index, <5; 0.3 ± 0.5 events per hour) and 12 sleep-deprived apneic subjects (apnea-hypopnea index, ⩾5; 35.2 ± 18.1 events per hour) during wake and sleep and analyzed for airway measures and soft-tissue/mandibular movement. Results: In the retropalatal region, control subjects showed sleep-dependent reductions (P ⩽ 0.037) in average cross-sectional airway area (CSA), minimum CSA, and anteroposterior and lateral dimensions. Apneic subjects showed sleep-dependent reductions (P ⩽ 0.002) in average CSA, minimum CSA, and anteroposterior and lateral dimensions. In the retroglossal region, control subjects had no sleep-dependent airway reductions. However, apneic subjects had sleep-dependent reductions in minimal CSA (P = 0.001) and lateral dimensions (P = 0.014). Control subjects only showed sleep-dependent posterior movement of the anterior-inferior tongue octant (P = 0.039), whereas apneic subjects showed posterior movement of the soft palate (P = 0.006) and all tongue octants (P ⩽ 0.012). Sleep-dependent medial movement of the lateral walls was seen at the retropalatal minimum level (P = 0.013) in control subjects and at the retropalatal and retroglossal minimum levels (P ⩽ 0.017) in apneic subjects. There was posterior movement of the mandible in apneic subjects (P ⩽ 0.017). Conclusions: During sleep, control and apneic subjects showed reductions in retropalatal airway caliber, but only the apneic subjects showed retroglossal airway narrowing. Reductions in anteroposterior and lateral airway dimensions were primarily due to posterior soft palate, tongue and mandibular movement and to medial lateral wall movement. These data provide important initial insights into obstructive sleep apnea pathogenesis.

The Association of Upper Airway Anatomy with Brain Structure: The Multi-Ethnic Study of Atherosclerosis.

Sleep apnea, affecting an estimated 1 in 4 American adults, has been reported to be associated with both brain structural abnormality and impaired cognitive function. Obstructive sleep apnea is known to be affected by upper airway anatomy. To better understand the contribution of upper airway anatomy to pathways linking sleep apnea with impaired cognitive function, we investigated the association of upper airway anatomy with structural brain abnormalities. Based in the Multi-Ethnic Study of Atherosclerosis, a longitudinal cohort study of community-dwelling adults, a comprehensive sleep study and an MRI of the upper airway and brain were performed on 578 participants. Machine learning models were used to select from 74 upper airway measures those measures most associated with selected regional brain volumes and white matter hyperintensity volume. Linear regression assessed associations between the selected upper airway measures, sleep measures, and brain structure. Maxillary divergence was positively associated with hippocampus volume, and mandible length was negatively associated with total white and gray matter volume. Both coefficients were small (coefficients per standard deviation 0.063 mL, p = 0.04, and - 7.0 mL, p < 0.001 respectively), and not affected by adjustment for sleep study measures. Self-reported snoring >2 times per week was associated with larger hippocampus volume (coefficient 0.164 mL, p = 0.007), and higher percentage of time in the N3 sleep stage was associated with larger total white and gray matter volume (4.8 mL, p = 0.004). Despite associations of two upper airway anatomy measures with brain volume, the evidence did not suggest that these upper airway and brain structure associations were acting primarily through the pathway of sleep disturbance.

Automatic Segmentation and Quantification of Upper Airway Anatomic Risk Factors for Obstructive Sleep Apnea on Unprocessed Magnetic Resonance Images.

RATIONALE AND OBJECTIVES: Accurate segmentation of the upper airway lumen and surrounding soft tissue anatomy, especially tongue fat, using magnetic resonance images is crucial for evaluating the role of anatomic risk factors in the pathogenesis of obstructive sleep apnea (OSA). We present a convolutional neural network to automatically segment and quantify upper airway structures that are known OSA risk factors from unprocessed magnetic resonance images. MATERIALS AND METHODS: Four datasets (n = [31, 35, 64, 76]) with T1-weighted scans and manually delineated labels of 10 regions of interest were used for model training and validations. We investigated a modified U-Net architecture that uses multiple convolution filter sizes to achieve multi-scale feature extraction. Validations included four-fold cross-validation and leave-study-out validations to measure generalization ability of the trained models. Automatic segmentations were also used to calculate the tongue fat ratio, a biomarker of OSA. Dice coefficient, Pearson's correlation, agreement analyses, and expert-derived clinical parameters were used to evaluate segmentations and tongue fat ratio values. RESULTS: Cross-validated mean Dice coefficient across all regions of interests and scans was 0.70 ± 0.10 with highest mean Dice coefficient in the tongue (0.89) and mandible (0.81). The accuracy was consistent across all four folds. Also, leave-study-out validations obtained comparable accuracy across uniquely acquired datasets. Segmented volumes and the derived tongue fat ratio values showed high correlation with manual measurements, with differences that were not statistically significant (p < 0.05). CONCLUSION: High accuracy of automated segmentations indicate translational potential of the proposed method to replace time consuming manual segmentation tasks in clinical settings and large-scale research studies.

Facial and Intraoral Photographic Traits Related to Sleep Apnea in a Clinical Sample with Genetic Ancestry Analysis.

Rationale: Craniofacial and pharyngeal morphology influences risk for obstructive sleep apnea (OSA). Quantitative photography provides phenotypic information about these anatomical factors and is feasible in large samples. However, whether associations between morphology and OSA severity differ among populations is unknown. Objectives: The aim of this study was to examine this question in a large sample encompassing people from different ancestral backgrounds. Methods: Participants in SAGIC (Sleep Apnea Global Interdisciplinary Consortium) with genotyping data were included (N = 2,393). Associations between photography-based measures and OSA severity were assessed using linear regression, controlling for age, sex, body mass index, and genetic ancestry. Subgroups (on the basis of 1000 Genomes reference populations) were identified: European (EUR), East Asian, American, South Asian, and African (AFR). Interaction tests were used to assess if genetically determined ancestry group modified these relationships. Results: Cluster analysis of genetic ancestry proportions identified four ancestrally defined groups: East Asia (48.3%), EUR (33.6%), admixed (11.7%; 46% EUR, 27% Americas, and 22% AFR), and AFR (6.4%). Multiple anatomical traits were associated with more severe OSA independent of ancestry, including larger cervicomental angle (standardized ß [95% confidence interval (CI)] = 0.11 [0.06-0.16]; P < 0.001), mandibular width (standardized ß [95% CI] = 0.15 [0.10-0.20]; P < 0.001), and tongue thickness (standardized ß [95% CI] = 0.06 [0.02-0.10]; P = 0.001) and smaller airway width (standardized ß [95% CI] = -0.08 [-0.15 to -0.002]; P = 0.043). Other traits, including maxillary and mandibular depth angles and lower face height, demonstrated different associations with OSA severity on the basis of ancestrally defined subgroups. Conclusions: We confirm that multiple facial and intraoral photographic measurements are associated with OSA severity independent of ancestral background, whereas others differ in their associations among the ancestrally defined subgroups.

The effect of mandibular advancement on upper airway structure in obstructive sleep apnoea.

BACKGROUND: The mechanisms by which mandibular advancement splints (MAS) improve obstructive sleep apnoea (OSA) are not well understood. This study aimed to evaluate the mechanism of action of MAS by assessing their effect on upper airway structure in patients with OSA. METHODS: Patients were recruited from a sleep disorders clinic for treatment with a custom-made MAS. MRI of the upper airway was performed during wakefulness in the supine position, with and without the MAS. RESULTS: Sixty-nine patients with OSA were recruited. Treatment with the MAS reduced the apnoea-hypopnoea index (AHI) from 27.0+/-14.7 events/h to 12.2+/-12.5 events/h (p<0.001). There was an increase in the total airway volume with mandibular advancement (16.5+/-0.7 cm(3) vs 18.1+/-0.8 cm(3); p<0.01) that occurred predominantly because of an increase in the volume of the velopharynx (5.7+/-0.3 cm(3) vs 6.5+/-0.3 cm(3); p<0.001). This increase in airway calibre was associated with an increase in the lower anterior facial height (6.8+/-0.1 cm vs 7.5+/-0.1 cm; p<0.001), reduction in the distance between the hyoid and posterior nasal spine (7.4+/-0.1 cm vs 7.2+/-0.1 cm; p<0.001), lateral displacement of the parapharyngeal fat pads away from the airway (right parapharyngeal fat pad 0.17+/-0.02 cm; left parapharyngeal fat pad 0.22+/-0.02 cm) and anterior movement of the tongue base muscles (0.33+/-0.03 cm). Subanalyses in responders and non-responders to MAS treatment showed that the increase in upper airway calibre with mandibular advancement occurred only in responders. CONCLUSION: These results suggest that the mechanism of action of MAS is to increase the volume of the upper airway, predominantly by increasing the volume of the velopharynx, and this increased volume is associated with changes in the surrounding bony and soft tissue structures.

Differences in three-dimensional upper airway anatomy between Asian and European patients with obstructive sleep apnea.

STUDY OBJECTIVES: This study evaluated differences in upper airway, soft tissues and craniofacial structures between Asians from China and Europeans from Iceland with OSA using three-dimensional magnetic resonance imaging (MRI). METHODS: Airway sizes, soft tissue volumes, and craniofacial dimensions were compared between Icelandic (N = 108) and Chinese (N = 57) patients with oxygen desaturation index (ODI) ≥ 10 events/h matched for age, gender, and ODI. Mixed effects models adjusting for height or BMI and residual differences in age and ODI were utilized. RESULTS: In our matched sample, compared to Icelandic OSA patients, Chinese patients had smaller BMI (p < 0.0001) and neck circumference (p = 0.011). In covariate adjusted analyses, Chinese showed smaller retropalatal airway size (p ≤ 0.002), and smaller combined soft tissues, tongue, fat pads, and pterygoid (all p ≤ 0.0001), but male Chinese demonstrated a larger soft palate volume (p ≤ 0.001). For craniofacial dimensions, Chinese demonstrated bigger ANB angle (p ≤ 0.0196), differently shaped mandibles, including shorter corpus length (p < 0.0001) but longer ramus length (p < 0.0001), and a wider (p < 0.0001) and shallower (p ≤ 0.0001) maxilla. CONCLUSIONS: Compared to Icelandic patients of similar age, gender and ODI, Chinese patients had smaller retropalatal airway and combined soft tissue, but bigger soft palate volume (in males), and differently shaped mandible and maxilla with more bony restrictions. Results support an ethnic difference in upper airway anatomy related to OSA, which may inform targeted therapies.

Anatomic predictors of response and mechanism of action of upper airway stimulation therapy in patients with obstructive sleep apnea.

Study Objectives: Upper airway stimulation has been shown to be an effective treatment for some patients with obstructive sleep apnea. However, the mechanism by which hypoglossal nerve stimulation increases upper airway caliber is not clear. Therefore, the objective of this study was to identify the mechanism of action of upper airway stimulation. We hypothesized that, with upper airway stimulation, responders would show greater airway opening in the retroglossal (base of the tongue) region, greater hyoid movement toward the mandible, and greater anterior motion in the posterior, inferior region of the tongue compared with nonresponders. Methods: Seven participants with obstructive sleep apnea who had been successfully treated with upper airway stimulation (responders) and six participants who were not successfully treated (nonresponders) underwent computed tomography imaging during wakefulness with and without hypoglossal nerve stimulation. Responders reduced their apnea-hypopnea index (AHI) by 22.63 ± 6.54 events per hour, whereas nonresponders had no change in their AHI (0.17 ± 14.04 events per hour). We examined differences in upper airway caliber, the volume of the upper airway soft tissue structures, craniofacial relationships, and centroid tongue and soft palate movement between responders and nonresponders with and without hypoglossal nerve stimulation. Results: Our data indicate that compared with nonresponders, responders had a smaller baseline soft palate volume and, with stimulation, had (1) a greater increase in retroglossal airway size; (2) increased shortening of the mandible-hyoid distance; and (3) greater anterior displacement of the tongue. Conclusions: These results suggest that smaller soft palate volumes at baseline and greater tongue movement anteriorly with stimulation improve the response to upper airway stimulation.

In Vivo Evaluation of the Mechanical and Viscoelastic Properties of the Rat Tongue.

The tongue is a highly innervated and vascularized muscle hydrostat on the floor of the mouth of most vertebrates. Its primary functions include supporting mastication and deglutition, as well as taste-sensing and phonetics. Accordingly, the strength and volume of the tongue can impact the ability of vertebrates to accomplish basic activities such as feeding, communicating, and breathing. Human patients with sleep apnea have enlarged tongues, characterized by reduced muscle tone and increased intramuscular fat that can be visualized and quantified by magnetic resonance imaging (MRI). The abilities to measure force generation and viscoelastic properties of the tongue constitute important tools for obtaining functional information to correlate with imaging data. Here, we present techniques for measuring tongue force production in anesthetized Zucker rats via electrical stimulation of the hypoglossal nerves and for determining the viscoelastic properties of the tongue by applying passive Lissajous force/deformation curves.

Genetic determinants of upper airway structures that predispose to obstructive sleep apnea.

Genetic factors are thought to play an important role in human development. Recent data indicate that obstructive sleep apnea may have a genetic basis. Sleep apnea is a very common disorder with significant cardiovascular and neurophysiologic morbidity. The pathogenesis of sleep apnea is related to a reduction in the size of the upper airway. The reduction in airway size is secondary to increased adipose tissue (enlargement of the parapharyngeal fat pads), alterations in craniofacial structure (reduction in mandibular size) and enlargement of the surrounding soft tissue structures (tongue, lateral pharyngeal walls). Genetic factors are one of the factors that have been proposed to mediate the size of each of these anatomic risk factors for sleep apnea. Recent evidence is accumulating about the genetic loci for these structural risk factors that predispose to the development of obstructive sleep apnea.

Mandibular dimensions in children with obstructive sleep apnea syndrome.

OBJECTIVE: We hypothesized that mandibular size may play a role in the etiology of obstructive sleep apnea syndrome (OSAS) in children, since a smaller mandible may reduce airway size. We used magnetic resonance imaging to determine the mandible dimensions of children with OSAS. DESIGN: Case control study. SETTING: Tertiary-care pediatric hospital. PARTICIPANTS: Twenty-four subjects (mean age 4.9 +/- 1.7 years) with mild to moderate OSAS (Apnea Index 3.5 +/- 5.1), and 24 matched controls (mean age 4.9 +/- 1.8 years). INTERVENTION: Magnetic resonance imaging of the upper airway under sedation. MEASUREMENTS: Eight measurements were obtained from a 3-dimensional segmentation of the mandible using 3DVIEWNIX software. Measurements included length, height, width, midsymphysis menti angle, angle of mandible, enclosure area, surface area, and volume. Descriptive comparisons using Student t test and multivariate analyses of variance were performed. RESULTS: Individual measurement comparisons revealed no significant differences between groups. Multivariate analysis showed a lower bound of a 95% confidence interval for an effect size measure for "general mandibular size," including all 6 linear, the area, and the volume measurements, to be -0.25. CONCLUSION: Our study shows that a smaller mandible is not a feature in children with OSAS who do not have apparent craniofacial abnormalities.

Facial phenotyping by quantitative photography reflects craniofacial morphology measured on magnetic resonance imaging in Icelandic sleep apnea patients.

STUDY OBJECTIVES: (1) To determine whether facial phenotype, measured by quantitative photography, relates to underlying craniofacial obstructive sleep apnea (OSA) risk factors, measured with magnetic resonance imaging (MRI); (2) To assess whether these associations are independent of body size and obesity. DESIGN: Cross-sectional cohort. SETTING: Landspitali, The National University Hospital, Iceland. PARTICIPANTS: One hundred forty patients (87.1% male) from the Icelandic Sleep Apnea Cohort who had both calibrated frontal and profile craniofacial photographs and upper airway MRI. Mean ± standard deviation age 56.1 ± 10.4 y, body mass index 33.5 ± 5.05 kg/m(2), with on-average severe OSA (apnea-hypopnea index 45.4 ± 19.7 h(-1)). INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Relationships between surface facial dimensions (photos) and facial bony dimensions and upper airway soft-tissue volumes (MRI) was assessed using canonical correlation analysis. Photo and MRI craniofacial datasets related in four significant canonical correlations, primarily driven by measurements of (1) maxillary-mandibular relationship (r = 0.8, P < 0.0001), (2) lower face height (r = 0.76, P < 0.0001), (3) mandibular length (r = 0.67, P < 0.0001), and (4) tongue volume (r = 0.52, P = 0.01). Correlations 1, 2, and 3 were unchanged when controlled for weight and neck and waist circumference. However, tongue volume was no longer significant, suggesting facial dimensions relate to tongue volume as a result of obesity. CONCLUSIONS: Significant associations were found between craniofacial variable sets from facial photography and MRI. This study confirms that facial photographic phenotype reflects underlying aspects of craniofacial skeletal abnormalities associated with OSA. Therefore, facial photographic phenotyping may be a useful tool to assess intermediate phenotypes for OSA, particularly in large-scale studies.

Heritability of craniofacial structures in normal subjects and patients with sleep apnea.

OBJECTIVES: Accumulating evidence has shown that there is a genetic contribution to obstructive sleep apnea (OSA).The objectives were to use magnetic resonance imaging (MRI) cephalometry to (1) confirm heritability of craniofacial risk factors for OSA previously shown by cephalometrics; and (2) examine the heritability of new craniofacial structures that are measurable with MRI. DESIGN: A sib pair "quad" design examining apneics, apneic siblings, controls, and control siblings. The study design used exact matching on ethnicity and sex, frequency matching on age, and statistical control for differences in age, sex, ethnicity, height, and weight. SETTING: Academic medical center. PATIENTS: We examined 55 apneic probands (apnea-hypopnea index [AHI]: 46.8 ± 33.5 events/h), 55 proband siblings (AHI: 11.1 ± 15.9 events/h), 55 controls (AHI: 2.2 ± 1.7 events/h), and 55 control siblings (AHI: 4.1 ± 4.0 events/h). INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Five independent domains reflecting different aspects of the craniofacial structure were examined. We confirmed heritability of sella-nasion-subspinale (38%, P = 0.002), saddle angle (55%, P < 0.0001), mandibular length (24%, P = 0.02) and lower facial height (33%, P = 0.006) previously measured by cephalometry. In addition, the current study added new insights by demonstrating significant heritability of mandibular width (30%, P = 0.005), maxillary width (47%, P < 0.0001), distance from the hyoid bone to the retropogonion (36%, P = 0.0018) and size of the oropharyngeal space (31%, P = 0.004). Finally, our data indicate that heritability of the craniofacial structures is similar in normal patients and those with apnea. CONCLUSIONS: The data support our a priori hypothesis that the craniofacial structures that have been associated with obstructive sleep apnea (OSA) are heritable. We have demonstrated heritability for several intermediate craniofacial phenotypes for OSA. Thus, we believe that future studies should be able to identify genes associated with these intermediate craniofacial phenotypes.

Examining the mechanism of action of a new device using oral pressure therapy for the treatment of obstructive sleep apnea.

STUDY OBJECTIVES: The objective of this study was to explore the mechanism of action of the oral pressure therapy (OPT) device, a new treatment for sleep apnea. DESIGN: Case series. SETTING: Academic medical center. PATIENTS: Fifteen subjects with sleep apnea who had been successfully treated (responders) with the OPT device and 4 subjects who were not successfully treated (non-responders) with the OPT device. INTERVENTIONS: All subjects underwent a MRI (without the device, with the device in place without vacuum and with the device in place with vacuum) to examine the biomechanical changes associated with the OPT device. MEASUREMENTS AND RESULTS: Oral pressure therapy significantly (P = 0.002) increased the size of the retropalatal airway in both the lateral and anterior-posterior dimensions by moving the soft palate anteriorly and superiorly and the anterior-superior segment of the tongue forward, toward the teeth. The percentage and absolute increase in the cross-sectional area of the retropalatal region, the superior movement of the soft palate, and the anterior displacement of the tongue were significantly greater in the responders than in the non-responders. In responders, there were significant increases in the mean (P = 0.002), maximum (P = 0.0002), and minimum (P = 0.04) cross-sectional areas of the retropalatal region with the OPT device. However, in the retroglossal region, airway caliber decreased with the OPT device. CONCLUSIONS: In those who responded to oral pressure therapy, it increased airway caliber in the retropalatal region by moving the soft palate anteriorly and superiorly and the anterior-superior segment of the tongue forward. CITATION: Schwab RJ, Kim C, Siegel L, Keenan BT, Black J, Farid-Moayer M, Podmore J, Vaska M. Examining the mechanism of action of a new device using oral pressure therapy for the treatment of obstructive sleep apnea.

Comparative effects of two oral appliances on upper airway structure in obstructive sleep apnea.

STUDY OBJECTIVES: Oral appliances are increasingly being used for treatment of obstructive sleep apnea (OSA). Mandibular advancement splint (MAS) mechanically protrudes the mandible, while the tongue stabilizing device (TSD) protrudes and holds the tongue using suction. Although both appliances can significantly improve or ameliorate OSA, their comparative effects on upper airway structure have not been investigated. DESIGN: Cohort study. SETTING: Sleep Investigation Unit. PATIENTS: 39 patients undergoing oral appliance treatment for OSA. INTERVENTIONS: OSA patients underwent magnetic resonance imaging (MRI) of the upper airway during wakefulness at baseline and with MAS and TSD in randomized order. Treatment efficacy was determined by polysomnography in a subset of 18 patients. MEASUREMENTS AND RESULTS: Upper airway lumen and surrounding soft tissue structures were segmented using image analysis software. Upper airway dimensions and soft tissue centroid movements were determined. Both appliances altered upper airway geometry, associated with movement of the parapharyngeal fat pads away from the airway. TSD increased velopharyngeal lateral diameter to a greater extent (+0.35 ± 0.07 vs. +0.18 ± 0.05 cm; P<0.001) and also increased antero-posterior diameter with anterior displacement of the tongue (0.68 ± 0.04 cm; P<0.001) and soft palate (0.12 ± 0.03 cm; P<0.001). MAS resulted in significant anterior displacement of the tongue base muscles (0.35 ± 0.04 cm). TSD responders (AHI reduction ≥50%) increased velopharyngeal volume more than non-responders (+2.65 ± 0.9 vs. -0.44 ± 0.8 cm(3); P < 0.05). Airway structures did not differ between MAS responders and non-responders. CONCLUSIONS: These results indicate that the patterns and magnitude of changes in upper airway structure differ between appliances. Further studies are warranted to evaluate the clinical relevance of these changes, and whether they can be used to predict treatment outcome.

Clinical guideline for the evaluation, management and long-term care of obstructive sleep apnea in adults.

BACKGROUND: Obstructive sleep apnea (OSA) is a common chronic disorder that often requires lifelong care. Available practice parameters provide evidence-based recommendations for addressing aspects of care. OBJECTIVE: This guideline is designed to assist primary care providers as well as sleep medicine specialists, surgeons, and dentists who care for patients with OSA by providing a comprehensive strategy for the evaluation, management and long-term care of adult patients with OSA. METHODS: The Adult OSA Task Force of the American Academy of Sleep Medicine (AASM) was assembled to produce a clinical guideline from a review of existing practice parameters and available literature. All existing evidence-based AASM practice parameters relevant to the evaluation and management of OSA in adults were incorporated into this guideline. For areas not covered by the practice parameters, the task force performed a literature review and made consensus recommendations using a modified nominal group technique. RECOMMENDATIONS: Questions regarding OSA should be incorporated into routine health evaluations. Suspicion of OSA should trigger a comprehensive sleep evaluation. The diagnostic strategy includes a sleep-oriented history and physical examination, objective testing, and education of the patient. The presence or absence and severity of OSA must be determined before initiating treatment in order to identify those patients at risk of developing the complications of sleep apnea, guide selection of appropriate treatment, and to provide a baseline to establish the effectiveness of subsequent treatment. Once the diagnosis is established, the patient should be included in deciding an appropriate treatment strategy that may include positive airway pressure devices, oral appliances, behavioral treatments, surgery, and/or adjunctive treatments. OSA should be approached as a chronic disease requiring long-term, multidisciplinary management. For each treatment option, appropriate outcome measures and long-term follow-up are described.

Linear dimensions of the upper airway structure during development: assessment by magnetic resonance imaging.

The upper airway undergoes progressive changes during childhood. Using magnetic resonance imaging (MRI), we studied the growth relationships of the tissues surrounding the upper airway (bone and soft tissues) in 92 normal children (47% males; range, 1 to 11 yr) who underwent brain MRI. None had symptoms of sleep-disordered breathing or conditions that impacted on their upper airway. MRI was performed under sedation. Sequential T1-weighted spin echo sagittal and axial sections were obtained and analyzed on a computer. We measured lower face skeletal growth along the midsagittal and axial oropharyngeal planes. In the midsagittal plane the mental spine-clivus distance related linearly to age (r = 0.86, p < 0.001). Along this axis, the dimensions of tongue, soft palate, nasopharyngeal airway, and adenoid increased with age and maintained constant proportion to the mental spine-clivus distance. Similarly, a linear relationship was noted for mandibular growth measured along the intermandibular line on the axial plane and age (r = 0.78, p < 0.001). In addition, the intertonsillar, tonsils, parapharyngeal fat pads, and pterygoids widths maintained constant proportion to intermandibular width with age. We conclude that the lower face skeleton grows linearly along the sagittal and axial planes from the first to the eleventh year. Our data indicate that soft tissues, including tonsils and adenoid, surrounding the upper airway grow proportionally to the skeletal structures during the same time period.