Zachary R. Abramson

Three-Dimensional Computed Tomographic Airway Analysis of Patients With Obstructive Sleep Apnea Treated by Maxillomandibular Advancement

PURPOSE To evaluate changes in airway size and shape in patients with obstructive sleep apnea (OSA) after maxillomandibular advancement (MMA) and genial tubercle advancement (GTA). MATERIALS AND METHODS This was a retrospective cohort study, enrolling a sample of adults with polysomnography-confirmed OSA who underwent MMA + GTA. All subjects who had preoperative and postoperative 3-dimensional computed tomography (CT) scans to evaluate changes in airway size and shape after MMA + GTA were included. Preoperative and postoperative sleep- and breathing-related symptoms were recorded. Descriptive and bivariate statistics were computed. For all analyses, P < .05 was considered statistically significant. RESULTS During the study period, 13 patients underwent MMA + GTA, of whom 11 (84.6%) met the inclusion criteria. There were 9 men and 2 women with a mean age of 39 years. The mean body mass index was 26.3; mean respiratory disturbance index (RDI), 48.8; and mean lowest oxygen saturation, 80.5%. After MMA + GTA, there were significant increases in lateral and anteroposterior airway diameters (P < .01), volume (P = .02), surface area (P < .01), and cross-sectional areas at multiple sites (P < .04). Airway length decreased (P < .01) and airway shape (P = .04) became more uniform. The mean change in RDI was -60%. CONCLUSIONS Results of this preliminary study indicate that MMA + GTA appears to produce significant changes in airway size and shape that correlate with a decrease in RDI.

Age-related changes of the upper airway assessed by 3-dimensional computed tomography.

The purposes of this study were to establish normative data for airway size and shape and to evaluate differences associated with age and sex using 3-dimensional (3-D) imaging. Patients being evaluated by computed tomography (CT) for pathologic conditions not related to the airway were included. Using 3-D Slicer (Harvard Surgical Planning Laboratory, Brigham and Womens Hospital, Boston, MA), a software program, digital 3-D CT reconstructions were made and parameters of airway size analyzed: volume (VOL), surface area (SA), length (L), mean cross-sectional area (mean CSA), minimum retropalatal (RP), minimum retroglossal (RG), minimum cross-sectional area (min CSA), and lateral (LAT) and anteroposterior (AP) retroglossal airway dimensions. Evaluation of airway shape included LAT/AP and RP/RG ratios, uniformity (U), and sphericity, a measure of compactness (&PSgr;). Children were stratified by stage of dentition: primary, 0 to 5 years; mixed, 6 to 11 years; permanent, 12 to 16 years; and adults, older than 16 years. Differences in airway parameters by age and sex were analyzed. Forty-six CT scans (31 males) were evaluated. Adults had larger (VOL, SA, L, mean CSA, and LAT), more elliptical (increased LAT/AP, P = 0.01), less uniform (U, P = 0.02), and less compact (decreased &PSgr;, P = 0.001) airways than children. Among children, those in the permanent dentition demonstrated greater VOL (P < 0.01), SA (P < 0.01), L (P < 0.01), and mean CSA (P < 0.01) than those in the primary dentition. There were no gender differences in airway parameters. Understanding differences in 3-D airway size and morphology by age may serve as a basis for evaluation of patients with obstructive sleep apnea and may help to predict and to evaluate outcomes of treatment.

Three-Dimensional Computed Tomographic Analysis of Airway Anatomy in Patients With Obstructive Sleep Apnea

PURPOSE To identify abnormalities in airway size and shape that correlate with the presence and severity of obstructive sleep apnea (OSA). MATERIALS AND METHODS This was a retrospective case series of patients undergoing treatment of OSA who had preoperative computed tomographic (CT) scans of the upper airway available. Patients who had undergone CT scanning for nonairway pathologic features during the same period served as the controls. Digital 3D-CT reconstructions were made and 12 parameters of airway size and 4 of shape were analyzed. The posterior airway space, middle airway space, and hyoid to mandibular plane distance were measured on the lateral cephalograms of the patients with OSA. Bivariate analysis was used to identify the factors associated with the presence and severity of OSA as measured by the respiratory disturbance index (RDI). Multiple regression analysis identified the factors that correlated with the RDI. RESULTS Of the 44 patients with OSA, 15 (10 men and 5 women) had pre- and postoperative CT scans available. In addition, 17 patients (11 men and 6 women) were used as controls. The airway length was significantly increased in the patients with OSA (P < .01). On bivariate analysis, the length, lateral/retroglossal anteroposterior dimension ratio and genial tubercle to hyoid bone distance were associated with the RDI (P < .03). On multiple regression analysis, length (P < .01) had a positive correlation and the lateral/retroglossal anteroposterior dimension ratio (P = .04) an inverse correlation with the RDI. CONCLUSIONS The results of this study indicate that the presence of OSA is associated with an increase in airway length. Airways that were more elliptical in shape and mediolaterally oriented (greater lateral/retroglossal anteroposterior dimension ratio) had a decreased tendency toward obstruction.

Three-dimensional computed tomographic analysis of airway anatomy.

PURPOSE To test the reliability of a 3-dimensional computed tomographic (3D-CT) analysis of airway size and shape and to correlate the 3D-CT findings with lateral cephalometric measurements. MATERIALS AND METHODS Fifteen pairs of preoperative maxillofacial 3D-CT scans and digital lateral cephalograms of patients treated for obstructive sleep apnea were used in the present study. Digital 3D-CT reconstructions were created and 12 measurements of airway size and 4 of shape were analyzed. The posterior airway space (PAS), middle airway space, and hyoid to mandibular plane distances were measured on the cephalograms. We then randomly selected 5 CT scans and 5 cephalograms which were analyzed blindly on 5 separate occasions by 2 investigators (Z.A., J.T.) to establish the intraclass correlation coefficients for inter- and intraexaminer reliability. All 15 pairs of images were used to compute the Pearson correlation coefficients to establish the relationship between the CT and cephalometric measurements. RESULTS The intra- and interexaminer reliabilities were high for all CT (0.86 to 1.0 and 0.89 to 1.0, respectively; P < .001) and cephalometric measurements (0.84 to 1.0 and 0.91 to 0.99, respectively; P < .001). The CT measurements retroglossal anteroposterior dimension and distance between the genial tubercle and hyoid exhibited a positive correlation with the PAS (r = .60, P = 02 and r = .54, P = .04, respectively), and the lateral/anteroposterior dimension demonstrated an inverse correlation (r = -.68, P = .01) with the PAS. CONCLUSION The results of the present study indicate that the 3D-CT and lateral cephalometric measurements we selected are reliable and reproducible. The only cephalometric measurement that exhibited any correlation with the CT parameters was PAS.

Cephalometric Measurement of Upper Airway Length Correlates With the Presence and Severity of Obstructive Sleep Apnea

PURPOSE The purpose of this study was to measure upper airway length (UAL) on lateral cephalograms and to assess its relationship with the presence and severity of obstructive sleep apnea (OSA). MATERIALS AND METHODS Using a case-control study design, the investigators enrolled a sample of cases defined as adult subjects with OSA and controls who were adult patients with skeletal Class II malocclusions. The primary predictor variable was UAL. Other variables were demographic and cephalometric parameters. The respiratory disturbance index (RDI) was used to measure disease severity in cases. Bivariate analyses were computed to evaluate the associations between predictor and outcome variables. Multiple regression analyses were used to provide adjusted measures of association, controlling for the effects of confounders/effect modifiers. Diagnostic test characteristics were computed for threshold airway lengths. P ≤ .05 was considered statistically significant. RESULTS The sample consisted of 96 cases with OSA (76 males) and 56 controls without OSA (36 males). OSA subjects were older, were predominately male, and had higher body mass indexes and longer and narrower airways (P < .05). After controlling for confounding variables, UALs ≥ 72 mm for males and ≥ 62 mm for females were significantly associated with the presence of OSA (P = .03). The sensitivity and specificity of UAL as a diagnostic test for OSA were ≥ 0.8. UAL was strongly correlated with RDI (disease severity) in males (r = 0.72, P < .01) and moderately correlated with RDI in females (r = 0.52, P < .01). CONCLUSION Increased upper airway length was correlated with the presence and severity of OSA in this sample of adult patients.

Biomechanics of the upper airway: Changing concepts in the pathogenesis of obstructive sleep apnea.

Obstructive sleep apnea (OSA) is a disorder characterized by repetitive, episodic collapse of the pharyngeal airway. Over the last two decades, understanding of the pathophysiology of sleep disordered breathing, which includes OSA, has improved. Once thought to be predominately related to anatomic constriction of the maxillomandibular complex, central nervous system regulation of breathing is now recognized as a significant contributor to the pathogenesis of OSA. Ventilator control, the central response to chemoreceptor phenomena, has important implications for oral and maxillofacial surgeons who treat OSA, particularly for patients who appear refractory to treatment with maxillomandibular advancement (MMA). The purpose of this article is to review the biomechanics of the upper airway as it relates to the pathophysiology of OSA, to discuss emerging concepts of ventilator control mechanisms in normal sleep versus sleep-disordered breathing and to discuss the concept of complex sleep apnea, a new category of sleep disordered breathing with both obstructive and central features.

Upper airway length decreases after maxillomandibular advancement in patients with obstructive sleep apnea.

PURPOSE Most reports on airway anatomy after maxillomandibular advancement (MMA) for obstructive sleep apnea (OSA) have focused on changes in airway diameter, ie, posterior airway space (PAS), rather than airway length. The purpose of this study was to evaluate changes in cephalometrically measured upper airway length (UAL) after MMA. MATERIALS AND METHODS This was a retrospective cohort study. The sample was composed of subjects who underwent MMA for OSA. The primary outcome measurement was change in UAL measured on lateral cephalograms. Predictor variables included patient demographic and cephalometric characteristics. Secondary outcome measurements were changes in sleep disturbance. Descriptive, bivariate, and regression statistics were computed. For all analyses, P ≤ .05 was considered statistically significant. RESULTS The sample included 23 adult subjects (mean age, 39.3 ± 12.1 years; 6 women). Subjects had average maxillary and mandibular advancements of 9.8 ± 2.0 and 10.8 ± 2.2 mm, respectively. Mean pre- and postoperative UALs were 75.8 ± 7.0 and 67.0 ± 5.7 mm, respectively (P < .001). Mean pre- and postoperative respiratory disturbance indexes were 53.2 ± 22.4 and 19.0 ± 12.0 events/hour, respectively (P = .003). All patients had improvement in OSA symptoms, but 3 (13%) required continuous positive airway pressure. CONCLUSION The results of this study suggest that UAL decreases as a result of MMA. In addition, these results support the observation that MMA is associated with objective and subjective improvements in patients with OSA.

Effects of mandibular distraction osteogenesis on three-dimensional airway anatomy in children with congenital micrognathia.

PURPOSE To assess the 3-dimensional (3D) computed tomography (CT) changes in airway size and shape in children with congenital micrognathia treated by mandibular distraction osteogenesis (DO). PATIENTS AND METHODS This was a retrospective study of patients with congenital micrognathia, treated by mandibular DO, who had pre- and postoperative 3D maxillofacial CT scans from the hard palate to the hyoid bone. Digital 3D-CT reconstructions were made before and after distraction. Demographic (age, gender, and diagnosis) and anatomic (airway size and shape) variables were recorded and analyzed. The pre-distraction measures of size and shape were compared with the post-distraction measures. P≤.05 was considered significant. RESULTS During the study period (1999 to 2010), 17 children with congenital micrognathia underwent mandibular DO. Of these patients, 11 (3 females) met the inclusion criteria. The mean age was 6.8 years (range 1.3 to 20.6). All subjects had first and second pharyngeal arch deformities. Nine were tracheostomy dependent before distraction. Postdistraction increases in the anteroposterior diameter (153%), lateral airway diameter (70%), airway volume (76%), minimal retroglossal (162%) and retropalatal (77%), and minimal cross-sectional areas (282%) were obtained. The mean airway length decreased after distraction by 4 mm DO also affected the airway shape: the airway surface area and airway compactness increased after distraction. Six subjects were decannulated or had their tracheostomies capped. Three subjects remained tracheostomy dependent after distraction. The reasons for continued tracheostomy included copious secretions, muscle hypotonia, hypopharnygeal stenosis, and mandibular hypomobility. CONCLUSIONS DO for congenital micrognathia increases airway size, decreases airway length, and alters the shape as measured using 3D-CT.

Radiology of Cleft Lip and Palate: Imaging for the Prenatal Period and throughout Life

Recent advances in prenatal imaging have made possible the in utero diagnosis of cleft lip and palate and associated deformities. Postnatal diagnosis of cleft lip is made clinically, but imaging still plays a role in detection of associated abnormalities, surgical treatment planning, and screening for or surveillance of secondary deformities. This article describes the clinical entities of cleft lip with or without cleft palate (CLP) and isolated cleft palate and documents their prenatal and postnatal appearances at radiography, ultrasonography (US), magnetic resonance (MR) imaging, and computed tomography (CT). Imaging protocols and findings for prenatal screening, detection of associated anomalies, and evaluation of secondary deformities throughout life are described and illustrated. CLP and isolated cleft palate are distinct entities with shared radiologic appearances. Prenatal US and MR imaging can depict clefting of the lip or palate and associated anomalies. While two- and three-dimensional US often can depict cleft lip, visualization of cleft palate is more difficult, and repeat US or fetal MR imaging should be performed if cleft palate is suspected. Postnatal imaging can assist in identifying associated abnormalities and dentofacial deformities. Dentofacial sequelae of cleft lip and palate include missing and supernumerary teeth, oronasal fistulas, velopharyngeal insufficiency, hearing loss, maxillary growth restriction, and airway abnormalities. Secondary deformities can often be found incidentally at imaging performed for other purposes, but detection is necessary because they may have considerable implications for the patient.

Geometry of anterior open bite correction.

Correction of anterior open bite is a frequently encountered and challenging problem for the craniomaxillofacial surgeon and orthodontist. Accurate clinical evaluation, including cephalometric assessment, is paramount for establishing the diagnosis and appropriate treatment plan. The purposes of this technical note were to discuss the basic geometric principles involved in the surgical correction of skeletal anterior open bites and to offer a simple mathematical model for predicting the amount of posterior maxillary impaction with concomitant mandibular rotation required to establish an adequate overbite. Using standard geometric principles, a mathematical model was created to demonstrate the relationship between the magnitude of the open bite and the magnitude of the rotational movements required for correction. This model was then validated using a clinical case. In summary, the amount of open bite closure for a given amount of posterior maxillary impaction depends on anatomic variables, which can be obtained from a lateral cephalogram. The clinical implication of this relationship is as follows: patients with small mandibles and steep mandibular occlusal planes will require greater amounts of posterior impaction.