Three-dimensional CT reconstructions of tongue and airway in adult subjects with obstructive sleep apnea

A new method for determining the optimal CT threshold for extracting the upper airway

OBJECTIVES

The purpose of this study was to evaluate the optimal upper threshold levels of a number of individuals and determine the most suitable upper threshold.

METHODS

A phantom model and ten patients were used in this study. The phantom was made of acrylic resin and urethane resin and had nine pillar-shaped air spaces. The subjects were ten female patients with jaw deformities who were not affected by respiratory disease. The optimal threshold levels were determined using the "calculation of CT value disparities" (CCTD) technique, which we devised. In other words, the mean CT values along two lines (air space and soft tissue) were calculated and the optimal threshold level was determined as the level that produced the maximum difference between the CT values measured inside and outside of the air-space border.

RESULTS

The optimal upper threshold levels of the nine phantom holes calculated using the CCTD technique in the front-on standing position and side-on standing position were -434 HU and -456 HU, respectively. The optimal upper threshold level of the ten patients calculated using the CCTD technique was -472 HU. The true threshold level of each patient was defined as the optimal threshold level calculated using the CCTD technique. The mean threshold level was defined as -472 HU. The absolute differences between the volume measurements obtained with these two measures were considered. Therefore, the no error values were -460 HU and -470 HU.

CONCLUSIONS

We consider that the most suitable upper threshold level for extracting the airway is from -460 HU to -470 HU.

Effects of complete dentures on respiratory performance: spirometric evaluation

OBJECTIVES

There is a lack of data regarding whether edentulous subjects should remove dentures during spirometric measurements or not. The purpose of this study is to determine influences of complete dentures on spirometric parameters in edentulous subjects.

MATERIALS AND METHODS

A total of 46 complete denture wearers were included in this study. Respiratory functions of the subjects were evaluated by spirometric tests that were performed in four different oral conditions: without dentures (WOD), with dentures, lower denture only and upper denture only. Forced vital capacity (FVC), peak expiratory flow, forced expiratory volume in 1 s and forced expiratory flow between 25% and 75% were evaluated. The data were analyzed with Friedman, Wilcoxon and paired-samples t tests (α = 0.05).

RESULTS

Significant differences were found between spirometric parameters in different oral conditions (p < 0.05). In all spirometric parameters, the most important significant differences were found between conditions WOD, FVC and with lower dentures (FVC), and WOD (forced expiratory volume in 1 s) and with upper dentures (forced expiratory volume in 1 s) (p < 0.001).

CONCLUSION

It was observed that complete dentures may unfavourably affect spirometric values of edentulous subjects. However, current findings need to be confirmed with advanced respiratory function tests.

Cone beam computed tomography: craniofacial and airway analysis

Imaging plays a role in the anatomic assessment of the airway and adjacent structures. This article discusses the use of 3-dimensional (3D) imaging (cone beam computed tomography [CBCT]) to evaluate the airway and selected regional anatomic variables that may contribute to obstructive sleep-disordered breathing (OSDB) in patients. CBCT technology uses a cone-shaped x-ray beam with a special image intensifier and a solid-state sensor or an amorphous silicon plate for capturing the image. Incorporation of 3D imaging into daily practice will allow practitioners to readily evaluate and screen patients for phenotypes associated with OSDB.

Cephalometric assessment of craniofacial morphology in Japanese male patients with obstructive sleep apnea-hypopnea syndrome

Craniofacial morphological anomalies can be divided into two principal categories: skeletal anomalies and soft tissue anomalies. This study examined the hypothesis that the assessment of indices representing both skeletal and soft tissue can be used to appropriately identify the risk factor of obstructive sleep apnea–hypopnea syndrome (OSAHS). 232 suspected OSAHS male patients were examined with polysomnography and divided into two groups (202 males with OSAHS and 30 male controls without OSAHS). Cephalometric analysis was performed on all patients to evaluate craniofacial morphological anomalies. The measurement sites were as follows: skeletal morphology; soft tissue morphology; mixed morphology including mandibular plane to hyoid bone (MP-H); and jaw soft tissue (JS) ratio; a novel ratio we defined, between the area of jaw and area of tongue with soft palate. JS ratio increased with AHI as well as MP-H. MP-H and JS ratio showed significant but weak correlation with apnea–hypopnea index. JS ratio was significantly associated with an increased risk for severe OSAHS, even after adjusting age and BMI, its odds ratio was the greatest among these variables. These results showed that mixed craniofacial, skeletal and soft tissue morphology are correlated with AHI, and JS ratio may be a useful parameters to explain the characteristics of OSAHS in male patients.

Cone-beam computerized tomography imaging and analysis of the upper airway: a systematic review of the literature

A systematic review of the literature concerning upper airway imaging and analysis using cone-beam computed tomography (CBCT) was performed. A PubMed search (National Library of Medicine, NCBI; revised 9th January 2011) yielded 382 papers published between 1968 and 2010. The 382 full papers were screened in detail. 46 articles were considered clinically or technically relevant and were included in this systematic review. These were classified as articles on accuracy and reliability of CBCT imaging of the upper airway (n=4), accuracy and reliability of DICOM viewers (n=2), synopsis (n=10), technical (n=7) and clinical applications (n=27). When one paper was considered related to two or more categories, it was assigned to each relevant group. Results indicate that three-dimensional (3D) analysis of the upper airway using CBCT can be achieved in an accurate and reliable manner. Important obstacles still need to be addressed, including the impact of respiration phase, influence of tongue position and mandible morphology, longitudinal and cross-sectional 3D CBCT upper airway evaluation, and 3D CBCT definition of the anatomical boundaries of the upper airway.

Maxillary, mandibular, and chin advancement: treatment planning based on airway anatomy in obstructive sleep apnea

Surgical correction of obstructive sleep apnea (OSA) syndrome involves understanding a number of parameters, of which the 3-dimensional airway anatomy is important. Visualization of the upper airway based on cone beam computed tomography scans and automated computer analysis is an aid in understanding normal and abnormal airway conditions and their response to surgery. The goal of surgical treatment of OSA syndrome is to enlarge the velo-oropharyngeal airway by anterior/lateral displacement of the soft tissues and musculature by maxillary, mandibular, and possibly, genioglossus advancement. Knowledge of the specific airway obstruction and characteristics based on 3-dimensional studies permits a directed surgical treatment plan that can successfully address the area or areas of airway obstruction. The end occlusal result can be improved when orthodontic treatment is combined with the surgical plan. The individual with OSA, though, is more complicated than the usual orthognathic patient, and both the medical condition and treatment length need to be judiciously managed when OSA and associated conditions are present. The perioperative management of the patient with OSA is more complex and the margin for error is reduced, and this needs to be taken into consideration and the care altered as indicated.

Changes in the pharyngeal airway space and hyoid bone position after mandibular setback surgery for skeletal Class III jaw deformity in Japanese women

INTRODUCTION

The purpose of the study was to examine the changes in stability of pharyngeal airway space (PAS) and hyoid bone position after 2 types of mandibular osteotomies in comparison with a control group.

METHODS

The subjects included 46 Japanese women with skeletal Class III malocclusion. Twenty-five patients with mandibular prognathism underwent single-jaw surgery with bilateral sagittal split ramus osteotomy (SSRO), and 21 patients underwent bilateral intraoral vertical ramus osteotomy (IVRO). The control subjects included 30 volunteer women with normal occlusion. The treated subjects were assessed at the beginning of treatment, immediately after surgery, and after postsurgical treatment.

RESULTS

The Class III subjects had a significantly wider PAS than did the control subjects. Significant decreases in the lower PAS were observed after orthognathic surgery. The hyoid bone showed upward and forward movement with upward movement of the lower border of the PAS during the postsurgical stage in the SSRO group. In contrast, the anterior border of the PAS and the hyoid bone showed considerable backward movement in the IVRO group.

CONCLUSIONS

The posttreatment morphology of the PAS in both Class III groups approached that of the control group. The IVRO group showed a reduction in the airway dimensions, especially during the postsurgical period, which occurred during surgery in the SSRO group.

Modified mandibular advancement appliance for an edentulous obstructive sleep apnea patient: a clinical report

Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder with periodic reduction or cessation of airflow during sleep. It is associated with loud snoring, disrupted sleep and observed apneas with prevalence up to 54% in elderly people. Treatment of OSA varies from simple measures such as dental appliances and nasal continuous positive airway pressure (CPAP) to surgical procedures like uvulopalatopharyngoplasty and tracheostomy. Dental appliances are a viable nonsurgical treatment alternative in patients with OSA, of which mandibular advancement appliances are most common. Edentulism which contributes to the worsening of OSA reduces the number of available therapeutic strategies and is considered a contraindication to oral appliance therapy. This clinical report describes the treatment of a 61-year old edentulous OSA patient for whom a modified mandibular advancement appliance was designed. The patient reported an improvement in AHI index and he was satisfied with the modified appliance. This clinical report describes the newer technique of fabricating oral appliance for edentulous OSA patient.

Two- and three-dimensional evaluation of the upper airway after bimaxillary correction of Class III malocclusion

OBJECTIVE

The aim the study was to evaluate area and volumetric changes in the upper airway after bimaxillary correction of Class III malocclusion by the means of computer tomography (CT), and to compare these to the changes in linear measurements from lateral cephalograms.

STUDY DESIGN

This was a prospective clinical trial. Lateral cephalograms and CT scans of 10 Class III patients were evaluated 1 week before and 6 months after surgery. Wilcoxon matched pairs signed ranks test was used to determine the differences in measurements pre- and postoperatively. Spearman's rank correlation was used to test the association between the CT and cephalometric measurements.

RESULTS

CT measurements: The oropharyngeal and hypopharyngeal volumes increased by 3.98 +/- 4.18 cm(3) (P = .015) and 2.51 +/- 1.92 cm(3) (P = .021), respectively. The total volume of the posterior airway space increased, but the increase was not statistically significant. After surgery no change in the cross-sectional area of the upper airway was recorded at the retropalatal, oropharyngeal, or hypopharyngeal levels. Cephalometric measurements: The nasopharyngeal space increased 4.08 +/- 5.07 mm (P = .039) and the tongue increased in length by 4.84 +/- 5.93 mm (P = .22). No correlation was found between the measurements on CT scans and corresponding measurements on the lateral cephalograms.

CONCLUSIONS

Bimaxillary surgery for correction of Class III malocclusion did not cause decrease of the posterior airway space. Three-dimensional imaging techniques are preferable to 2-dimensional lateral cephalograms for evaluation of the upper airway after orthognathic procedures.

Pharyngeal airway volume and shape from cone-beam computed tomography: relationship to facial morphology

INTRODUCTION

The aim of this study was to assess the differences in airway shape and volume among subjects with various facial patterns.

METHODS

Cone-beam computed tomography records of 62 nongrowing patients were used to evaluate the pharyngeal airway volume (superior and inferior compartments) and shape. This was done by using 3-dimensional virtual surface models to calculate airway volumes instead of estimates based on linear measurements. Subgroups of the sample were determined by anteroposterior jaw relationships and vertical proportions.

RESULTS

There was a statistically significant relationship between the volume of the inferior component of the airway and the anteroposterior jaw relationship (P = 0.02), and between airway volume and both size of the face and sex (P = 0.02, P = 0.01). No differences in airway volumes related to vertical facial proportions were found. Skeletal Class II patients often had forward inclination of the airway (P <0.001), whereas skeletal Class III patients had a more vertically oriented airway (P = 0.002).

CONCLUSIONS

Airway volume and shape vary among patients with different anteroposterior jaw relationships; airway shape but not volume differs with various vertical jaw relationships. The methods developed in this study make it possible to determine the relationship of 3-dimensional pharyngeal airway surface models to facial morphology, while controlling for variability in facial size.

Sleep Endoscopy Versus Modified Mallampati Score in Sleep Apnea and Snoring

OBJECTIVES/HYPOTHESIS

The aim of this study is to quantify the correlation between a large tongue classified by the modified Mallampati score (MMS) and obstruction at the tongue base observed during sleep endoscopy in patients with socially unacceptable snoring (SUS) and obstructive sleep apnea syndrome (OSAS).

STUDY DESIGN

Prospective.

METHODS

One hundred twenty-seven patients with obstructive sleep apnea and SUS underwent sleep endoscopy. Patients were classified into four specific groups according to their MMS. After intravenous administration of midazolam, obstructive events in the upper airway were classified. The level of obstruction was expressed as palatal (2), palatal and to a lesser degree base of the tongue/laryngeal level (2), tongue base/laryngeal level and to a lesser degree palatal (3), and tongue base/laryngeal level (3). The degree of correlation between the level of obstruction and the MMS was analyzed by means of Spearman's rank-order correlation.

RESULTS

No linear association between the level of obstruction and MMS could be found. A large tongue (MMS 3 or 4) does not predict obstruction at the base of the tongue. Patients classified as MMS 1 or 2 did not frequently show obstruction at the base of the tongue (9 of 38, 23,6%). The majority of the population showed retropalatal obstruction. A large tongue (MMS 3 or 4) was often accompanied by retropalatal obstruction, 76% of the cases (64 of 89).

CONCLUSIONS

No positive correlation exists between a large tongue and obstruction at tongue base level. In both groups, retropalatal obstruction occurred more often than retrolingual obstruction. Sleep endoscopy provides qualitative insight into important changes during sleep in patients with SUS and OSAS. In addition, anatomic aberrations are clearly visualized in a dynamic setting. Classification of the size of the tongue, as assessed by the MMS, may be of great importance as well.

Airway and Craniofacial Changes With Mandibular Advancement Device in Chinese With Obstructive Sleep Apnoea

Introduction: The objective of this study was to investigate whether a reduction of obstructive sleep apnoea (OSA) severity is associated with significant airway and craniofacial changes with mandibular advancement device (MAD) in Chinese subjects. Materials and Methods: A total of 14 Chinese subjects (8 males, 6 females) diagnosed with OSA by overnight polysomnography (PSG), were fitted with the MAD. The mean ± standard deviation baseline apnoea-hypopnoea index (AHI) was 38.4 ± 17.2 and minimum arterial oxygen saturation (SaO2) was 75.5 ± 11.1%. The second lateral cephalogram was taken (wearing the MAD) after the second PSG. The second PSG was indicated when symptoms have improved as shown by the Epworth Sleepiness Score and sleep questionnaire after wearing the MAD for 1 month. Comparison of cephalometric variables was done to evaluate the effects of the MAD on the upper airway and anatomical variables. Pre-treatment versus post-treatment variables were compared using Wilcoxon signedrank test to determine the statistical significance at the 5% levels. The changes in airway variables were correlated with the changes in AHI using the Spearman correlation test. Results: At the second polysomnogram, AHI was significantly reduced to 10.9 ± 14.7. Minimum SaO2 was significantly increased to 86 ± 8.4%. Mean airway dimension was significantly increased at the nasopharyngeal area from 22.7 ± 3.0 mm to 24.8 ± 2.1 mm. The distance of the hyoid bone to the mandibular plane was significantly reduced with the MAD from a mean of 21.2 ± 5.7 mm to 13.9 ± 7.0 mm (P <0.05). This reduction of the distance of the hyoid bone to the mandibular plane was significantly correlated with the reduction in the AHI. Conclusion: An increase in the nasopharyngeal airway and reduction of the distance of the hyoid bone to the mandibular plane was observed for this sample of Chinese OSA subjects. This study forms the baseline for future studies on the effects of MAD on the airway and craniofacial structures in a larger sample. Key words: Lateral cephalogram, Mandibular advancement splint, Mandibular advancement device, Obstructive sleep apnoea, Polysomnogram

Long-term effects of symphyseal distraction and rapid maxillary expansion on pharyngeal airway dimensions, tongue, and hyoid position

INTRODUCTION

The aim of this study was to evaluate the effects of mandibular symphyseal distraction osteogenesis (MSDO) followed by rapid maxillary expansion (RME) on the pharyngeal and nasal airway dimensions and the tongue and hyoid positions.

METHODS

The material consisted of lateral and posteroanterior cephalometric radiographs of 13 female and 7 male patients (mean age, 20.0 +/- 2.3 years). Records were taken before treatment, after distraction (11.4 +/- 2.2 days after surgery), after RME (94.9 +/- 5.8 days after surgery), and at follow-up appointments (24.1 +/- 4.2 months after surgery). MSDO was performed with a custom-made tooth-and-bone-borne device. RME was performed with an acrylic bonded device. The average amounts of mandibular and maxillary expansion were 8.1 +/- 1.7 and 5.9 +/- 1.0 mm, respectively.

RESULTS

Posteroanterior cephalometric analysis showed significant transversal width increases between the mandibular canines and molars. No significant pharyngeal or transverse nasal airway changes occurred with MSDO except for a significant decrease in tongue length. However, MSDO followed by RME caused statistically significant but clinically small changes in oropharyngeal width (+1.0 mm), tongue length (-2.2 mm), vertical airway length (-2.3 mm), and vertical position of the hyoid bone (-1.4 mm), which were all stable at the 2-year follow-up.

CONCLUSIONS

The results suggest that MSDO alone or MSDO followed by RME does not significantly affect the pharyngeal airway dimensions or the hyoid position in adults. Any changes caused by these procedures might have been counteracted by the reflex mechanisms that protect airway potency.

Diagnostic Studies in Obstructive Sleep Apnea

The standard for the diagnosis of obstructive sleep apnea (OSA) is polysomnography (PSG). Although PSG helps identify individuals who have OSA and guides medical management, it does not identify the obstruction site or predict surgical results. Radiologic and diagnostic studies have been used to direct surgical intervention and predict outcomes of sleep apnea surgery. These studies include lateral cephalometric radiographs, CT, MRI, asleep fluoroscopy, asleep and awake endoscopy, upper airway manometry, and acoustic reflection techniques. The ideal diagnostic study would identify individuals who have OSA, be cost-effective and readily accessible, and guide therapeutic, site-specific intervention with predictable results. In this article, the various modalities are reviewed in terms of their capability to effectively diagnose and guide treatment of OSA.

Pharyngeal dimensions in healthy men and women

INTRODUCTION

Epidemiological studies reveal a high male prevalence of obstructive sleep apnea syndrome. A possible explanation for this male predominance is the existence of anatomical differences in the upper airway between men and women.

METHODS

The upper airways of 10 male and 10 female healthy volunteers were prospectively evaluated by magnetic resonance imaging. Anatomical pharyngeal and column cross-sectional linear measurements were made in sagittal T1 and axial T1 and T2 weighted fast spin-echo images.

RESULTS

Men had significantly greater mean sagittal pharyngeal structural dimensions compared to women for all structures with the exception of the craniocaudal length of the soft palate and the thickness of the submentonian fat. In contrast, cross-sectional linear dimensions were similar in men and women with the exception of the laterolateral tongue length, which was greater in men. All mean linear measurements of the pharyngeal air column were similar in men and women at all studied levels.

CONCLUSIONS

Men and women present pharyngeal air columns with similar dimensions, but in women this column is surrounded by smaller structures, which might imply a smaller effort to keep its patency. Our data suggest the existence of an anatomical protective factor in women against the upper airway collapse.

Ocena przydatności pomiarów cefalometrycznych w diagnostyce pacjentów z obturacyjnym zespołem snu z bezdechami – doniesienie wstępne

INTRODUCTION

The pathophysiology of OSAS is related with local anatomical predispositions to OSA such as craniofacial anomalies, adenoid and tonsillar hypertrophy, macroglossia, hypertonic oropharyngeal soft tissue, base of tongue proptosis, mandibular hypoplasia, posterior mandibular displacement, maxillary retrusion, enlarged uvula, retrognathia, and inferior positioning of the hyoid. The AIM of the study was to evaluate the usefulness of cephalometric measurements in patients with obstructive sleep apnea syndrome (OSAS).

MATERIAL AND METHODS

Eighteen randomly selected patients with snoring and varying degrees of sleep-disordered breathing were included in this study. All patients underwent completed otolaryngological examination, somnographic test using Poly-Mesam device, cephalometric radiographs and craniofacial CT scans. A control group had the same examinations and cephalometric tests. These patients had no snoring or clinical evidence of sleep-disordered breathing. No patients had prior pharyngeal or maxillomandibular surgery. Lateral cephalometric radiographs were obtained on all subjects in standing position using a standard technique. Each subject had also an awake CT scan in supine position on the back.

RESULTS

According all parameters we gathered from the study, OSAS is associated with significant changes in cephalometric measurements. Cephalometric analysis adds further information regarding the anatomical assessment of OSAS patients however we found craniofacial CT scans easier, more accurate measurements especially applying to soft tissues.

[Volumetry of the human tongue by MRI]

AIM

The purpose of this study was to determine the volume of the tongue using MRI. The correlation of the individual volume of the tongue and the size of the oral cavity was to be investigated.

MATERIAL AND METHODS

To analyze the tongue volume we combined coronal and sagittal data acquisition, which divided the tongue virtually into two lateral and one medial part. This procedure helped to decrease artefacts by partial volume effect. In 20 probands (m/f 7/13, average age of 36.3 years) the volume of the tongue was determined. Imaging protocol: Magnetom 63 SP (Siemens, Erlangen), T1-weighted sequences (TR/TE 500 ms/10 ms), slice thickness 5 mm, matrix 256 x 256, FOV 250 mm.

RESULTS

There was a significant linear regression between the tongue volume and height of the mouth cavity. This correlation can be used to calculate the normal volume of a patient's tongue.

DISCUSSION

Volumetry of the tongue can be carried out by means of MRI without application of injurious X-rays. It can be employed before as well as after tongue reduction surgeries for therapy control. The individual ideal tongue volume can be determined easily by determination of the height of the oral cavity.

Surgical management of obstructive sleep apnea

Obstructive sleep apnea (OSA) syndrome is a common disorder that has recently received much attention by the medical community due to its potentially serious physiological consequences. The clinical significance of OSA results from hypoxemia and sleep fragmentation caused by collapse of the airway, which leads to apnea or hypopnea during sleep. This paper reviews common surgical techniques used for clinical management of OSA patients, with emphasis on jaw advancement surgical procedures.

Predicting the Pharyngeal Airway Space After Mandibular Setback Surgery

PURPOSE

The purpose of this study is to propose a mathematical model to predict the change in pharyngeal airway space (PAS) associated with mandibular setback surgery.

PATIENTS AND METHODS

Twenty-three female adults, who were diagnosed as having skeletal Class III deformity, underwent mandibular setback surgery by bilateral sagittal split ramus osteotomy (BSSO) and orthodontic multibracket treatment. The subjects were assessed within 6 months before operation (T1) and 1 to 1.5 years after mandibular setback surgery (T2). The PAS change in the level of the base of the tongue was predicted.

RESULTS

The equation is: PAS narrowing = 0.386 - 0.541 ANB (T1 - T2) + 0.253 Co-Gn (T1 - T2) - 0.098 SN-GoGn (T1 - T2), where ANB is the angle formed by the planes nasion-point A and nasion-point B, Co is condylion, Go is gonion, and Gn is gnathion. The PAS change can be predicted by the mandibular changes after setback surgery 66.2% with the regression equation using the change of the ANB angle, the total mandibular length (Co-Gn) and the mandibular plane (SN-GoGn), where SN is sella-nasion.

CONCLUSIONS

The equation can be used to predict the change of pharyngeal airway space after mandibular setback surgery. In patients who have other risk factors, such as obesity, short neck, macroglossia, large uvula, and excessive soft tissue around the nasopharyngeal region, a mandibular setback surgery could possibly predispose to the development of sleep apnea syndrome.

Sleep nasendoscopy: a diagnostic tool for predicting treatment success with mandibular advancement splints in obstructive sleep apnoea

This prospective, cohort study evaluated the role of sleep nasendoscopy (SNE) with simultaneous mandibular protrusion in predicting successful mandibular advancement splint (MAS) therapy in subjects with obstructive sleep apnoea (OSA). Nineteen OSA subjects diagnosed by overnight polysomnography were referred for MAS therapy, following SNE investigation. A Herbst MAS was fabricated for each subject. Once this had been adjusted for maximal, subjective, therapeutic effect, follow-up sleep studies were undertaken with the appliance in situ. The SNE was repeated with the appliance in place to allow the effects of the original mandibular protrusion and the actual effect of the MAS to be compared. The MAS was removed and the original and current site(s) of obstruction evaluated. Pre-treatment SNE showed airway obstruction at the following levels: intermittent multi-level (16 subjects), sustained multi-level (two subjects) and tongue base (one subject). In all individuals, gentle advancement of the mandible during SNE improved airway patency and reduced snoring. When the SNE was repeated with the MAS in situ, all subjects showed improvements in snoring and airway patency. Follow-up sleep studies confirmed the efficacy of the MAS, with all patients showing a reduction in the apnoea/hypopnoea index (AHI). Median reductions in AHI (from 28.1 to 6.1, P < 0.001) and Epworth Sleepiness Scale (ESS) scores (from 9 to 6, P < 0.001) were highly statistically significant. The results suggest that SNE with concomitant mandibular advancement to mimic MAS wear, could be a valuable prognostic indicator of successful MAS treatment.

Computerized tomographic evaluation of effects of mandibular anterior repositioning on the upper airway: a pilot study

STATEMENT OF PROBLEM

Snoring is related to narrowing of the upper airway. Treatment options for snoring may have potential side effects or discomfort which may not be tolerated by some patients. Mandibular advancement devices may cause fewer negative side effects than other treatment modalities and have been advocated as a treatment for snoring.

PURPOSE

The aim of the pilot study was to evaluate effects of the anterior mandibular positioner (AMP) on upper airway structures in patients with a snoring problem.

MATERIAL AND METHODS

Fifteen subjects with snoring problems as identified by spouses or close relatives were selected to complete a questionnaire related to snoring, respiratory symptoms, body mass index (BMI), and smoking habits. Computerized tomography (CT) scans were obtained with and without AMP device fabricated as a monoblock of acrylic resin. Measurements of the oropharynx including length (mm), cross-sectional area (mm2), and plane angle (degrees) were made using anatomic landmarks on standardized CT images and lateral scanograms. The data were statistically evaluated using Wilcoxon signed rank test (alpha=.05).

RESULTS

When the AMP was inserted, the cross-sectional area of the oropharynx increased by 60 mm2 on average (P<.05). A mean increase of 2.4 mm (range 1-7 mm) was observed in the posterior airway space on lateral scanograms (P<.005). The range for mandibular advancement was between 4 and 8 mm (mean 5.73 mm).

CONCLUSION

The primary effect of the AMP was enlargement of the oropharyngeal airway. Within the limitations of this pilot study, the results suggest that CT evaluation of the upper airway structures may be helpful in determining treatment modality and monitoring the effectiveness of the positioner.

Contributions of upper airway mechanics and control mechanisms to severity of obstructive apnea

The contributions of pharyngeal mechanical abnormalities, flow demand, and compensatory effectiveness to obstructive sleep apnea severity were determined in 82 patients. Flow demand was estimated from mean inspiratory flow on continuous positive airway pressure. Mechanical load on upper airway muscles was estimated from minimal effective continuous positive airway pressure, flow demand, and minimum flow observed during brief pressure dial downs. Compensatory effectiveness was estimated by relating polysomnographic severity and mechanical load. Mechanical load was more severe in men, in supine position, and in older and heavier patients. Higher flow demand contributed significantly to mechanical load in men and in those who are obese. At the same mechanical load, severity was independent of age, sex, or body mass index but was greater in the supine position and in REM sleep. Mechanical load accounted for only 34% of variability in severity. Eighty-two percent of patients experienced periods of stable breathing despite mechanical loads that would produce continuous cycling without compensation. I conclude that most patients can adequately compensate for the abnormal mechanics, at least part of the time. Higher flow demand contributes to severity in men and in obesity. Severity is largely due to factors other than mechanical load. Compensatory effectiveness is impaired in the supine position and in REM sleep, but not by age, sex, or body mass index.

Identification of upper airway anatomic risk factors for obstructive sleep apnea with volumetric magnetic resonance imaging

We used sophisticated volumetric analysis techniques with magnetic resonance imaging in a case-control design to study the upper airway soft tissue structures in 48 control subjects (apnea-hypopnea index, 2.0 +/- 1.6 events/hour) and 48 patients with sleep apnea (apnea-hypopnea index, 43.8 +/- 25.4 events/hour). Our design used exact matching on sex and ethnicity, frequency matching on age, and statistical control for craniofacial size and visceral neck fat. The data support our a priori hypotheses that the volume of the soft tissue structures surrounding the upper airway is enlarged in patients with sleep apnea and that this enlargement is a significant risk factor for sleep apnea. After covariate adjustments the volume of the lateral pharyngeal walls (p < 0.0001), tongue (p < 0.0001), and total soft tissue (p < 0.0001) was significantly larger in subjects with sleep apnea than in normal subjects. These data also demonstrated, after covariate adjustments, significantly increased risk of sleep apnea the larger the volume of the tongue, lateral pharyngeal walls, and total soft tissue: (1) total lateral pharyngeal wall (odds ratio [OR], 6.01; 95% confidence interval [CI], 2.62-17.14); (2) total tongue (OR, 4.66; 95% CI, 2.31-10.95); and (3) total soft tissue (OR, 6.95; 95% CI, 3.08-19.11). In a multivariable logistic regression analysis the volume of the tongue and lateral walls was shown to independently increase the risk of sleep apnea.

Surgical management of obstructive sleep apnea

Nasal CPAP is and should be the first-line treatment for OSA. Any physician who uses nasal CPAP undoubtedly recognizes that this treatment modality has limitations, however. The authors believe that surgery offers a viable alternative to nasal CPAP in patients who are intolerant of nasal CPAP. Potential risks and complications must be explained fully to any potential surgical candidate. The selection of surgical procedure(s) should be determined based on a patient's airway anatomy, medical status, severity of sleep apnea, and his or her desire and preference.

Supine-dependent changes in upper airway size in awake obstructive sleep apnea patients

The purpose of this study was to define the changes in upper airway size in response to a body position change from upright to supine. A total of 15 male Caucasian obstructive sleep apnea (OSA) patients with a mean apnea hypopnea index of 31.0 +/- 13.9/hr were recruited for this study. A set of upright and supine cephalograms was traced and digitized for each patient. The most constricted site in the upright position was located in the velopharynx. When the body position was changed from upright to supine, a significant reduction in the anteroposterior dimension was observed only at the level of the velopharynx (p < 0.05). Sagittal cross-sectional areas of the velopharynx and the oropharynx significantly decreased (p < 0.05), but the soft palate area increased (p < 0.05). We conclude that the velopharynx is not only the narrowest site in both upright and supine body positions but also the most changeable site in response to an alteration in body position during wakefulness. Backward displacement of the soft palate with a change in shape may reflect less functional compensation in the velopharynx than that in the oropharynx and the hypopharynx and partly explain why upper airway occlusion occurs primarily in the velopharynx in OSA patients.

Dentofacial morphology and tongue function during swallowing

To understand the role of the tongue in the development of occlusion, we examined the relationship between tongue movements during swallowing and dentofacial morphology with ultrasonography, cephalometric radiography, and dental casts. Duration, magnitude, and speed of tongue movements were measured in 112 healthy adult volunteers and compared with their dentofacial morphology with a simple correlation analysis. The results showed that the movements of tongue during swallowing are related to dentofacial morphology, especially in the motion magnitude of the early final phase (phase IIIa), but that few correlations are found when analyzing the duration and the speed of swallowing. The results also showed that the intermaxillary vertical dimension is significantly and positively correlated with the motion magnitude of the tongue movements. Furthermore, we found that arch length increased with prolonged duration of swallowing. This study showed that the computer-aided B+M mode of ultrasonography combined with the cushion-scanning technique is a valuable tool for investigating the relationship between tongue movements during swallowing and dentofacial morphology.

A practical method for describing patterns of tongue-base narrowing (modification of Fujita) in awake adult patients with obstructive sleep apnea

PURPOSE

The purpose of the present study was to evaluate a clinically practical classification system for tongue-base narrowing and to assess intrarater and interrater reliability of the proposed system.

PATIENTS AND METHODS

A population of 248 consecutive patients with polysomnographically proven upper airway obstructive pathology were evaluated (using the hypotonic method) for evidence of upper airway narrowing with the commonly available techniques of fiberoptic nasopharyngoscopy, clinical examination and lateral cephalometric analysis.

RESULTS

Four basic patterns of tongue-base narrowing have been discerned to occur in awake adult patients with diagnosed obstructive upper airway pathology. These include type A (high tongue base), type B1 (high tongue base with retroepiglottic narrowing), type B2 (diffuse tongue-base narrowing), and type 3 (isolated retrogepiglottic narrowing). These recognized patterns have been found to have high intraexaminer and interexaminer reliability. No statistical correlation was found between tongue-base pattern and severity of obstructive sleep apnea, age, or facial skeletal pattern. Males had a higher percentage of type C pattern, and the type A pattern patients tended to have a higher body mass index.

CONCLUSIONS

Potential future uses of this classification system include the ability to more practically assess and describe anatomic locations of tongue-base narrowing and to permit an improved means of comparing the results of various surgical and nonsurgical therapies.

Contribution of body habitus and craniofacial characteristics to segmental closing pressures of the passive pharynx in patients with sleep-disordered breathing

Obesity and craniofacial abnormalities may contribute to the pathogenesis of obstructive sleep apnea. The purpose of this study was to evaluate the influence of body habitus and craniofacial characteristics on types of pharyngeal closure. The types of pharyngeal closure were determined by endoscopic evaluations of closing pressures of the passive pharynx in 54 paralyzed and anesthetized patients with sleep-disordered breathing (SDB). Assessment of craniofacial characteristics of the SDB patients and 24 normal subjects were made by lateral cephalometry. As compared with normal subjects, SDB patients demonstrated receded mandibles and long lower faces with downward mandible development. SDB patients with positive closing pressures at both the velopharynx and oropharynx (VP + OP group) demonstrated smaller maxillas and mandibles than those with positive closing pressures at the velopharynx only (VP-only group). Obesity was more prominent in the VP-only group than in the VP + OP group. Our results suggest that obesity and craniofacial abnormalities contribute synergistically to increases in collapsibility of the passive pharyngeal airway in patients with SDB. Furthermore, the relative contribution of obesity and craniofacial anomaly appears to determine the type of pharyngeal closure in SDB.

Pharyngeal airway space changes after counterclockwise rotation of the maxillomandibular complex

The purpose of this study was to evaluate the effects of double-jaw surgery with counterclockwise rotation of the maxillomandibular complex on the pharyngeal airway space and velopharyngeal anatomy in patients with high occlusal plane facial morphology. Fifty patients (22 men, 28 women) with high occlusal plane facial morphology underwent double-jaw surgery with counterclockwise rotation of the maxillomandibular complex. The patients were divided into 2 groups: group 1, 30 patients (8 men, 22 women) who underwent maxillary and mandibular advancement and group 2, 20 patients (14 men, 6 women) who underwent maxillary advancement and mandibular setback. Presurgery and postsurgery lateral cephalometric radiographs were analyzed to correlate changes in pharyngeal airway space dimensions and velopharyngeal anatomy with maxillary and mandibular positional changes. The calibration showed a more than 0.94 correlation for both intra- and interoperator error. The average follow-up time was 29.6 months in group 1 and 22.2 months in group 2. Mean maxillary surgical change at point A was 4.15 mm in group 1 and 2.5 mm in group 2. Mean mandibular surgical change at the genial tubercles was 7.5 mm in group 1 and -4.95 mm in group 2. After surgery, group 1 patients had an increase in pharyngeal airway space of 47% at the soft palate and 76% at the base of the tongue relative to the amount of mandibular advancement. Group 2 patients had a decrease in pharyngeal airway space of 47% at the soft palate and 65% at the base of the tongue relative to the amount of mandibular setback. Double-jaw surgery with counterclockwise rotation of the maxillomandibular complex significantly affects the pharyngeal airway space and velopharyngeal anatomy in patients with high occlusal plane facial morphology, with both mandibular advancement and setback.

Cephalometric and polysomnographic analyses of functional magnetic system therapy in patients with obstructive sleep apnea

The therapeutic effect of a functional magnetic system on obstructive sleep apnea and the system's operating mechanism have not been examined. Two hypotheses are postulated: a functional magnetic system increases the size of the oral cavity airway passage, or it increases the pharyngeal space. Twenty-eight patients with mild-to-moderate obstructive sleep apnea were examined; 10 patients (9 men and 1 woman; aged, 50.5 +/- 2.6 years) met the study criteria. After baseline nocturnal polysomnography and daytime tiredness self-evaluation, a functional magnetic system was inserted. The functional magnetic system is a mandibular repositioning appliance that uses a pair of attractive magnets (Sm2Co17), placed opposite each other in the jaws, which results in an advancement-to-opening ratio of 1:2. After 8 weeks of functional magnetic system treatment, polysomnography, daytime tiredness, and nighttime snoring were evaluated, and cephalogram radiographs with and without the appliance were taken. It was found that the respiratory disturbance index decreased significantly; minimal oxygen saturation increased significantly, reaching a normal value; day time tiredness improved; snoring declined; the oral cavity anterior region increased significantly, and the pharyngeal airway passages did not change. Reduction in the respiratory disturbance index and enlargement of the anterior oral cavity area were highly and significantly correlated. In conclusion, the functional magnetic system is a reliable mandibular repositioning appliance that has no apparent adverse effects. A functional magnetic system operates by increasing the anterior region of the oral cavity, mainly vertically, with no change in the posterior oral cavity region and pharyngeal airway passages.

Frontal and Lateral Cephalometry in Patients With Sleep-Disordered Breathing

OBJECTIVES/HYPOTHESIS

The traditional lateral-view cephalometric analysis is limited because it provides only two-dimensional analysis of the three-dimensional craniofacial structure. The objectives were to analyze lateral and frontal cephalometric radiographs in a series of normal patients and those with varying degrees of sleep-disordered breathing and to define the degrees of narrowing or other unfavorable anatomical changes that might differentiate the patients with sleep-disordered breathing from normal subjects.

STUDY DESIGN

A prospective study of 100 adult patients with sleep-disordered breathing and 60 age-matched normal subjects.

METHODS

An analysis of the lateral and frontal cephalometric measurements was performed to assess velopharyngeal anatomical features. A comparison was made between the patients' polysomnographic and cephalometric analyses.

RESULTS

The compromised cephalometric parameters that may be found in patients with sleep-disordered breathing include acute skull-base and bony nasopharynx angles, inferior hyoid position, thickening of the velum, reduced retrovelar posterior air space along with thickening of the velum, thickening of the posterior pharyngeal wall, and narrowing of the velopharyngeal lumen. Worsening of sleep-disordered breathing was generally associated with increased numbers of compromised cephalometric parameters. As body mass index increases, there is reduced velopharyngeal width, the velum thickness is increased, and the posterior pharyngeal wall thickness is increased.

CONCLUSIONS

Sleep-disordered breathing is associated with statistically significant changes in a number of cephalometric measurements. Frontal cephalometric analysis adds further information regarding the anatomical assessment of patients with upper airway obstruction, enhancing the traditional lateral cephalometric view.

Migraine and masticatory muscle volume, bite force, and craniofacial morphology

The purpose of this investigation was to compare the masticatory muscle volume, bite force, and craniofacial morphology of migrainous subjects with age- and sex-matched controls. Ten adult dentate migraineurs were matched with 10 dentate age- and sex-matched controls. The groups consisted of nine women and one man (mean age, 43 years; range, 29 to 51 years). Volumetric analysis of the masseter and medial pterygoid muscles was performed using magnetic resonance imaging. Craniofacial morphology was analyzed from standard cephalometric radiographs using 30 angular and linear variables. Recordings of bite force were made using a strain gauge transducer. There was a significant difference in the volume of both masseter and medial pterygoid muscles between the two subject groups (P<.0001), with the muscles of the migraineurs nearly 70% larger. The migraineurs recorded significantly higher maximal bite forces (P<.0001) than did the controls. No significant differences for any craniofacial morphological measurement were demonstrated between the two groups. It was concluded that the migraineurs had larger masseter and medial pterygoid muscle volumes, and greater bite forces than the controls, which could not be explained by any change in craniofacial morphology.

Effects of head and body position on two- and three-dimensional configurations of the upper airway

This study was carried out to test the hypothesis that changes in head/body position induce changes in upper-airway dimensions. Contiguous images were obtained by means of magnetic resonance imaging in normal awake subjects during nasal breathing. A statistical analysis was made on 5 consecutive slices, including the most constricted sites in both the retropalatal and retroglossal regions. Dimensional changes in the upper airway in association with changes in head/body position were evaluated. In the retropalatal region, there was a significant decrease in the lateral dimension in the lateral recumbent position compared with that in the supine position. The cross-sectional area in the retroglossal region was significantly increased in both the "supine with the head rotated" and "lateral recumbent" positions. This change was accompanied by significant volumetric changes in the retroglossal region. Thus, sleeping with the head rotated may be effective for improving upper-airway obstruction.

Three-dimensional computed tomographic evaluation of morphologic airway changes after mandibular setback osteotomy for prognathism

OBJECTIVE

To observe changes in the pharyngeal airway and the hyoid bone position after mandibular setback osteotomy in 30 patients with mandibular prognathism by means of 3-dimensional computed tomography (3DCT).

STUDY DESIGN

Preoperative and postoperative computed tomography (CT) examinations were performed on 17 patients treated by sagittal split ramus osteotomy with rigid osteosynthesis and on 13 patients treated by intraoral vertical ramus osteotomy without osteosynthesis. The amount of mandibular setback was measured by the preoperative to postoperative difference of the mandibular position in axial CT images. The sizes of the preoperative and postoperative pharyngeal airway were evaluated from semitransparent and crosscut 3DCT images. Postoperative displacement of the hyoid bone was evaluated by a technique to superimpose a postoperative hard tissue 3DCT image on the preoperative image. The helical scan technique was used in the CT examination. The volume rendering technique was used to create 3DCT images.

RESULTS

The mean mandibular setback was 7.8 +/- 2.1 mm with a range of 5 to 11 mm. Three months after surgery, the lateral and frontal widths of the pharyngeal airway had decreased significantly in comparison with the preoperative width. The mean reduction rates of the lateral and frontal width were 23.6% and 11.4%, respectively. The diminished airway did not recover by either 6 months or 1 year after surgery in most cases. Downward and posterior displacement of the hyoid bone was seen postoperatively. There were positive correlations between the amount of mandibular setback and reduction of the lateral width of the pharyngeal airway (r = 0.54) and the amount of hyoid bone displacement (r = 0.42). There were no significant differences between the two surgical techniques.

CONCLUSION

Three-dimensional computed tomography was a practical imaging technique to evaluate the morphologic airway changes. The pharyngeal airway may have irreversible narrowing after mandibular setback surgery.

Effects of surgical reduction of the tongue

There are still no objective diagnostic criteria for macroglossia. The aims of this study were to examine the effect of reduction of the tongue on its position, and to suggest a standard measurement point for the objective diagnosis of macroglossia. Twenty-four patients were studied. Lateral cephalometric radiographs were taken with the tongue in the rest position, and preoperative and postoperative measurements were made on cephalometric lateral roentgenograms from all 14 patients with macroglossia and the 10 control subjects. The results suggested that measurement of length of the tongue, and the tongue area: oral cavity ratio on lateral cephalometric radiographs are useful in the more accurate diagnosis of macroglossia.