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

Dental considerations in upper airway sleep disorders: A review of the literature

STATEMENT OF PROBLEM

Upper airway sleep disorders are becoming recognized as common medical concerns. Multiple treatment options have been advocated, including the use of dental devices. Dental practitioners are being asked by the medical profession to become a part of the treatment team. This may be a challenging task because of the large number of dental devices available, rapid advancement in the understanding of this disease, and numerous publications.

PURPOSE

This article reviews the anatomic features and etiologic factors of upper airway sleep disorders and medical and dental treatment options.

METHODS

The literature review was conducted with an accepted literature research tool, PubMed, developed by the National Library of Medicine. Key words searched included "obstructive sleep apnea," "sleep apnea," "sleep disorders," and "snoring".

CONCLUSION

Dental devices are indicated in snoring and mild-to-moderate obstructive sleep apnea patients after medical evaluation and referral.

Overview of Phase I Surgery for Obstructive Sleep Apnea Syndrome

It is well established that obstructive sleep apnea syndrome is associated with increased morbidity and mortality. Surgical therapy has been demonstrated to be a viable treatment option for cure. Thorough presurgical evaluation with the identification of the type of airway abnormality is mandatory to allow for the utilization of a surgical protocol that results in improved clinical outcomes. Phase I surgical protocol is designed to apply specific surgical procedures to alleviate the obstruction(s) present. Following a logical, stepwise surgical approach in airway reconstruction will minimize surgical interventions and avoid unnecessary operations. The incorporation of a risk-management protocol will minimize treatment complications while achieving cure.

Proposed cephalometric diagnosis for osteogenic obstructive sleep apnea (OSA): the mandibular/pharyngeal ratio

The purpose of this laboratory study is to devise a simple, diagnostic test to assess possible osteological deficiency as a probable cause of OSA. Modern day skulls of fifty males and forty eight females of Tuscan origin and an additional seventy-five skulls, from India, with their cephalograms were used for this study. Mandibular length and antero-posterior dimension of the nasopharynx--pharyngeal tubercle (PhT) to posterior nasal spine (PNS)--were measured on the Tuscan skulls. The nasopharynx was similarly measured on the Indian skulls and readings multiplied by 1.14, the magnification factor of the cephalometric apparatus used. The PhT-PNS distance was then plotted on the cephalogram of Indian skulls with point PhT at the basiocciput. The possible presence of an osteogenic etiology of OSA can be determined by comparison of the mandibular/pharyngeal ratio obtained from the skull cephalograms to that of the individual patient.

Comparative clinical and physiological features of Maori, Pacific Islanders and Europeans with sleep related breathing disorders

Recent studies have suggested that there is a familial association of sleep apnoea syndrome and that this is not entirely explained by inheritance of known risk factors. Maori (M) and Pacific Islanders (PI) have many of the body habitus features associated with sleep apnoea and therefore might be expected to exhibit more severe disease than Europeans (E).

OBJECTIVE

To compare the clinical and physiological characteristics of the different ethnic groups and to determine if race was an independent predictor of severity of sleep apnoea.

METHODOLOGY

A prospective evaluation of patients attending the Sleep Disordered Breathing Clinic which serves the whole of Auckland (population 1.1 million), New Zealand was conducted for the period July 1994 to August 1995. The evaluation included history including a 26 question questionnaire, Epworth sleepiness score, examination, and where indicated, full polysomnography.

RESULTS

A total of 233 patients (154 E, 48 M and 33 PI), underwent full polysomnography. Forty-one (85%) of the M and 31 (94%) of PI had obstructive or mixed sleep apnoea compared with only 74 (49%) of the E (P < 0.0001; chi 2). There were few racial differences in the responses to the sleep questionnaire. M and PI were shown to have much greater neck and waist circumference and body mass indices. Severity parameters (apnoea-hypopnoea index, wake and minimum oxygen saturation, and apnoea duration) were greater for both M and PI compared with E (P < 0.001; Mann-Whitney U-test). Stepwise regression identified neck size, body mass index and age as independent predictors of severity.

CONCLUSION

When other factors were controlled for, race was not an important independent predictor of severity of sleep apnoea.

Upper airway assessment: radiographic and other imaging techniques

Upper airway imaging is a powerful technique to study the mechanisms underlying the pathogenesis and biomechanics of sleep apnea and the mechanisms underlying the efficacy of therapeutic interventions in patients with sleep disordered breathing. The primary upper airway imaging modalities include nasopharyngoscopy, cephalometrics, CT scanning, and MR imaging. Imaging studies using these modalities have provided important insights into the static and dynamic structure and function of the upper airway and surrounding soft-tissue structures during wakefulness and sleep. Such imaging studies have highlighted the importance of the lateral pharyngeal walls in mediating upper airway caliber. These imaging modalities have also been used to study the effect of respiration, weight loss, mandibular repositioning devices, and upper airway surgery on the upper airway. Three-dimensional reconstruction of the airway and surrounding soft-tissue structures can be performed with MR imaging and CT scanning. Clinical indications for upper airway imaging are evolving such that imaging studies should be considered in patients with sleep apnea who are being treated with dental appliances or upper airway surgery.

State-related changes in upper airway caliber and surrounding soft-tissue structures in normal subjects

State-dependent changes in upper airway caliber were studied with magnetic resonance imaging (MRI) techniques. We hypothesized that changes in airway caliber during sleep in normal subjects would result from positional and dimensional changes in upper airway soft-tissue structures, including the lateral pharyngeal walls, tongue, and soft palate. We used MRI to study 15 normal subjects during wakefulness and sleep. Sleep was facilitated by one night of sleep deprivation prior to MRI. During sleep, the volume of the retropalatal (RP) airway was reduced by 19% (p = 0.03). The volume of the retroglossal (RG) airway was not significantly reduced during sleep, suggesting that the RP region may be more likely to collapse. The mean minimal cross-sectional airway area was reduced by 228% (p = 0.004) in the RP and by 22% (p = 0.02) in the RG region during sleep as compared with values in anatomically matched axial images during wakefulness. Airway anteroposterior (AP) and lateral dimensions were also significantly reduced in the RP region. Airway narrowing in the RP region was associated with a 7% increase in thickness of the lateral pharyngeal walls (p = 0.04). In nine subjects, sagittal data showed significant posterior displacement of the soft palate during sleep as compared with wakefulness. Multiple linear regression analyses indicated that reduction in the RP airway area during sleep resulted from posterior movement of the soft palate, thickening of the lateral pharyngeal walls, and an increase in tongue oblique distance. We conclude that the lateral pharyngeal walls play an important role in upper airway narrowing during sleep in normal subjects.

Upper airway imaging

Upper airway imaging is a powerful technique to study the mechanisms underlying the pathogenesis, biomechanics, and efficacy of treatment options in patients with obstructive sleep apnea. Imaging studies have provided significant insight into the static and dynamic structure, and function of the upper airway and surrounding soft-tissue structure during wakefulness and sleep. Upper airway imaging modalities primarily include nasopharyngoscopy, cephalometrics, computed tomography (CT), and magnetic resonance (MR) scanning. These imaging modalities have been used to study the effect of respiration, weight loss, dental appliances, and upper airway surgery on the upper airway. MR imaging and CT have allowed quantification of the airway and surrounding soft-tissue structures in three dimensions. Clinical indications for upper airway imaging are evolving for patients being treated with dental appliances and upper airway surgery.

Three-dimensional computed tomography bronchoscopy using clinical datasets: a comparison with fibreoptic bronchoscopy

OBJECTIVE

To assess three-dimensional computed tomography 'bronchoscopic' (3-DCTB) reconstruction of routine CT data as a non-invasive method of airway visualization, and compare it with fibreoptic bronchoscopy (FOB).

METHODS

Fourteen datasets were acquired from 13 patients undergoing both FOB and CT examination of the chest. Standard continuous volume CT using 6 mm collimation and clinical FOB techniques were employed. Images were obtained from 3-DCTB reconstructions by segmentation and surface recognition algorithms generating surface rendered 'bronchoscopic views'. These were scored for technical quality and anatomical detail. The most distal bronchi seen in left upper and right lower lobes were recorded for FOB and 3-DCTB.

RESULTS

On FOB, the subsegmental bronchi were seen in right lower and in left upper lobe in 10/14 cases and 4/14 cases, respectively. Visualization of the subsegmental airways was not achieved with 3-DCTB, as they could not be identified with confidence. 3-DCTB never achieved a more distal view than obtained by FOB. Using 3-DCT, the right, lower lobe segmental bronchi were seen in 10/14 cases, and lobar bronchus in 14/14 cases (two occluded). In the left upper lobe, 3-DCT showed segmental bronchi in 6/14 cases, lobar bronchus in 11/14 cases (one occluded) and the left main bronchus appeared occluded in 3/14 cases. Overall, technical quality and anatomical detail scores of the carina and proximal bronchi ranked significantly higher than views of segmental bronchi.

CONCLUSIONS

3-DCTB cannot routinely replace FOB for inspection of major and segmental bronchi. Subsegmental bronchi cannot be adequately demonstrated by 3-DCTB using 6 mm collimation datasets.

Anatomy of pharynx in patients with obstructive sleep apnea and in normal subjects

Anatomic abnormalities of the pharynx are thought to play a role in the pathogenesis of obstructive sleep apnea (OSA), but their contribution has never been conclusively proven. The present study tested this anatomic hypothesis by comparing the mechanics of the paralyzed pharynx in OSA patients and in normal subjects. According to evaluation of sleep-disordered breathing (SDB) by nocturnal oximetry, subjects were divided into three groups: normal group (n = 17), SDB-1 (n = 18), and SDB-2 (n = 22). The static pressure-area relationship of the passive pharynx was quantified under general anesthesia with complete paralysis. Age and body mass index were matched among the three groups. The site of the primary closure was the velopharynx in 49 subjects and the oropharynx in only 8 subjects. Distribution of the location of the primary closure did not differ among the groups. Closing pressure (PC) of the velopharynx for SDB-1 and SDB-2 groups (0.90 +/- 1.34 and 2.78 +/- 2.78 cmH2O, respectively) was significantly higher than that for the normal group (-3.77 +/- 3.44 cmH2O; P < 0.01). Maximal velopharyngeal area for the normal group (2.10 +/- 0.85 cm2) was significantly greater than for SDB-1 and SDB-2 groups (1.15 +/- 0.46 and 1.06 +/- 0.75 cm2, respectively). The shape of the pressure-area curve for the velopharynx differed between normal subjects and patients with SDB, being steeper in slope near Pc in patients with SDB. Multivariate analysis of mechanical parameters and oxygen desaturation index (ODI) revealed that velopharyngeal Pc was the only variable highly correlated with ODI. Velopharyngeal Pc was associated with oropharyngeal Pc, suggesting mechanical interdependence of these segments. We conclude that the passive pharynx is more narrow and collapsible in sleep-apneic patients than in matched controls and that velopharyngeal Pc is the principal correlate of the frequency of nocturnal desaturations.

Effect of body position on tongue posture in awake patients with obstructive sleep apnoea

BACKGROUND

Snoring and obstructive sleep apnoea (OSA) are worse or may only occur in the supine position. The effect of body position on upper airway size has been reported, but the effect on tongue posture has not previously been examined.

METHODS

Detailed measurements were made of tongue posture from upright and supine lateral cephalograms on 24 men with OSA and 13 men with non-apnoeic snoring matched for age, body mass index, and craniofacial skeletal pattern. Patients with OSA had apnoea/hypopnoea indices (AHI) of > 50/hour and/or apnoea indices (AI) of > 25/hour while non-apnoeic snorers had AHI of < 10/hour and AI of < 5/hour.

RESULTS

In non-apnoeic snorers the tongue depth measurements for the superior-posterior portion of the tongue were larger in the supine than in the upright position (p < 0.05). There was no significant difference in tongue depth measurements between the upright and the supine position in the patients with OSA.

CONCLUSIONS

When awake patients with OSA move from the upright to the supine position they maintain their upright tongue posture which may tend to protect against upper airway collapse secondary to the increased gravitational load on the tongue. In contrast, when awake non-apnoeic snorers move from the upright to the supine position a significant dorsal movement in the superior-posterior portion of the tongue is observed.

Tongue volume in human female adults with mandibular prognathism

It has often been hypothesized that a large tongue leads to an enlargement of the mandible and therefore contributes to the development of mandibular prognathism. We examined (1) whether the tongue volume in human subjects with mandibular prognathism was larger than that in subjects with good occlusion and (2) whether the tongue volume and the pharyngeal capacity correlated with the morphological characteristics of dento-skeletal structures. Magnetic resonance images of the tongue and its surrounding structures were recorded for female adult volunteers with good occlusion (control group, n = 10) and patients with mandibular prognathism (test group, n = 16). Lateral cephalograms were obtained for the patients. No significant differences were determined for the tongue volume or the pharyngeal capacity between the two groups. The tongue volume did not correlate with the pharyngeal capacity (r = 0.280, p = 0.166). The tongue volume correlated with the facial angle (r = 0.548, p = 0.028), the Y-axis (r = 0.539, p = 0.031), and the angle nasion-A point-pogonion (r = 0.540, p = 0.031). These results suggest that the tongue volume is accounted for by the combined horizontal and vertical location of the chin and symphysis, but do not support the conventional clinical surmise that large tongue volume is inherent in patients with mandibular prognathism.

A three-dimensional airway assessment for the treatment of snoring and/or sleep apnea with jaw repositioning intraoral appliances: a case study

The purpose of this snoring/sleep apnea study was to assess the role of 3-D magnetic resonance imaging (MRI) of the airway correlated to jaw reposturing/intraoral appliance design. A clinical case is presented utilizing this technology, integrating a diagnostic baseline and follow-up sleep study/ polysomnograph. The baseline polysomnography, prior to jaw repositioning appliance design, indicated a respiratory disturbance index (RDI) of 21.5 hypopnea/apneas per hour. The follow-up sleep study, with use of an intraoral repositioning appliance, showed a 3.9 per hour RDI, an 82% RDI reduction/improvement. Magnetic resonance TMJ and airway images were done. The MRI enhanced airway assessment computer software program analyzed the 3-dimensional volume and cross sectional area changes from hard/soft palate junction to epiglottis. Imaged were the oropharynx nasopharynx and hypopharynx regional anatomy. The baseline, without mandibular positioning device, showed a total airway volume of 5,801.31 cubic mm, whereas with the mandibular positioning device in place, the total airway volume was increased to 8,657.22 cubic mm or a total increased volume of 32%. The largest improvement site in the airway was the mid-soft palatal uvula/nasopharynx region, with base of tongue moving forward. Along with traditional polysomnography, 3-dimensional MRI airway imaging should be considered as a diagnostic procedure in assessing sleep apnea patients. The necessity of a combined medical/dental team approach is emphasized.

Associations among upper airway structure, body position, and obesity in skeletal Class I male patients with obstructive sleep apnea

Interactions between upper airway structure and posture in relation to obesity were studied in a sample of 61 adult Class I skeletal type male patients with obstructive sleep apnea (OSA) and 10 homologous control subjects. A pair of upright and supine lateral cephalometric films were taken for each subject. A Pearson correlation analysis identified significant r values for several demographic variables in patients with OSA such as apnea and hypopnea index, percentage of predicted neck circumference, minimum arterial oxygen saturation, and body mass index (BMI). The difference between cephalometric variables identified in upright and supine subjects was calculated. When patients with OSA changed their posture from upright to supine, significant correlations were observed between the cranial base to upper cervical column angle and the hypopharynx cross-sectional area and BMI. Moreover, the mandibular plane angle and the sella-nasion plane was significantly correlated with BMI. This occurred along with a significant positive correlation between the sella-nasion plane angle and BMI and a significant inverse correlation between the mandibular plane angle in reference to the absolute vertical and horizontal planes, with BMI after the positional change. Such correlations were not observed in control subjects. No correlations were observed between the variables related to the position of the hyoid bone with BMI in either patients with OSA or control subjects after the change in posture. On the basis of these findings, we propose that when patients with OSA change their body position from upright to supine (1) the patient's neck is more extended, and (2) the hyoid bone moves more anterosuperiorly in conjunction with an upward and forward rotation of the mandible. This change in craniofacial structure may be a compensatory geometrical change in the upper airway to secure its patency.

Sleeping positions and dental arch dimensions in children with suspected obstructive sleep apnea syndrome

The present paper analyzed the association between children's sleeping positions and dental arch morphology. The sleeping patterns of 27 children, aged 3 to 10 yr, suspected of having the obstructive sleep apnea syndrome (OSAS) were studied by polysomnography (PSG) and videotape recordings under laboratory conditions. The PSG recordings were used to calculate the apnea index (AI) and the relative time spent sleeping on the back, and the videotapes to categorize distinctly different sleep and head postures. Plaster casts were made for the assessment of dental arch morphology. Sleeping predominantly on one's back, was associated with a reduced maxillary intercanine width, while prolonged head extension during sleep correlated inversely with the overjet. The subjects with the highest AI scores (> 4) had larger dental arches. We suggest that sleeping on the back causes a more posterior tongue position, reducing its moulding effect on the anterior dental arch. As nasopharyngeal airway obstruction in OSAS-patients might trigger an anterior tongue position to secure a free airway passage, there will be increased lingual pressure on the dental arches, leading to their dimensional increase.

Cephalometric comparison of characteristics in chronically snoring patients with and without sleep apnea syndrome

OBJECTIVE

The purpose of this investigation is to cephalometrically study 50 snoring patients with and without sleep apnea and to determine whether cephalograms can be used as a diagnostic tool to differentiate persons who are chronic snorers from persons with sleep apnea.

STUDY DESIGN

A sample of 30 sleep apnea patients was compared with a sample of 20 chronic snorers without sleep apnea as documented by polysomnography. Forty cephalometric measurements were determined to study various skeletal, soft tissue, and airway abnormalities.

RESULTS

This study showed that both groups presented multiple cephalometric abnormalities. Only four measurements differed significantly between the two samples. In the sleep apnea group the maxilla was retropositioned and the hypoid bone displaced inferiorly and distally as compared to nonapneic snorers.

CONCLUSIONS

Because of the overall presence of abnormal cephalometric findings in both samples and given similar age and weight ranges, a differential diagnosis between chronic snorers with and without sleep apnea cannot be reliably based on standard cephalometric evaluation alone.

Cephalometric and computed tomographic predictors of obstructive sleep apnea severity

The interaction between craniofacial structure assessed by lateral cephalometry, and tongue, soft palate, and upper airway size determined from computed tomography (CT) scans was examined in 25 control subjects and 80 patients with obstructive sleep apnea (OSA). On the basis of the cephalometric analyses, the patients with OSA had retruded mandibles with larger ANB angle differences, elongated maxillary and mandibular incisors and mandibular molars, and high total upper and lower face heights The computed tomographic evaluations revealed that patients with OSA also had larger tongue, soft palate, and upper airway volumes. Men with OSA and skeletal Class I malocclusions had significantly larger soft palates than comparable controls. Both tongue and soft palate volumes were positively correlated with body mass index. A principal component analysis reduced the database, and one significant correlation was identified. Subjects with high total, upper and lower face heights, elongated maxillary and mandibular teeth, and proclined lower incisors were observed to have large tongue, soft palate, and upper airway volumes, to have a higher apnea index and to be obese. Linear regression analysis indicated that a high apnea index was seen in association with large tongue and soft palate volumes, a retrognathic mandible, an anteroposterior discrepancy between the maxilla and mandible, an open bite tendency between the incisors, and obesity.

A cephalometric and electromyographic study of upper airway structures in the upright and supine positions

Obstructive sleep apnea (OSA) is characterized by recurrent upper airway obstruction during sleep, usually in the supine position. To investigate the relationship between upper airway size and genioglossus (GG) muscle activity, upright and supine cephalograms were obtained in 20 OSA patients and 10 symptom-free control subjects. Tongue electromyographic (EMG) recordings were obtained with surface electrodes, and pressure transducers were placed in the 10 symptom-free controls. The tongue cross-sectional area increased 4.3% (p < 0.05), and the oropharyngeal area decreased 36.5% (p < 0.01) when the OSA patients changed their body position from upright to supine. No changes were observed in the tongue area, but soft palate thickness increased (p < 0.01) when the control subjects changed from the upright to the supine position. Furthermore, the oropharyngeal cross-sectional area decreased 28.8% (p < 0.01) despite a 34% increase (p < 0.05) in resting GG EMG activity. Posterior tongue pressure increased 17% (p < 0.05) with the change from upright to supine. On the basis of these findings, we propose that body posture has a substantial effect on upper airway structure and muscle activity. This postural effect should be taken into account when assessing upper airway size in the erect posture (conventional cephalography) and in the supine position (computed tomography). The vertical and anteroposterior position of the tongue and its relationship to airway size may be more important than soft palate size in the pathogenesis of OSA.

Genioglossus muscle activity and inspiratory timing in obstructive sleep apnea

Atypical tongue muscle activity during sleep may contribute to the development of obstructive sleep apnea (OSA). Inspiratory genioglossus (GG) muscle activity was investigated in 10 OSA adults and 4 symptom-free controls. On the basis of overnight monitoring during nonREM sleep, the duration of the inspiratory GG activity and the total GG activity cycle is shorter in patients with OSA. The duration of inspiration and the duration of one total respiratory cycle is also shorter in patients with OSA. The commencement time lag between inspiratory GG activity and the onset of inspiration is shorter in patients with OSA during nonapneic breathing which indicates that inspiratory GG activity is activated relatively later in these patients. Furthermore, the inspiratory GG activity occurs after inspiration during an apnea, but the timing of GG activity onset progressively advances during the apnea. Earlier GG reactivation occurs before inspiration during the first nonoccluded breath at the end of an apnea. During subsequent tidal breathing, the timing of the GG onset progressively decreases after the onset of inspiration until the next obstructive apnea occurs. This observation suggests that the timing relationship between GG inspiratory activity and inspiratory effort is of physiologic importance in the pathogenesis of OSA. Furthermore, it may explain why dental appliances, such as the tongue retaining device, are highly effective in the resolution of OSA in selected patients.

Mandible enclosure of upper airway and weight in obstructive sleep apnea

Although anatomic lesions and obesity can produce obstructive sleep apnea (OSA), most subjects with OSA have no recognizable anatomic lesion. We hypothesized that the occurrence of OSA is related to the size of the region enclosed by the mandible and the degree of obesity. We studied 30 subjects with a range of OSA and obesity with magnetic resonance imaging (MRI). MRI was performed with T-1 weighted sequences. Nocturnal polysomnography was performed in all subjects. Univariate regression analysis indicated there was a significant correlation between the number of apneas and hypopneas per hour of sleep (AH/h) and (1) the area enclosed by the mandible ramus (AMR1) (r = 0.48, p < 0.01) and (2) the distance from the teeth to the posterior mandible ramus (r = 0.39, p < 0.05). Stepwise multiple regression analysis indicated that weight, AMR1, and height explained 69% of the variance of AH/h (r2 = 0.69). We conclude that the occurrence of OSA in these subjects is related to the size of the region enclosed by the mandible as well as to their weight.

Site of pharyngeal narrowing predicts outcome of surgery for obstructive sleep apnea

Uvulopalatopharyngoplasty (UPPP), an operation that enlarges the pharyngeal airway at the level of the soft palate, improves respiratory status during sleep in only 50% of patients with obstructive sleep apnea (OSA). This poor outcome suggests that narrowing of the pharyngeal airway at nonpalatal sites contributes to the obstructive process in many patients with OSA. We have used a novel endoscopic method to identify regions of the passive pharyngeal airway most susceptible to narrowing or complete closure. In order to test the hypothesis that narrowing of the passive airway at the nasopharynx predicts a favorable surgical outcome, we have preoperatively assessed the local mechanics of the passive pharyngeal airway in 18 patients with OSA undergoing UPPP. The patient population was prospectively divided into two groups: an exclusively nasopharyngeal (ENP) group, consisting of patients exhibiting narrowing only in the nasopharynx, and a not exclusively nasopharyngeal (NENP) group, consisting of patients having at least one site of narrowing outside the nasopharynx. The frequency of respiratory disturbances and arousals and the cumulative time in apnea-hypopnea were significantly reduced after surgery for the ENP group, but not for the NENP group. Improvement rate for the ENP group (86%) exceeded that for the NENP group (18%) (p < 0.01). These differences became even greater when selection criteria for the ENP group were made more restrictive (i.e., restricted to the velopharynx) or more liberal (i.e., including secondary narrowing of the oropharynx). Our results show that evaluation of passive pharyngeal mechanics identifies patients with OSA likely to improve after UPPP.

Obstructive sleep apnea subtypes by cluster analysis

A sample of 84 adult male patients with obstructive sleep apnea (OSA) were classified by a cluster analysis on the basis of apnea index (AI) and body mass index (BMI). Demographic, cephalometric, tongue, soft palate, and upper airway-size data were evaluated for the two subgroups of OSA patients and for 18 control subjects. One OSA group consisted of 43 patients with a high AI and low BMI ratio, the other group was comprised of 41 patients with a low AI and high BMI ratio. The patients with a high AI and low BMI ratio had retruded mandibles with high mandibular plane angles and proclined lower incisors. The patients with a low AI and high BMI ratio had inferior hyoid bones and large soft palates. A multiple regression analysis was performed between AI (the dependent variable) and the other variables (independent variables) for each of the subgroups. In the patients with a high AI and low BMI ratio, a high AI was related to a large skeletal anteroposterior discrepancy, a steep mandibular plane, and an inferoanterior position of the hyoid bone. In the patients with a low AI and high BMI ratio, a high AI was related to a large tongue and a small upper airway. In both groups, BMI was the major contributor to AI. In conclusion, these two groups may represent distinct subgroups of OSA patients and provide some insight into the contribution of obesity to the pathogenesis of OSA. The patients with a high AI and low BMI ratio have a skeletal mismatch, whereas the patients with a low AI and high BMI have atypical soft tissue structures.

Hallermann-Streiff syndrome: a review

The Hallermann-Streiff syndrome is characterized by dyscephaly, hypotrichosis, microphthalmia, cataracts, beaked nose, micrognathia, and proportionate short stature. Cause is unknown; sporadic occurrence is the rule. Data presented in this review include the characteristics of pregnancy, growth and development, principal manifestations, radiographic and ophthalmological characteristics, and the results of cephalometric study. Potential complications in the syndrome are related to the narrow upper airway associated with the craniofacial configuration. Severe complications may include early pulmonary infection, respiratory embarrassment, obstructive sleep apnea, and anesthetic risk. Topics for future study are suggested.

Relationship between tongue volume and lower dental arch sizes

The interrelation between the tongue volume and the lower dental arch sizes (arch width and area) was studied by the original methods that we developed. A plane perpendicular to the occlusal plane and 40 mm posterior to the lower incisal point was taken as the posterior border of the tongue and the arch. The tongue volume and the lower dental arch sizes were measured anterior to this border with plaster models. The correlations between the parameters obtained from 74 Japanese adults (37 men and 37 women) with normal occlusion were statistically analyzed. The results showed that (1) both the mean tongue volume and the mean lower dental arch sizes were significantly larger in men than in women; (2) the tongue volume and the lower dental arch sizes were significantly correlated; and (3) these correlations tended to be higher at the more posterior part of the dental arch.

Mandible, tongue, and airway in Pierre Robin sequence: a longitudinal cephalometric study

The purpose of this retrospective longitudinal cephalometric study was to analyze size, growth, and relations of the mandible, tongue, and airway in the isolated, nonsyndromic Pierre Robin Sequence (PRS) infant. The objective was to understand better the early morphologic changes that occur in these structures. The data were obtained from lateral cephalometric radiographs taken in the first 2 years of life on 17 PRS infants, 26 isolated cleft palate (CP), and 26 normal control (N) infants. Mean values of each variable were compared using a univariate analysis of variance. A multivariate discriminant function analysis (DFA) was also used to characterize group differences. The three groups were distinct throughout the period of study. Differences were greater at the earliest age and the distinction was greater between the PRS and N infants with the CP infant in between, but having more similarity to the PRS infant. Initially, the PRS infant had a shorter tongue and mandibular length, narrower airway, smaller tongue area and the hyoid position was more posterior and inferior as compared to N. The tongue shape and position were specific to the PRS infants. This group distinction diminished with age and resulted from an increased mandibular growth rate in the PRS infant. These findings support the hypothesis of "partial mandibular catch-up growth" in the PRS infant. The increased growth rate in the PRS infant improved the airway dimension, which might be partly responsible for the natural resolution of the respiratory distress. This increased growth rate did not allow for the various structures to reach values equal to normal.

Magnetic resonance imaging of the upper airway in obstructive sleep apnea before and after chronic nasal continuous positive airway pressure therapy

Magnetic resonance imaging (MRI) provides high-resolution images of the upper airway and is useful for assessing conditions associated with increased tissue water content. To determine whether nasal continuous positive airway pressure (CPAP) changes awake upper airway morphology in obstructive sleep apnea (OSA), we performed awake upper airway MRI scans on five male patients with moderate to severe OSA before and after 4 to 6 wk of nasal CPAP therapy. MRI scans were performed using spin echo pulse sequences to examine detailed anatomy and inversion recovery sequences to assess mucosal water content. Patients did not have nasal CPAP applied during the MRI scans. Axial and sagittal images were obtained, and tracings were made of the upper airway, tongue, and soft palate. Utilizing computer graphics, cross-sectional areas and volumes were calculated for each anatomic structure. A subjective grading system was used to assess upper airway mucosal water content. Pharyngeal volume and minimum pharyngeal cross-sectional area increased (p less than 0.05) and tongue volume decreased (p less than 0.01) following chronic nasal CPAP therapy. The increase in pharyngeal volume occurred mainly in the oropharynx (p less than 0.01). Upper airway mucosal water content decreased in the oropharynx (p less than 0.05). We conclude that chronic nasal CPAP therapy during sleep in patients with OSA produces changes in awake upper airway morphology. These changes may be due to resolution of upper airway edema. The upper airway of patients with OSA can be accurately and repeatedly assessed using MRI.

Cephalometric analysis of long-term airway space changes with maxillary osteotomies

The cephalometric radiographs of 13 patients without sleep apnea who had undergone isolated maxillary surgery were studied. The authors found increases in both the nasopharyngeal and hypopharyngeal airway spaces 3 to 5 years after surgery. The results suggest that adaptive processes occur in both the upper and lower jaw, which contribute to an enlarged airway after surgery.

Long-term airway space changes after mandibular setback using bilateral sagittal split osteotomy

Eleven patients were evaluated retrospectively for their long-term changes in hypopharyngeal airway space after surgical correction of mandibular hyperplasia. All patients had undergone mandibular setbacks by way of bilateral sagittal split osteotomies using rigid fixation. The cephalometric evaluation of hypopharyngeal airway space was based on stable craniofacial landmarks. The results of this study indicate that mandibular setback procedures create relative narrowing of the hypopharyngeal airway space, as seen on lateral cephalometric radiographs, which in isolated cases might contribute to the development of an obstructive sleep apnea syndrome. The 2-dimensional evaluation of hypopharyngeal airway space and the clinical implications of the results are discussed.

Obstructive sleep apnea syndrome in patients with class II malocclusion

This study was designed to analyze the effect of class II malocclusion as a factor in the development of obstructive sleep apnea syndrome. Although mandibular retrusion has been reported coincidentally with obstructive sleep apnea syndrome many times, no causal relationship has been established. No previous study has analyzed the occurrence of obstructive sleep apnea syndrome in patients with class II malocclusion without sleep complaints. In this study, we selected 12 patients with class II malocclusion who required surgical mandibular-lengthening or repositioning procedures. These patients were surveyed for sleep habits or sleep complaints and then studied with overnight polysomnography for sleeping or breathing abnormalities. None of these patients had obstructive sleep apnea syndrome. From this sample population, an incidence of obstructive sleep apnea syndrome of no more than 26.5% in the surgical population of patients with class II malocclusion can be extrapolated.

Relationship between jaw muscle volume and craniofacial form

To study the relationship between craniofacial form and jaw muscle function, we evaluated 25 adult male subjects with Obstructive Sleep Apnea (age, 30-61 years; weight, 58-122 kg) on the basis of CT scans obtained for routine diagnostic purposes. All scans were obtained with the Frankfort horizontal plane at right angles to the floor; each CT slice was 8 mm thick. Masseter and medial pterygoid muscle outlines were traced, digitized, and stored, and three-dimensional reconstructions were made for calculation of muscle volume. Lateral cephalometric radiographs were analyzed for quantification of selected craniofacial variables. Significant correlations could not be identified between physiological apnea variables and jaw muscle volume. An intersubject variability in masseter muscle volume was identified (range, 22.4-38.1 cm3). Medial pterygoid muscle volume revealed more variability (range, 7.4-15.2 cm3). Masseter muscle volume had a negative correlation with mandibular plane and gonial angle, and a positive correlation with posterior face height, ramus height, posterior face length, condylar center to first molar point length, gonion to pterygomaxillary fissure length, and the ramus height/anterior face height ratio. Medial pterygoid muscle volume showed a positive correlation with posterior face height, ramus height, posterior face length, and the lengths between condylar center to first molar contact point, gonion to pterygomaxillary fissure, and antegonion to key ridge. Subjects with large masseter and medial pterygoid muscle volumes had flat mandibular and occlusal planes, and small gonial angles.

Dental appliances for the treatment of obstructive sleep apnea

Obstructive sleep apnea (OSA) is a syndrome in which the airflow created from breathing ceases through the upper airway although diaphragm movement continues. Resulting complications include severe daytime sleepiness, morning headaches, loud snoring, and disturbed nighttime sleep. Patients affected with OSA are frequently hypertensive and can have dangerous cardiac arrhythmias. The diagnosis of OSA requires an all-night polysomnographic recording; neither snoring nor other subjective complaints constitute adequate criteria for treatment. The treatment objective for OSA is to maintain airway patency. A potential treatment discussed here is temporary advancement of the mandible or tongue during sleep with the use of dental appliances.

Naso- and oropharyngeal dimensions in children with obstructive sleep apnea

Sixty children (3-11 years) were evaluated to determine variations in naso- and oropharyngeal dimensions associated with tonsil and adenoid hypertrophy. The subjects were grouped according to tonsil size and a clinical history of chronic upper airway obstruction. Intraoperative measurements included oropharyngeal diameter, length of the hard and soft palates, width and arch of the hard palate, nasopharyngeal volume, as well as tonsil and adenoid weights and volumes. A significantly larger oropharyngeal diameter was found in children with small, non-obstructing tonsils (P less than 0.01). Children with large, non-obstructing tonsils had a similar oropharyngeal diameter to those children with large, obstructing tonsils. However, tonsil volume, not weight, was increased in the children with large obstructing tonsils as compared to those with large non-obstructing tonsils and small non-obstructing tonsils (P less than 0.04). A shorter soft palate was associated with larger, obstructing tonsils (P less than 0.004). The length of the hard palate was similar in all patients, however, a trend towards a higher arched palate was seen in patients with larger, obstructing tonsils. The distance from the soft palate to the posterior pharyngeal wall was greater in obstructed patients with adenotonsillar hypertrophy (P less than 0.003). In patients requiring adenoidectomy, the nasopharyngeal volume prior to adenoidectomy was significantly smaller in patients with obstructive symptoms (P less than 0.001). Postadenoidectomy, no significant difference was found in the nasopharynx volume amongst all subjects. These data indicate that subtle differences in oropharyngeal dimensions exist which along with increased lymphoid tissue volume, lead to the development of obstructive symptoms. Etiologic considerations are discussed.

Current surgical concepts for treating obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome is a relatively common disorder with potentially serious psychologic and physiologic consequences. A comprehensive method of evaluation is described. Presurgical tests are mandatory in order to logically direct surgical treatment. Current surgical treatment and new techniques are discussed.