Hyoid Position Research Articles

Effects of fixed functional therapy on tongue and hyoid positions and posterior airway

To evaluate how therapy with a fixed functional appliance affects airway dimensions, dentoalveolar changes, and tongue and hyoid positions. A retrospective study was carried out on 46 pre- and posttreatment lateral cephalometric radiographs of 23 post-peak Class II patients (12 girls, 11 boys) treated with a Forsus Fatigue Resistant Device (FRD) appliance. The radiographies were taken at the start and at the end of Forsus FRD appliance therapy when a Class I or overcorrected Class I canine and molar relationship was achieved. The process took an average of 5 months 13 days ± 1 month 4 days. Skeletal and dental parameters were measured using Dolphin software, and the sagittal airway area was measured by AutoCAD software. Analyses of the pre- and posttreatment means revealed that there was no statistically significant skeletal correction of the sagittal malocclusion; increase of lower incisor inclination, decrease of upper incisor inclination, decrease of interincisal angle, and rotation of occlusal plane all contributed to the reduction of overjet. The tongue area and intermaxillary space area increased in response to these dentoalveolar changes; however, there was no statistically significant change in the hyoid position or the oropharyngeal area between the two time points. The dentoalveolar changes produced by Forsus FRD appliance did not cause any significant posterior airway changes in young adult patients.

코골이 및 폐쇄성 수면 무호흡증의 두부 규격 방사선 계측학적 기여 인자

Purpose: This study was intended to perform a cephalometric comparison between the patients with and without obstructive sleep apnea (OSA). The factors influencing the OSA in the lateral cephalogram were also investigated. Methods: Fifty patients who had visited the Sleep Disorder Clinic at the Ajou University Hospital and evaluated with the polysomnograph (PSG) and cephalogram, were included in the study. The patients had the apnea-hypopnea episode over 5 times per hour (apnea-hypopnea index <TEX>$[AHI</TEX><TEX>]</TEX><TEX>{\geq}5$</TEX>) were diagnosed as OSA after the overnight PSG. To evaluate the hard and soft tissue profiles, the cephalometric radiograms were taken at the maximal intercuspation. The correlation between the patient's age, height, weight, body mass index (BMI) and AHI was inspected in the OSA and control group. The difference between the OSA and control group was evaluated (Mann-Whitney U Test). The cephalometric influencing factors to OSA were analyzed (Pearson's correlation coefficient) statistically using SPSS statistics. Results: The OSA Group had a significantly higher BMI than the control group. The mean lower facial height (ANS-Me) was longer in the OSA group; however, statistically significant difference was not detected in the anteroposterior craniofacial measurements. The distance between mandibular plane and hyoid bone of the OSA group was significantly longer than that of the control group. The hyoid position (MP-Hyoid) had a positive correlation between AHI (P<0.001). However, the measurements of oropharyngeal airway were not different between the two groups. The hypothesis, that the antero-posteriorly narrow oropharyngeal airway may aggravate the airway resistance and give rise to a higher AHI, was rejected in the study. Conclusion: We suggest that the lateral cephalogram may be utilized as a useful method to evaluate OSA. The patients with a lower hyoid position can be expected to have higher risks of OSA. However, a comprehensive intraoral inspection, including the soft palate and tonsilar hypertrophy, is emphasized, as the lateral cepahlogram cannot visualize the oropharyngeal status completely.

Upper airway changes in Pierre Robin sequence from childhood to adulthood

To investigate pharyngeal airway changes in patients with Pierre Robin sequence (PRS) longitudinally from childhood to adulthood. Cleft Lip and Palate Unit, Clinic of Orthodontics, University of Zurich. Twenty-four patients born between 1970 and 1990 with non-syndromic PRS. Lateral cephalograms at age 5 (T1), 10 (T2), 15 (T3) and 20 (T4)years were available. Variables describing pharyngeal airway dimensions, soft palate morphology, tongue and hyoid position, skeletal morphology and head posture were assessed. A significant increase in nasopharyngeal depth was found over the entire observation period (T1 10.7 to T4 19.1mm, p<0.001), especially between T2 and T3 (change 3.8mm, p<0.001), and was mainly due to adenoid recession (r=-0.75, p<0.001; variation explained by 56%). Increase in velopharyngeal depth mainly took place between T3 and T4 (change 2.3mm, p<0.01). It was due to more anterior tongue posture (r=0.65, p<0.001; 42.5% of variation explained), in turn allowing the soft palate to take a more vertical position (r=-0.52, p<0.001). Increase in oropharyngeal depth was associated with head extension and anterior mandibular positioning (36% of variation explained). However, significance was not reached (T1 8.3 to T4 9.8mm, p>0.05). Upper airway dimensions in children with PRS improve with time, except for the oropharyngeal airway. Despite large interindividual variation, the mean remained in the lower reaches of normality described in other studies. Thus, further research should investigate the prevalence of obstructive sleep apnoea in adults with PRS.

Definition of pharyngeal airway, tongue dimensions and hyoid position in healthy subjects

Definition of pharyngeal airway, tongue dimensions and hyoid position in healthy subjects

舌骨位は嚥下機能に影響を与えるか

舌骨位は嚥下機能に影響を与えるか

Evaluation of Upper Airway Dimensional Changes and Hyoid Position Following Mandibular Advancement in Patients With Skeletal Class II Malocclusion

Class II skeletal malocclusion due to mandibular deficiency is considered a risk factor for sleep disorders due to oropharyngeal airway deficiencies. In view of the above, a prospective interventional study was undertaken to evaluate upper airway dimensional changes and position of hyoid bone by comparing pretreatment and posttreatment lateral cephalograms. The objective also included the establishment of the ratio of mandibular advancement to increase in airway dimensions. Pretreatment and posttreatment lateral cephalograms of 20 adults (13 females and 7 males) with skeletal class II malocclusion treated by combined orthodontics and bilateral sagittal split ramus osteotomy was evaluated for changes in posterior airway space (PAS), superior airway space (SAS), minimum airway space (MAS), hyoid bone position (MP-H), effective mandibular length (Co-Gn), mandibular corpus length (Go-Pg), and pogonion position (N perpendicular-Pg). The cephalograms were manually traced by a single operator and the data analyzed using MINITAB 13.2 version software. There was a statistically highly significant (P = 0.0001) increase in PAS, SAS, MP-H, Co-Gn, and Go-Pg. The mean ratio of mandibular advancement to increase PAS, SAS, and MAS was 1:0.35, 1:0.34, and 1:0.24, respectively. Hyoid bone moved superiorly and in an anterior direction by 2.1 ± 2.8 mm and was found to be statistically highly significant (P = 0.0001). The study showed an overall increase in airway dimension and improvement in hyoid position. Thus, the procedure may be considered beneficial in reducing upper airway collapsibility and preventing sleep disorders due to oropharyngeal airway deficiencies in skeletal class II malocclusion.

Comparison Between Palpatory Findings of the Hyoid Position and Their Acoustic, Videostroboscopic, and Perceptual Attributes in Patients With Muscle Tension Dysphonia (With and Without Organic Lesions)

The direction in which the hyoid is pulled may change as a result of muscle tension dysphonia (MTD). The disposition usually occurs owing to paralaryngeal muscular imbalance (decompensation), which can create laryngeal dysfunction and consequently deteriorating the voice quality. This study aimed at reporting on a comparison between palpatory findings of hyoid position and their acoustic and perceptual and stroboscopic attributes among patients with MTD. Cross-sectional random triple-blinded study. Palpatory, acoustic, audioperceptual, and stroboscopic findings of 39 patients with MTD were analyzed descriptively and using independent sample t test. Dominant perceptual vocal characteristic of patients with pulled-up hyoid position was rough and the degrees of jitter and shimmer were higher in patients with pulled-up hyoid position than in patients with pulled-down hyoid position (jitter, P=0.019; shimmer, P=0.004), whereas signal-to-noise (S/N) ratio was lower in patients with pulled-up hyoid position than in pulled-down hyoid patients, but not significantly (S/N ratio, P=0.56). The dominant perceptual characteristic of patients with pulled-up hyoid position was rough voice, whereas that for pulled-down hyoid patients was strained voice. On the other hand, the dominant observable pattern in patients with pulled-up hyoid was MTD type II (lateral constriction), whereas that in patients with pulled-down hyoid was MTD type III (moderate anteroposterior constriction). There is a general congruence between the hyoid pulled direction and its perceptual, acoustic, and videostroboscopic findings in patients with MTD.

Systematic analysis of cephalometry in obstructive sleep apnea in Asian children

This study was designed to systematically analyze the relationship between a cephalometric analysis and the apnea-hypopnea index in a group of Asian children with obstructive sleep apnea. Retrospective study. Data were collected from 56 children with obstructive sleep apnea who were between 3 and 13 years old. Each child underwent attended overnight polysomnography and cephalometry. We measured nine angles, 10 lines, and two ratios as well as adenoid size on each cephalometric film. Data included five segments of the upper airway: nasal cavity (segment 1), nasopharyngeal space (segment 2), retropalatal space (segment 3), retroglossal space and hyoid (segment 4), and oral cavity-related space (segment 5). Four cephalometric anthropomorphic findings (Gn-Go-H, MP-H, MPH/GnGo, Ad/Na) were related to the apnea-hypopnea index. Three of the four parameters belonged to segment 4, indicating the importance of hyoid position in pediatric obstructive sleep apnea. This study showed that segment 4 was the most important segment affecting the apnea-hypopnea index. Most of the cephalometric parameters in segment 4 did not show a difference from the results of Caucasian groups, except that mandibular length and position appeared to have more positive findings in the Caucasian results. In segment 2, the apnea-hypopnea index was less affected by the skull base-related parameters in our data. The reason why the other segments appeared to play a lesser role in pediatric obstructive sleep apnea might due to the limitations of two-dimensional imaging. Further cephalometric studies with anterior-posterior view and on the differences between Caucasian and Asian children are mandatory.

Effect of large incisor retraction on upper airway morphology in adult bimaxillary protrusion patients

To evaluate, using multislice computed tomography (MSCT), the morphologic changes in the upper airway after large incisor retraction in adult bimaxillary protrusion patients. Thirty adult patients with bimaxillary protrusion had four first premolars extracted, and then miniscrews were placed to provide anchorage. A CT scan was performed before incisor retraction and again posttreatment. Three-dimensional (3D) reconstruction of the pre- (T1) and post- (T2) CT data was used to assess for morphological changes of the upper airway. A paired t-test was used to compare changes from T1 to T2. The relationship among the three variables (upper incisor retraction amount, upper airway size, and hyoid position) was analyzed by Pearson correlation coefficient. The amounts of upper incisor retraction at the incisal edge and apex were 7.64 ± 1.68 mm and 3.91 ± 2.10 mm, respectively. The hyoid was retracted 2.96 ± 0.54 mm and 9.87 ± 2.92 mm, respectively, in the horizontal and vertical directions. No significant difference was observed in the mean cross-sectional area of the nasopharynx (P > .05) between T1 and T2, while significant differences between T1 and T2 were found in the mean cross-sectional areas of the palatopharynx, glossopharynx, and hypopharynx (P < .05); these mean cross-sectional areas were decreased by 21.02% ± 7.89%, 25.18% ± 13.51%, and 38.19% ± 5.51%, respectively. The largest change in the cross-sectional area is always noted in the hypopharynx. There was a significant correlation among the retraction distance of the upper incisor at its edge, the retraction distance of the hyoid in the horizontal direction, and the decrease of the hypopharynx. Large incisor retraction leads to narrowing of the upper airway in adult bimaxillary protrusion patients.

Hyoid advancement to the mandible (hyo-mandibular advancement)

Hyoid advancement to the mandible was first described in 1984, but was later abandoned by most surgeons for the easier to perform advancement to the laryngeal cartilage. New modifications of the hyo-mandibular advancement technique has made this approach easier to perform and are described in this paper. The hyo-mandibular advancement technique has a higher success rate for the treatment of sleep apnea, especially in women.

A case–control study of craniofacial features of children with obstructed sleep apnea

This study aims to analyze differences in the skeletal, dental, and soft tissue components of craniofacial structure predisposing to the pediatric obstructive sleep apnea, by a comparison of the cephalograms between children with obstructive sleep apnea (OSA) and controls. The study enrolled a total of 30 children who were composed of the following two groups: 15 OSA patients and 15 controls. The two groups were strictly matched by age and sex. Lateral head radiographs were obtained and then cephalometric measurements were compared between the two. Fifty-six measurements were determined to study various skeletal, soft tissue, and airway structure. Marked differences were demonstrated in terms of SNB, PG-NB, lower facial height, H-C3Me, and adenoid (A) and tonsil (T/P). The SNB angle (75.82 ± 4.30) in case group was smaller than in the control (78.71 ± 2.61; p = 0.035), the PG/NB value in case group (1.32 ± 0.84 mm) was higher than that in the control (0.62 ± 0.60 mm; p = 0.015). The anterior lower facial height was 65.12 ± 5.91 mm in case group (p = 0.048), while the anterior lower facial height in control was 61.51 ± 3.22 mm. The position of hyoid was lower in case group (5.30 ± 3.67 mm) compared with the control one (2.64 ± 2.58 mm; p = 0.029). Furthermore, the patients with OSA had larger As and T/Ps than the controls. The case group differed from the control group in the length of mandible, anterior lower facial height, position of hyoid and the chin, and the size of the As and T/Ps.

Position of the hyoid and larynx in people with muscle tension dysphonia

To determine whether radiographic measures of hyoid position, laryngeal position, and hyolaryngeal space during phonation were different for people with primary muscle tension dysphonia (MTD) as compared to control participants without voice disorders. Prospective, quasi-experimental research design. Twenty participants, 10 with primary MTD and 10 without voice disorders who were age and sex matched were studied radiographically while producing phonation. Lateral x-ray images were obtained for each participant during three tasks: resting state, sustained phonation, and a swallow-hold maneuver. Vertical positions of the hyoid and larynx were measured on a Cartesian coordinate system and were normalized to reflect change from rest during phonation. Normalized, vertical hyoid, and laryngeal positions during phonation were significantly higher for people with MTD than for control participants. Normalized hyolaryngeal space during phonation did not show differences between groups. A low to moderate significant correlation for radiographically measured hyoid and laryngeal position and the total score from a subjective laryngeal palpatory scale were evidenced, but no relationship was evidenced for radiographic laryngeal position and the laryngeal position subscore of the palpatory examination. Objective determinants of physiology are critical for the differential diagnosis of MTD and its effective treatment. Radiographic findings from this study indicate that hyoid and laryngeal positions during phonation are higher in people with primary MTD as compared to people without voice disorders.

Mechanics of snout expansion in suction feeding seahorses: musculoskeletal force transmission

Seahorses and other syngnathid fishes rely on a widening of the snout to create the buccal volume increase needed to suck prey into the mouth. This snout widening is caused by abduction of the suspensoria, the long and flat bones outlining the lateral sides of the mouth cavity. However, it remains unknown how seahorses can generate a forceful abduction of the suspensoria. To understand how force is transmitted to the suspensoria via the hyoid and the lower jaw, we performed mathematical simulations with models based on computerized tomography scans of Hippocampus reidi. Our results show that the hinge joint between the left and right hyoid bars, as observed in H. reidi, allows for an efficient force transmission to the suspensorium from a wide range of hyoid angles, including the extremely retracted hyoid orientations observed in vivo for syngnathids. Apart from the hyoid retraction force by the sternohyoideus-hypaxial muscles, force generated in the opposite direction on the hyoid by the mandibulohyoid ligament also has an important contribution to suspensorium abduction torque. Forces on the lower jaw contribute only approximately 10% of the total suspensorium torque. In particular, when dynamical aspects of hyoid retraction are included in the model, a steep increase is shown in suspensorium abduction torque at highly retracted hyoid positions, when the linkages to the lower jaw counteract further hyoid rotation in the sagittal plane. A delayed strain in these linkages allows syngnathids to postpone suction generation until the end of cranial rotation, a fundamental difference from non-syngnathiform fishes.

Sagittal plane kinematics of the adult hyoid bone

The hyoid bone is a unique bone in the skeleton not articulated to any other bone. The hyoid muscles, which attach to the hyoid bone, may play a role in neck mechanics, but analysis of their function requires quantifying hyoid bone mechanics. The goal of this study was to obtain the detailed kinematics of the hyoid bone over a large range of flexion-extension motion using radiographs at 5 postures. The position of the hyoid bone in the sagittal plane was characterized with respect to head, jaw, and vertebral movements. Sex differences in hyoid kinematics were also investigated. We hypothesized that (1) the position of the hyoid bone in the sagittal plane is linearly correlated with motion of the head, jaw, and vertebrae, and (2) the hyoid position, size, and kinematics are sex-specific. We found that the hyoid bone X, Y, and angular position generally had strong linear correlations with the positions of the head, jaw, and the cervical vertebrae C1–C4. Hyoid X and angular position was also correlated to C5. Sex differences were found in some regressions of the hyoid bone with respect to C1–C5. The angular and linear measurements of the hyoid bone showed sex differences in absolute values, which were not evident after normalization by posture or neck size. Incorporating these results to neck models would enable accurate modeling of the hyoid muscles. This may have implications for analyzing the mechanics of the cervical spine, including loads on neck structures and implants.

Modelling stress in the feeding apparatus of seahorses and pipefishes (Teleostei: Syngnathidae)

Seahorses and pipefishes are extremely fast suction feeders, and the fast strikes probably result in large and rapid pressure drops in the buccal cavity. These rapid drops in pressure imply heavy mechanical loading on the cranium; hence, the feeding apparatus is thought to experience high levels of stress. We used finite element analysis (FEA) to investigate where stress accumulates under strong suction pressure, and whether there is a difference in craniofacial stress distribution between long- and short-snouted species. The expectation was that high stress levels would occur at the articulations and in the cartilaginous regions of the cranium, and that, given the same pressure, the skulls of long-snouted species would exhibit lower stress levels than the skulls of short-snouted species, as an evolutionary increase in snout length might have made these species structurally better adapted to deal with high suction pressures. The results partially support the first hypothesis: except for Dunckerocampus dactyliophorus, all models show peak stress concentrations at the articulations and cartilaginous regions. However, no simple relationship between snout length and the magnitudes of stress predicted by the FEA was found. In an attempt to explain this lack of a relationship, the methodology was evaluated by assessing the effect of hyoid position and model construction on the stress distribution.

Intra‐ and inter‐rater reliability for analysis of hyoid displacement measured with sonography

Anterior hyoid displacement is essential for efficient swallowing and is usually investigated with videofluoroscopy. Ultrasound offers a less expensive and noninvasive method of investigation. The present study investigated the viability of a novel method of quantifying hyoid displacement from sonograms using an anatomic reference point, through an evaluation of inter- and intra-rater reliability. Three raters reviewed the sonographic video sweeps of five discrete swallows from each of five participants for inter-rater reliability. The primary investigator measured each swallow on two occasions for intra-rater reliability. Electronic calipers were used to measure distances from a "rest" frame prior to the swallow of interest and a "maximal displacement" frame, at which the hyoid bone was at maximal anterior displacement during each swallow. Single-measure intraclass correlation coefficient was high for inter-rater agreement at 0.86 for rest measures and 0.86 for maximal displacement. Intra-rater reliability was even higher at 0.95 for rest and 0.98 for maximal displacement. These preliminary results suggest that by using a novel analysis approach involving an anatomic reference point, raters can achieve high agreement on measurement of position of hyoid at maximal displacement relative to rest.

Changes of pharyngeal airway size and hyoid bone position following orthodontic treatment of Class I bimaxillary protrusion

To test the hypothesis that the sagittal position of the anterior teeth has no effect on pharyngeal airway dimension or hyoid bone position and to investigate the influence of orthodontic retraction of the anterior teeth on each section of pharynx and hyoid position. Forty-four Class I bimaxillary protrusion adults, treated with preadjusted appliances and maximum anchorage after extraction of four premolars, were divided into two groups according to their vertical craniofacial skeletal patterns. Pretreatment and posttreatment variables were compared using paired t-test, and the relationship between pharyngeal airway size and dentofacial variables was analyzed using Pearson correlation coefficient. The changes of pharyngeal airway size and hyoid position after treatment were compared between two groups using independent t-test. Upon retraction of the incisors, the upper and lower lips were retracted by 2.60 mm and 3.87 mm, respectively. The tip of upper incisor was retracted by 6.84 mm and lower incisor retracted by 4.95 mm. There was significant decrease in SPP-SPPW, U-MPW, TB-TPPW, V-LPW, VAL, C3H, and SH (P < .05). No statistically significant different changes were observed in the dentofacial structures, pharyngeal airway, and hyoid position between the two groups after the treatment. There was a significant correlation between the retraction distance of lower incisor and the airway behind the soft palate, uvula, and tongue. The pharyngeal airway size became narrower after the treatment. Extraction of four premolars with retraction of incisors did affect velopharyngeal, glossopharyngeal, hypopharyngeal, and hyoid position in bimaxillary protrusive adult patients.

Evaluation of airway obstruction at soft palate level in male patients with obstructive sleep apnea/hypopnea syndrome: Dynamic 3-dimensional CT imaging of upper airway

This study examined the dynamic characteristics of upper airway collapse at soft palate level in patients with obstructive sleep apnea/hypopnea syndrome (OSAHS) by using dynamic 3-Dimensional (3-D) CT imaging. A total of 41 male patients who presented with 2 of the following symptoms, i.e., daytime sleepiness and fatigue, frequent snoring, and apnea with witness, were diagnosed as having OSAHS. They underwent full-night polysomnography and then dynamic 3-D CT imaging of the upper airway during quiet breathing and in Muller's maneuver. The soft palate length (SPL), the minimal cross-sectional area of the retropalatal region (mXSA-RP), and the vertical distance from the hard palate to the upper posterior part of the hyoid (hhL) were compared between the two breathing states. These parameters, together with hard palate length (HPL), were also compared between mild/moderate and severe OSAHS groups. Association of these parameters with the severity of OSAHS [as reflected by apnea hypopnea index (AHI) and the lowest saturation of blood oxygen (LSaO(2))] was examined. The results showed that 31 patients had severe OSAHS, and 10 mild/moderate OSAHS. All the patients had airway obstruction at soft palate level. mXSA-RP was significantly decreased and SPL remarkably increased during Muller's maneuver as compared with the quiet breathing state. There were no significant differences in these airway parameters (except the position of the hyoid bone) between severe and mild/moderate OSAHS groups. And no significant correlation between these airway parameters and the severity of OSAHS was found. The position of hyoid was lower in the severe OSAHS group than in the mild/moderate OSAHS group. The patients in group with body mass index (BMI)≥26 had higher collapse ratio of mXSA-RP, greater neck circumference and smaller mXSA-RP in the Muller's maneuver than those in group with BMI<26 (P<0.05 for all). It was concluded that dynamic 3-D CT imaging could dynamically show the upper airway changes at soft palate level in OSAHS patients. All the OSAHS patients had airway obstruction of various degrees at soft palate level. But no correlation was observed between the airway change at soft palate level and the severity of OSAHS. The patients in group with BMI≥26 were more likely to develop airway obstruction at soft palate level than those with BMI<26.

Correlation between skeletal changes by maxillary protraction and upper airway dimensions

To describe the correlation between the skeletal changes induced by maxillary protraction treatment and the sagittal airway dimension associated with tongue, soft palate, and hyoid bone position in skeletal Class III children. Twenty Class III patients (5 boys, 15 girls; mean age, 9.4 ± 1.8 years) treated with a maxillary protraction appliance were included in this study. Pretreatment and posttreatment cephalometric radiographs were analyzed; linear and angular measurements were performed by an expert orthodontist. The correlation between treatment changes in craniofacial morphology and those in upper airway, tongue, soft palate, and hyoid position was evaluated by Pearson's correlation analysis. A significant increase in maxillary forward displacement, inhibition of mandibular forward growth, and clockwise rotation of the mandible were observed. Simultaneously, nasopharyngeal airway measurements PNS-ad1 and PNS-ad2 significantly increased by 1.4 mm and 1.9 mm, respectively. A correlation analysis revealed that maxillary protraction had a positive relationship with PNS-ad1 and PNS-ad2. The nasopharyngeal airway dimensions can be improved in the short term with maxillary protraction in skeletal Class III children.

Identification of craniofacial risk factors for obstructive sleep apnoea using three-dimensional MRI

The alteration of craniofacial structures has been associated with obstructive sleep apnoea (OSA). We hypothesised that: 1) a smaller mandible is a risk factor for OSA; and 2) the previously observed inferiorly positioned hyoid bone in apnoeics is associated with enlarged tongue volume. This is a case-control study using three-dimensional magnetic resonance imaging cephalometry. 55 apneics and 55 controls were matched for age, sex and race. The analysis was stratified by sex and controlled for age, race, height, neck visceral fat, skeletal type and tongue volume. We found that a 1-sd increase in mandibular length and depth were associated with decreased risk of sleep apnoea (OR 0.52, 95% CI 0.28-0.99 and OR 0.46, 95% CI 0.23-0.91, respectively) in males but not in females. Greater hyoid-to-nasion (OR 2.64, 95% CI 1.19-5.89 in males and OR 5.01, 95% CI 2.00-12.52 in females) and supramentale-to-hyoid (OR 2.39, 95% CI 1.12-5.14) in males and OR 3.38, 95% CI 1.49-7.68 in females) distances were associated with increased risk of OSA. The difference for hyoid position between apnoeics and controls was lost after controlling for tongue volume. Enlargement of tongue is likely to be the pathogenic factor for inferior-posterior positioning of hyoid. A small and shallow mandible is an independent risk factor for OSA in males but not in females.