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

Intermediate phenotypes of childhood obstructive sleep apnea

An intermediate phenotype of a disease is a trait in the path of pathogenesis from genetic predisposition to disease manifestation. Identifying intermediate phenotypes with high heritability is helpful in delineating the genetics of a disorder. In this study, we aimed to examine various traits with regards to obesity, cardiovascular risk and upper airway structure to identify potential intermediate phenotypes of childhood obstructive sleep apnea (OSA). Children aged between 6 and 18 years and their parents and siblings were recruited. All subjects underwent anthropometric measurements, cardiovascular risk assessment, sonographic measurement of lateral parapharyngeal wall (LPW) thickness, X-ray cephalometry and overnight polysomnography. A total of 34 phenotypes were examined. One hundred and one families consisting of 127 children (46 overweight) and 198 adults (84 overweight) were recruited. Heritability of obstructive apnea-hypopnea index (OAHI) was significant in overweight (h²  = 0.54) but not normal-weight individuals (h²  = 0.12). LPW thickness (h²  = 0.68) and resting blood pressure (h²  = 0.36 and 0.43 for systolic blood pressure [SBP] and diastolic blood pressure [DBP], respectively) were significantly heritable and associated with OAHI. Moreover, these traits were found to have shared genetic variance with OAHI in the overweight subgroup. Hyoid bone position also had significant heritability (h²  = 0.55) and association with OAHI but genetic correlation with OSA severity was not demonstrated. These findings suggest that LPW thickness and resting blood pressure are possible intermediate phenotypes of OSA independent of body mass index, especially in overweight patients. Identifying genes relevant to these phenotypes may help to elucidate the genetic susceptibility of OSA.

Imaging of sleep-disordered breathing in adults

Sleep-disordered breathing (SDB) is a term that includes several chronic conditions in which partial or complete cessation of breathing occurs multiple times throughout the night. Central sleep apnoea (CSA) is uncommon and defined by the episodic cessation of airflow without respiratory effort. Lesions involving the respiratory centre in the brainstem or the origin of the phrenic nerve from the mid-cervical cord are the commonest structural causes of CSA; magnetic resonance imaging (MRI) will demonstrate the lesion and frequently suggest the likely aetiology. In contrast, obstructive sleep apnoea (OSA) is defined as upper airway obstruction despite ongoing respiratory effort. Repetitive episodes of narrowing or closure of the upper airway are the predominant cause leading to snoring and OSA, respectively. OSA affects 33-40% of the adult population and is associated with multiple adverse health consequences, including a significantly increased risk of serious morbidity and mortality. The incidence is increasing proportionally to the worldwide rise in obesity. Imaging, performed primarily without the involvement of radiologists, has been integral to understanding the anatomical basis of SDB and especially OSA. This article will review the pathophysiology, imaging findings, and sequelae of these common conditions. The role of imaging both in suggesting the incidental diagnoses of SDB and in the investigation of these conditions when the diagnosis is suspected or has been established are also discussed.

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

STUDY OBJECTIVES

This study evaluated differences in upper airway, soft tissues and craniofacial structures between Asians from China and Europeans from Iceland with OSA using three-dimensional magnetic resonance imaging (MRI).

METHODS

Airway sizes, soft tissue volumes, and craniofacial dimensions were compared between Icelandic (N = 108) and Chinese (N = 57) patients with oxygen desaturation index (ODI) ≥ 10 events/h matched for age, gender, and ODI. Mixed effects models adjusting for height or BMI and residual differences in age and ODI were utilized.

RESULTS

In our matched sample, compared to Icelandic OSA patients, Chinese patients had smaller BMI (p < 0.0001) and neck circumference (p = 0.011). In covariate adjusted analyses, Chinese showed smaller retropalatal airway size (p ≤ 0.002), and smaller combined soft tissues, tongue, fat pads, and pterygoid (all p ≤ 0.0001), but male Chinese demonstrated a larger soft palate volume (p ≤ 0.001). For craniofacial dimensions, Chinese demonstrated bigger ANB angle (p ≤ 0.0196), differently shaped mandibles, including shorter corpus length (p < 0.0001) but longer ramus length (p < 0.0001), and a wider (p < 0.0001) and shallower (p ≤ 0.0001) maxilla.

CONCLUSIONS

Compared to Icelandic patients of similar age, gender and ODI, Chinese patients had smaller retropalatal airway and combined soft tissue, but bigger soft palate volume (in males), and differently shaped mandible and maxilla with more bony restrictions. Results support an ethnic difference in upper airway anatomy related to OSA, which may inform targeted therapies.

Multi-perspective clustering of obstructive sleep apnea towards precision therapeutic decision including craniofacial intervention

PURPOSE

Previous studies focusing on phenotyping obstructive sleep apnea (OSA) have outlined its heterogeneity in clinical symptoms, comorbidities, and polysomnographic features. However, the role of anatomical or pathophysiological causality including craniofacial skeletal deformity has not been studied. We aimed to identify and characterize phenotypes of OSA based on multi-perspective clustering by incorporating craniofacial risks with obesity, apnea severity, arousability, symptom, and comorbidity.

METHODS

A total of 421 Korean patients with OSA (apnea-hypopnea index, AHI ≥ 5; age ≥ 20 years old) were recruited. A K-means cluster analysis was performed following principal component analysis with sagittal and vertical skeletal variables (ANB and mandibular plane angle), AHI, body mass index, and Epworth sleepiness scale. Inter-cluster comparison was conducted using demographic, cephalometric, and polysomnographic variables in addition to presence of diabetes and hypertension. Risk factors contributing to OSA severity were evaluated in each cluster using multivariable regression analysis with adjustment for age and gender.

RESULTS

Three phenotypic clusters were identified and characterized as follows: Cluster-1 (noncraniofacial phenotype, 39%), non-obese moderate-to-severe OSA with no skeletal discrepancy representing low arousal threshold (ArTh), little sleepiness, and low comorbidity; Cluster-2 (craniofacial skeletal phenotype, 33%), non-obese moderate OSA with definite skeletal discrepancy showing low ArTh, mild sleepiness, and low comorbidity; and Cluster-3 (complicated phenotype, 28%), obese severe OSA with skeletal discrepancy exhibiting high ArTh, excessive daytime sleepiness, and high incidence of hypertension.

CONCLUSIONS

The three OSA phenotypes from multi-perspective clustering may provide a basis for precise therapeutic decision-making including craniofacial skeletal intervention beyond usual characterization of OSA subgroups.

TORS for OSA: a practice, pitfalls and literature review

PURPOSE

Trans-oral robotic surgery (TORS) is increasingly employed in obstructive sleep apnoea (OSA) management. Objective outcomes are generally assessed through polysomnography. Pre-operative magnetic resonance imaging (MRI) can be a useful adjunct in objective upper airway assessment, in particular the tongue base, providing useful information for surgical planning and outcome assessment, though care must be taken in patient positioning during surgery. The purpose of this paper is to identify pitfalls in this process and suggest a protocol for pre-operative MRI scanning in OSA.

DESIGN/METHODOLOGY/APPROACH

This study is a four-patient prospective case-series and literature review. Outcome measures include pre- and post-operative volumetric changes in the pharynx as measured on MRI and apnoea-hypopnea indices (AHI), with cure being OSA resolution or a 50 per cent reduction in AHI.

FINDINGS

All patients achieved AHI reduction and/or OSA cure following TORS, despite a decrease in pharyngeal volume measurements at the tongue base level. This study and others lacked standardisation in the MRI scanning protocol, which resulted in an inability to effectively compare pre- and post-operative scans. Pitfalls were related to variation in head/tongue position, soft-tissue marker usage and assessed area boundary limits.

PRACTICAL IMPLICATIONS

TORS appears to be effective in OSA management. A new protocol for patient positioning and anatomical landmarks is suggested.

ORIGINALITY/VALUE

The findings could provide directly comparable data between scans and may allow correlation between tongue base volumetric changes and AHI through subsequent and historical study meta-analysis.

[Pathophysiology of obstructive sleep apnea]

The prevalence of obstructive sleep apnea (OSA) is considered to be very high in western industrialized countries. There are conservative and surgical forms of treatment for OSA; however, the pathophysiology is largely unexplained and cannot be explained by anatomical abnormalities alone. In recent years, a number of non-anatomical factors have been found that favor the development of OSA. These include the respiratory excitation threshold (arousals), the respiratory drive (loop gain), as well as the control and function of the muscular upper airway dilators. The understanding of the individual pathophysiological processes may be helpful in the future to develop individual treatment approaches for patients.

A Screening Algorithm for Obstructive Sleep Apnea in Pregnancy

Rationale: Obstructive sleep apnea (OSA) is common in pregnancy and associated with maternal and fetal complications. Early detection of OSA may have important implications for maternal-fetal well-being. A screening tool combining several methods of assessment may better predict OSA among pregnant women compared with tools that rely solely on self-reported information.Objectives: To develop a screening tool combining subjective and objective measures to predict OSA in pregnant women.Methods: This study is a secondary analysis using data collected from a completed cohort of pregnant women (n = 121 during the first and n = 87 during the third trimester). Participants underwent full polysomnography and completed the Multivariable Apnea Prediction Questionnaire. The Obstructive Sleep Apnea/Hypopnea Syndrome Score and Facco apnea predictive model were obtained. Logistic regression analysis and area under the curve (AUC) were used to identify models predicting OSA risk.Results: Participants' mean age was 27.4 ± 7.0 years. The prevalence of OSA during the first and third trimester was 10.7% and 24.1%, respectively. The final model predicting OSA risk consisted of body mass index, age, and presence of tongue enlargement. During the first trimester, the AUC was 0.86 (95% confidence interval [CI], 0.76-0.96). During the third trimester, the AUC was 0.87 (95% CI, 0.77-0.96). When the first-trimester data were used to predict third-trimester OSA risk, the AUC was 0.87 (95% CI, 0.77-0.97). This model had high sensitivity and specificity when used during both trimesters. The negative posttest probabilities (probability of OSA given a negative test result) ranged from 0.03 to 0.07.Conclusions: A new model consisting of body mass index, age, and presence of tongue enlargement provided accurate screening of OSA in pregnant women, particularly African-Americans. This tool can be easily and rapidly administered in busy clinical practices without depending on patients' awareness of experiencing apnea symptoms.

More Than the Sum of the Respiratory Events: Personalized Medicine Approaches for Obstructive Sleep Apnea

Traditionally, the presence and severity of obstructive sleep apnea (OSA) have been defined by the apnea-hypopnea index (AHI). Continuous positive airway pressure is generally first-line therapy despite low adherence, because it reliably reduces the AHI when used, and the response to other therapies is variable. However, there is growing appreciation that the underlying etiology (i.e., endotype) and clinical manifestation (i.e., phenotype) of OSA in an individual are not well described by the AHI. We define and review the important progress made in understanding and measuring physiological mechanisms (or endotypes) that help define subtypes of OSA and identify the potential use of genetics to further refine disease classification. This more detailed understanding of OSA pathogenesis should influence clinical treatment decisions as well as help inform research priorities and clinical study design. In short, treatments could be individualized on the basis of the underlying cause of OSA; patients could better understand which symptoms and outcomes will respond to OSA treatment and by how much; and researchers could select populations most likely to benefit from specific treatment approaches for OSA.

Evaluation of upper airway volume and craniofacial volumetric structures in obstructive sleep apnoea adults: A descriptive CBCT study

OBJECTIVE

The aim of this investigation was to assess, with a descriptive three-dimensional evaluation, the volume of upper airway (UAWV) and the volume of craniofacial structures in adult patients suffering from obstructive sleep apnoea (OSA) and compare them to the corresponding findings in adults with no sleep disorders.

MATERIALS AND METHODS

The sample consisted of 54 adult males, 27 suffering from OSA diagnosed by means of the Apnoea Hypopnea Index and 27 with no history of sleep disorders. All subjects had a cone beam computerized tomography scan performed with the same head position. UAWV was assessed with the Amira® software, and craniofacial volumes by means of a specially developed data-processing program, which allowed the construction of tetrahedrons using anatomical landmarks. Assessed volumes were naso-maxillary, cranium upper anterior, oral cavity, post-oral cavity, hyoid to mandible, and post-hyoid. SPSS (version 19.0) was used for the statistical analysis. The Levene's test for Equality of Variance, the t-test for Equality of Means and the Mann-Whitney test were used to evaluate the variables. The level of significance was set at P ≤ 0.05.

RESULTS

The mean value of UAWV was smaller in the OSA group. The post-hyoid volume, the calculated posterior volume, and the ratio of posterior to total volume showed differences between the groups.

CONCLUSIONS

Craniofacial structures did not show significant differences between the groups, but in the OSA group the posterior space released for upper airway was significantly bigger and UAWV was significantly smaller.

Effects of adiposity and metabolic dysfunction on cognition: A review

Obesity and metabolic dysfunction are both correlated with increased rates of cognitive decline. However, because these two conditions often co-occur, it remains unclear whether their cognitive consequences are independent. In this review, we carefully consider literature examining the effects of metabolic dysfunction and increased adiposity on cognition across the lifespan, including only well-controlled studies that attempt to dissociate their effects. We found a total of 36 studies, 17 examining metabolic dysfunction and 19 examining the effects of adiposity. We found evidence from the literature suggesting that increased adiposity and metabolic dysfunction may contribute to deficits in executive function, memory, and medial temporal lobe structures largely independent of one another. These deficits are thought to arise principally from physiological changes associated with inflammation, vascularization, and oxidative stress, among others. Such processes may result from excess adipose tissue and insulin resistance that occur independently and can further exacerbate when the two conditions co-occur. However, we also find it likely that impaired cognition plays a role in behavioral and lifestyle choices that lead to increased adiposity and metabolic dysfunction, which can then perpetuate and augment cognitive decline. We recommend additional prospective and longitudinal studies to examine whether impaired cognition is a cause and/or consequence of these factors.

State-dependent changes in the upper airway assessed by multidetector CT in healthy individuals and during obstructive events in patients with sleep apnea

Objective:

To determine whether airway narrowing during obstructive events occurs predominantly at the retropalatal level and results from dynamic changes in the lateral pharyngeal walls and in tongue position.

Methods:

We evaluated 11 patients with severe obstructive sleep apnea (OSA) and 7 healthy controls without OSA during wakefulness and during natural sleep (documented by full polysomnography). Using fast multidetector CT, we obtained images of the upper airway in the waking and sleep states.

Results:

Upper airway narrowing during sleep was significantly greater at the retropalatal level than at the retroglossal level in the OSA group (p < 0.001) and in the control group (p < 0.05). The retropalatal airway volume was smaller in the OSA group than in the control group during wakefulness (p < 0.05) and decreased significantly from wakefulness to sleep only among the OSA group subjects. Retropalatal pharyngeal narrowing was attributed to reductions in the anteroposterior diameter (p = 0.001) and lateral diameter (p = 0.006), which correlated with an increase in lateral pharyngeal wall volume (p = 0.001) and posterior displacement of the tongue (p = 0.001), respectively. Retroglossal pharyngeal narrowing during sleep did not occur in the OSA group subjects.

Conclusions:

In patients with OSA, upper airway narrowing during sleep occurs predominantly at the retropalatal level, affecting the anteroposterior and lateral dimensions, being associated with lateral pharyngeal wall enlargement and posterior tongue displacement.

Further Development of P4 Approach to Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a heterogeneous disorder. Cluster analysis has identified different physiologic subtypes with respect to symptoms. A difference exists in cardiovascular risk from OSA between the 7 subtypes identified. There are 3 basic subtypes replicated in multiple studies: (a) a group where insomnia is the main symptom; (b) an asymptomatic group; (c) a group with marked excessive sleepiness. The symptomatic benefit from treatment with nasal CPAP varies between these 3 subtypes. Data from the Sleep Heart Health Study reveal that the increased risk of cardiovascular disease from OSA occurs only in the excessively sleepy group.

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

Study Objectives

Upper airway stimulation has been shown to be an effective treatment for some patients with obstructive sleep apnea. However, the mechanism by which hypoglossal nerve stimulation increases upper airway caliber is not clear. Therefore, the objective of this study was to identify the mechanism of action of upper airway stimulation. We hypothesized that, with upper airway stimulation, responders would show greater airway opening in the retroglossal (base of the tongue) region, greater hyoid movement toward the mandible, and greater anterior motion in the posterior, inferior region of the tongue compared with nonresponders.

Methods

Seven participants with obstructive sleep apnea who had been successfully treated with upper airway stimulation (responders) and six participants who were not successfully treated (nonresponders) underwent computed tomography imaging during wakefulness with and without hypoglossal nerve stimulation. Responders reduced their apnea-hypopnea index (AHI) by 22.63 ± 6.54 events per hour, whereas nonresponders had no change in their AHI (0.17 ± 14.04 events per hour). We examined differences in upper airway caliber, the volume of the upper airway soft tissue structures, craniofacial relationships, and centroid tongue and soft palate movement between responders and nonresponders with and without hypoglossal nerve stimulation.

Results

Our data indicate that compared with nonresponders, responders had a smaller baseline soft palate volume and, with stimulation, had (1) a greater increase in retroglossal airway size; (2) increased shortening of the mandible-hyoid distance; and (3) greater anterior displacement of the tongue.

Conclusions

These results suggest that smaller soft palate volumes at baseline and greater tongue movement anteriorly with stimulation improve the response to upper airway stimulation.

The Interaction Between Craniofacial Computed Tomographic Dimensional Parameters and BMI in Obstructive Sleep Apnea

Introduction

The impact of the dimensional parameters of the pharyngeal bony frame by its length, width and the position of the hyoid upon the severity of obstructive sleep apnea syndrome (OSAS) has not been investigated in depth. Interactions of those parameters with body mass index (BMI) and their overall reciprocal effect on OSAS severity have also not been established.

Materials and Methods

This retrospective cross-sectional study was conducted on 108 male OSAS patients followed in OSAS outpatient clinics between November 2014 and October 2015. They all underwent a polysomnography test, and an apnea-hypopnea index (AHI) was calculated. They also underwent an upper airway computerized tomographic scan in which three craniofacial parameters were evaluated: inter-pterygoid distance (IPD), hard palate-to-hyoid (HP-H) distance, and gnathion plane-to-hyoid (GP-H) distance.

Results

A longer pharynx and an inferiorly placed hyoid bone correlated with the AHI (r = 0.33, p = 0.001 and r = 0.226, p = 0.03, respectively). GP-H correlated with body mass index (BMI) (r = 0.3243, p < 0.001), while HP-H and IPD did not. We found an interaction between BMI and HP-H, but none between GP-H and BMI. IPD did not correlate with OSAS severity, but it correlates with the age of the OSAS patients (r = 0.235, p = 0.015).

Conclusion

Pharynx length and hyoid position have significant effects upon OSAS severity, and they interact differently with BMI in terms of those effects. Hard palate width increases with age but has no correlation with OSAS severity.

Continuous positive airway pressure alters brain microstructure and perfusion patterns in patients with obstructive sleep apnea

OBJECTIVES

To assess the effects of continuous positive airway pressure (CPAP) treatment on brain structure and function in patients with obstructive sleep apnea (OSA).

METHODS

A prospective study of seven OSA patients recruited from the sleep center at our institution was carried out. Patients were treated with six weeks of CPAP treatment. Pre-treatment and post-treatment magnetic resonance imaging (MRI) perfusion scans were obtained and compared to assess for treatment-induced changes. Microstructural changes were quantified using functional anistrophy (FA) and mean diffusivity (MD), and brain perfusion was quantified using cerebral blood flow (CBF) and cerebral blood volume (CBV).

RESULTS

Of the seven patients included the in study, six (85.7%) were male, and the mean age was 51 years (standard deviation = 13.14). Increased FA and decreased MD were found in the hippocampus, temporal lobes, fusiform gyrus, and occipital lobes. Decreased FA and increased MD were found in frontal regions for all patients (p < 0.05). Increased CBF and CBV were also observed following treatment (p < 0.05).

CONCLUSION

In addition to symptom resolution, CPAP treatment may allow for healing of OSA-induced brain damage as seen by restoration of brain structure and perfusion.

Mandibular width as a novel anthropometric measure for assessing obstructive sleep apnea risk

Craniofacial abnormalities are a known obstructive sleep apnea (OSA) risk factor, but still need to be better characterized. This study investigates the relationship between mandibular width and the risk of developing OSA.We retrospectively analyzed 3D reconstructions of head and neck computed tomography (CT) scans at our institution for mandibular width, neck circumference, neck fat volume (NFV), airway volume (AWV), and NFV:AWV ratio. Age, gender, and BMI were also documented. Patients were contacted to complete a STOP-BANG survey to assess OSA risk. Only patients with reconstructable scans and completed STOP-BANG questionnaires were included in the study. Survey results were analyzed to assess the correlation between mandible width and STOP-BANG. Mandible association was also compared to the associations of the other known risk factors.The final analysis included 427 patients with a mean age of 58.98 years (standard deviation = 16.77), 56% of whom were male. Mandibular width was found to positively correlate with STOP-BANG score (r = .416, P < .001). Statistically significant differences between mandible size for each risk group was seen (P < .001). After controlling for age and sex, mandible size was significantly different only for the low risk vs. high risk groups (odds ratio = 1.11; 95% confidence interval = 1.03-1.20; P = .007). Furthermore, when stratified according to mandible size, the small mandible group (<77.50 mm) predominantly consisted of low risk patients; the medium size mandible group (77.50-84.40 mm) was predominated by intermediate risk patients, and large mandible (>84.40 mm) was predominantly seen in high risk patients. Mandible width expressed a stronger association than NFV:AWV ratio, but neck circumference and NFV had stronger associations than did mandible width.In addition to previously documented OSA risk factors, mandibular width is positively correlated with OSA as an independent risk factor. Observation of a wide mandible (jaw) should raise awareness of OSA risk and increase screening methods when appropriate.

Potential Anatomic Markers of Obstructive Sleep Apnea in Prepubertal Children

STUDY OBJECTIVES

Adenotonsillar hypertrophy is the major cause of obstructive sleep apnea (OSA) in prepubertal children, but children without enlarged lymphoid tissues may still suffer from OSA. This study aimed to identify other potential anatomic features associated with childhood OSA.

METHODS

This prospective study took place between January 2010 and April 2014. Prepubertal children suspected to have OSA, aged 6 to 11 years, were recruited. They underwent anthropometric measurements, nocturnal polysomnography, tonsil size evaluation, x-ray cephalometry, and sonographic measurement of lateral parapharyngeal wall (LPW) thickness. Linear regression analyses were used to test for the association between anatomic measurements and OSA severity. Logistic regression analyses were used to identify potential anatomic markers for different cutoffs (obstructive apneahypopnea index (OAHI) ≥ 1 and ≥ 5 events/h) for OSA.

RESULTS

Forty-seven children with OSA (20 with moderate to severe disease) and 43 children for the control group were recruited. Sonographic measurement of LPW thickness and position of hyoid bone taken from x-ray cephalometry were risk factors associated with OSA. Linear regression analyses found that these two phenotypes were associated with OAHI. Multivariate models adjusted for age, sex, body mass index, z score, and tonsil size revealed that lower position of hyoid bone was independently associated with higher risk for OSA, whereas both lower position of hyoid bone and greater LPW thickness were associated with higher OAHI and also a higher risk for moderate to severe OSA.

CONCLUSIONS

Position of hyoid bone and LPW thickness are anatomical markers of childhood OSA independent of obesity and tonsil size. Screening tools may include cephalometry and sonographic measurement of LPW to allow better delineation of OSA risk.

Trans-Oral Robotic Tongue Reduction for OSA: Does Lingual Anatomy Influence the Surgical Outcome?

STUDY OBJECTIVES

To evaluate both the influence of the volume of the excised base of tongue (BOT) on the surgical outcome after robotic tongue reduction in patients affected by obstructive sleep apnea (OSA) and the role of the lymphatic or muscular predominance within the removed tissue.

METHODS

Fifty-one patients with OSA were included in this study. All patients were treated with a robotic tongue base reduction. Data registered for the analysis were: age, sex, preoperative body mass index, preoperative and postoperative apnea-hypopnea index (AHI), delta AHI (preoperative AHI - postoperative AHI), total volume of the excised BOT, total thickness of excised BOT, isolated lymphatic thickness and soft tissue thickness (including muscular component) of the excised BOT, and lymphatic/soft tissue ratio (lymphatic thickness / soft tissue thickness).

RESULTS

A statistically significant reduction of AHI values was seen postoperatively, and a success rate of 74.5% was recorded. However, no significant correlations between delta AHI and tongue volume in cubic centimeters, lymphatic/soft tissue ratio, and total thickness were found.

CONCLUSIONS

These findings reinforce the general opinion that OSA is not only influenced by anatomic factors but other phenomena may play a fundamental role in its genesis. A deeper understanding of OSA pathogenesis is needed in order to tailor an individual treatment strategy that could lead to a more effective therapy.

The influential factors on the morphological changes of upper airway associated with mouth opening

OBJECTIVE

This study aimed to evaluate the influential factors on the morphological changes of upper airway caused by mouth opening (MO).

METHODS

One hundred and thirty-eight obstructive sleep apnea-hypopnea syndrome (OSAHS) patients were enrolled. Anthropometric and demographic data, Friedman tongue position (FTP), and tonsil scores were recorded. Overnight polysomnography and upper airway computed tomography scans under two conditions (mouth closed [MC] and MO) were acquired. Morphological parameters of upper airway were compared between MC and MO. Stepwise multiple linear regression analyses were performed with the variation ratio of upper airway parameters (Para-VRs) from MC to MO as the dependent variable, with age, gender, body mass index, neck circumference, waist circumference, four mandibular indexes, net angle or amount of MO, FTP, and tonsil scores as the independent variables.

RESULTS

Overall analysis and subgroup analyses based on OSAHS severity revealed that the minimal cross-sectional area of oropharyngeal lumen (OXmin) significantly decreased (P < 0.05) with MO, whereas the minimal cross-sectional area of velopharyngeal lumen (VXmin) did not significantly change with MO (P > 0.05). The net angle of MO or amount of MO combined with tonsil scores were identified to have significant positive correlation with EXP (OXmin-VR), [OXmin-VR was logarithmically transformed with an exponential function, EXP(n) = eⁿ ]; FTP appeared to be more related to EXP (VXmin-VR). Mouth opening induced a significant increase VXmin for patient subgroup with FTP grading I and a significant decrease VXmin for patient subgroup with FTP grading IV (P < 0.05).

CONCLUSION

Wider MO combined with larger tonsils lead to narrower oropharyngeal airway. The relative position of tongue to soft palate is the main factor influencing the changes of velopharyngeal lumen with MO.

LEVEL OF EVIDENCE

4 Laryngoscope, 128:2902-2909, 2018.

Application of Personalized, Predictive, Preventative, and Participatory (P4) Medicine to Obstructive Sleep Apnea. A Roadmap for Improving Care?

Dr. Leroy Hood promotes a paradigm to advance medical care that he calls P4 medicine. The four Ps are: personalized, predictive, preventative, and participatory. P4 medicine encourages a convergence of systems medicine, the digital revolution, and consumer-driven healthcare. Might P4 medicine be applicable to obstructive sleep apnea (OSA)? OSA should be personalized in that there are different structural and physiological pathways to disease. Obesity is a major risk factor. The link between obesity and OSA is likely to be fat deposits in the tongue compromising the upper airway. Clinical features at presentation also vary between patients. There are three distinct subgroups: (1) patients with a primary complaint of insomnia, (2) relatively asymptomatic patients with a high prevalence of cardiovascular comorbidities, and (3) excessively sleepy patients. Currently, there have been limited efforts to identify subgroups of patients on the basis of measures obtained by polysomnography. Yet, these diagnostic studies likely contain considerable predictive information. Likewise, there has currently been limited application of -omic approaches. Determining the relative role of obesity and OSA for particular consequences is challenging, because they both affect the same molecular pathways. There is evidence that the effects of OSA are modified by the level of obesity. These insights may lead to improvements in predicting outcomes to personalized therapies. The final P-participatory-is ideally suited to OSA, with technology to obtain extensive data remotely from continuous positive airway pressure machines. Providing adherence data directly to patients increases their use of continuous positive airway pressure. Thus, the concept of P4 medicine is very applicable to obstructive sleep apnea and can be the basis for future research efforts.

Obstructive sleep apnea: in search of precision

Introduction

Obstructive sleep apnea (OSA) is a highly prevalent condition that is viewed as a major global health concern, while affecting approximately 10% of the middle-aged population. OSA is a chronic disease that has been conclusively associated with poor quality of life, cognitive impairments and mood alterations, enhanced cardiovascular and metabolic morbidity, thereby leading to marked increments in healthcare costs.

Areas covered

The authors have reviewed the current evidence on the pathophysiology of OSA and its consequences, the heterogeneity of its phenotypic expression, the current therapeutic applications and their efficacy, and the implications for diagnosis, treatment and follow-up strategies in the context of the clinical management of OSA.

Expert commentary

Personalized medicine in OSA identifies different needs and approaches: i) phenotyping and defining the different and segregated clusters of OSA patients whose recognition may improve prognostic predictions and guide therapeutic strategies; ii) to further characterize and predict the impact of OSA and its treatment, particularly revolving around mortality and the processes closely related to ageing (cardiovascular diseases, cancer and neurocognitive diseases); iii) the introduction of new technologies including telemedicine that have shown promise in the implementation of personalized medicine approaches.

Digital Morphometrics: A New Upper Airway Phenotyping Paradigm in OSA

BACKGROUND

OSA is associated with changes in pharyngeal anatomy. The goal of this study was to objectively and reproducibly quantify pharyngeal anatomy by using digital morphometrics based on a laser ruler and to assess differences between subjects with OSA and control subjects and associations with the apnea-hypopnea index (AHI). To the best of our knowledge, this study is the first to use digital morphometrics to quantify intraoral risk factors for OSA.

METHODS

Digital photographs were obtained by using an intraoral laser ruler and digital camera in 318 control subjects (mean AHI, 4.2 events/hour) and 542 subjects with OSA (mean AHI, 39.2 events/hour).

RESULTS

The digital morphometric paradigm was validated and reproducible over time and camera distances. A larger modified Mallampati score and having a nonvisible airway were associated with a higher AHI, both unadjusted (P < .001) and controlling for age, sex, race, and BMI (P = .015 and P = .018, respectively). Measures of tongue size were larger in subjects with OSA vs control subjects in unadjusted models and controlling for age, sex, and race but nonsignificant controlling for BMI; similar results were observed with AHI severity. Multivariate regression suggests photography-based variables capture independent associations with OSA.

CONCLUSIONS

Measures of tongue size, airway visibility, and Mallampati scores were associated with increased OSA risk and severity. This study shows that digital morphometrics is an accurate, high-throughput, and noninvasive technique to identify anatomic OSA risk factors. Morphometrics may also provide a more reproducible and standardized measurement of the Mallampati score. Digital morphometrics represent an efficient and cost-effective method of examining intraoral crowding and tongue size when examining large populations, genetics, or screening for OSA.

Test-retest repeatability of human speech biomarkers from static and real-time dynamic magnetic resonance imaging

Static anatomical and real-time dynamic magnetic resonance imaging (RT-MRI) of the upper airway is a valuable method for studying speech production in research and clinical settings. The test-retest repeatability of quantitative imaging biomarkers is an important parameter, since it limits the effect sizes and intragroup differences that can be studied. Therefore, this study aims to present a framework for determining the test-retest repeatability of quantitative speech biomarkers from static MRI and RT-MRI, and apply the framework to healthy volunteers. Subjects (n = 8, 4 females, 4 males) are imaged in two scans on the same day, including static images and dynamic RT-MRI of speech tasks. The inter-study agreement is quantified using intraclass correlation coefficient (ICC) and mean within-subject standard deviation (σ_e). Inter-study agreement is strong to very strong for static measures (ICC: min/median/max 0.71/0.89/0.98, σ_e: 0.90/2.20/6.72 mm), poor to strong for dynamic RT-MRI measures of articulator motion range (ICC: 0.26/0.75/0.90, σ_e: 1.6/2.5/3.6 mm), and poor to very strong for velocities (ICC: 0.21/0.56/0.93, σ_e: 2.2/4.4/16.7 cm/s). In conclusion, this study characterizes repeatability of static and dynamic MRI-derived speech biomarkers using state-of-the-art imaging. The introduced framework can be used to guide future development of speech biomarkers. Test-retest MRI data are provided free for research use.

Fat accumulation in the tongue is associated with male gender, abnormal upper airway patency and whole-body adiposity

OBJECTIVE

To examine associations between tongue adiposity with upper airway measures, whole-body adiposity and gender. We hypothesized that increased tongue adiposity is higher in males and positively associated with abnormal upper airway measures and whole-body adiposity.

METHODS

We studied subjects who underwent whole-body positron emission tomography/computed tomography to obtain tongue attenuation (TA) values and cross-sectional area, pharyngeal length (PL) and mandibular plane to hyoid distance (MPH), as well as abdominal circumference, abdominal subcutaneous and visceral (VAT) adipose tissue areas, neck circumference (NC) and neck adipose tissue area. Metabolic syndrome was determined from available clinical and laboratory data.

RESULTS

We identified 206 patients (104 females, 102 males) with mean age 56±17years and mean body mass index (BMI) 28±6kg/m² (range 16-47kg/m²). Males had lower TA values (P=0.0002) and higher upper airway measures (P<0.0001) independent of age and BMI (P<0.001). In all subjects, TA was negatively associated with upper airway measures (P<0.001). TA was negatively associated with body composition parameters (all P<0.0001), most notably with VAT (r=-0.53) and NC (r=-0.47). TA values were lower in subjects with metabolic syndrome (P<0.0001).

CONCLUSION

Increased tongue adiposity is influenced by gender and is associated with abnormal upper airway patency and body composition parameters.

Obstructive sleep apnoea pathogenesis from mild to severe: Is it all the same?

Obstructive sleep apnoea (OSA) is a common disorder caused by not only an impaired upper airway anatomy (i.e. anatomically narrow/collapsible airway), but also by several non-anatomical factors. In this review, we summarise what is known about how each of the pathological factors that cause OSA vary according to disease severity as measured by the apnoea-hypopnoea index. Our synthesis of the available literature indicates that most of the key factors that cause OSA vary with disease severity. However, there is substantial heterogeneity such that the relative contribution of each of these traits varies both between patients and within different severities of disease. These differences likely contribute to variable efficacy of many non-continuous positive airway pressure treatments and inconsistencies in responses with regard to different OSA severities at baseline.

Cephalometric risk factors associated with myocardial infarction in patients suffering from obstructive sleep apnea: A pilot case-control study

INTRODUCTION

Obstructive sleep apnea (OSA) and its craniofacial anatomic risk factors might play a role in several cardiovascular diseases, including myocardial infarction (MI). However, there are no data about cephalometric findings among OSA patients with MI.

METHODS

In this pilot case-control study, about 2000 individuals referred to the sleep center were evaluated according to apnea - hypopnea index (AHI) and other inclusion criteria. Included were 62 OSA male patients (AHI > 10), of whom 6 had an MI history. In both control (n = 56) and MI groups (n = 6), 18 cephalometric parameters were traced. Data were analyzed using independent samples t-test.

RESULTS

Compared with control OSA patients, OSA patients with MI showed a significantly larger tongue length (p = 0.015). The other cephalometric variables were not significantly different between the two groups.

CONCLUSION

An elongated tongue might be considered a risk factor for MI in OSA patients. The role of other variables remains inconclusive and open to investigation with larger samples (determined based on pilot studies such as this report) collected in longitudinal fashion.

Three-dimensional imaging of the upper airway anatomy in obstructive sleep apnea: a systematic review

INTRODUCTION

The pathogenesis of upper airway collapse in people with obstructive sleep apnea (OSA) is not fully understood. The aim of this study was to systematically review the literature in order to assess the most relevant anatomical characteristics of the upper airway related to the pathogenesis of OSA by analyzing the three-dimensional upper airway anatomy.

METHOD

A PICO (population/patient, intervention, comparison, outcome) search strategy, focusing on the upper airway anatomy of people with OSA, was conducted using the following databases: MEDLINE (PubMed), Excerpta Medica database (EMBASE), Web of Science, and Cochrane Library. The studies in which three-dimensional images were made from the participants who were awake and in the supine position during quiet breathing were selected in this systematic review.

RESULTS

Of the 758 unique retrieved studies, eight fulfilled the criteria for this systematic review. The minimum cross-sectional area of the upper airways of people with OSA, which is influenced by many factors such as hard and soft tissues surrounding the upper airway, was significantly smaller than that of those without OSA.

CONCLUSION

Within the limitation of the selected studies, this systematic review suggested that a small minimum cross-sectional area is the most relevant anatomical characteristic of the upper airway related to the pathogenesis of OSA.

Speech Signal and Facial Image Processing for Obstructive Sleep Apnea Assessment

Obstructive sleep apnea (OSA) is a common sleep disorder characterized by recurring breathing pauses during sleep caused by a blockage of the upper airway (UA). OSA is generally diagnosed through a costly procedure requiring an overnight stay of the patient at the hospital. This has led to proposing less costly procedures based on the analysis of patients' facial images and voice recordings to help in OSA detection and severity assessment. In this paper we investigate the use of both image and speech processing to estimate the apnea-hypopnea index, AHI (which describes the severity of the condition), over a population of 285 male Spanish subjects suspected to suffer from OSA and referred to a Sleep Disorders Unit. Photographs and voice recordings were collected in a supervised but not highly controlled way trying to test a scenario close to an OSA assessment application running on a mobile device (i.e., smartphones or tablets). Spectral information in speech utterances is modeled by a state-of-the-art low-dimensional acoustic representation, called i-vector. A set of local craniofacial features related to OSA are extracted from images after detecting facial landmarks using Active Appearance Models (AAMs). Support vector regression (SVR) is applied on facial features and i-vectors to estimate the AHI.

Relationship between morphological characteristics of hyoid bone and mandible in Japanese cadavers using three-dimensional computed tomography

The aim of this study is to obtain a quantitative anatomical description of the hyoid bone and mandible using three-dimensional computed tomography. Hyoid bones were obtained from a total of 101 cadavers varying in age from 67 to 102 years. The percentage of symmetrical U-type and asymmetrical-type hyoid bones was low compared with symmetrical V type (14.9, 15.8, and 69.3 %, respectively), and no significant sex difference was observed. We found bilateral nonfusion in cadavers of advanced age at a rate of 22.7 % and bilateral complete fusion at a rate of 51.5 %. There were significant differences in metric variables (length and width) between males and females, but no significant differences in width among the different fusion types. There was no significant interaction effect of sex and degree of fusion. Strong significant associations were observed between size (length and width) of the hyoid bone and mandible in the nonfusion group, while the complete fusion group revealed a moderate correlation. We also investigated the hypothesis that the junction between the hyoid body and greater horn plays an important role in the movement of bones that have not yet ossified. However, no statistical difference was observed in the width between the two greater horns. The degree of fusion of the greater horn with the hyoid body may also affect relations of interdependencies between the hyoid bone and mandible, an important component to consider when assessing risk factors in the development of masticatory and swallowing function.

Diagnostic Role of Magnetic Resonance Imaging in Obstructive Sleep Apnea Syndrome

We aim to review the diagnostic role of magnetic resonance (MR) imaging in obstructive sleep apnea syndrome (OSAS). Basic background about sleep apnea, MR anatomy of the pharyngeal airway, and MR imaging sequences applied in obstructive sleep apnea are discussed. Static and dynamic MR imaging is used in the assessment of patients with OSAS. Magnetic resonance imaging can detect the level, degree, and cause of obstruction in the upper airway that guide the clinical diagnosis and treatment. Imaging is used for prediction of treatment outcome and monitoring and follow-up of patients with OSAS after therapy.

Understanding the anatomic basis for obstructive sleep apnea syndrome in adolescents

RATIONALE

Structural risk factors for obstructive sleep apnea syndrome (OSAS) in adolescents have not been well characterized. Because many adolescents with OSAS are obese, we hypothesized that the anatomic OSAS risk factors would be more similar to those in adults than those in children.

OBJECTIVES

To investigate the anatomic risk factors in adolescents with OSAS compared with obese and lean control subjects using magnetic resonance imaging (MRI).

METHODS

Three groups of adolescents (age range: 12-16 yr) underwent MRI: obese individuals with OSAS (n = 49), obese control subjects (n = 38), and lean control subjects (n = 50).

MEASUREMENTS AND MAIN RESULTS

We studied 137 subjects and found that (1) obese adolescents with OSAS had increased adenotonsillar tissue compared with obese and lean control subjects; (2) obese OSAS adolescents had a smaller nasopharyngeal airway than control subjects; (3) the size of other upper airway soft tissue structures (volume of the tongue, parapharyngeal fat pads, lateral walls, and soft palate) was similar between subjects with OSAS and obese control subjects; (4) although there were no major craniofacial abnormalities in most of the adolescents with OSAS, the ratio of soft tissue to craniofacial space surrounding the airway was increased; and (5) there were sex differences in the pattern of lymphoid proliferation.

CONCLUSIONS

Increased size of the pharyngeal lymphoid tissue, rather than enlargement of the upper airway soft tissue structures, is the primary anatomic risk factor for OSAS in obese adolescents. These results are important for clinical decision making and suggest that adenotonsillectomy should be considered as the initial treatment for OSAS in obese adolescents, a group that has poor continuous positive airway pressure adherence and difficulty in achieving weight loss.

Tongue Volume Influences Lowest Oxygen Saturation but Not Apnea-Hypopnea Index in Obstructive Sleep Apnea

Objectives

The aim of this study was to identify correlations between sleep apnea severity and tongue volume or posterior airway space measured via three-dimensional reconstruction of volumetric computerized tomography (CT) images in patients with obstructive sleep apnea (OSA) for use in predicting OSA severity and in surgical treatment. We also assessed associations between tongue volume and Mallampati score.

Methods

Snoring/OSA male patients (n = 64) who underwent polysomnography, cephalometry, and CT scans were enrolled in this retrospective study. OSA was diagnosed when the apnea-hypopnea index (AHI) was greater than 5 (mild 5–14; moderate 15–29; severe>30). The patients were also categorized into the normal-mild group (n = 22) and the moderate-severe group (n = 42). Using volumetric CT images with the three-dimensional reconstruction technique, the volume of the tongue, posterior airway space volume, and intra-mandibular space were measured. The volumes, polysomnographic parameters, and physical examination findings were compared, and independent factors that are related to OSA were analysed.

Results

No associations between tongue volume or posterior airway space and the AHI were observed. However, multivariate linear analyses showed that tongue volume had significantly negative association with lowest O₂ saturation (r = 0.365, p = 0.027). High BMI was related to an increase in tongue volume. Modified Mallampati scores showed borderline significant positive correlations with absolute tongue volume (r = 0.251, p = 0.046) and standardized tongue volume (absolute tongue volume / intramandibular area; r = 0.266, p = 0.034). Between the normal-mild and moderate-severe groups, absolute tongue volumes were not different, although the standardized tongue volume in the moderate-severe group was significantly higher.

Conclusion

Absolute tongue volume showed stronger associations with lowest O₂ saturation during sleep than with the severity of AHI. We also found that high BMI was a relevant factor for an increase in absolute tongue volume and modified Mallampati grading was a useful physical examination to predict tongue size.

The Relationship Between Volume Overload in End-Stage Renal Disease and Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is common, underdiagnosed, and undertreated among patients with end-stage renal disease (ESRD). As in all cases, pathogenesis of OSA is related to repeated upper airway (UA) occlusion or narrowing, but in ESRD, additional contributory factors likely include uremic destabilization of central respiratory control and anatomic changes in the UA related to fluid status. Pulmonary congestion is common in acute and chronic kidney failure and is a consequence of cardiomyopathy and fluid overload, two potentially reversible risk factors. Emerging evidence suggests that volume overload also reduces the UA caliber. The diminution in UA area as well as destabilization of ventilatory control in ESRD have been postulated as causes of increased OSA prevalence and severity in these patients, and creates a vicious cycle wherein OSA exacerbates fluid overload disorders such as in congestive heart failure (CHF) and ESRD, which then further worsen OSA. Dialysis modalities may differ in their effects on volume status, the accumulation of uremic toxins, and acid-base status, and as a consequence, on the emergence and severity of OSA. Given the contribution of excess fluid to both the severity of nocturnal hypoxia and UA narrowing, establishing and maintaining dry weight is of particular importance when managing OSA in ESRD. Clinical trials to determine the extent to which more aggressive fluid removal in ESRD patients may alleviate OSA are needed.

Comparative analysis of upper airway volume with lateral cephalograms and cone-beam computed tomography

INTRODUCTION

In this study, we aimed to evaluate the adenoidal nasopharyngeal ratio (ANR) on lateral cephalograms by assessing upper airway volumes using cone-beam computed tomography (CBCT) images as the validation method.

METHODS

Fifty-five patients were included in the study, and it was essential that the lateral cephalograms and CBCT images taken at their examinations were not more than 1 week apart. There were 32 subjects in group A (age ≤15 years) and 23 subjects in group B (age >15 years). The ANR was measured on the lateral cephalograms. The area and volumetric measurements of the nasopharynx and the total upper airway were obtained from CBCT images. Repeated measurements of the ANR and airway volume were performed on 10 subjects by 2 observers.

RESULTS

Group A had a higher correlation (r = -0.78) between the ANR and the nasopharynx volume than did group B (r = -0.57). The ANR had a weak correlation with the total upper airway volume (group A, r = -0.48; group B, r = -0.32). Both measurements made on lateral cephalograms and CBCT were highly reproducible in terms of intraobserver and interobserver agreement.

CONCLUSIONS

Based on our results, the measurement of the ANR on lateral cephalograms can be used as an initial screening method to estimate the nasopharynx volumes of younger patients (age ≤15 years).