Sleep apnea syndrome. Examination of pharyngeal obstruction with high-speed MR and polysomnography

The association of OSAS and uvula: the role of MRI in this egg-chicken problem in OSAS

PURPOSE

Obstructive sleep apnea syndrome (OSAS) is a condition resulting from repetitive partial or complete upper airway obstruction, and its etiology remains uncertain. Polysomnography is the gold standard diagnostic test for OSAS. However, there are long wait times for this evaluation, so questionnaires or ancillary diagnostic methods are used to select appropriate patients. One of these is magnetic resonance imaging (MRI). The present study aimed to investigate the association between clinical features of OSAS and uvular changes on MRI.

MATERIALS AND METHODS

A total of 102 participants, 80 with OSAS and 22 controls, were included in the study. All participants underwent full-night polysomnography, MRI, and anthropometric measurements.

RESULTS

In comparisons of MRI measurements of the uvula, statistically significant differences in uvular length, thickness, and angle were observed between the OSAS and control groups. MRI measurement significantly associated with apnea-hypopnea index was uvular thickness. Evaluation of anthropometric and MRI measurements revealed statistically significant associations between waist circumference and uvular thickness, uvular width, and oropharyngeal space among the OSAS patients.

CONCLUSION

Thickened uvula on MRI is associated with the presence of OSAS, and its thickness is well correlated with the severity of the diseases. Thus, it may be a reliable indicator of OSAS and could be used as a supportive finding to identify patients suitable for referral for diagnostic polysomnography.

Dynamic comparison of pharyngeal stability during sleep in patients with obstructive sleep apnea syndrome treated with maxillomandibular advancement

PURPOSE

To compare the dynamic differences occurring in the pharynx during sleep after maxillomandibular advancement (MMA) surgery for the treatment of patients with obstructive sleep apnea syndrome.

METHODS

This was a prospective, cross-sectional study conducted on 20 patients (15 men and 5 women) with a polysomnography diagnosis of obstructive sleep apnea (OSA) submitted to surgical treatment with MMA. All patients were submitted to magnetic resonance (MR) during propofol-induced sleep before and 6 months after surgery. Thirty linear measurements (30 sections) were obtained over time in the retrolingual (RL) region to compare their variability before and after MMA.

RESULTS

The mean linear anteroposterior increase of the pharynx during induced sleep after MMA was 66 % in the RL region (P < 0.01). The coefficient of variation of the linear measurements was 117.5 % before surgery, being reduced to 51 % after surgery.

CONCLUSIONS

MMA promoted an important increase of the pharynx during induced sleep and a more significant change in the variability of its lumen. With a lower variation in the diameter of the organ during the respiratory movements, there is greater airway stability and a consequent maintenance of the pharyngeal lumen that reduces or even prevents pharyngeal collapse.

Recent advances in the management of obstructive sleep apnea: The dental perspective

Obstructive sleep apnea (OSA) is common in adult population. OSA shows detrimental effects on health, neuropsychological development, quality-of-life, and economic potential and now it is recognized as a public health problem. Despite the availability of expanded therapeutic options, polysomnography and nasal continuous positive airway pressure (CPAP) are the gold standards for the diagnosis and treatment for OSA. Recently, American Academy of Sleep Medicine has recommended oral appliances for OSA. Hence the therapeutic interventions that are directed at the site of airway obstruction in the maxillofacial region are within the scope of dentistry. Treatment of OSA can improve vitality, social and daytime functioning, family life and mental health of a person and hence the quality-of-life. Obesity is the main predisposing factor for OSA. Other than obesity, craniofacial abnormalities such as micrognathia and retrognathia, age, ethnic background and genetic predisposition, consumption of alcohol, smoking, and sedatives may also predispose to OSA. Treatment modalities for OSA are behavior modification, diet and medication, CPAP devices, surgical (maxillo-mandibular advancement surgery), and oral appliances. Treatment of a patient with OSA not only improves the physical health of the patients but also the mental and social well-being.

Comparison of the area of the pharynx during wakefulness and induced sleep in patients with Obstructive Sleep Apnea (OSA)

The study of obstructive sleep apnea (OSA) has received growing attention over the past years since various aspects have not been sufficiently established.

Aim

To evaluate, with the use of magnetic resonance imaging (MRI), changes in the area of the pharynx during wakefulness and induced sleep in patients with OSA.

Materials and Methods

A prospective study of thirty-two patients with a polysomnographic diagnosis of OSA. All patients were submitted to MR imaging in order to obtain high-definition anatomical sagittal sequences during wakefulness and during sleep induced with Propofol. An area was defined on the sagittal plane in the midline of the pharynx. This region was called pharyngeal midplane (PMP) area.

Results

A significant difference in PMP area (mm²) was observed between wakefulness and induced sleep in each patient (p < 0.000001).

Conclusion

The patients with OSA suffer a significant reduction of 75,5 % in the area of the pharynx during induced sleep compared to wakefulness.

Upper Airway and Its Surrounding Structures in Obese and Nonobese Patients With Sleep-Disordered Breathing

OBJECTIVES/HYPOTHESIS

The objective was to understand the pathophysiological relationship between obesity and sleep-disordered breathing by using cephalometry with the Muller maneuver.

STUDY DESIGN

A prospective study.

METHODS

One hundred habitually snoring men were evaluated for sleep-disordered breathing at the Sleep Center of Chang Gung Memorial Hospital (Taipei, Taiwan). Each subject received overnight polysomnography and two lateral cephalograms at the end-expiration phase (L1) and the Muller maneuver (L2), respectively, to evaluate the facial skeleton and the upper airway and its surrounding structures (soft palate, tongue, epiglottis, and hyoid bone). After excluding 14 patients from the study because of jaw opening during cephalometry, 86 (39 nonobese and 47 obese) patients with sleep-disordered breathing were enrolled.

RESULTS

Patients with varying degrees of obesity significantly differed in terms of the facial skeleton and the structure and function of the upper airway and its surrounding structures. The Muller maneuver caused dynamic changes in the hypopharyngeal airway and position of the tongue, and these dynamic changes were related to the pathogenesis of sleep-disordered breathing for the two groups (nonobese and obese patients). The regression model generated for the nonobese group revealed that the apnea hypopnea index was significantly related to the pharyngeal length (L2) and the soft palate thickness (L1). In contrast, the regression model generated for the obese group revealed that the apnea hypopnea index was significantly related to the soft palate (length [L1] and dynamic position change), the hyoid position (vertical [L1] and horizontal [L2]), the tongue (dynamic position change), and body mass index.

CONCLUSION

Cephalometry with the Muller maneuver may provide further insight into the pathogenesis of sleep-disordered breathing for the two groups of patients (nonobese and obese patients).

Sites of obstruction in obstructive sleep apnea

STUDY OBJECTIVE

The aim of this article was to identify the most common sites of obstruction in patients with obstructive sleep apnea (OSA) by a systematic review of published studies.

DESIGN

The review was conducted by a MEDLINE search of the English literature published during the years 1980 to 2002. The inclusion criteria were experiments involving five or more adult subjects, total rather than partial obstruction or narrowing of the upper airway, and techniques that were performed on the subjects while they were asleep.

CONCLUSION

Although there was considerable variability in the techniques and the results, the most common site of obstruction detected by these studies was at the level of the oropharynx, with extension to the laryngopharynx commonly observed.

Airway assessment by volumetric computed tomography in snorers and subjects with obstructive sleep apnea in a Far-East Asian population (Chinese)

OBJECTIVES

To evaluate the airway dimension of simple snorers and subjects with obstructive sleep apnea (OSA) in a Far-East Asian population (Chinese).

STUDY DESIGN

Prospective study of 117 near-consecutive patients evaluated for snoring and possible OSA from January 1998 to December 1998 in a sleep laboratory. Overnight polysomnography (PSG) was performed on all patients and the sleep parameters, including respiratory disturbance index (RDI), snoring index, minimal oxygen saturation (min O2), percentage of slow wave sleep (SWS), and rapid eye movement (REM) were recorded. Three-dimensional computerized tomography (CT) during awake periods was performed. The anteroposterior (AP) and the lateral distance of the retropalatal (RP) region in the oropharynx, the smallest area of RP, and retroglossal (RG) regions, and the total volume of the oropharynx were measured.

RESULT

Ninety-eight patients were diagnosed with OSA (mean RDI, 41.48 +/- 26.45 events per hour; min O2, 72.82 +/- 12.86%), whereas 19 were simple snorers. The AP and the lateral distance of the RP region, as well as the smallest area of the RP region, are significantly smaller in subjects with OSA. However, no differences in the RG region and the total volume of the oropharynx were found between the two groups. Linear regression analysis demonstrated that the lateral dimension and the smallest RP area in overweight subjects inversely correlated with the RDI, but only the AP dimension of the RP area was found to have an inverse correlation with the RDI in the underweight subjects.

CONCLUSION

In Far-East Asians (Chinese), the RP airway was found to be the primary site of narrowing in subjects with OSA, and the narrowest RP area was inversely correlated with RDI. Furthermore, weight may influence the pattern of RP narrowing by contributing to lateral collapse.

Quantitative assessment of the pharyngeal airway by dynamic magnetic resonance imaging in obstructive sleep apnea syndrome

Dynamic changes in the pharyngeal airway of patients with obstructive sleep apnea syndrome (OSAS) were evaluated by quantitating the findings of real-time imaging performed during wakefulness and spontaneous sleep by means of dynamic magnetic resonance imaging (MRI). Six patients with OSAS and 3 non-OSAS subjects, selected prospectively and randomly, underwent polysomnography and dynamic MRI. The cross-sectional areas of the soft palate and oropharynx and the anterior-posterior airway dimensions seen during wakefulness and spontaneous sleep were calculated by US National Institutes of Health imaging software. On the basis of a case control study, comparisons were made with age-matched and body mass index-matched obese non-OSAS snorers. Spontaneous sleep caused significant obstruction and narrowing of various sites of the pharyngeal airway in the OSAS patients, but not in the non-OSAS subjects. During wakefulness, the non-OSAS subjects showed no marked narrowing of the pharyngeal airways, whereas a transient but significant narrowing was observed in the OSAS patients. The mean values of both the cross-sectional area and the anterior-posterior diameter at the soft palate were significantly reduced by spontaneous sleep in the OSAS patients. Dynamic MRI in awake OSAS patients shows promise as a routine diagnostic tool for localizing the upper airway collapse for appropriate selection of surgical therapy.