Quantitative magnetic resonance imaging demonstrates alterations of the lingual musculature in obstructive sleep apnea

Imaging Assessment of Radiation Therapy-Related Normal Tissue Injury in Children: A PENTEC Visionary Statement

The Pediatric Normal Tissue Effects in the Clinic (PENTEC) consortium has made significant contributions to understanding and mitigating the adverse effects of childhood cancer therapy. This review addresses the role of diagnostic imaging in detecting, screening, and comprehending radiation therapy-related late effects in children, drawing insights from individual organ-specific PENTEC reports. We further explore how the development of imaging biomarkers for key organ systems, alongside technical advancements and translational imaging approaches, may enhance the systematic application of imaging evaluations in childhood cancer survivors. Moreover, the review critically examines knowledge gaps and identifies technical and practical limitations of existing imaging modalities in the pediatric population. Addressing these challenges may expand access to, minimize the risk of, and optimize the real-world application of, new imaging techniques. The PENTEC team envisions this document as a roadmap for the future development of imaging strategies in childhood cancer survivors, with the overarching goal of improving long-term health outcomes and quality of life for this vulnerable population.

Ultrasonography of the neck in patients with obstructive sleep apnea

INTRODUCTION

In resource-limited settings, obstructive sleep apnea (OSA) often goes undiagnosed as polysomnography (PSG) is expensive, time-consuming, and not readily available. Imaging studies of upper airway have been tried as alternatives to PSG to screen for OSA. However, racial differences in upper airway anatomy preclude generalizability of such studies. We sought to test the hypothesis that ultrasonography (USG), an inexpensive, readily available tool to study soft tissue structures of the upper airway, would have predictive value for OSA in South Asian people.

METHODS

Adult patients with sleep-related complaints suspicious for OSA were taken for overnight PSG. After the PSG, consecutive patients with and without OSA were studied with submental ultrasonography to measure tongue base thickness (TBT) and lateral pharyngeal wall thickness (LPWT).

RESULTS

Among 50 patients with OSA and 25 controls, mean age was 43.9 ± 11.4 years, and 39 were men. Patients with OSA had higher TBT (6.77 ± 0.63 cm vs 6.34 ± 0.54 cm, P value = 0.004) and higher LPWT (2.47 ± 0.60 cm vs 2.12 ± 0.26 cm, P value = 0.006) compared to patients without OSA. On multivariate analysis, TBT, LPWT, and neck circumference were identified as independent factors associated with OSA. These variables could identify patients with severe OSA with a sensitivity of 72% and a specificity of 76%.

CONCLUSION

Patients with OSA have higher tongue base thickness and lateral pharyngeal wall thickness proportionate to the severity of the disease, independent of BMI and neck circumference. These findings suggest that sub-mental ultrasonography may be useful to identify patients with severe OSA in resource-limited settings.

Respiratory modulation of lingual muscle activity across sleep-wake states in rats

In obstructive sleep apnea (OSA) patients, inspiratory activation (IA) of lingual muscles protects the upper airway from collapse. We aimed to determine when rats' lingual muscles exhibit IA. In 5 Sprague-Dawley and 3 Wistar rats, we monitored cortical EEG and lingual, diaphragmatic and nuchal electromyograms (EMGs), and identified segments of records when lingual EMG exhibited IA. Individual segments lasted 2.4-269 s (median: 14.5 s), most (89%) occurred during slow-wave sleep (SWS), and they collectively occupied 0.3-6.1% of the total recording time. IA usually started to increase with a delay after SWS onset and ended with an arousal, or declined prior to rapid eye movement sleep. IA of lingual EMG was not accompanied by increased diaphragmatic activity or respiratory rate changes, but occurred when cortical EEG power was particularly low in a low beta-1 frequency range (12.5-16.4 Hz). A deep SWS-related activation of upper airway muscles may be an endogenous phenomenon designed to protect the upper airway against collapse.

Insights into puberty: the relationship between sleep stages and pulsatile LH secretion

CONTEXT

During the pubertal transition, LH secretion initially increases only during sleep; however, its relationship to sleep stage is unknown.

OBJECTIVES

Our objective was to determine whether the initiation of LH pulses is related to a specific sleep stage in pubertal children.

DESIGN AND SETTING

Frequent blood sampling and polysomnographic studies were performed in a Clinical Research Center.

SUBJECTS

Fourteen studies were performed in nine healthy pubertal children, ages 9.9-15.6 yr.

INTERVENTIONS

Subjects underwent one to two overnight studies with polysomnography and blood sampling for LH at 10-min intervals.

RESULTS

Alignment of polysomnographic records and LH pulses demonstrated that LH pulses (n = 58) occurred most frequently during slow-wave sleep (SWS) (1.1 pulse/h, n = 30) compared with all other sleep stages or periods of wake after sleep onset (P < 0.001). There was also a significant increase in the amount of SWS in the 15 min preceding and the 5 min following each pulse compared with the amount of SWS seen across the study night (P < 0.01).

CONCLUSIONS

During puberty, the majority of LH pulses that occur after sleep onset are preceded by SWS, suggesting that SWS is intimately involved in the complex control of pubertal onset. These studies raise concerns about the potential hormonal repercussions of the increasing prevalence of sleep disturbances in adolescents.

The management of surgical patients with obstructive sleep apnea

Obstructive sleep apnea (OSA) is a leading public health problem in both developed and developing nations. However, awareness regarding diagnostic options, management, and consequences of untreated OSA remains inadequate in the perioperative period. Adverse surgical outcomes appear to be more frequent in OSA patients. Immediate postoperative complications may be partially attributed to the negative effects of sedative, analgesic, and anesthetic agents that can worsen OSA by decreasing pharyngeal tone and the arousal responses to hypoxia, hypercarbia, and obstruction. Rebound rapid eye movement sleep after anesthesia and the use of opioids may contribute to adverse events in the postoperative period. Even though data to guide clinicians in the perioperative period is scarce, heightened awareness is recommended.

Anatomy and physiology of the upper airway

The nose is the major portal of air exchange between the internal and external environment. The nose participates in the vital functions of conditioning inspired air toward a temperature of 37°C and 100% relative humidity, providing local defense and filtering inhaled particulate matter and gases. It also functions in olfaction, which provides both a defense and pleasure for the individual. Understanding normal physiology provides the basis for recognizing abnormalities.

Diagnostic imaging and sleep medicine

Obstructive sleep apnea syndrome (OSAS) is a relatively common disorder characterized by recurrent episodes of upper airway collapse and obstruction during sleep. It results in apneic events (or in the case of partial obstruction, hypopneic events) that lead to loud snoring, hypoxia, and arousals that interrupt the normal sleep cycle. Typically, these nocturnal arousals cause patients to complain of excessive daytime sleepiness, which may interfere with routine daily activities. More importantly, when moderate to severe, OSAS can lead to a wide variety of medical complications, some of which can result in severe consequences or even death.

Diagnostic Studies in Obstructive Sleep Apnea

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

A neurotoxinological approach to the treatment of obstructive sleep apnoea

Current treatment approaches to the problem of obstructive sleep apnoea (OSA) have limitations. Specifically, invasive anatomical-based surgery and dental appliances typically do not alleviate obstruction at an acceptable rate, and compliance to continuous positive airway pressure (CPAP) devices is frequently suboptimal. Neurotoxinological treatment approaches are widespread in the field of medicine, but as yet have not been evaluated as a treatment for sleep-disordered breathing. In this review, it is argued that despite widespread recognition of the loss of upper airway (UA) muscular tone and/or reflexes in the expression of OSA, most treatment interventions to date have focused on anatomical principles alone. Several hypothesised neurotoxinological interventions aimed at either enhancing UA neuromuscular tone and/or reflexes are proposed, and some preliminary data is presented. Although in its early infancy, with considerable toxicity studies in animals yet to be done, a neurotoxinological approach to the problem of OSA holds promise as a future treatment, with the potential for both high effectiveness and patient compliance.

Design of surface electrode array for electromyography in the genioglossus muscle

The patency of the upper airway is dependent on the sustained activity of upper airway muscles, in particular the genioglossus (GG) muscles which act to protrude the tongue. Obstructive sleep apnea syndrome (OSAS) is a common and serious disorder in which this mechanism fails, resulting in frequent collapse of the airway during sleep. The properties of the upper airway muscles are therefore of interest in both normal and OSAS subjects, so that their role in the pathogenesis of OSAS can be better understood. Electromyography (EMG) is an important tool for assessing muscle activity and has been used in many GG studies. We have designed a new appliance incorporating a surface electrode array for GG EMG recording. The electrode configuration enables estimation of muscle fibre conduction velocity (CV), an important parameter for monitoring muscle fatigue, which has not been studied before in the GG. The appliance is also designed to provide accurate and repeatable placement of electrodes. Preliminary results presented demonstrate the performance of our appliance, which will now be used to measure GG CV in a range of fatiguing conditions.

Acute and chronic responses of the upper airway to inspiratory loading in healthy awake humans: an MRI study

We assessed upper airway responses to acute and chronic inspiratory loading. In Experiment I, 11 healthy subjects underwent T(2)-weighted magnetic resonance imaging (MRI) of upper airway dilator muscles (genioglossus and geniohyoid) before and up to 10 min after a single bout of pressure threshold inspiratory muscle training (IMT) at 60% maximal inspiratory mouth pressure (MIP). T(2) values for genioglossus and geniohyoid were increased versus control (p<0.001), suggesting that these airway dilator muscles are activated in response to acute IMT. In Experiment II, nine subjects underwent 2D-Flash sequence MRI of the upper airway during quiet breathing and while performing single inspirations against resistive loads (10%, 30% and 50% MIP); this procedure was repeated after 6 weeks of IMT. Lateral narrowing of the upper airway occurred at all loads, whilst anteroposterior narrowing occurred at the level of the laryngopharynx at loads > or =30% MIP. Changes in upper airway morphology and narrowing after IMT were undetectable using MRI.

Measurement of pharyngeal cross-sectional area by finite element analysis

A noninvasive measurement of pharyngeal cross-sectional area (CSA) during sleep would be advantageous for research studies. We hypothesized that CSA could be calculated from the measured pharyngeal pressure and flow by finite element analysis (FEA). The retropalatal airway was visualized by using a fiber-optic scope to obtain the measured CSA (mCSA). Flow was measured with a pneumotachometer, and pharyngeal pressure was measured with a pressure catheter at the palatal rim. FEA was performed as follows: by using a three-dimensional image of the upper airway, a mesh of finite elements was created. Specialized software was used to allow the simultaneous calculation of velocity and area for each element by using the measured pressure and flow. In the development phase, 677 simultaneous measurements of CSA, pressure, and flow from one subject during non-rapid eye movement (NREM) and rapid eye movement (REM) sleep were entered into the software to determine a series of equations, based on the continuity and momentum equations, that could calculate the CSA (cCSA). In the validation phase, the final equations were used to calculate the CSA from 1,767 simultaneous measurements of pressure and flow obtained during wakefulness, NREM, and REM sleep from 14 subjects. In both phases, mCSA and cCSA were compared by Bland-Altman analysis. For development breaths, the mean difference between mCSA and cCSA was 0.0 mm2 (95% CI, −0.1, 0.1 mm2). For NREM validation breaths, the mean difference between mCSA and cCSA was 1.1 mm2 (95% CI 1.3, 1.5 mm2). Pharyngeal CSA can be accurately calculated from measured pharyngeal pressure and flow by FEA.

Obstructive sleep apnea and ageing

Upper airway dilator muscles are important in the pathogenesis of obstructive sleep apnea syndrome (OSAS). The present study compares changes of tissue properties between the soft palate and tongue in different age groups of apnea patients and healthy subjects. Materials and methods: OSAS patients diagnosed by polysomnography (15 patients - aged 30-70 years; 10 patients - aged 18-29 years) and healthy volunteers (10 subjects - aged 30-70 years; 10 patients - aged 18-29 years) participated in the study. Computerized endopharyngeal myotonometry was used to measure the biomechanical properties - stiffness and elasticity of the soft palate [M. Veldi, V. Vasar, A. Vain, T. Hion, M. Kull, Computerized endopharyngeal myotonometry (CEM): a new method to evaluate the tissue tone of the soft palate in patients with obstructive sleep apnea syndrome, J. Sleep Res. 9 (2000) 279-284; M. Veldi, V. Vasar, T. Hion, M. Kull, A. Vain, Ageing, soft-palate tone and sleep-related breathing disorders, Clin. Physiol. 21 (2001) 358-364] and lingual tissues [M. Veldi, V. Vasar, T. Hion, A. Vain, M. Kull, Myotonometry demonstrates changes of lingual musculature in obstructive sleep apnea, Eur. Arch. Otorhinolaryngol. 259 (2002) 108-112; M. Veldi, V. Vasar, T. Hion, A. Vain, M. Kull, Myotonometry demonstrates changes of soft palate and genioglossal muscle in obstructive sleep apnea, Sleep Med. 4 (Suppl. 1) (2003) S49] during wakefulness. Results: We did not find any statistical differences in tissue properties between the soft palate and the tongue tissues, either stiffness or elasticity, in young non-snorers and young patients of apnea (P > 0.05). The stiffness of the soft palate of middle-aged apnea patients was increased compared with the tongue (P < 0.001). The elasticity of tongue of middle-aged patients of apnea was decreased compared with the soft palate (P < 0.001). Conclusions: The biomechanical properties of the soft palate and the tongue undergo different changes in the case of snoring and upper airway obstruction and ageing.

Molecular and physiologic basis of obstructive sleep apnea

Obstructive sleep apnea-hypopnea syndrome occurs because of various combinations of anatomic, mechanical, and neurologic anomalies that jeopardize ventilation only when normal state-dependent reductions in drive to upper airway respiratory muscles and pump muscles occur. A well thought out and carefully described infrastructure of the normal and abnormal physiology in persons with OSAHS has been developed over the past few decades, which enables the development of innovative and largely effective therapies. The most recent data complement the infrastructure with the neurochemical changes underlying the state-dependent respiratory disorder and observations that the disease process itself can impair muscles, neural inputs, and soft tissue in a manner that has the potential to worsen disease. Oxidative and nitrosative stress from the repeated oxyhemoglobin desaturations and re-oxygenations is implicated in the injury to these tissues. An improved understanding of the mechanisms through which OSAHS progresses may lead to alternative therapies and aid in the identification of persons at risk for disease progression.

The upper airway in sleep: physiology of the pharynx

The upper airway is the primary conduit for passage of air into the lungs. Its physiology has been the subject of intensive study: both passive mechanical and active neural influences contribute to its patency and collapsibility. Different models can be used to explain behavior of the upper airway, including the "balance of forces" (airway suction pressure during inspiration versus upper airway dilator tone) and the Starling resistor mechanical model. As sleep is the primary state change responsible for sleep disordered breathing (SDB) and the obstructive apnea/hypopnea syndrome (OSAHS), understanding its effects on the upper airway is critical. These include changes in upper airway muscle dilator activity and associated changes in mechanics and reflex activity of the muscles. Currently SDB is thought to result from a combination of anatomical upper airway predisposition and changes in neural activation mechanisms intrinsic to sleep. Detection of SDB is based on identifying abnormal (high resistance) breaths and events, but the clinical tools used to detect these events and an understanding of their impact on symptoms is still evolving. Outcomes research to define which events are most important, and a better understanding of how events lead to physiologic consequences of the syndrome, including excessive daytime somnolence (EDS), will allow physiologic testing to objectively differentiate between "normal" subjects and those with disease.

Evaluating the upper airway with standardized magnetic resonance imaging

OBJECTIVES/HYPOTHESIS

Magnetic resonance imaging (MRI) potentially offers various advantages in assessing the upper airway. The aims of the presented study were 1) to evaluate which anatomical parameters of upper airway soft tissue morphology (distances, areas, volumes) could be defined using MRI scans, 2) to examine the stability or variability of these parameters over time and between different investigators, and 3) to develop a standardized protocol for MRI measurements of the upper airway.

STUDY DESIGN

Prospective clinical trial.

METHODS

Twenty-four scans were performed on six healthy subjects over a period of 4 weeks. Various parameters such as tongue dimensions, volumes and spaces, posterior airway spaces, and soft palate dimensions were established, and their variation over time between different investigators and with repeated analysis was assessed.

RESULTS

All the parameters were of high stability and reproducibility. The time of day had no significant influence on the results. An abbreviated method for the evaluation of the tongue volume was developed. Four-millimeter slices with a conventional MRI scan generate pictures of high quality in a maintainable acquisition time.

CONCLUSIONS

We were able to evaluate which anatomical parameters of upper airway could be defined using MRI scans. The variability of these parameters over time and between different investigators was assessed. We developed a standardized protocol for MRI measurements of the upper airway. Standardized protocols are mandatory, and the variability of the measurements must be taken into account if results of different clinical centers must be compared or if changes after therapeutic interventions are to be investigated.

Magnetic resonance imaging of the upper airway in children with Down syndrome

As compared with control subjects, children with Down syndrome have different size and shape relationships among tissues composing the upper airway, which may predispose them to obstructive sleep apnea (OSA). We hypothesized that Down syndrome children without OSA have similar subclinical differences. We used magnetic resonance imaging to study the upper airway in 11 Down syndrome children without OSA (age, 3.2 +/- 1.4 yr) and in 14 control subjects (age, 3.3 +/- 1.1 yr). Sequential T1- and T2-weighted spin-echo axial and sagittal images were obtained. We found a smaller airway volume in subjects with Down syndrome (1.4 +/- 0.4 versus 2.3 +/- 0.8 cm(3) in controls, p < 0.005). Subjects with Down syndrome had a smaller mid- and lower face skeleton. They had a shorter mental spine-clivus distance (5.7 +/- 0.6 versus 6.2 +/- 0.4 cm, p < 0.05), hard palate length (3.2 +/- 0.4 versus 3.7 +/- 0.2 cm, p < 0.005), and mandible volume (11.5 +/- 3.7 versus 16.9 +/- 2.9 cm3, p < 0.0005). Adenoid and tonsil volume was significantly smaller in the subjects with Down syndrome. However, the tongue, soft-palate, pterygoid, and parapharyngeal fat pads were similar to those of control subjects. This study shows that Down syndrome children without OSA do not have increased adenoid or tonsillar volume; reduced upper airway size is caused by soft tissue crowding within a smaller mid- and lower face skeleton.

Epidemiology and pathogenesis of sleep-disordered breathing

Sleep-disordered breathing is common in the general population, but the observed prevalence depends on the criteria used to establish the diagnosis. Obesity is a strong risk factor, but other conditions such as allergic upper and lower airways disease may also be important. Differences in risk between the sexes and ethnic groups appear to be present even after established risk factors have been considered. The pathogenesis is likely mutifactorial with anatomic and physiologic factors of varying importance in different individuals. The natural history is uncertain, but without treatment or reduction in risk factors, some progression is likely. Ongoing epidemiologic investigations such as the Sleep Heart Health Study are beginning to provide important information on these questions.