Assessment of Sleep and Breathing in Adults with Prader-Willi Syndrome: A Case Control Series

Hypoventilation in patients with Prader-Willi syndrome across the pediatric age

OBJECTIVES

Few data on alveolar hypoventilation in Prader-Willi syndrome (PWS) are available and the respiratory follow-up of these patients is not standardized. The objectives of this study were to evaluate the prevalence of alveolar hypoventilation in children with PWS and identify potential risk factors.

STUDY DESIGN

This retrospective study included children with PWS recorded by polysomnography (PSG) with transcutaneous carbon dioxide pressure (PtcCO2) or end-tidal CO2 (ETCO2) measurements, between 2007 and 2021, in a tertiary hospital center. The primary outcome was the presence of alveolar hypoventilation defined as partial pressure of carbon dioxide (pCO2) ≥ 50 mmHg during ≥2% of total sleep time (TST) or more than five consecutive minutes.

RESULTS

Among the 57 included children (38 boys, median age 4.8 years, range 0.1-15.6, 60% treated with growth hormone [GH], 37% obese), 19 (33%) had moderate-to-severe obstructive sleep apnea syndrome (defined as obstructive apnea-hypopnea index ≥5/h) and 20 (35%) had hypoventilation. The median (range) pCO2 max was 49 mmHg (38-69). Among the children with hypoventilation, 25% were asymptomatic. Median age and GH treatment were significantly higher in children with hypoventilation compared to those without. There was no significant difference in terms of sex, BMI, obstructive or central apnea-hypopnea index between both groups.

CONCLUSION

The frequency of alveolar hypoventilation in children and adolescents with PWS is of concern and may increase with age and GH treatment. A regular screening by oximetry-capnography appears to be indicated whatever the sex, BMI, and rate of obstructive or central apneas.

Sleep and Circadian Disturbances in Children With Neurodevelopmental Disorders

Sleep problems are highly prevalent in those with neurodevelopmental disorders (NDDs). We propose this is secondary to multiple factors that directly and indirectly negatively impact sleep and circadian processes in those with NDDs, which in turn, further perturbs development, resulting in a "developmental and sleep/circadian-related encephalopathy." In this review, we discuss select NDDs with known or suspected sleep and circadian phenotypes. We also highlight important considerations when evaluating and treating sleep and circadian disorders in these populations.

Automated sleep staging in people with intellectual disabilities using heart rate and respiration variability

BACKGROUND

People with intellectual disabilities (ID) have a higher risk of sleep disorders. Polysomnography (PSG) remains the diagnostic gold standard in sleep medicine. However, PSG in people with ID can be challenging, as sensors can be burdensome and have a negative influence on sleep. Alternative methods of assessing sleep have been proposed that could potentially transfer to less obtrusive monitoring devices. The goal of this study was to investigate whether analysis of heart rate variability and respiration variability is suitable for the automatic scoring of sleep stages in sleep-disordered people with ID.

METHODS

Manually scored sleep stages in PSGs of 73 people with ID (borderline to profound) were compared with the scoring of sleep stages by the CardioRespiratory Sleep Staging (CReSS) algorithm. CReSS uses cardiac and/or respiratory input to score the different sleep stages. Performance of the algorithm was analysed using input from electrocardiogram (ECG), respiratory effort and a combination of both. Agreement was determined by means of epoch-per-epoch Cohen's kappa coefficient. The influence of demographics, comorbidities and potential manual scoring difficulties (based on comments in the PSG report) was explored.

RESULTS

The use of CReSS with combination of both ECG and respiratory effort provided the best agreement in scoring sleep and wake when compared with manually scored PSG (PSG versus ECG = kappa 0.56, PSG versus respiratory effort = kappa 0.53 and PSG versus both = kappa 0.62). Presence of epilepsy or difficulties in manually scoring sleep stages negatively influenced agreement significantly, but nevertheless, performance remained acceptable. In people with ID without epilepsy, the average kappa approximated that of the general population with sleep disorders.

CONCLUSIONS

Using analysis of heart rate and respiration variability, sleep stages can be estimated in people with ID. This could in the future lead to less obtrusive measurements of sleep using, for example, wearables, more suitable to this population.

Sleep Consequences of Prader-Willi Syndrome

PURPOSE OF REVIEW

This paper reviews how sleep is impacted in patients with Prader-Willi syndrome (PWS), focusing on sleep-related breathing disturbances and excessive daytime sleepiness (EDS).

RECENT FINDINGS

Hypothalamic dysfunction may underlie several aspects of the PWS phenotype. Central sleep apnea (CSA) can persist beyond infancy. Nocturnal hypoventilation is common and may occur without central or obstructive sleep apnea (OSA). Adenotonsillectomy, a mainstay of OSA treatment, may cause velopharyngeal insufficiency. Growth hormone (GH) is considered safe, but close surveillance for OSA remains important. Cardiac autonomic dysfunction occurs during slow wave sleep and may increase the risk of cardiovascular events. EDS and narcolepsy are also common. Modafinil and pitolisant are treatment options currently being studied. Sleep disorders are prevalent in individuals with PWS. Sleep-related breathing disorders present as CSA in infancy and later in life as OSA and hypoventilation. GH therapy has improved the clinical outcomes of patients with PWS, but close surveillance and treatment for OSA is recommended. EDS can persist even after sleep-related breathing disorders are treated, and some individuals may even develop narcolepsy. Early recognition and treatment of sleep-related disorders may prevent morbidity and result in improved survival of patients with PWS.

Body composition and obstructive sleep apnoea assessment in adult patients with Prader-Willi syndrome: a case control study

INTRODUCTION

In Prader-Willi syndrome (PWS) adult patients, sleep-breathing disorders, especially obstructive sleep apnoea syndrome (OSAS), are very common, whose missed or delayed diagnosis can contribute to further increase cardiovascular morbidity and mortality.

PURPOSE

The aim of this cross-sectional study was to evaluate differences in sleep-breathing parameters obtained by overnight cardiorespiratory polygraphy in 13 adult PWS patients and 13 individuals with non-syndromic obesity as controls matched by age, sex, and BMI.

METHODS

In all subjects' anthropometric parameters, body composition using bioimpedance analysis and overnight cardiorespiratory monitoring parameters were obtained.

RESULTS

Ten (76.9%) PWS patients were diagnosed with OSAS, most notably nine (69.2%) and one PWS (7.7%) with mild and severe OSAS, respectively. Compared with the control group, PWS patients had evidence of higher apnoea-hypopnea index (AHI) (p = 0.04) and oxyhaemoglobin desaturation index (ODI) (p = 0.009). However, no differences were found between the two groups regarding OSAS categories or diagnosis of nocturnal respiratory failure. In the PWS group, there were no significant correlations among AHI, ODI and hypoxemia index (T90) and anthropometric measurements, fat mass (FM), and FM percentage (%). Conversely, in the control group, the sleep-related respiratory indices evaluated correlated positively with BMI, waist circumference, FM and FM%.

CONCLUSIONS

This study confirmed that AHI and ODI indices were worse in PWS than in age, sex and BMI-matched controls. The lack of their significant association with the anthropometric parameters and FM supported the existence of PWS-related mechanisms in OSAS pathophysiology that are independent of visceral obesity and FM.

Diagnosis and management of sleep disorders in Prader-Willi syndrome

Clinical experience and a growing body of evidence suggest that sleep disturbances are common in people with Prader-Willi syndrome (PWS). PWS is a rare neuroendocrine disorder characterized by early hypotonia and feeding difficulties; developmental delays; endocrinopathies; and behavioral concerns, especially rigidity, anxiety, and behavioral outbursts. PWS is also characterized by decreased resting energy expenditure and transition to hyperphagia and obesity. We propose that, for many people with PWS, clinical diagnosis and management of sleep disorders is an unmet need. We present current information to suggest disordered sleep is a significant burden for individuals with PWS and often overlooked. While central and obstructive sleep apnea are more widely recognized in PWS, other sleep disorders have increasingly gained recognition, including hypersomnia, narcolepsy-like phenotypes, and insomnia. Sleep disorders can impact behavior, cognition, and quality of life and health for individuals with PWS. Our goal is to bring sleep disorders to the forefront of therapeutic intervention for patients with PWS. This paper presents a review of the literature and recommendations for clinical practice based on published research and our clinical experience as sleep specialists, geneticists, psychiatrists, pediatricians, otolaryngologists, and pulmonologists with extensive experience with this patient population. We recommend that management of sleep be considered an integral part of successful medical management of PWS. Further research concerning sleep problems in PWS is urgently needed to develop best practices and work toward a consensus statement for medical management to meet the needs of people with PWS.

CITATION

Duis J, Pullen LC, Picone M, et al. Diagnosis and management of sleep disorders in Prader-Willi syndrome. J Clin Sleep Med. 2022;18(6):1687-1696.

Sleep Disorders in Adults with Prader–Willi Syndrome: Review of the Literature and Clinical Recommendations Based on the Experience of the French Reference Centre

Prader–Willi syndrome (PWS) is a rare, genetic, multisymptomatic, neurodevelopmental disease commonly associated with sleep alterations, including sleep-disordered breathing and central disorders of hypersomnolence. Excessive daytime sleepiness represents the main manifestation that should be addressed by eliciting the detrimental effects on quality of life and neurocognitive function from the patients’ caregivers. Patients with PWS have impaired ventilatory control and altered pulmonary mechanics caused by hypotonia, respiratory muscle weakness, scoliosis and obesity. Consequently, respiratory abnormalities are frequent and, in most cases, severe, particularly during sleep. Adults with PWS frequently suffer from sleep apnoea syndrome, sleep hypoxemia and sleep hypoventilation. When excessive daytime sleepiness persists after adequate control of sleep-disordered breathing, a sleep study on ventilatory treatment, followed by an objective measurement of excessive daytime sleepiness, is recommended. These tests frequently identify central disorders of hypersomnolence, including narcolepsy, central hypersomnia or a borderline hypersomnolent phenotype. The use of wake-enhancing drugs (modafinil, pitolisant) is discussed in multidisciplinary expert centres for these kinds of cases to ensure the right balance between the benefits on quality of life and the risk of psychological and cardiovascular side effects.

The consequences of hyperphagia in people with Prader-Willi Syndrome: A systematic review of studies of morbidity and mortality

Prader-Willi Syndrome (PWS) is a multi-system genetically determined neurodevelopmental disorder and the commonest cause of syndromal obesity. The development of hyperphagia in early childhood is part of the phenotype arising as a result of an impaired neural response to food intake and the inability to regulate food intake in line with energy needs. Severe obesity develops if access to food is not controlled. In this review we evaluate the evidence for increased morbidity and mortality in PWS in order to establish the extent to which it is directly related to the obesity; a consequence of the eating behaviour itself independent of obesity; or associated with other characteristics of the syndrome. Medline, Cochrane, PsychINFO, CINAHL, Web of Science and Scopus databases were used to systematically identify published material on PWS and hyperphagia and syndrome-related morbidity and mortality. One hundred and ten key papers were selected. Data on 500 people with PWS indicated that the average age of death was 21 years and obesity was, as expected, a significant factor. However, the behaviour of hyperphagia itself, independent of obesity, was also important, associated with choking, gastric rupture, and/or respiratory illness. Other syndrome-related factors increased the risk for, and seriousness of, co-morbid illness or accidents. We conclude that improving life-expectancy largely depends on managing the immediate non-obesity and obesity-related consequences of the hyperphagia, through improved support. The development of new treatments that significantly reduce the drive to eat are likely to decrease morbidity and mortality improving quality of life and life expectancy.

Obesity Hypoventilation: Traditional Versus Nontraditional Populations

Obesity hypoventilation syndrome is the most frequent cause of chronic hypoventilation and is increasingly more common with rising obesity rates. It leads to considerable morbidity and mortality, particularly when not recognized and treated adequately. Long-term nocturnal noninvasive ventilation is the mainstay of treatment but evidence suggests that CPAP may be effective in stable patients. Specific perioperative management is required to reduce complications. Some unique syndromes associated with obesity and hypoventilation include rapid-onset obesity with hypoventilation, hypothalamic, autonomic dysregulation (ROHHAD), and Prader-Willi syndrome. Congenital central hypoventilation syndrome (early or late-onset) is a genetic disorder resulting in hypoventilation. Several acquired causes of chronic central hypoventilation also exist. A high level of clinical suspicion is required to appropriately diagnose and manage affected patients.

Obstructive sleep apnea in people with intellectual disabilities: adherence to and effect of CPAP

PURPOSE

Obstructive sleep apnea (OSA) is common in people with intellectual disabilities (ID), but in practice continuous positive airway pressure (CPAP) is often deemed unfeasible. We investigated adherence to and effect of CPAP in patients with ID and OSA.

METHODS

Patients with ID were started on CPAP using an intensive training program. Acceptable adherence was defined as use of ≥ 4 h/night during ≥ 70% of the nights. Treatment effect was measured with a patient global impression scale and customized questionnaires. Reasons for not starting CPAP, factors influencing treatment, and reasons for terminating CPAP were explored.

RESULTS

Of 39 patients with ID, 87% after 8-10 weeks and 70% at 8 months still used CPAP, of whom 74% and 77% showed acceptable adherence. Baseline apnea-hypopnea (AHI) index decreased from 41.2/h to 5.3/h after 8-10 weeks (p < 0.001), and 4.3/h after 8 months (p < 0.001). At 8-10 weeks and after 8 months, there was an improvement in the most restrictive reported complaint (both p < 0.0005), difficulty waking up (p < 0.01; p < 0.0005), handling behavior (p < 0.03; p < 0.02), presence of irritability (p < 0.01), and sleepiness (p < 0.05). The expectation that CPAP would not be tolerated was the main reason for not starting. CPAP use in the first 2 weeks predicted adherence at 8-10 weeks and 8 months (r = 0.51, p < 0.01; r = 0.69, p < 0.01). Of 13 patients who terminated CPAP, the reasons for termination included behavioral problems, comorbid insomnia, anxiety, discomfort, or other side effects.

CONCLUSIONS

With adequate guidance, CPAP is both feasible and effective in people with ID and OSA.

Baby food and bedtime: Evidence for opposite phenotypes from different genetic and epigenetic alterations in Prader-Willi and Angelman syndromes

Prader–Willi and Angelman syndromes are often referred to as a sister pair of neurodevelopmental disorders, resulting from different genetic and epigenetic alterations to the same chromosomal region, 15q11-q13. Some of the primary phenotypes of the two syndromes have been suggested to be opposite to one another, but this hypothesis has yet to be tested comprehensively, and it remains unclear how opposite effects could be produced by changes to different genes in one syndrome compared to the other. We evaluated the evidence for opposite effects on sleep and eating phenotypes in Prader–Willi syndrome and Angelman syndrome, and developed physiological–genetic models that represent hypothesized causes of these differences. Sleep latency shows opposite deviations from controls in Prader–Willi and Angelman syndromes, with shorter latency in Prader–Willi syndrome by meta-analysis and longer latency in Angelman syndrome from previous studies. These differences can be accounted for by the effects of variable gene dosages of UBE3A and MAGEL2, interacting with clock genes, and leading to acceleration (in Prader–Willi syndrome) or deceleration (in Angelman syndrome) of circadian rhythms. Prader–Willi and Angelman syndromes also show evidence of opposite alterations in hyperphagic food selectivity, with more paternally biased subtypes of Angelman syndrome apparently involving increased preference for complementary foods (“baby foods”); hedonic reward from eating may also be increased in Angelman syndrome and decreased in Prader–Willi syndrome. These differences can be explained in part under a model whereby hyperphagia and food selectivity are mediated by the effects of the genes SNORD-116, UBE3A and MAGEL2, with outcomes depending upon the genotypic cause of Angelman syndrome. The diametric variation observed in sleep and eating phenotypes in Prader–Willi and Angelman syndromes is consistent with predictions from the kinship theory of imprinting, reflecting extremes of higher resource demand in Angelman syndrome and lower demand in Prader–Willi syndrome, with a special emphasis on social–attentional demands and attachment associated with bedtime, and feeding demands associated with mother-provided complementary foods compared to offspring-foraged family-type foods.

Gastro-oesophageal reflux - an important causative factor of severe tooth wear in Prader-Willi syndrome?

BACKGROUND

Prader-Willi syndrome (PWS) is the most common genetic human obesity syndrome and is characterized by hypotonia, endocrine disturbances, hyperphagia, obesity and mild mental retardation. Oral abnormalities, such as decreased salivary flow rates and extreme tooth wear, have also been described. Studies have shown a significant increase in reflux symptoms in individuals with obstuctive sleep apnoea syndrome and increased BMI, both of which are typical findings in PWS. Gastro-oesophageal reflux disease (GORD) has been identified in some individuals with PWS and is a significant intrinsic factor in dental tooth wear. The aim of this study was therefore to estimate the prevalence of GORD in adults and children and to evaluate a possible correlation between GORD and tooth wear in adults with PWS. They were all registered at the TAKO-centre.

RESULTS

Twenty-nine individuals, 17 adults with a mean age of 32.6 years (range 18-48) and 12 children with a mean age of 8.8 years (range 3-17), agreed to undergo 24-hour oesophageal pH monitoring, and 90% of those enrolled managed to complete the examination. Four children and eleven adults were diagnosed with pathological gastro-oesophageal reflux, which is defined as acid exposure (pH less than 4) more than 3.6 or 4.3 percent of the time, respectively. Manometry performed in the adult group showed a pathologically high lower oesophageal sphincter pressure in four of the five individuals who had normal oesophageal pH values (pH under 4 less than 4.3% of the time). The two groups (reflux and non-reflux) were well balanced according to BMI, genotype, tooth grinding and hyposalivation. However, twice as many individuals in the reflux group as in the non-reflux group reported high consumption of acidic foods and drinks. Increased tooth wear was significantly correlated with GORD in the two groups (reflux n=6 and non-reflux n=6).

CONCLUSIONS

The prevalence of gastro-oesophageal reflux is high in individuals with PWS. Tooth wear was strongly associated with GORD and acidic drinks, and both may be important aetiological factors underlying the extreme tooth wear in this group. Our data suggest a need for routine screening for GORD and dental wear in young individuals with Prader-Willi syndrome.

Effectiveness of Adenotonsillectomy and Risk of Velopharyngeal Insufficiency in Children With Prader-Willi Syndrome

Objectives:

(1) Review effectiveness of adenotonsillectomy (T&A) for obstructive sleep apnea (OSA) in children with Prader-Willi syndrome (PW). (2) Examine the incidence of velopharyngeal insufficiency (VPI) after T&A in this population. (3) Compare outcomes of T&A in PW and Trisomy 21 (T21) patients.

Methods:

Outcomes after T&A in a PW cohort were retrospectively reviewed and compared to those in patients with T21.

Results:

The study cohort included 22 PW patients. They were compared to 47 T21 patients who also underwent T&A. Eighteen percent (N = 4) of the PW patients had postoperative VPI requiring a corrective procedure, while there were no patients within the T21 cohort who had identified VPI ( P < .05). In those patients that had a postoperative polysomnogram, the mean decrease in obstructive apnea-hypopnea index (OAHI) of the PW and T21 patients measured 8.4 and 4.7 points, respectively ( P = .3).

Conclusions:

This study demonstrated a higher rate of VPI after T&A in PW children as compared to another at-risk cohort, T21 patients. While the OAHI decreased after T&A in both groups, a significant number of children with PW or T21 had persistent OSA. Further investigation into the optimal management of OSA, while preventing treatment complications such as VPI, is needed for children with these high-risk conditions

Diagnosis and treatment of GH deficiency in Prader-Willi syndrome

Prader-Willi syndrome (PWS) results from under-expression of the paternally-derived chromosomal region 15q11-13. Growth failure is a recognized feature of PWS, and both quantitative and qualitative defects of the GH/IGF-I axis revealing GH deficiency (GHD) have been demonstrated in most children with PWS. In PWS adults, criteria for GHD are biochemically fulfilled in 8-38% of the studied cohorts. Published data support benefits of early institution of GH therapy (GHT) in PWS children, with positive effects on statural growth, body composition, metabolic homeostasis, and neurocognitive function. Like in pediatric PWS, GHT also yields beneficial effects on lean and body fat, exercise capacity, and quality of life of PWS adults. Although GHT has been generally administered safely in PWS children and adults, careful surveillance of risks is mandatory during prolonged GH replacement for all PWS individuals.

Disorders of Sleep and Ventilatory Control in Prader-Willi Syndrome

Prader-Willi syndrome (PWS) is an imprinted genetic disorder conferred by loss of paternal gene expression from chromosome 15q11.2-q13. Individuals with PWS have impairments in ventilatory control and are predisposed toward sleep disordered breathing due to a combination of characteristic craniofacial features, obesity, hypotonia, and hypothalamic dysfunction. Children with PWS progress from failure to thrive during infancy to hyperphagia and morbid obesity during later childhood and onward. Similarly, the phenotype of sleep disordered breathing in PWS patients also evolves over time from predominantly central sleep apnea in infants to obstructive sleep apnea (OSA) in older children. Behavioral difficulties are common and may make establishing effective therapy with continuous positive airway pressure (CPAP) more challenging when OSA persists after adenotonsillectomy. Excessive daytime sleepiness (EDS) is also common in patients with PWS and may continue after OSA is effectively treated. We describe here the characteristic ventilatory control deficits, sleep disordered breathing, and excessive daytime sleepiness seen in individuals with PWS. We review respiratory issues that may contribute to sudden death events in PWS patients during sleep and wakefulness. We also discuss therapeutic options for treating sleep disordered breathing including adenotonsillectomy, weight loss, and CPAP. Lastly, we discuss the benefits and safety considerations related to growth hormone therapy.

Weight control and behavior rehabilitation in a patient suffering from Prader Willi syndrome

BACKGROUND

This study reports a case of Prader Willi syndrome (PWS), a genomic imprinting disease related to chromosome regions 15q11.2-q13 15, which includes hypothalamic dysfunction leading to hyperphagia, obesity, shortness, sleep abnormalities. Our case is extremely severe, in comparison to other PWS cases described in literature, due to the association with severe emotional and psychiatric symptoms: oppositional behaviour, rigidity of thought, skin picking and pathological hoarding.

CASE PRESENTATION

We described the case of a Caucasian male patient suffering from PWS, treated in outpatient care by local Mental Health Centre and supported by Social Service, who was admitted to a residential rehabilitative facility. After a 2-year follow-up, the patient showed a global improvement in symptoms and functioning, as registered by the rating scales administered. At the end of observation period, we also reported an important improvement in weight control, reducing the risk of obesity and related diseases, therefore improving the prognosis of life.

CONCLUSION

This case highlights the need for long-term, individualized and multi-professional treatment in patients suffering from a complex genetic syndrome with both organic and psychological alterations, for which medical care setting and pharmacological treatments are not sufficient. Clinical observation of this case leads us to compare PWS to drug addiction and indirectly endorse the neurophysiological hypothesis that food and drugs stimulate the same brain circuits in the limbic system.

Sleep disordered breathing in patients with Prader-Willi syndrome: A multicenter study

OBJECTIVES

Sleep disordered breathing (SDB) is common in patients with Prader-Willi syndrome (PWS) and systematic screening is recommended, especially before growth hormone treatment. The aim of the study was to describe the baseline SDB and therapeutic interventions in a large cohort of patients.

STUDY DESIGN

Retrospective study.

SUBJECT SELECTION

Eighty-eight patients with PWS, median [interquartile range] age of 5.1 [1.0-14.5] years old (range 0.3-44.3), who were followed in three centers (France, Italy).

METHODOLOGY

Anthropometrics, polygraphy (PG), and gas exchange data were analyzed.

RESULTS

Median body mass index (BMI) was 20 [16-34] kg/m(2), BMI z-score for patients aged 2-20 years old was 2.1 [1.2-2.8] SD, mixed-obstructive apnea-hypopnea index (MOAHI) 1.8 [0.6-5.0] events/hr, and central apnea index (CAI) 0.1 [0.0-0.6] events/hr. Minimum pulse oximetry (SpO2) was 88 [84-91]%, percentage of time with SpO2 <90% 0.1 [0.0-1.0]%, and oxygen desaturation index 2 [1-4]/hr. An apnea-hypopnea index (AHI) ≥ 1.5 and ≥ 5 events/hr was observed in 53% of children and 41% of adults, respectively. No correlations were observed between MOAHI and anthropometrics data (age, BMI, BMI z-score), while MOAHI significantly correlated with SpO2 indexes. Age and BMI only weakly correlated with SpO2 indexes. Growth hormone could be initiated in 48 patients. Regarding post-PG therapy, 9 patients had upper airway surgery, and noninvasive CPAP/bilevel ventilation was started in 16 patients.

CONCLUSIONS

Patients with PWS exhibit a high prevalence of SDB. The lack of association between obesity and SDB leads to hypothesize that hypotonia and/or facial dysmorphic features may play a major role in the occurrence of SDB.

[Obstructive sleep apnea-hypopnea syndrome in children: beyond adenotonsillar hypertrophy]

The prevalence of obstructive sleep apnea-hypopnea syndrome in the general childhood population is 1-2% and the most common cause is adenotonsillar hypertrophy. However, beyond adenotonsillar hypertrophy, there are other highly prevalent causes of this syndrome in children. The causes are often multifactorial and include muscular hypotonia, dentofacial abnormalities, soft tissue hypertrophy of the airway, and neurological disorders). Collaboration between different specialties involved in the care of these children is essential, given the wide variability of conditions and how frequently different factors are involved in their genesis, as well as the different treatments to be applied. We carried out a wide literature review of other causes of obstructive sleep apnea-hypopnea syndrome in children, beyond adenotonsillar hypertrophy. We organised the prevalence of this syndrome in each pathology and the reasons that cause it, as well as their interactions and management, in a consistent manner.

Genetic diseases: congenital central hypoventilation, Rett, and Prader-Willi syndromes

The present review summarizes current knowledge on three rare genetic disorders of respiratory control, congenital central hypoventilation syndrome (CCHS), Rett syndrome (RTT), and Prader-Willi syndrome (PWS). CCHS is characterized by lack of ventilatory chemosensitivity caused by PHOX2B gene abnormalities consisting mainly of alanine expansions. RTT is associated with episodes of tachypneic and irregular breathing intermixed with breathholds and apneas and is caused by mutations in the X-linked MECP2 gene encoding methyl-CpG-binding protein. PWS manifests as sleep-disordered breathing with apneas and episodes of hypoventilation and is caused by the loss of a group of paternally inherited genes on chromosome 15. CCHS is the most specific disorder of respiratory control, whereas the breathing disorders in RTT and PWS are components of a more general developmental disorder. The main clinical features of these three disorders are reviewed with special emphasis on the associated brain abnormalities. In all three syndromes, disease-causing genetic defects have been identified, allowing the development of genetically engineered mouse models. New directions for future therapies based on these models or, in some cases, on clinical experience are delineated. Studies of CCHS, RTT, and PWS extend our knowledge of the molecular and cellular aspects of respiratory rhythm generation and suggest possible pharmacological approaches to respiratory control disorders. This knowledge is relevant for the clinical management of many respiratory disorders that are far more prevalent than the rare diseases discussed here.

Severe tooth wear in Prader-Willi syndrome. A case-control study

BACKGROUND

Prader-Willi syndrome (PWS) is a rare complex multsystemic genetic disorder characterized by severe neonatal hypotonia, endocrine disturbances, hyperphagia and obesity, mild mental retardation, learning disabilities, facial dysmorphology and oral abnormalities. The purpose of the present study was to explore the prevalence of tooth wear and possible risk factors in individuals with Prader-Willi syndrome.

METHODS

Forty-nine individuals (6-40 years) with PWS and an age- and sex-matched control group were included. Tooth wear was evaluated from dental casts and intraoral photographs and rated by four examiners using the Visual Erosion Dental Examination (VEDE) scoring system and the individual tooth wear index IA. In accordance with the VEDE scoring system, tooth wear was also evaluated clinically. Whole saliva was collected.

RESULTS

Mean VEDE score was 1.70 ± 1.44 in the PWS group and 0.46 ± 0.36 in the control group (p < 0.001). Median IA was 7.50 (2.60-30.70) in the PWS group and 2.60 (0.90-4.70) among controls (p < 0.001). In the PWS group tooth wear correlated significantly with age (VEDE; r = 0.79, p < 0.001, IA; r = 0.82, p < 0.001) and saliva secretion (VEDE; r = 0.46, p = 0.001, IA; r = 0.43, p = 0.002). Tooth grinding was also associated with tooth wear in the PWS group, as indicated by the mean VEDE 2.67 ± 1.62 in grinders and 1.14 ± 0.97 in non-grinders (p = 0.001) and median IA values 25.70 (5.48-68.55) in grinders and 5.70 (1.60-9.10) in non-grinders (p = 0.003). Multivariate linear regression analysis was performed with tooth wear as the dependent variable and PWS (yes/no), age, tooth grinding and saliva secretion as independent variables. PWS (yes/no), age and tooth grinding retained a significant association with tooth wear, VEDE (p < 0.001) and log IA (p < 0.001). The only factor significantly associated with tooth wear in the control group was age.

CONCLUSIONS

Our study provides evidence that tooth wear, in terms of both erosion and attrition, is a severe problem in Prader-Willi syndrome. There is therefore considerable need for prosthodontic rehabilitation in young adults with PWS.

Co-morbidity of complex genetic disorders and hypersomnias of central origin: lessons from the underlying neurobiology of wake and sleep

Appropriate wake and sleep cycles are important to physical well-being, and are modulated by neuronal networks in the brain. A variety of medical conditions can disrupt sleep or cause excessive daytime sleepiness. Clinical diagnostic classification schemes have historically lumped genetic disorders together into a category that considers the sleep dysfunction to be secondary to a medical condition. The unique nature of sleep endophenotypes that occur more frequently in particular genetic disorders has been underappreciated. Increased understanding of the pathophysiology of wake/sleep dysfunction in rare genetic disorders could inform studies of the neurological mechanisms that underlie more common forms of wake and sleep dysfunction. In this review, we highlight genetic developmental disorders in which sleep endophenotypes have been described, and then consider genetic neurodegenerative disorders with sleep characteristics that set them apart from the disruptions to sleep that are typically associated with aging and dementia.

A review of genetic association studies of obstructive sleep apnea: field synopsis and meta-analysis

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is a multifactorial disorder with a heritable component. We performed a field synopsis of genetic association studies of OSA to synthesize the available evidence.

DESIGN

Systematic literature review and meta-analysis.

SETTING

Genetic association studies.

PATIENTS OR PARTICIPANTS

We searched multiple databases to identify studies of non-HLA genetic associations in OSA. We assessed the power of the primary studies to identify odds ratios (OR) in a plausible range and performed random effects meta-analyses for genetic associations investigated by at least 3 studies. We explored the consistency of the findings between population- and family-based studies.

INTERVENTIONS

None

MEASUREMENTS AND RESULTS

We identified a total of 31 population-based case-control studies reporting allele-frequency data on 48 polymorphism-OSA associations. Sample sizes were generally small (median number of cases = 102, 25th-75th percentile = 55-151; median number of controls = 79, 25th-75th percentile = 58-137), and genetic effects were moderate in magnitude (median OR = 1.15, 25th-75th percentile = 0.89-1.40). Studies were severely underpowered to detect ORs as high as 2; only eight comparisons (in 6 studies) had more than 90% power to identify a genetic effect of that magnitude at its current sample size. Four genetic associations had been investigated in ≥ 3 studies: TNFA (-308 A/G) rs1800629, ACE I/D, APOE ε2, and APOE ε4. Only TNFA rs1800629 was significantly associated with OSA under an allele frequency model (3 studies, odds ratio [OR] = 1.82, 95% confidence interval [CI] 1.26-2.61). These results were robust to alternative genetic models; findings for APOE variants were consistent with those from family-based studies.

CONCLUSIONS

The developing field of OSA genetics is currently dominated by small and underpowered investigations. Promising findings regarding TNFA rs1800629 need to be replicated in larger studies using more comprehensive genotyping methods.

Prader-Willi syndrome and autism spectrum disorders: an evolving story

Prader-Willi syndrome (PWS) is well-known for its genetic and phenotypic complexities. Caused by a lack of paternally derived imprinted material on chromosome 15q11-q13, individuals with PWS have mild to moderate intellectual disabilities, repetitive and compulsive behaviors, skin picking, tantrums, irritability, hyperphagia, and increased risks of obesity. Many individuals also have co-occurring autism spectrum disorders (ASDs), psychosis, and mood disorders. Although the PWS 15q11-q13 region confers risks for autism, relatively few studies have assessed autism symptoms in PWS or directly compared social, behavioral, and cognitive functioning across groups with autism or PWS. This article identifies areas of phenotypic overlap and difference between PWS and ASD in core autism symptoms and in such comorbidities as psychiatric disorders, and dysregulated sleep and eating. Though future studies are needed, PWS provides a promising alternative lens into specific symptoms and comorbidities of autism.

Sleep disturbances and behavioural problems in adults with Prader-Willi syndrome

BACKGROUND

Individuals with Prader-Willi syndrome (PWS) are at risk of sleep disturbances, such as excessive daytime sleepiness (EDS) and sleep apnoea, and behavioural problems. Sleep disturbances and their relationship with other variables had not been researched extensively in adults with PWS.

METHOD

Sleep disturbances and behavioural problems were investigated in adults with genetically confirmed PWS using standardised questionnaires. Results of adults with paternal deletion (n=45) were compared with those of adults with maternal uniparental disomy (n=33).

RESULTS

Eleven adults with PWS (i.e. 15%) had a current sleep problem, mostly night waking problems. Twenty-six adults with PWS (i.e. 33%) suffered from severe EDS. No differences in prevalence of sleep disturbances between genetic subtypes were found. Seventeen adults with deletion (i.e. 38%) and 17 adults with maternal uniparental disomy (i.e. 52%) had behavioural problems. No significant relationships were found between sleep disturbances and behavioural problems.

CONCLUSIONS

In adults with PWS, EDS is the most common type of sleep disturbance. Men and individuals with relative high body mass index are at increased risk for EDS. More research, aimed at developing a suitable screening instrument for sleep apnoea in adults with PWS, is necessary. Clinical implications of the findings are discussed.

Scoliosis in patients with Prader Willi Syndrome - comparisons of conservative and surgical treatment

In children with Prader Willi syndrome (PWS), besides growth hormone (GH) therapy, control of the food environment and regular exercise, surgical treatment of scoliosis deformities seems the treatment of choice, even though the risks of spinal surgery in this specific population is very high. Therefore the question arises as to whether the risks of spinal surgery outweigh the benefits in a condition, which bears significant risks per se. The purpose of this systematic review of the Pub Med literature was to find mid or long-term results of spinal fusion surgery in patients with PWS, and to present the conservative treatment in a case study of nine patients with this condition.

METHODS

Types of studies included; all kinds of studies; retrospective and prospective ones, which reported upon the outcome of scoliosis surgery in patients with PWS.Types of participants included: patients with scoliosis and PWS.Type of intervention: surgery.Search strategy for identification of the studies; Pub Med; limited to English language and bibliographies of all reviewed articles.Nine patients with PWS from our data-base treated conservatively have been found, being 19 years or over at the time this study has been performed. The results of conservative management are described and related to the natural history and treatment results found in the Pub Med review.

RESULTS

From 2210 titles displayed in the Pub Med database with the key word being "Prader Willi syndrome", 5 different papers were displayed at the date of the search containing some information on the outcome of surgery and none appeared to contain a mid or long-term follow-up. The PWS patients treated conservatively from our series all stayed below 70 degrees and some of which improved.

DISCUSSION

If the curve of scoliosis patients with PWS can be kept within certain limits (usually below 70 degrees) conservatively, this treatment seems to have fewer complications than surgical treatments. The results of our retrospective study of nine patients demonstrate that scoliosis in this entity plays only a minor role and surgery is unnecessary when high quality conservative management exists.

CONCLUSION

There is lack of the long follow-up studies in post-surgical cases in patients with PWS and scoliosis. The rate of complications of spinal fusion in patients with PWS and scoliosis is very high and the death rates have been found to be higher than in patients with Adolescent Idiopathic Scoliosis (AIS). The long-term side-effects of the intervention are detrimental, so that the risk-benefit ratio favours the conservative approaches over spinal fusion surgery.

Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a highly variable genetic disorder affecting multiple body systems whose most consistent major manifestations include hypotonia with poor suck and poor weight gain in infancy; mild mental retardation, hypogonadism, growth hormone insufficiency causing short stature for the family, early childhood-onset hyperphagia and obesity, characteristic appearance, and behavioral and sometimes psychiatric disturbance. Many more minor characteristics can be helpful in diagnosis and important in management. PWS is an example of a genetic condition involving genomic imprinting. It can occur by three main mechanisms, which lead to absence of expression of paternally inherited genes in the 15q11.2-q13 region: paternal microdeletion, maternal uniparental disomy, and imprinting defect.