Sleep problems in Rett syndrome

The Efficacy of Noninvasive Ventilation in Patients Affected by Rett Syndrome With Hypoventilation

BACKGROUND

Rett syndrome is a progressive neurological disorder associated to several comorbidities that contribute significantly to impair lung function. Respiratory morbidity represents a major cause of death in this population. Little is known about the benefit of noninvasive ventilation.

METHODS

We retrospectively enrolled patients with Rett syndrome who underwent a pneumological evaluation combined with a cardiorespiratory polygraphy and/or a pulse oximetry and capnography from 2012 to 2022.

RESULTS

Medical records of 11 patients with Rett syndrome, mean age 13 ± 6 years, were evaluated. Most patients presented with both epilepsy and scoliosis. Five patients showed a pathologic sleep study and/or impaired night gas exchange: mean obstructive apnea-hypopnea index was 4 ± 3 events/hour; mean and minimal SpO2 were, respectively, 93% ± 2% and 83% ± 6%, while mean and maximal transcutaneous carbon dioxide monitoring (PtcCO2) were, respectively, 51 ± 5 mm Hg and 55 ± 8 mm Hg; and mean oxygen desaturation index was 13 ± 11 events/hour. These patients started noninvasive ventilation with clinical benefit and improved gas exchange mostly in terms of PtcCO2 (mean PtcCO2 51 ± 5 mm Hg before and 46 ± 6 mm Hg after noninvasive ventilation).

CONCLUSIONS

Noninvasive ventilation is a suitable option for patients with Rett syndrome.

Management of respiratory issues in patients with Rett syndrome: Italian experts' consensus using a Delphi approach

BACKGROUND

Despite the publication of the 2020 guidelines on how to manage Rett Syndrome (RS), some fundamental topics are still open, in particular respiratory problems.

OBJECTIVE

Identification and reinforcement of current recommendations concerning the management of respiratory issues in RS patients.

MATERIALS AND METHODS

Using a Delphi approach, the leading group reviewed the literature and formulated 14 statements. A multidisciplinary panel of 29 experts were invited to score, for each statement, their agreement on a 1-5 scale. The cut-off level for consensus was 75%, obtained through multiple rounds.

RESULTS

The panel agreed that in all RS types, respiratory issues should be faced at an early stage, regardless of epilepsy onset. It is recommended to perform periodically sleep studies in all Congenital Rett Syndrome, and in selected cases with other RS types. Noninvasive ventilation should be considered in all RS subjects with sleep respiratory disorders and in those with hypotonia associated with hypercapnia. Chest physiotherapy should be performed in all RS patients with difficult management of the accumulation of respiratory secretions, using airway clearance techniques and devices (PEP-mask, AMBU bag, or cough machine), more appropriate and tolerated by the patients. The panel recommended individualized programs for the management of scoliosis, and to consider performing gastrostomy in patients at increased risk of ab ingestis pneumonia.

CONCLUSIONS

This consensus could support everyday clinical practice on respiratory issues in RS patients, complementary to existing recommendations by regulatory agencies and guidelines.

24-h continuous non-invasive multiparameter home monitoring of vitals in patients with Rett syndrome by an innovative wearable technology: evidence of an overlooked chronic fatigue status

Background

Sleep is disturbed in Rett syndrome (RTT), a rare and progressive neurodevelopmental disorder primarily affecting female patients (prevalence 7.1/100,000 female patients) linked to pathogenic variations in the X-linked methyl-CpG-binding protein 2 (MECP2) gene. Autonomic nervous system dysfunction with a predominance of the sympathetic nervous system (SNS) over the parasympathetic nervous system (PSNS) is reported in RTT, along with exercise fatigue and increased sudden death risk. The aim of the present study was to test the feasibility of a continuous 24 h non-invasive home monitoring of the biological vitals (biovitals) by an innovative wearable sensor device in pediatric and adolescent/adult RTT patients.

Methods

A total of 10 female patients (mean age 18.3 ± 9.4 years, range 4.7-35.5 years) with typical RTT and MECP2 pathogenic variations were enrolled. Clinical severity was assessed by validated scales. Heart rate (HR), respiratory rate (RR), and skin temperature (SkT) were monitored by the YouCare Wearable Medical Device (Accyourate Group SpA, L'Aquila, Italy). The average percentage of maximum HR (HRmax%) was calculated. Heart rate variability (HRV) was expressed by consolidated time-domain and frequency-domain parameters. The HR/LF (low frequency) ratio, indicating SNS activation under dynamic exercise, was calculated. Simultaneous continuous measurement of indoor air quality variables was performed and the patients' contributions to the surrounding water vapor partial pressure [PH2O (pt)] and carbon dioxide [PCO2 (pt)] were indirectly estimated.

Results

Of the 6,559.79 h of biovital recordings, 5051.03 h (77%) were valid for data interpretation. Sleep and wake hours were 9.0 ± 1.1 h and 14.9 ± 1.1 h, respectively. HRmax % [median: 71.86% (interquartile range 61.03-82%)] and HR/LF [median: 3.75 (interquartile range 3.19-5.05)] were elevated, independent from the wake-sleep cycle. The majority of HRV time- and frequency-domain parameters were significantly higher in the pediatric patients (p ≤ 0.031). The HRV HR/LF ratio was associated with phenotype severity, disease progression, clinical sleep disorder, subclinical hypoxia, and electroencephalographic observations of multifocal epileptic activity and general background slowing.

Conclusion

Our findings indicate the feasibility of a continuous 24-h non-invasive home monitoring of biovital parameters in RTT. Moreover, for the first time, HRmax% and the HR/LF ratio were identified as potential objective markers of fatigue, illness severity, and disease progression.

The sleep problems in individuals with Rett syndrome and their caregivers

LAY ABSTRACT

Sleep problems are common and impactful among individuals with Rett syndrome (RTT) and their caregivers. We examined the sleep patterns of 29 RTT patients and their primary caregivers using various assessment tools. The study found that a majority of the patients experienced sleep disturbances, with younger patients showing more sleep difficulties. Caregivers also reported poor sleep quality. The findings emphasize the need to address sleep problems in RTT management, as improving sleep quality can positively impact the well-being of individuals with RTT and their caregivers.

MECP2-related disorders while gene-based therapies are on the horizon

The emergence of new genetic tools has led to the discovery of the genetic bases of many intellectual and developmental disabilities. This creates exciting opportunities for research and treatment development, and a few genetic disorders (e.g., spinal muscular atrophy) have recently been treated with gene-based therapies. MECP2 is found on the X chromosome and regulates the transcription of thousands of genes. Loss of MECP2 gene product leads to Rett Syndrome, a disease found primarily in females, and is characterized by developmental regression, motor dysfunction, midline hand stereotypies, autonomic nervous system dysfunction, epilepsy, scoliosis, and autistic-like behavior. Duplication of MECP2 causes MECP2 Duplication Syndrome (MDS). MDS is found mostly in males and presents with developmental delay, hypotonia, autistic features, refractory epilepsy, and recurrent respiratory infections. While these two disorders share several characteristics, their differences (e.g., affected sex, age of onset, genotype/phenotype correlations) are important to distinguish in the light of gene-based therapy because they require opposite solutions. This review explores the clinical features of both disorders and highlights these important clinical differences.

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.

Melatonin in Neurodevelopmental Disorders: A Critical Literature Review

The article presents a review of the relationships between melatonin and neurodevelopmental disorders. First, the antioxidant properties of melatonin and its physiological effects are considered to understand better the role of melatonin in typical and atypical neurodevelopment. Then, several neurodevelopmental disorders occurring during infancy, such as autism spectrum disorder or neurogenetic disorders associated with autism (including Smith-Magenis syndrome, Angelman syndrome, Rett's syndrome, Tuberous sclerosis, or Williams-Beuren syndrome) and neurodevelopmental disorders occurring later in adulthood like bipolar disorder and schizophrenia, are discussed with regard to impaired melatonin production and circadian rhythms, in particular, sleep-wake rhythms. This article addresses the issue of overlapping symptoms that are commonly observed within these different mental conditions and debates the role of abnormal melatonin production and altered circadian rhythms in the pathophysiology and behavioral expression of these neurodevelopmental disorders.

An investigation of the sleep macrostructure of girls with Rett syndrome

OBJECTIVE/BACKGROUND

Methyl-CpG-binding protein 2 (MeCP2) is of utmost importance in neuronal function. We aim to characterize phenotypic traits in the sleep of individuals with Rett Syndrome (RTT, OMIM # 312750), a rare disorder predominantly caused by mutations of the MECP2 gene.

PATIENTS/METHODS

An overnight polysomnographic recording was performed. Outcomes investigated were parameters of nocturnal sleep macrostructure, and sample stratification per genetic and clinical characteristics, and six key features of clinical severity was applied.

RESULTS

The sleep of our 21 RTT female subjects with a mutant MECP2 gene, aged 8.8 ± 5.4 years, showed no significant differences within strata. However, compared to a normative dataset, we found longer duration of wake time after sleep onset and total sleep time (TST) but shorter sleep onset latency, in RTT. Regarding the proportion of sleep stages per TST, higher stage N3 (%) with lower stage N2 (%) and REM (%) were generally seen. Such abnormalities became more uniformly expressed at the severe level of clinical features, particularly for hand functioning and walking.

CONCLUSIONS

RTT girls with MECP2 mutations in our study demonstrated an increased deep sleep and reduced rapid eye movement sleep proportion, which is mostly allied with their hand dysfunction severity. Poor sleep-on/off switching in RTT since embryogenesis is possibly linked to (psycho)motor impairment in the cases with MECP2 mutations.

Feasibility of wearable devices and machine learning for sleep classification in children with Rett syndrome: A pilot study

Sleep is vital to many processes involved in the well-being and health of children; however, it is estimated that 80% of children with Rett syndrome suffer from sleep disorders. Caregiver reports and questionnaires, which are the current method of studying sleep, are prone to observer bias and missed information. Polysomnography is considered the gold standard for sleep analysis but is labor and cost-intensive and limits the frequency of data collection for sleep disorder studies. Wearable digital health technologies, such as actigraphy devices, have shown potential and feasibility as a method for sleep analysis in Rett syndrome, but have not been validated against polysomnography. Furthermore, the collected accelerometer data has limitations due to the rigidity, periodic limb movement, and involuntary muscle contractions prevalent in Rett syndrome. Heart rate and electrodermal activity, along with other physiological signals, have been linked to sleep stages and can be utilized with machine learning to provide better resistance to noise and false positives than actigraphy. This research aims to address the gap in Rett syndrome sleep analysis by comparing the performance of a machine learning model utilizing both accelerometer data and physiological data features to the gold-standard polysomnography for sleep analysis in Rett syndrome. Our analytical validation pilot study (n = 7) found that using physiological and accelerometer features, our machine learning models can differentiate between awake, non-rapid eye movement sleep, and rapid eye movement sleep in Rett syndrome children with an accuracy of 85.1% when using an individual model. Additionally, this work demonstrates that it is feasible to use digital health technologies in Rett syndrome, even at a young age, without data loss or interference from repetitive movements that are characteristic of Rett syndrome.

Sleep Respiratory Disturbances in Girls with Rett Syndrome

Individuals with Rett Syndrome (RTT), a rare neurodevelopmental disorder, present disordered breathing during wakefulness. Whilst findings on breathing during sleep are contradictory, the relation between sleep breathing and their clinical features, genetic characteristics, age, and sleep phase is rarely investigated, which is the objective of this study. Overnight polysomnography (PSG) was performed. Sleep macrostructure parameters were compared between the RTT subjects with and without sleep-disordered breathing (SDB). The association between the apnea-hypopnea index (AHI) with age at PSG was tested. Particularly for RTT subjects with SDB, the respiratory indexes in REM and NREM sleep were compared. Stratified analyses per clinical characteristics, genetic characteristics, and clinical features' severity were performed. Non-parametric statistics were applied. A sample of 11 female RTT subjects, aged 8.69 ± 5.29 years with ten confirmed with MECP2 mutations, were studied. The average AHI was 3.94 ± 1.19/h TST, of which eight (72.73%) had obstructive sleep apnea, i.e., six in 1/h TST ≤ AHI ≤ 5/h TST, and two in AHI > 5/h TST. The mean SpO₂% was 81.00 ± 35.15%. The AHI was not significantly correlated with their age at PSG (r_s = -0.15, p = 0.67). Sleep macrostructure in SDB-absent and SDB-present groups was not different. Respiratory indexes in those with obstructive sleep apnea showed no difference between REM and NREM sleep nor any of the strata. In our clinical sample, more than half of the RTT subjects with MECP2 mutations had obstructive sleep apnea in both NREM and REM sleep which was unrelated to their clinical features. Our results also indicated hypoxemia throughout nocturnal sleep in RTT. To conclude, our results suggest that disordered breathing during sleep is prevalently present in RTT as an independent clinical feature.

Children with neurodevelopmental disorders: how do they sleep?

PURPOSE OF REVIEW

In this review we summarized the available evidence on sleep disorders in children with neurodevelopmental disorders (NDDs) in particular: intellectual disability (including some genetic conditions such as Prader-Willi Syndrome, Smith-Magenis Syndrome), Autism spectrum disorder, attention-deficit/hyperactivity disorder (ADHD), Developmental Coordination Disorder, language disorders, and specific learning disorders.

RECENT FINDINGS

Children with NDDs frequently suffer from sleep disturbances, with a higher prevalence than that of the general pediatric population.

SUMMARY

These problems tend to be chronic and may cause additional cognitive and behavioral difficulties, often affecting the whole family's well-being. Sleep behaviors are also related to other important developmental skills, such as attention and listening. Investigating sleep disorders in children with NDDs is therefore crucial in clinical practice. For a systematic approach in clinical practice, we propose the use of a short and easy to remember sleep screening tool.

Sleep dysregulation in sympathetic-mediated diseases: implications for disease progression

The autonomic nervous system (ANS) plays an important role in the coordination of several physiological functions including sleep/wake process. Significant changes in ANS activity occur during wake-to-sleep transition maintaining the adequate cardiorespiratory regulation and brain activity. Since sleep is a complex homeostatic function, partly regulated by the ANS, it is not surprising that sleep disruption trigger and/or evidence symptoms of ANS impairment. Indeed, several studies suggest a bidirectional relationship between impaired ANS function (i.e. enhanced sympathetic drive), and the emergence/development of sleep disorders. Furthermore, several epidemiological studies described a strong association between sympathetic-mediated diseases and the development and maintenance of sleep disorders resulting in a vicious cycle with adverse outcomes and increased mortality risk. However, which and how the sleep/wake control and ANS circuitry becomes affected during the progression of ANS-related diseases remains poorly understood. Thus, understanding the physiological mechanisms underpinning sleep/wake-dependent sympathetic modulation could provide insights into diseases involving autonomic dysfunction. The purpose of this review is to explore potential neural mechanisms involved in both the onset/maintenance of sympathetic-mediated diseases (Rett syndrome, congenital central hypoventilation syndrome, obstructive sleep apnoea, type 2 diabetes, obesity, heart failure, hypertension, and neurodegenerative diseases) and their plausible contribution to the generation of sleep disorders in order to review evidence that may serve to establish a causal link between sleep disorders and heightened sympathetic activity.

The evolutionarily conserved miRNA-137 targets the neuropeptide hypocretin/orexin and modulates the wake to sleep ratio

The hypocretin (Hcrt, also known as orexin) neuropeptides regulate sleep and wake stability, and disturbances of Hcrt can lead to sleep disorders. MicroRNAs (miRNAs) are short noncoding RNAs that fine-tune protein expression levels, and miRNA-based therapeutics are emerging. We report a functional interaction between miRNA (miR-137) and Hcrt. We demonstrate that intracellular miR-137 levels in Hcrt neurons regulate Hcrt expression with downstream effects on wakefulness. Specifically, lowering of miR-137 levels increased wakefulness in mice. We further show that the miR-137:Hcrt interaction is conserved across mice and humans, that miR-137 also regulates sleep–wake balance in zebrafish, and that the MIR137 locus is genetically associated with sleep duration in humans. Together, our findings reveal an evolutionarily conserved sleep–wake regulatory role of miR-137.

Hypocretin (Hcrt), also known as orexin, neuropeptide signaling stabilizes sleep and wakefulness in all vertebrates. A lack of Hcrt causes the sleep disorder narcolepsy, and increased Hcrt signaling has been speculated to cause insomnia, but while the signaling pathways of Hcrt are relatively well-described, the intracellular mechanisms that regulate its expression remain unclear. Here, we tested the role of microRNAs (miRNAs) in regulating Hcrt expression. We found that miR-137, miR-637, and miR-654-5p target the human HCRT gene. miR-137 is evolutionarily conserved and also targets mouse Hcrt as does miR-665. Inhibition of miR-137 specifically in Hcrt neurons resulted in Hcrt upregulation, longer episodes of wakefulness, and significantly longer wake bouts in the first 4 h of the active phase. IL-13 stimulation upregulated endogenous miR-137, while Hcrt mRNA decreased both in vitro and in vivo. Furthermore, knockdown of miR-137 in zebrafish substantially increased wakefulness. Finally, we show that in humans, the MIR137 locus is genetically associated with sleep duration. In conclusion, these results show that an evolutionarily conserved miR-137:Hcrt interaction is involved in sleep–wake regulation.

Breathing Abnormalities During Sleep and Wakefulness in Rett Syndrome: Clinical Relevance and Paradoxical Relationship With Circulating Pro-oxidant Markers

Background

Breathing abnormalities are common in Rett syndrome (RTT), a pervasive neurodevelopmental disorder almost exclusively affecting females. RTT is linked to mutations in the methyl-CpG-binding protein 2 (MeCP2) gene. Our aim was to assess the clinical relevance of apneas during sleep-wakefulness cycle in a population with RTT and the possible impact of apneas on circulating oxidative stress markers.

Methods

Female patients with a clinical diagnosis of typical RTT (n = 66), MECP2 gene mutation, and apneas were enrolled (mean age: 12.5 years). Baseline clinical severity, arterial blood gas analysis, and red blood cell count were assessed. Breathing was monitored during the wakefulness and sleep states (average recording time: 13 ± 0.5 h) with a portable polygraphic screening device. According to prevalence of breath holdings, the population was categorized into the wakefulness apnea (WA) and sleep apnea (SA) groups, and apnea-hypopnea index (AHI) was calculated. The impact of respiratory events on oxidative stress was assessed by plasma and intra-erythrocyte non-protein-bound iron (P-NPBI and IE-NPBI, respectively), and plasma F2-isoprostane (F2-IsoP) assays.

Results

Significant prevalence of obstructive apneas with values of AHI > 15 was present in 69.7% of the population with RTT. The group with SA showed significantly increased AHI values > 15 (p = 0.0032), total breath holding episodes (p = 0.007), and average SpO2 (p = 0.0001) as well as lower nadir SpO2 (p = 0.0004) compared with the patients with WAs. The subgroups of patients with WA and SA showed no significant differences in arterial blood gas analysis variables (p > 0.089). Decreased mean cell hemoglobin (MCH) (p = 0.038) was observed in the group with WAs. P-NPBI levels were significantly higher in the group with WA than in that with SAs (p = 0.0001). Stepwise multiple linear regression models showed WA being related to nadir SpO2, average SpO2, and P-NPBI (adjusted R2 = 0.613, multiple correlation coefficient = 0.795 p < 0.0001), and P-NPBI being related to average SpO2, blood PaCO2, red blood cell mean corpuscular volume (MCV), age, and topiramate treatment (adjusted R2 = 0.551, multiple correlation coefficient = 0.765, p < 0.0001).

Conclusion

Our findings indicate that the impact of apneas in RTT is uneven according to the sleep-wakefulness cycle, and that plasma redox active iron represents a potential novel therapeutic target.

Sleep Disorders in Rett Syndrome and Rett-Related Disorders: A Narrative Review

Rett Syndrome (RTT) is a rare and severe X-linked developmental brain disorder that occurs primarily in females, with a ratio of 1:10.000. De novo mutations in the Methyl-CpG Binding protein 2 (MECP2) gene on the long arm of X chromosome are responsible for more than 95% cases of classical Rett. In the remaining cases (atypical Rett), other genes are involved such as the cyclin-dependent kinase-like 5 (CDKL5) and the forkhead box G1 (FOXG1). Duplications of the MECP2 locus cause MECP2 duplication syndrome (MDS) which concerns about 1% of male patients with intellectual disability. Sleep disorders are common in individuals with intellectual disability, while the prevalence in children is between 16 and 42%. Over 80% of individuals affected by RTT show sleep problems, with a higher prevalence in the first 7 years of life and some degree of variability in correlation to age and genotype. Abnormalities in circadian rhythm and loss of glutamate homeostasis play a key role in the development of these disorders. Sleep disorders, epilepsy, gastrointestinal problems characterize CDKL5 Deficiency Disorder (CDD). Sleep impairment is an area of overlap between RTT and MECP2 duplication syndrome along with epilepsy, regression and others. Sleep dysfunction and epilepsy are deeply linked. Sleep deprivation could be an aggravating factor of epilepsy and anti-comitial therapy could interfere in sleep structure. Epilepsy prevalence in atypical Rett syndrome with severe clinical phenotype is higher than in classical Rett syndrome. However, RTT present a significant lifetime risk of epilepsy too. Sleep disturbances impact on child's development and patients' families and the evidence for its management is still limited. The aim of this review is to analyze pathophysiology, clinical features, the impact on other comorbidities and the management of sleep disorders in Rett syndrome and Rett-related syndrome.

Literature Cases Summarized Based on Their Polysomnographic Findings in Rett Syndrome

Rett syndrome (RTT) is a severe and rare neurodevelopmental disorder affecting mostly girls. In RTT, an impaired sleep pattern is a supportive criterion for the diagnosis, yet little is known regarding the sleep structure and sleep respiratory events. Aiming to delineate sleep by aggregating RTT case (series) data from published polysomnographic studies, seventy-four RTT cases were collected from eleven studies up until 6 February 2022 (PROSPERO: CRD 42020198099). We compared the polysomnographic data within RTT stratifications and to a typically developing population. MECP2 cases demonstrated shortened total sleep time (TST) with increased stage N3 and decreased REM sleep. In cases with CDKL5 mutations, TST was longer and they spent more time in stage N1 but less in stage N3 than those cases affected by MECP2 mutations and a typically developing population. Sleep-disordered breathing was confirmed by the abnormal apnea/hypopnea index of 11.92 ± 23.67/h TST in these aggregated cases. No association of sleep structure with chronological age was found. In RTT, the sleep macrostructure of MECP2 versus CDKL5 cases showed differences, particularly regarding sleep stage N3. A severe REM sleep propensity reduction was found. Aberrant sleep cycling, possibly characterized by a poor REM ‘on switch’ and preponderance in slow and high-voltage sleep, is proposed.

Oral parafunction and bruxism in Rett syndrome and associated factors: An observational study

OBJECTIVES

To explore patterns of parafunction, and bruxism, and its relationships with genotype and snoring in individuals with Rett syndrome (RTT).

METHODS

Retrospective observational data of those with confirmed MECP2 mutations in the InterRett database (n = 216) were used to investigate experience of parafunctional habits, and bruxism and their relationships with genotype and snoring using multivariable linear regression.

RESULTS

The prevalence of parafunction was 98.2%. Bruxism was reported (66.2%) with the patterns mostly both diurnal and nocturnal (44.1%) and exclusively diurnal (42.7%). Compared to individuals with C-terminal deletion, individuals with p.Arg106Trp mutations were less likely to have bruxism reported (aOR = 0.15; 95% CI 0.02-0.98, p = 0.05) and those with p.Arg168* mutation were more likely to have frequent bruxism than none or occasional bruxism reported (aROR 3.4; 95% CI 1.1-10.7 p = 0.04). The relative odds of having nocturnal bruxism constantly, compared to none/occasionally, were higher among those 'always' snoring (aROR 6.24; 95% CI 2.1-18.2, p = 0.001) than those with no snoring.

CONCLUSIONS

There appeared to be genotypic association with bruxism in p.Arg168* and p.Arg106Trp mutations and association between nocturnal bruxism and frequent snoring in an international sample of individuals with RTT. Clinical significance of the high prevalence of bruxism should be highlighted in relation to difficulty communicating pain and increased dental treatment need in RTT.

Determinants of sleep problems in children with intellectual disability

Children with intellectual disabilities are more likely to experience sleep disorders of insomnia, excessive daytime sleepiness and sleep breathing disorders than typically developing children. The present study examined risk factors for these sleep disorders in 447 children (aged 5-18 years), diagnosed with an intellectual disability and comorbid autism spectrum disorder, cerebral palsy, Down syndrome or Rett syndrome. Primary caregivers reported on their child's sleep using the Sleep Disturbance Scale for Children (SDSC), as well as medical comorbidities and functional abilities. Multivariate linear and logistic regressions were used to examine the effects of these factors on SDSC t scores and a binary indicator, respectively for the relevant subscales. Receiving operating characteristic curves were generated for each logistic regression model to determine their ability to discriminate between poor and good sleep. Comorbidities rather than functional abilities were associated with poorer sleep. In particular, recurrent pain, frequent seizures, frequent coughing, constipation and prescription of sleep medications were associated with abnormal sleep across the entire sample, but predictors differed between diagnostic groups. The present study suggests that comorbidities are more strongly associated with quality of sleep than functional impairments. The present study provides new information on potential associations between frequent coughing, prescription sleep medications and sleep quality that should be further investigated.

The role of GABAergic signalling in neurodevelopmental disorders

GABAergic inhibition shapes the connectivity, activity and plasticity of the brain. A series of exciting new discoveries provides compelling evidence that disruptions in a number of key facets of GABAergic inhibition have critical roles in the aetiology of neurodevelopmental disorders (NDDs). These facets include the generation, migration and survival of GABAergic neurons, the formation of GABAergic synapses and circuit connectivity, and the dynamic regulation of the efficacy of GABAergic signalling through neuronal chloride transporters. In this Review, we discuss recent work that elucidates the functions and dysfunctions of GABAergic signalling in health and disease, that uncovers the contribution of GABAergic neural circuit dysfunction to NDD aetiology and that leverages such mechanistic insights to advance precision medicine for the treatment of NDDs.

Overshooting Subcellular Redox-Responses in Rett-Mouse Hippocampus during Neurotransmitter Stimulation

Rett syndrome (RTT) is a neurodevelopmental disorder associated with disturbed neuronal responsiveness and impaired neuronal network function. Furthermore, mitochondrial alterations and a weakened cellular redox-homeostasis are considered part of the complex pathogenesis. So far, overshooting redox-responses of MeCP2-deficient neurons were observed during oxidant-mediated stress, hypoxia and mitochondrial inhibition. To further clarify the relevance of the fragile redox-balance for the neuronal (dys)function in RTT, we addressed more physiological stimuli and quantified the subcellular redox responses to neurotransmitter-stimulation. The roGFP redox sensor was expressed in either the cytosol or the mitochondrial matrix of cultured mouse hippocampal neurons, and the responses to transient stimulation by glutamate, serotonin, dopamine and norepinephrine were characterized. Each neurotransmitter evoked more intense oxidizing responses in the cytosol of MeCP2-deficient than in wildtype neurons. In the mitochondrial matrix the neurotransmitter-evoked oxidizing changes were more moderate and more uniform among genotypes. This identifies the cytosol as an important reactive oxygen species (ROS) source and as less stably redox buffered. Fura-2 imaging and extracellular Ca²⁺ withdrawal confirmed cytosolic Ca²⁺ transients as a contributing factor of neurotransmitter-induced redox responses and their potentiation in the cytosol of MeCP2-deficient neurons. Chemical uncoupling demonstrated the involvement of mitochondria. Nevertheless, cytosolic NADPH- and xanthine oxidases interact to play the leading role in the neurotransmitter-mediated oxidizing responses. As exaggerated redox-responses were already evident in neonatal MeCP2-deficient neurons, they may contribute remarkably to the altered neuronal network performance and the disturbed neuronal signaling, which are among the hallmarks of RTT.

Dream enactment behavior: review for the clinician

NONE

Dream enactment behavior commonly occurs on occasion in normal children and adults. Disruptive and frequent dream enactment behavior may come to the attention of the clinician either as the primary reason for consultation or as a prominent characteristic of a patient with other sleep disorders. Questioning patients with chronic neurologic and psychiatric disorders may also reveal previously unrecognized behavior. In the absence of sleep pathology, process of dream enactment likely begins with active, often emotionally charged dream content that may occasionally break through the normal REM sleep motor suppressive activity. Disrupted sleep resulting from many possible causes, such as circadian disruption, sleep apnea, or medications, may also disrupt at least temporarily the motor-suppressive activity in REM sleep, allowing dream enactment to occur. Finally, pathological neurological damage in the context of degenerative, autoimmune, and infectious neurological disorders may lead to chronic recurrent and severe dream enactment behavior. Evaluating the context, frequency, and severity of dream enactment behavior is guided first and foremost by a structured approach to the sleep history. Physical exam and selected testing support the clinical diagnosis. Understanding the context and the likely cause is essential to effective therapy.

Protective role of mirtazapine in adult female Mecp2+/- mice and patients with Rett syndrome

BACKGROUND

Rett syndrome (RTT), an X-linked neurodevelopmental rare disease mainly caused by MECP2-gene mutations, is a prototypic intellectual disability disorder. Reversibility of RTT-like phenotypes in an adult mouse model lacking the Mecp2-gene has given hope of treating the disease at any age. However, adult RTT patients still urge for new treatments. Given the relationship between RTT and monoamine deficiency, we investigated mirtazapine (MTZ), a noradrenergic and specific-serotonergic antidepressant, as a potential treatment.

METHODS

Adult heterozygous-Mecp2 (HET) female mice (6-months old) were treated for 30 days with 10 mg/kg MTZ and assessed for general health, motor skills, motor learning, and anxiety. Motor cortex, somatosensory cortex, and amygdala were analyzed for parvalbumin expression. Eighty RTT adult female patients harboring a pathogenic MECP2 mutation were randomly assigned to treatment to MTZ for insomnia and mood disorders (mean age = 23.1 ± 7.5 years, range = 16-47 years; mean MTZ-treatment duration = 1.64 ± 1.0 years, range = 0.08-5.0 years). Rett clinical severity scale (RCSS) and motor behavior assessment scale (MBAS) were retrospectively analyzed.

RESULTS

In HET mice, MTZ preserved motor learning from deterioration and normalized parvalbumin levels in the primary motor cortex. Moreover, MTZ rescued the aberrant open-arm preference behavior observed in HET mice in the elevated plus-maze (EPM) and normalized parvalbumin expression in the barrel cortex. Since whisker clipping also abolished the EPM-related phenotype, we propose it is due to sensory hypersensitivity. In patients, MTZ slowed disease progression or induced significant improvements for 10/16 MBAS-items of the M1 social behavior area: 4/7 items of the M2 oro-facial/respiratory area and 8/14 items of the M3 motor/physical signs area.

CONCLUSIONS

This study provides the first evidence that long-term treatment of adult female heterozygous Mecp2^tm1.1Bird mice and adult Rett patients with the antidepressant mirtazapine is well tolerated and that it protects from disease progression and improves motor, sensory, and behavioral symptoms.

Sleep problems in Rett syndrome animal models: A systematic review

Due to the discovery of Rett Syndrome (RTT) genetic mutations, animal models have been developed. Sleep research in RTT animal models may unravel novel neural mechanisms for this severe neurodevelopmental heritable rare disease. In this systematic literature review we summarize the findings on sleep research of 13 studies in animal models of RTT. We found disturbed efficacy and continuity of sleep in all genetically mutated models of mice, cynomolgus monkeys, and Drosophila. Models presented highly fragmented sleep with distinct differences in 24-hr sleep/wake cyclicity and circadian arrhythmicity. Overall, animal models mimic sleep complaints reported in individuals with RTT. However, contrary to human studies, in mutant mice, attenuated sleep delta waves, and sleep apneas in non-rapid eye movement sleep were reported. Future studies may focus on sleep structure and EEG alterations, potential central mechanisms involved in sleep fragmentation and the occurrence of sleep apnea across different sleep stages. Given that locomotor dysfunction is characteristic of individuals with RTT, studies may consider to integrate its potential impact on the behavioral analysis of sleep.

Detection of neurophysiological features in female R255X MeCP2 mutation mice

Rett syndrome (RTT) is a severe neurodevelopmental disorder (NDD) that is nearly always caused by loss of function mutations in Methyl-CpG-binding Protein 2 (MECP2) and shares many clinical features with other NDD. Genetic restoration of Mecp2 in symptomatic mice lacking MeCP2 expression can reverse symptoms, providing hope that disease modifying therapies can be identified for RTT. Effective and rapid clinical trial completion relies on well-defined clinical outcome measures and robust biomarkers of treatment responses. Studies on other NDD have found evidence of differences in neurophysiological measures that correlate with disease severity. However, currently there are no well-validated biomarkers in RTT to predict disease prognosis or treatment responses. To address this, we characterized neurophysiological features in a mouse model of RTT containing a knock-in nonsense mutation (p.R255X) in the Mecp2 locus. We found a variety of changes in heterozygous female Mecp2^R255X/X mice including age-related changes in sleep/wake architecture, alterations in baseline EEG power, increased incidence of spontaneous epileptiform discharges, and changes in auditory evoked potentials. Furthermore, we identified association of some neurophysiological features with disease severity. These findings provide a set of potential non-invasive and translatable biomarkers that can be utilized in preclinical therapy trials in animal models of RTT and eventually within the context of clinical trials.

Dosage-sensitive genes in autism spectrum disorders: From neurobiology to therapy

Autism spectrum disorders (ASDs) are a group of heterogenous neurodevelopmental disorders affecting 1 in 59 children. Syndromic ASDs are commonly associated with chromosomal rearrangements or dosage imbalance involving a single gene. Many of these genes are dosage-sensitive and regulate transcription, protein homeostasis, and synaptic function in the brain. Despite vastly different molecular perturbations, syndromic ASDs share core symptoms including social dysfunction and repetitive behavior. However, each ASD subtype has a unique pathogenic mechanism and combination of comorbidities that require individual attention. We have learned a great deal about how these dosage-sensitive genes control brain development and behaviors from genetically-engineered mice. Here we describe the clinical features of eight monogenic neurodevelopmental disorders caused by dosage imbalance of four genes, as well as recent advances in using genetic mouse models to understand their pathogenic mechanisms and develop intervention strategies. We propose that applying newly developed quantitative molecular and neuroscience technologies will advance our understanding of the unique neurobiology of each disorder and enable the development of personalized therapy.

Sleep as a translationally-relevant endpoint in studies of autism spectrum disorder (ASD)

Sleep has numerous advantages for aligning clinical and preclinical (basic neuroscience) studies of neuropsychiatric illness. Sleep has high translational relevance, because the same endpoints can be studied in humans and laboratory animals. In addition, sleep experiments are conducive to continuous data collection over long periods (hours/days/weeks) and can be based on highly objective neurophysiological measures. Here, we provide a translationally-oriented review on what is currently known about sleep in the context of autism spectrum disorder (ASD), including ASD-related conditions, thought to have genetic, environmental, or mixed etiologies. In humans, ASD is frequently associated with comorbid medical conditions including sleep disorders. Animal models used in the study of ASD frequently recapitulate dysregulation of sleep and biological (diurnal, circadian) rhythms, suggesting common pathophysiologies across species. As our understanding of the neurobiology of ASD and sleep each become more refined, it is conceivable that sleep-derived metrics may offer more powerful biomarkers of altered neurophysiology in ASD than the behavioral tests currently used in humans or lab animals. As such, the study of sleep in animal models for ASD may enable fundamentally new insights on the condition and represent a basis for strategies that enable the development of more effective therapeutics.

Non-medical interventions for individuals with Rett syndrome: A systematic review

BACKGROUND

Research into Rett syndrome has included various medical interventions. Non-medical interventions are relatively under-researched. Recent technological communication intervention advances have contributed to the evidence base in Rett syndrome.

METHOD

The Embase, PsycINFO and MEDLINE were systematically searched for peer-reviewed papers describing non-medical interventions for Rett syndrome. All identified papers were evaluated for methodological quality.

RESULTS

Thirteen studies of adequate methodological quality were reviewed (across N = 60 participants). Interventions were primarily communication interventions including music, assistive technology, augmentative and alternative communication strategies, attentional training and cognitive rehabilitation training. All studies reported positive outcomes across communication, quality of life, brain stem activity, physical fitness and a reduction in stereotyped behaviour. However, methodological challenges to generalizability, standardization, lack of follow-up and/or small-N samples were common.

CONCLUSIONS

The review highlights the paucity of high-quality research. Future research is needed to build on current research and improve validity and generalizability of interventions.

The incidence, prevalence and clinical features of MECP2 duplication syndrome in Australian children

AIM

The aim of this study was to assess the incidence and prevalence of MECP2 duplication syndrome in Australian children and further define its phenotype.

METHODS

The Australian Paediatric Surveillance Unit was used to identify children with MECP2 duplication syndrome between June 2014 and November 2017. Reporting clinicians were invited to complete a questionnaire. Clinician data (n = 20) were supplemented with information from the International Rett Syndrome Phenotype Database and from caregivers (n = 7). Birth prevalence and diagnostic incidence were calculated.

RESULTS

The birth prevalence of MECP2 duplication syndrome in Australia was 0.65/100 000 for all live births and 1/100 000 for males. Diagnostic incidence was 0.07/100 000 person-years overall and 0.12/100 000 person-years for males. The median age at diagnosis was 23.5 months (range 0 months-13 years). A history of pneumonia was documented in three quarters of the clinical cases, half of whom had more than nine episodes. Cardiovascular abnormalities were reported in three cases. A clinical vignette is presented for one child who died due to severe idiopathic pulmonary hypertension. The majority (13/15) of males had inherited the duplication from their mothers, and two had an unbalanced translocation.

CONCLUSIONS

MECP2 duplication syndrome is a rare but important diagnosis in children because of the burden of respiratory illness and recurrence risk. Pulmonary hypertension is a rare life-threatening complication. Array comparative genomic hybridisation testing is recommended for children with undiagnosed intellectual disability or global developmental delay. Early cardiac assessment and ongoing monitoring is recommended for MECP2 duplication syndrome.

Rett Syndrome and CDKL5 Deficiency Disorder: From Bench to Clinic

Rett syndrome (RTT) and CDKL5 deficiency disorder (CDD) are two rare X-linked developmental brain disorders with overlapping but distinct phenotypic features. This review examines the impact of loss of methyl-CpG-binding protein 2 (MeCP2) and cyclin-dependent kinase-like 5 (CDKL5) on clinical phenotype, deficits in synaptic- and circuit-homeostatic mechanisms, seizures, and sleep. In particular, we compare the overlapping and contrasting features between RTT and CDD in clinic and in preclinical studies. Finally, we discuss lessons learned from recent clinical trials while reviewing the findings from pre-clinical studies.

Sleep-Disordered Breathing in Pediatric Patients With Rett Syndrome

STUDY OBJECTIVES

Although respiratory abnormalities occurring during wakefulness are well recognized in patients with Rett syndrome (RS), less has been reported regarding sleep-disordered breathing (SDB) in this population. This study aims to characterize the presenting complaints, types and severity of SDB, and treatment modalities of patients with RS and sleep concerns.

METHODS

Retrospective chart review of pediatric patients with RS referred to our academic tertiary care institution from January 2007 to July 2017.

RESULTS

Thirteen patients were identified, 11 female (84.6%); mean age at polysomnography (PSG) was 10.3 years (standard deviation 4.94). Eleven were white (84.6%), 2 were black (15.4%). The most common presenting symptoms were snoring (10/13, 77%) and witnessed apnea (7/13, 53.8%). On baseline PSG, all patients (100%) exhibited hyperapneas followed by a central apnea during wake. Nine (69.2%) had obstructive sleep apnea (OSA) (obstructive apnea-hypopnea index (oAHI) > 1); four had severe OSA (oAHI ≥ 10). One had central sleep apnea (central apnea index > 5) and severe OSA. No patients exhibited hypoventilation on baseline PSG. Mean AHI of all patients was 8.77 ± 8.82 (oAHI 6.51 ± 6.91) events/h. Mean oxyhemoglobin nadir was 88.52 ± 5.6%. Treatment modalities included observation: 5 (38%), acetazolamide: 2 (15%), nasal mometasone: 1 (7.7%), adenotonsillectomy: 3 (23.1%), and positive airway pressure: 2 (15%).

CONCLUSIONS

Regarding patients with RS referred to the sleep medicine clinic, snoring and witnessed apneas were the most common presenting complaints. In addition to breathing abnormalities during wake, OSA was very common in our cohort. Further studies are needed to examine the pathogenesis of OSA in RS and relationships between disease genotype and respiratory abnormality phenotype.

Transcriptomic Analysis of Mecp2 Mutant Mice Reveals Differentially Expressed Genes and Altered Mechanisms in Both Blood and Brain

Rett syndrome is a rare neuropsychiatric disorder with a wide symptomatology including impaired communication and movement, cardio-respiratory abnormalities, and seizures. The clinical presentation is typically associated to mutations in the gene coding for the methyl-CpG-binding protein 2 (MECP2), which is a transcription factor. The gene is ubiquitously present in all the cells of the organism with a peak of expression in neurons. For this reason, most of the studies in Rett models have been performed in brain. However, some of the symptoms of Rett are linked to the peripheral expression of MECP2, suggesting that the effects of the mutations affect gene expression levels in tissues other than the brain. We used RNA sequencing in Mecp2 mutant mice and matched controls, to identify common genes and pathways differentially regulated across different tissues. We performed our study in brain and peripheral blood, and we identified differentially expressed genes (DEGs) and pathways in each tissue. Then, we compared the genes and mechanisms identified in each preparation. We found that some genes and molecular pathways that are differentially expressed in brain are also differentially expressed in blood of Mecp2 mutant mice at a symptomatic-but not presymptomatic-stage. This is the case for the gene Ube2v1, linked to ubiquitination system, and Serpin1, involved in complement and coagulation cascades. Analysis of biological functions in the brain shows the enrichment of mechanisms correlated to circadian rhythms, while in the blood are enriched the mechanisms of response to stimulus-including immune response. Some mechanisms are enriched in both preparations, such as lipid metabolism and response to stress. These results suggest that analysis of peripheral blood can reveal ubiquitous altered molecular mechanisms of Rett and have applications in diagnosis and treatments' assessments.

Treating Rett syndrome: from mouse models to human therapies

Rare diseases are very difficult to study mechanistically and to develop therapies for because of the scarcity of patients. Here, the rare neuro-metabolic disorder Rett syndrome (RTT) is discussed as a prototype for precision medicine, demonstrating how mouse models have led to an understanding of the development of symptoms. RTT is caused by mutations in the X-linked gene methyl-CpG-binding protein 2 (MECP2). Mecp2-mutant mice are being used in preclinical studies that target the MECP2 gene directly, or its downstream pathways. Importantly, this work may improve the health of RTT patients. Clinical presentation may vary widely among individuals based on their mutation, but also because of the degree of X chromosome inactivation and the presence of modifier genes. Because it is a complex disorder involving many organ systems, it is likely that recovery of RTT patients will involve a combination of treatments. Precision medicine is warranted to provide the best efficacy to individually treat RTT patients.

Polysomnographic findings in Rett syndrome

INTRODUCTION

Rett syndrome (RS) is a severe neurodevelopment disorder associated with abnormal breathing during wakefulness and disturbed nocturnal behaviour. Breathing abnormalities during daytime have been extensively reported but polysomnographic (PSG) findings have been poorly studied.

MATERIALS AND METHODS

Consecutive patients with RS carrying distinct mutations in MECP2 gene, who underwent a PSG between October 2014 and January 2018, were included in the study. Clinical and PSG data were collected.

RESULTS

Seventeen RS girls, mean age 9.5 ± 2.8 years, were included in the study. Mean total sleep time was 366 ± 102 min. Mean sleep efficiency was reduced (66 ± 19%) with only 3 girls presenting a sleep efficiency above 80%. Wake after sleep onset was increased (33 ± 20%) with an arousal index of 7 ± 6 events/hour. Sleep stages were altered with a normal N1 (2 ± 3%), a decreased N2 (34 ± 20%), an increase of N3 (51 ± 23%) and a decrease of REM sleep (12 ± 9%). Mean apnea hypopnea index (AHI) was increased at 19 ± 37 events/hour, with a predominance of obstructive events. Thirteen patients had an AHI > 1.5 event/hour. Four patients had an obstructive AHI >10 events/hour with one patient having associated tonsillar hypertrophy. Two patients had predominant severe central apneas (central AHI 53 and 132 events/hour) which resolved with noninvasive ventilation and nocturnal oxygen therapy respectively.

CONCLUSION

Girls with RS have poor sleep quality with alterations in slow wave and REM sleep stages. Obstructive respiratory events are uncommon in patients without adenotonsillar hypertrophy. Central respiratory events are rare. Longitudinal studies should help understanding the natural history of sleep disturbances in RS and their relationship with the neurocognitive decline.

Oral health experiences of individuals with Rett syndrome: a retrospective study

Background

There is relatively little literature on the oral health experiences of individuals with Rett syndrome. This study described the incidence of dental extractions and restorations in a population-based cohort, according to a range of demographic and clinical factors. The association between bruxism and age was also investigated.

Methods

Existing questionnaire data in the population-based Australian Rett Syndrome Database for the years 2004, 2006, 2009 or 2011 on genetically confirmed female cases (n = 242) were analysed.

Results

The incidence rate of restorations and extractions were 6.8 per 100 person years (py) and 9.3 per 100 py respectively. The incidence of extractions decreased with increasing levels of income. Compared to those with a C-terminal mutation, the incidence rate of extraction was higher for those with large deletions (Incidence Rate Ratio (IRR) 4.93; 95% CI 1.46–16.7, p = 0.01). There was a 5% decrease in the risk of frequent bruxism for every one-year increase in age (Risk Ratio 0.95; 95% CI 0.94–0.97).

Conclusions

Social advantage may provide some protection for dental health in individuals with Rett syndrome. Those with more severe genotypes seemed to have poorer oral health outcomes.

Sleep in children with neurodevelopmental difficulties

Sleep disorders in children with neurodevelopmental disorders are complex and reflect underlying genetic/biological and behavioural components. The sleep disorders are the same as in the typically developing child, although there may be some modifications to the presentation or the frequency depending on the phenotype. Consideration of the known phenotypes and environmental issues are important in defining management strategies. Despite this complexity, defined behavioural strategies with good sleep hygiene can have a significant effect on the sleep problem and on parental management of the behaviours.

Sleep disturbances in Rett syndrome: Impact and management including use of sleep hygiene practices

Sleep disturbances are debilitating for individuals with Rett syndrome (RTT) and their families yet the evidence base for management is poor. We investigated management strategies and their relationships with sleep problems. Data were provided by 364/461 (79%) families with a child with RTT and registered with the International RTT Phenotype Database. Logistic regression models were used to investigate relationships between impacts of sleep problems on the child and family with age group, mutation type, medication type, and sleep hygiene score. Linear regression models were used to estimate the association of disorders of initiating and maintaining sleep (DIMS) with age group, mutation type, medication type, and sleep hygiene. Among those who ever had difficulty falling asleep or night waking, use of any medication was associated with higher odds of moderate/major impact sleep problems (relative to minor/no impact) for the affected child and the family, as well as higher DIMS scores, when compared with the no treatment/nonmedication group accounting for the effects of age, mutation type, and sleep hygiene score. Better use of sleep hygiene practices was associated with lower odds of moderate/major impact on the family (odds ratio 0.60, 95% confidence intervals [CIs] 0.37, 0.98) and lower DIMS scores (geometric mean ratio 0.86, 95%CI 0.80, 0.92) compared with poorer use after adjusting for covariates. Attention to sleep hygiene remains an important management strategy for sleep problems in RTT. Further prospective research is required to investigate efficacy of pharmaceutical treatments.

The feasibility of using actigraphy to characterize sleep in Rett syndrome

BACKGROUND

Rett syndrome (RTT) is a neurodevelopmental disorder primarily caused by mutations in the MECP2 gene. Sleep problems are reported by the majority of caregivers of individuals with RTT.

METHODS

The present study aimed to replicate and extend previous work about the feasibility of measuring sleep with an actigraph device in a sample of girls with clinically diagnosed RTT (N = 13, mean age = 9 years, 5 months). Participants wore an actigraph device day and night for seven consecutive days. Materials also included a parent-completed sleep diary to measure bedtime, duration of nighttime sleep, and daytime sleep, and the Child Sleep Habit's Questionnaire (CSHQ).

RESULTS

The means for the sample as measured by actigraphy were 492.3 min (SD = 47.3) of total night sleep (TNS), 76.0% (SD = 6.7) sleep efficiency, 86.0 min (SD = 34.2) of wake after sleep onset, and 46.1 min (50.8) of sleep when parents reported a nap occurring. Parents reported 589.7 min (SD = 53.6) of TNS, 15.9 min (SD = 12.0) of WASO, and 93.6 min (SD = 66.8) of daytime sleep according to sleep diaries, with all parents reporting at least one nap during the week. Relations were found between sleep characteristics and seizure status and CSHQ total scores. No age-related changes were observed for any sleep characteristic, regardless of collection method. Five of nine participants above the cutoff score on the CSHQ indicate the need for further evaluation for a sleep disorder.

CONCLUSIONS

Overall, actigraphy was feasible in this community-based sample of girls with RTT. The results replicated some aspects of previous studies of sleep in RTT (e.g., no age-related changes in total nighttime sleep or efficiency). Some participants met the American Academy of Sleep Medicine guidelines for recommended total sleep time, with others showing too much or too little sleep. Each of the three methods for describing sleep presented its own advantages and challenges. Future work should be prospectively designed, validate the use of actigraphy in this population, and include a typically developing comparison sample to improve the precision of our understanding of sleep in RTT.

Sleep Disorders in Childhood Neurological Diseases

Sleep problems are frequently addressed as a primary or secondary concern during the visit to the pediatric neurology clinic. Sleep disorders can mimic other neurologic diseases (e.g., epilepsy and movement disorders), and this adds challenges to the diagnostic process. Sleep disorders can significantly affect the quality of life and functionality of children in general and those with comorbid neurological diseases in particular. Understanding the pathophysiology of sleep disorders, recognizing the implications of sleep disorder in children with neurologic diseases and behavioral difficulties, and early intervention continue to evolve resulting in better neurocognitive outcomes.

Clinical and biological progress over 50 years in Rett syndrome

In the 50 years since Andreas Rett first described the syndrome that came to bear his name, and is now known to be caused by a mutation in the methyl-CpG-binding protein 2 (MECP2) gene, a compelling blend of astute clinical observations and clinical and laboratory research has substantially enhanced our understanding of this rare disorder. Here, we document the contributions of the early pioneers in Rett syndrome (RTT) research, and describe the evolution of knowledge in terms of diagnostic criteria, clinical variation, and the interplay with other Rett-related disorders. We provide a synthesis of what is known about the neurobiology of MeCP2, considering the lessons learned from both cell and animal models, and how they might inform future clinical trials. With a focus on the core criteria, we examine the relationships between genotype and clinical severity. We review current knowledge about the many comorbidities that occur in RTT, and how genotype may modify their presentation. We also acknowledge the important drivers that are accelerating this research programme, including the roles of research infrastructure, international collaboration and advocacy groups. Finally, we highlight the major milestones since 1966, and what they mean for the day-to-day lives of individuals with RTT and their families.

Rett syndrome: a wide clinical and autonomic picture

Background

Rett Syndrome is a neurodevelopmental disorder almost exclusively affecting females, characterized by a broad clinical spectrum of signs and symptoms and a peculiar course. The disease affects different body systems: nervous, muscolo-skeletal, gastro-enteric. Moreover, part of the symptoms are related to the involvement of the autonomic nervous system.

In the Tuscany Rett Center at Versilia Hospital, we collected data from 151 subjects with a clinical diagnosis of classical or variant RTT syndrome. For each subject, we assessed the severity of the condition with clinical-rating scales (ISS, PBZ), we quantified the performance of the autonomic nervous system, and we performed genetic analysis. We used multivariate statistical analysis of the data to evaluate the relation between the different clinical RTT forms, the cardiorespiratory phenotype, the different genetic mutations and the severity of the clinical picture. Individuals were classified according to existing forms: Classical RTT and three atypical RTT: Z-RTT, Hanefeld, Congenital. A correlation between C-Terminal deletions and lower severity of the clinical manifestations was evident, in the previous literature, but, considering the analysis of autonomic behaviour, the original classification can be enriched with a more accurate subdivision of Rett subgroups, which may be useful for early diagnosis.

Results

Present data emphasize some differences, not entirely described in the literature, among RTT variants. In our cohort the Z-RTT variant cases show clinical features (communication, growth, epilepsy and development), well documented by specific ISS items, less severe, if compared to classical RTT and show autonomic disorders, previously not reported in the literature. In this form epilepsy is rarely present. In contrast, Hanefeld variant shows the constant presence of epilepsy which has an earlier onset In Hanefeld variant the frequency of apneas was rare and, among the cardiorespiratory phenotypes, the feeble type is lacking.

Conclusion

A quantitative analysis of the different autonomic components reveals differences across typical and atypical forms of RTT that leads to a more accurate classification of the groups. In our cohort of RTT individuals, the inclusion of autonomic parameter in the classification leads to an improved diagnosis at earlier stages of development.

Functional conservation of MBD proteins: MeCP2 and Drosophila MBD proteins alter sleep

Proteins containing a methyl-CpG-binding domain (MBD) bind 5mC and convert the methylation pattern information into appropriate functional cellular states. The correct readout of epigenetic marks is of particular importance in the nervous system where abnormal expression or compromised MBD protein function, can lead to disease and developmental disorders. Recent evidence indicates that the genome of Drosophila melanogaster is methylated and two MBD proteins, dMBD2/3 and dMBD-R2, are present. Are Drosophila MBD proteins required for neuronal function, and as MBD-containing proteins have diverged and evolved, does the MBD domain retain the molecular properties required for conserved cellular function across species? To address these questions, we expressed the human MBD-containing protein, hMeCP2, in distinct amine neurons and quantified functional changes in sleep circuitry output using a high throughput assay in Drosophila. hMeCP2 expression resulted in phase-specific sleep loss and sleep fragmentation with the hMeCP2-mediated sleep deficits requiring an intact MBD domain. Reducing endogenous dMBD2/3 and dMBD-R2 levels also generated sleep fragmentation, with an increase in sleep occurring upon dMBD-R2 reduction. To examine if hMeCP2 and dMBD-R2 are targeting common neuronal functions, we reduced dMBD-R2 levels in combination with hMeCP2 expression and observed a complete rescue of sleep deficits. Furthermore, chromosomal binding experiments indicate MBD-R2 and MeCP2 associate on shared genomic loci. Our results provide the first demonstration that Drosophila MBD-containing family members are required for neuronal function and suggest that the MBD domain retains considerable functional conservation at the whole organism level across species.

Determinants of sleep disturbances in Rett syndrome: Novel findings in relation to genotype

Rett syndrome is a rare but severe neurological disorder associated with a mutation in the methyl CpG binding protein 2 (MECP2) gene. Sleep problems and epilepsy are two of many comorbidities associated with this disorder. This study investigated the prevalence and determinants of sleep problems in Rett syndrome using an international sample. Families with a child with a confirmed Rett syndrome diagnosis and a MECP2 mutation registered in the International Rett Syndrome Phenotype Database (InterRett) were invited to participate. Questionnaires were returned by 364/461 (78.9%) either in web-based or paper format. Families completed the Sleep Disturbance Scale for Children and provided information on the presence, nature, and frequency of their child's sleep problems. Multivariate multinomial regression was used to investigate the relationships between selected sleep problems, age group, and genotype and linear regression for the relationships between sleep disturbance scales and a range of covariates. Night waking was the most prevalent sleep problem affecting over 80% with nearly half (48.3%) currently waking often at night. Initiating and maintaining sleep was most disturbed for younger children and those with a p.Arg294* mutation. Severe seizure activity was associated with poor sleep after adjusting for age group, mutation type, and mobility. We were surprised to find associations between the p.Arg294* mutation and some sleep disturbances given that other aspects of its phenotype are milder. These findings highlight the complexities of aberrant MECP2 function in Rett syndrome and explain some of the variation in manifestation of sleep disturbances. © 2016 Wiley Periodicals, Inc.

Melatonin treatment during the incubation of sensitization attenuates methamphetamine-induced locomotor sensitization and MeCP2 expression

Behavior sensitization is a long-lasting enhancement of locomotor activity after exposure to psychostimulants. Incubation of sensitization is a phenomenon of remarkable augmentation of locomotor response after withdrawal and reflects certain aspects of compulsive drug craving. However, the mechanisms underlying these phenomena remain elusive. Here we pay special attention to the incubation of sensitization and suppose that the intervention of this procedure will finally decrease the expression of sensitization. Melatonin is an endogenous hormone secreted mainly by the pineal gland. It is effective in treating sleep disorder, which turns out to be one of the major withdrawal symptoms of methamphetamine (MA) addiction. Furthermore, melatonin can also protect neuronal cells against MA-induced neurotoxicity. In the present experiment, we treated mice with low dose (10mg/kg) of melatonin for 14 consecutive days during the incubation of sensitization. We found that melatonin significantly attenuated the expression of sensitization. In contrast, the vehicle treated mice showed prominent enhancement of locomotor activity after incubation. MeCP2 expression was also elevated in the vehicle treated mice and melatonin attenuated its expression. Surprisingly, correlation analysis suggested significant correlation between MeCP2 expression in the nucleus accumbens (NAc) and locomotion in both saline control and vehicle treated mice, but not in melatonin treated ones. MA also induced MeCP2 over-expression in PC12 cells. However, melatonin failed to reduce MeCP2 expression in vitro. Our results suggest that melatonin treatment during the incubation of sensitization attenuates MA-induced expression of sensitization and decreases MeCP2 expression in vivo.

Heightened Delta Power during Slow-Wave-Sleep in Patients with Rett Syndrome Associated with Poor Sleep Efficiency

Sleep problems are commonly reported in Rett syndrome (RTT); however the electroencephalographic (EEG) biomarkers underlying sleep dysfunction are poorly understood. The aim of this study was to analyze the temporal evolution of quantitative EEG (qEEG) biomarkers in overnight EEGs recorded from girls (2-9 yrs. old) diagnosed with RTT using a non-traditional automated protocol. In this study, EEG spectral analysis identified high delta power cycles representing slow wave sleep (SWS) in 8-9h overnight sleep EEGs from the frontal, central and occipital leads (AP axis), comparing age-matched girls with and without RTT. Automated algorithms quantitated the area under the curve (AUC) within identified SWS cycles for each spectral frequency wave form. Both age-matched RTT and control EEGs showed similar increasing trends for recorded delta wave power in the EEG leads along the antero-posterior (AP). RTT EEGs had significantly fewer numbers of SWS sleep cycles; therefore, the overall time spent in SWS was also significantly lower in RTT. In contrast, the AUC for delta power within each SWS cycle was significantly heightened in RTT and remained heightened over consecutive cycles unlike control EEGs that showed an overnight decrement of delta power in consecutive cycles. Gamma wave power associated with these SWS cycles was similar to controls. However, the negative correlation of gamma power with age (r = -.59; p<0.01) detected in controls (2-5 yrs. vs. 6-9 yrs.) was lost in RTT. Poor % SWS (i.e., time spent in SWS overnight) in RTT was also driven by the younger age-group. Incidence of seizures in RTT was associated with significantly lower number of SWS cycles. Therefore, qEEG biomarkers of SWS in RTT evolved temporally and correlated significantly with clinical severity.