Sleep dysfunction in Rett syndrome: lack of age related decrease in sleep duration

Multidisciplinary Management of Rett Syndrome: Twenty Years' Experience

Over the last 20 years, the understanding and natural history of Rett syndrome has advanced, but to date no cure has emerged, with multidisciplinary management being symptomatic and supportive. This study provides a comprehensive review of the clinical features, comorbidities and multidisciplinary management of a well-characterized cohort of females with classical Rett syndrome. We aim to improve awareness and understanding of Rett syndrome amongst pediatricians, pediatric subspecialists and allied health professionals to enable early diagnosis and a streamlined enrolment approach for future clinical trials. Rett syndrome, a complex X-linked condition, affecting mainly females, is due to pathogenic variants of the MECP2 gene in most affected individuals. The Rett syndrome Multidisciplinary Management clinic at The Children's Hospital at Westmead, Sydney, Australia, was established in 2000. This retrospective analysis of individuals who attended the clinic from 2000 to 2020 was performed to identify the incidence and predicted age of onset of Rett syndrome related comorbidities, disease progression and to review management principles. Data collected included age of Rett syndrome diagnosis, MECP2 genotype, clinical features and medical comorbidities, such as sleep disturbance, seizures, breathing irregularities, scoliosis, mobility, hand stereotypies, hand function, constipation, feeding ability, use of gastrostomy, communication skills, QTc prolongation, anthropometry, and bruxism. Analysis of 103 girls who fulfilled the clinical diagnostic criteria for classical Rett syndrome with a pathogenic variant of the MECP2 gene showed a median age of diagnosis of 3 years. The most frequent MECP2 variant was c.502 C>T.

Long time polysomnographic sleep and breathing evaluations in children with CDKL5 deficiency disorder

STUDY OBJECTIVES

CDKL5 deficiency disorder (CDD) is a rare developmental and epileptic encephalopathy, developing in the first months of life, caused by a mutation in the cyclin-dependent kinase-like 5 (CDKL5) gene. Children with CDD often have sleep (90%) and breathing disorders in wake (50%). Sleep disorders may have a significant impact emotional wellbeing and quality of life of caregivers of children with CDD and are challenging to treat. The outcomes of these features are unknown in children with CDD.

METHODS

We retrospectively evaluated sleep and respiratory function changes over 5-10 years in a small cohort of Dutch children with CDD, using video-EEG and/or polysomnography (3 × 24 h) and a parental questionnaire, the Sleep Disturbance Scale for Children (SDSC). The present study is a follow-up sleep and PSG study to evaluate if sleep and breathing disturbances persist in children with CDD previously studied.

RESULTS

Sleep disturbances persisted during the study period (5.5-10 years). All five individuals had long sleep latency (SL, range 32-174.5 min) and frequent arousals and awakenings (14-50/night), unrelated to apneas/seizures, corresponding to the SDSC findings. Low sleep efficiency (SE, 41-80%) was present and did not improve. In our participants, total sleep time (TST, 3h52min-7h52min) was short and remained so. Time in bed (TIB) was typical for children aged 2-8 years, but did not adjust with ageing. Low duration (4.8-17.4%) or even absent REM sleep persisted over time. No sleep apneas were noted. Central apneas due to episodic hyperventilation were reported during wakefulness in two of the five.

CONCLUSION

Sleep disturbances were present and persisted in all. The decreased REM sleep and sporadic breathing disturbances in wake may indicate failure of brainstem nuclei. Sleep disturbances can severely affect the emotional wellbeing and quality of life of the caregivers and the individuals with CDD and are challenging to treat. Hopefully our polysomnographic sleep data contribute to find the optimal treatment of the sleep problems in CDD patients.

Improving clinical trial readiness to accelerate development of new therapeutics for Rett syndrome

Rett syndrome is associated with severe functional impairments and many comorbidities, each in urgent need of treatments. Mutations in the MECP2 gene were identified as causing Rett syndrome in 1999. Over the past 20 years there has been an abundance of preclinical research with some studies leading to human clinical trials. Despite this, few viable therapeutic options have emerged from this investment of effort. Reasons for this lack of success as they relate both to preclinical research and the clinical trial landscape are discussed. Considering what needs to be done to promote further success in the field, we take a positive and constructive approach and introduce the concept of clinical trial readiness and its necessary ingredients for Rett syndrome. These include: listening to the needs of families; support from advocacy groups; optimising use of existing clinic infrastructures and available natural history data; and, finally, the validation of existing outcome measures and/or the development and validation of new measures. We conclude by reiterating the need for a collaborative and coordinated approach amongst the many different stakeholder groups and the need to engage in new types of trial design which could be much more efficient, less costly and much less burdensome on families.

Evaluating Sleep Disturbances in Children With Rare Genetic Neurodevelopmental Syndromes

BACKGROUND

Adequate sleep is important for proper neurodevelopment and positive health outcomes. Sleep disturbances are more prevalent in children with genetically determined neurodevelopmental syndromes compared with typically developing counterparts. We characterize sleep behavior in Rett (RTT), Angelman (AS), and Prader-Willi (PWS) syndromes to identify effective approaches for treating sleep problems in these populations. We compared sleep-related symptoms across individuals with these different syndromes with each other, and with typically developing controls.

METHODS

Children were recruited from the Rare Diseases Clinical Research Network consortium registries; unaffected siblings were enrolled as related controls. For each participant, a parent completed multiple sleep questionnaires including Pediatric Sleep Questionnaire (Sleep-Disordered Breathing), Children's Sleep Habits Questionnaire (CSHQ), and Pediatric Daytime Sleepiness Scale.

RESULTS

Sleep data were analyzed from 714 participants, aged two to 18 years. Young children with AS had more reported sleep problems than children with RTT or PWS. Older children with RTT had more reported daytime sleepiness than those with AS or PWS. Finally, all individuals with RTT had more evidence of sleep-disordered breathing when compared with individuals with PWS. Notably, typically developing siblings were also reported to have sleep problems, except for sleep-related breathing disturbances, which were associated with each of the genetic syndromes.

CONCLUSIONS

Individuals with RTT, AS, and PWS frequently experience sleep problems, including sleep-disordered breathing. Screening for sleep problems in individuals with these and other neurogenetic disorders should be included in clinical assessment and managements. These data may also be useful in developing treatment strategies and in clinical trials.

Anti-Semaphorin 4D Rescues Motor, Cognitive, and Respiratory Phenotypes in a Rett Syndrome Mouse Model

Rett syndrome is a neurodevelopmental disorder caused by mutations of the methyl-CpG binding protein 2 gene. Abnormal physiological functions of glial cells contribute to pathogenesis of Rett syndrome. Semaphorin 4D (SEMA4D) regulates processes central to neuroinflammation and neurodegeneration including cytoskeletal structures required for process extension, communication, and migration of glial cells. Blocking SEMA4D-induced gliosis may preserve normal glial and neuronal function and rescue neurological dysfunction in Rett syndrome. We evaluated the pre-clinical therapeutic efficacy of an anti-SEMA4D monoclonal antibody in the Rett syndrome Mecp2T158A transgenic mouse model and investigated the contribution of glial cells as a proposed mechanism of action in treated mice and in primary glial cultures isolated from Mecp2T158A/y mutant mice. SEMA4D is upregulated in neurons while glial fibrillary acidic protein and ionized calcium binding adaptor molecule 1-positive cells are upregulated in Mecp2T158A/y mice. Anti-SEMA4D treatment ameliorates Rett syndrome-specific symptoms and improves behavioural functions in both pre-symptomatic and symptomatic cohorts of hemizygous Mecp2T158A/y male mice. Anti-SEMA4D also reduces astrocyte and microglia activation in vivo. In vitro experiments demonstrate an abnormal cytoskeletal structure in mutant astrocytes in the presence of SEMA4D, while anti-SEMA4D antibody treatment blocks SEMA4D–Plexin B1 signaling and mitigates these abnormalities. These results suggest that anti-SEMA4D immunotherapy may be an effective treatment option to alleviate symptoms and improve cognitive and motor function in Rett syndrome.

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.

Rett syndrome before regression: A time window of overlooked opportunities for diagnosis and intervention

Rett syndrome (RTT) is a rare neurological disorder primarily affecting females, causing severe cognitive, social, motor and physiological impairments for which no cure currently exists. RTT clinical diagnosis is based on the peculiar progression of the disease, since patients show an apparently normal initial development with a subsequent sudden regression at around 2 years of age. Accumulating evidences are rising doubts regarding the absence of early impairments, hence questioning the concept of regression. We reviewed the published literature addressing the pre-symptomatic stage of the disease in both patients and animal models with a particular focus on behavioral, physiological and brain abnormalities. The emerging picture delineates subtle, but reliable impairments that precede the onset of overt symptoms whose bases are likely set up already during embryogenesis. Some of the outlined alterations appear transient, suggesting compensatory mechanisms to occur in the course of development. There is urgent need for more systematic developmental analyses able to detect early pathological markers to be used as diagnostic tools and precocious targets of time-specific interventions.

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.

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.

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.

Prevalence and onset of comorbidities in the CDKL5 disorder differ from Rett syndrome

Background

Initially described as an early onset seizure variant of Rett syndrome, the CDKL5 disorder is now considered as an independent entity. However, little is currently known about the full spectrum of comorbidities that affect these patients and available literature is limited to small case series. This study aimed to use a large international sample to examine the prevalence in this disorder of comorbidities of epilepsy, gastrointestinal problems including feeding difficulties, sleep and respiratory problems and scoliosis and their relationships with age and genotype. Prevalence and onset were also compared with those occurring in Rett syndrome.

Methods

Data for the CDKL5 disorder and Rett syndrome were sourced from the International CDKL5 Disorder Database (ICDD), InterRett and the Australian Rett syndrome Database (ARSD). Logistic regression (multivariate and univariate) was used to analyse the relationships between age group, mutation type and the prevalence of various comorbidities. Binary longitudinal data from the ARSD and the equivalent cross-sectional data from ICDD were examined using generalized linear models with generalized estimating equations. The Kaplan-Meier method was used to estimate the failure function for the two disorders and the log-rank test was used to compare the two functions.

Results

The likelihood of experiencing epilepsy, GI problems, respiratory problems, and scoliosis in the CDKL5 disorder increased with age and males were more vulnerable to respiratory and sleep problems than females. We did not identify any statistically significant relationships between mutation group and prevalence of comorbidities. Epilepsy, GI problems and sleep abnormalities were more common in the CDKL5 disorder than in Rett syndrome whilst scoliosis and respiratory problems were less prevalent.

Conclusion

This study captured a much clearer picture of the CDKL5 disorder than previously possible using the largest sample available to date. There were differences in the presentation of clinical features occurring in the CDKL5 disorder and in Rett syndrome, reinforcing the concept that CDKL5 is an independent disorder with its own distinctive characteristics.

Why do seizures occur when they do? Situations perceived to be associated with increased or decreased seizure likelihood in people with epilepsy and intellectual disability

Seizure precipitants are commonly reported in the general population of people with epilepsy. However, there has been little research in this area in people with epilepsy and intellectual disability (ID). We conducted a survey of the situations associated with increased or decreased seizure likelihood in this population. The aim of the research was to identify situations of increased seizure likelihood (SISLs) and situations of decreased seizure likelihood (SDSLs) reported by carers of people with an ID and epilepsy. Three study groups were investigated: two groups comprising individuals with ID associated with a specific genetic diagnosis - Rett syndrome or fragile X syndrome - and one group consisting of individuals with a range of other etiologies. Responses relating to 100 people were received: 44 relating to people with Rett syndrome, 25 to people with fragile X syndrome, and 31 to people whose ID had some other etiologies. Ninety-eight percent of the respondents reported at least one SISL, and 60% reported at least one SDSL. Having more seizure types and greater seizure frequency were associated with a higher number of SISLs reported. The most commonly reported SISLs and SDSLs for each of the three groups are presented. The most common SISL overall was illness, which was reported as an SISL by 71% of the respondents. There was less consensus with regard to SDSLs. These findings provide a greater understanding of when seizures occur in those with ID and epilepsy, with possible implications for adjunctive behavioral management of seizures in those with treatment-refractory epilepsy.

The trajectories of sleep disturbances in Rett syndrome

Rett syndrome is a rare neurodevelopmental disorder usually affecting females, and is associated with a mutation in the MECP2 gene. Sleep problems occur commonly and we investigated the trajectories and influences of age, mutation and treatments. Data were collected at six time points over 12 years from 320 families registered with the Australian Rett Syndrome Database. Regression analysis was used to investigate relationships between sleep disturbances, age, mutation type and use of treatment, and latent class growth analysis was performed to identify sleep problem phenotypes and model the effect of mutation type. The age range of subjects was 2.0-35.8 years. The study showed that sleep problems occurred in more than 80% of individuals and the prevalence decreased with age. Night laughing and night screaming occurred in 77 and 49%, respectively, when younger. Those with a large deletion had a higher prevalence of night laughing, which often occurred frequently. Treatment was associated with a 1.7% reduction in risk of further sleep problems. High and low baseline prevalence groups were identified. Approximately three-quarters of girls and women with sleep disturbances were in the high baseline group and problems persisted into adulthood. Conversely, 57% with night laughing and 42% with night screaming in the high baseline group exhibited mild improvement over time. Mutation type was not found to be a significant predictor of group membership. In conclusion, the evolution of sleep problems differed between subgroups of girls and women with Rett syndrome, in part explained by age and genotype. Treatment was not associated with improvement in sleep problems.

Twenty-four hour quantitative-EEG and in-vivo glutamate biosensor detects activity and circadian rhythm dependent biomarkers of pathogenesis in Mecp2 null mice

Mutations in the X-linked gene encoding methyl-CpG-binding protein 2 (Mecp2) cause most cases of Rett syndrome (RTT). Currently there is no cure for RTT. Abnormal EEGs are found in 100% of RTT cases and are associated with severe sleep dysfunction, the cause of which is not well understood. Mice deficient in MeCP2 protein have been studied and characterized for their neuropathological and behavioral deficits to better understand RTT. With the goal to study the non-ictal EEG correlates in symptomatic Mecp2 KO mice (Mecp2(tm1.1Bird/y)), and determine novel EEG biomarkers of their reported progressive neurodegeneration, we used 24 h video-EEG/EMG with synchronous in-vivo cortical glutamate biosensor in the frontal cortex. We scored the EEG for activity states and spectral analysis was performed to evaluate correlations to the synchronous extracellular glutamate fluctuations underlying Mecp2 inactivation as compared to WT. Significant alterations in sleep structure due to dark cycle-specific long wake states and poor quality of slow-wave sleep were associated with a significant increase in glutamate loads per activity cycle. The dynamics of the activity-state-dependent physiological rise and fall of glutamate indicative of glutamate homeostasis were significantly altered in the KO mice. Colorimetric quantitation of absolute glutamate levels in frontal cortex also indicated the presence of significantly higher levels in KO. This study for the first time found evidence of uncompensated sleep deprivation-like EEG biomarkers that were associated with glutamate homeostatic dysfunction in the Mecp2 KO mice.

Respiratory and sleep disorders in female children with atypical Rett syndrome caused by mutations in the CDKL5 gene

AIM

In female children with drug-resistant seizures and developmental delay from birth, atypical Rett syndrome caused by mutations in the CDKL5 gene should be considered. Several clinical features resemble classic Rett syndrome. Respiratory and sleep abnormalities are frequently present in Rett syndrome, whereas little is known in patients with CDKL5 mutations.

METHOD

In four genetically confirmed female patients with CDKL5 mutations (age range 2-15 y), the presence of breathing and sleep abnormalities was evaluated using the validated Sleep Disturbance Scale for Children and polysomnography (PSG).

RESULTS

The Sleep Disturbance Scale for Children indicated disorders of initiating and maintaining sleep, daytime somnolence, and sleep breathing disorders. In one patient, PSG showed central apnoeas during sleep: her total apnoea-hypopnoea index (AHI) was 4.9, of which the central AHI was 3.4/h. When awake, central apnoeas were present in two of the four female children (central AHI 28/h and 41/h respectively), all preceded by hyperventilation. PSG showed low rapid eye movement (REM) sleep (9.7-18.3%), frequent awakenings, and low sleep efficiency (range 59-78%).

INTERPRETATION

Episodic hyperventilation followed by central apnoeas was present while awake in two of four patients. This may indicate failure of brainstem respiratory centres. In addition, low REM sleep, frequent arousals (not caused by apnoeas/seizures), and low sleep efficiency were present. Similar to Rett syndrome, in patients with CDKL5 mutations PSG seems warranted to evaluate breathing and sleep disturbances.

Daily rhythmic behaviors and thermoregulatory patterns are disrupted in adult female MeCP2-deficient mice

Mutations in the X-linked gene encoding Methyl-CpG-binding protein 2 (MECP2) have been associated with neurodevelopmental and neuropsychiatric disorders including Rett Syndrome, X-linked mental retardation syndrome, severe neonatal encephalopathy, and Angelman syndrome. Although alterations in the performance of MeCP2-deficient mice in specific behavioral tasks have been documented, it remains unclear whether or not MeCP2 dysfunction affects patterns of periodic behavioral and electroencephalographic (EEG) activity. The aim of the current study was therefore to determine whether a deficiency in MeCP2 is sufficient to alter the normal daily rhythmic patterns of core body temperature, gross motor activity and cortical delta power. To address this, we monitored individual wild-type and MeCP2-deficient mice in their home cage environment via telemetric recording over 24 hour cycles. Our results show that the normal daily rhythmic behavioral patterning of cortical delta wave activity, core body temperature and mobility are disrupted in one-year old female MeCP2-deficient mice. Moreover, female MeCP2-deficient mice display diminished overall motor activity, lower average core body temperature, and significantly greater body temperature fluctuation than wild-type mice in their home-cage environment. Finally, we show that the epileptiform discharge activity in female MeCP2-deficient mice is more predominant during times of behavioral activity compared to inactivity. Collectively, these results indicate that MeCP2 deficiency is sufficient to disrupt the normal patterning of daily biological rhythmic activities.

Polysomnographic findings in Rett syndrome: a case-control study

PURPOSE

Rett syndrome is a severe neurodevelopmental disorder mainly affecting females and usually linked to mutations in the methyl-CpG-binding protein 2 gene, with an estimated prevalence of 1 in 10,000 live female births. Clinical features which usually become more apparent over time include breathing dysfunction, seizures, spasticity, peripheral vasomotor disturbance, scoliosis, growth retardation, and hypotrophic feet, with a great variety of presentations. The clear immaturity in brainstem mechanisms is expressed by the presence of early sleep disorders such as nocturnal awakenings, bruxism, and difficulty falling asleep, and no conclusive findings were derived from the few polysomnographic studies about the sleep macrostructural aspects. The aim of this study is to analyze the sleep macrostructural parameters, the nocturnal respiratory characteristic, and the presence of periodic limb movements in a sample of children affected by Rett syndrome.

MATERIALS

Thirteen Rett subjects underwent a polysomnographic study, and the findings were compared with those obtained by a group of 40 healthy children.

RESULTS

The Rett group shows a great impairment in sleep macrostructural and respiratory parameters, with a higher percentage of pathological periodic limb movements than the controls.

CONCLUSIONS

This study may be considered a report about the ventilatory impairment during sleep in Rett syndrome and the first approach to the macrostructural aspects of sleep supported by the PSG data that could be considered mandatory for a better comprehension of this very complex syndrome.

Sleep disturbances in people with epilepsy; prevalence, impact and treatment

The interaction between epilepsy and sleep is thoroughly studied and is very complex. This review focuses on prevalence, impact on quality of life and effects of treatment of sleep disorders on the course of epilepsy. Self-reported sleep disturbances in people with epilepsy are about twice as prevalent as in healthy controls. People with epilepsy with sleep disturbances have a significant impairment of quality of life compared to those with no sleep disturbances. In children with epilepsy, sleep problems may lead to detrimental effects on daytime behavior and cognition. Most is known about obstructive sleep apnea syndrome (OSAS). Co-morbidity of epilepsy and OSAS is shown to be far higher than expected by chance. Treatment of OSAS significantly improves seizure control in people with epilepsy. More studies on the prevalence of other sleep disorders in people with epilepsy and the effect of treatment are required. Reports on the effect of treatment for other sleep disorders are scarce and not unequivocal.

Impact of scoliosis surgery on activities of daily living in females with Rett syndrome

BACKGROUND

Scoliosis is a common orthopaedic complication of Rett syndrome, and surgery is commonly used to reduce asymmetry in cases with severe scoliosis.

METHODS

Data from questionnaires administered to caregivers biennially from 2000 to 2006 were used to describe functional skill levels in subjects with Rett syndrome, and within-subject change in 16 subjects with scoliosis surgery were compared with within-subject change in 186 pairs of data from 86 subjects with conservatively managed scoliosis. Postsurgical assessment was conducted after a mean of 17.8 months.

RESULTS

Surgery was associated with improved activities of daily living as measured by the WeeFIM for subjects who were wheelchair bound (P = 0.05). Mobility levels, social interaction, communication skills, and the frequency of daytime napping remained similar for the group as a whole.

CONCLUSIONS

Improvements in activities of daily living are likely to represent an increase in the quality of life for subjects and caregivers and were mainly found in subjects who were wheelchair bound, indicating that those who were more severely affected were able to benefit from this intervention.

LEVEL OF EVIDENCE

Therapeutic study: level III.

Sleep problems in Rett syndrome

Rett syndrome (RTT) is a severe neurological disorder, affecting mainly females. It is generally caused by mutations in the MECP2 gene. Sleep problems are thought to occur commonly in Rett syndrome, but there has been little research on prevalence or natural history. An Australian population-based registry of cases born since 1976 has been operating since 1993, with current ascertainment at 300. The Australian Rett Syndrome Database (ARSD) consists of information about Rett syndrome cases including their functional ability, behaviour, sleep patterns, medical conditions and genotype. The cases range in age from 2 to 29 years. The aim of this study was to investigate the type and frequency of sleep problems, relationships with age and MECP2 mutation type and to evaluate changes over time. Parents or carers of the subjects with Rett syndrome were asked to complete a questionnaire about sleep problems on three separate occasions (2000, 2002 and 2004). Regression modelling was used to investigate the relationships between sleep problems, age and mutation type. Sleep problems were identified in over 80% of cases. The prevalence of night-time laughter decreased with age and the prevalence of reported night-time seizures and daytime napping increased with age. The prevalence of sleep problems was highest in cases with a large deletion of the MECP2 gene and in those with the p.R294X or p.R306C mutations. Sleep problems are common in Rett syndrome and there is some variation with age and mutation type.

The association between behavior and genotype in Rett syndrome using the Australian Rett Syndrome Database

This study compared the behavior profile of cases in the Australian Rett Syndrome Database (ARSD) with those in a British study using the Rett Syndrome Behavior Questionnaire (RSBQ) and then examined behavioral patterns as measured by the RSBQ by genetic status. There were 145 Australian cases meeting the criteria for the first arm of the study and 135 for the second arm. Comparison of the scores obtained from the British and Australian cohorts indicated that the RSBQ was a satisfactory measure for describing behaviors in Rett Syndrome (RS). Overall, there were some differences among the behavior patterns of cases with the well-known common mutations. Fear/anxiety was more commonly reported in those with R133C and R306C. Those with the R294X mutation were more likely to have mood difficulties and body rocking but less likely to have hand behaviors and to display repetitive face movements. In contrast, hand behaviors were more commonly reported in those with R270X or R255X. We found the RSBQ is an appropriate instrument for measuring behavior in girls with RS. Some behaviors differ according to genetic mutation but there is both inter and intra mutation variation in behavior and there is a need for larger studies involving international collaboration to improve statistical power.

Early behavior characteristics and sleep disturbance in Rett syndrome

This paper reviews the early features of Rett syndrome (RTT). The behavioral characteristics of RTT were analyzed retrospectively by taking history and asking about early infancy behaviors. The earliest behavioral characteristics are thought to be autistic features and hypotonia of trunkal muscles. Analysis of sleep-wake rhythm and all-night polysomnography suggested that the initial lesion is serotonergic and noradrenargic hypofunction at brainstem level. Dopaminergic (DA) hypofunction associated with DA receptor supersensitivity follows as the brain matures. Characteristic symptoms developing at specific age ranges are based on the neuronal connections of the brainstem aminergic neurons and DA neurons with the pedunculo-pontine nuclei, projecting to specific cortical areas.

Describing the phenotype in Rett syndrome using a population database

BACKGROUND

Mutations in the MECP2 gene have been recently identified as the cause of Rett syndrome, prompting research into genotype-phenotype relations. However, despite these genetic advances there has been little descriptive epidemiology of the full range of phenotypes.

AIMS

To describe the variation in phenotype in Rett syndrome using four different scales, by means of a population database.

METHODS

Using multiple sources of ascertainment including the Australian Paediatric Surveillance Unit, the development of an Australian cohort of Rett syndrome cases born since 1976 has provided the first genetically characterised population based study of Rett syndrome. Follow up questionnaires were administered in 2000 to families and used to provide responses for items in four different severity scales.

RESULTS

A total of 199 verified cases of Rett syndrome were reported between January 1993 and July 2000; 152 families provided information for the follow up study. The mean score using the Kerr scale was 22.9 (SD 4.8) and ranged from 20.5 in those under 7 years to 24.2 in those over 17 years. The mean Percy score was 24.9 (SD 6.6) and also increased with age group from 23.0 to 26.9. The mean Pineda score was 16.3 (SD 4.5) and did not differ by age group. The mean WeeFIM was 29.0 (SD 11.9), indicating extreme dependence, and ranged from 18 to 75.

CONCLUSION

We have expanded on the descriptive epidemiology of Rett syndrome and shown different patterns according to the severity scale selected. Although all affected children are severely functionally dependent, it is still possible to identify some variation in ability, even in children with identified MECP2 mutations.

Discussant--pathophysiologies of Rett syndrome

Studies on sleep parameters of Rett syndrome revealed hypoactivity of the noradrenaline (NA) and the serotonin (5HT) neuron in early infancy while preserving the function of the dopamine (DA) and the cholinergic neurons of the pons normally. The sleep-wake cycle remains in its development at the level of 4 months of age. Polysomnographies also showed a decrease of the function of the nigrostriatal (NS)-DA neuron in early childhood and suggested the development of receptor supersensitivity in late childhood. Neurohistochemical and neuroimaging (PET) studies revealed the hypofunction of the NS-DA neuron with receptor supersensitivity and of involvement of the cholinergic neurons to the cortical pathology, whereas no substantial pathological or histochemical abnormalities were observed in the NA and the 5HT neurons in the brainstem. The decrease of tyrosine hydroxylase without neurodegenerative changes observed in the substantia nigra of Rett syndrome had similarity to the pathology caused by excitotoxic lesion of the pedunculopontine nuclei (PPN) observed in an animal experiments. Clinically the grade of disability of locomotion was shown to correlate to the grade of the disabilities of language. These clinical manifestations were also correlated to the specific loci of the mutation in the methyl binding domain of the MECP2 gene. In rodents the axons of the brainstem 5HT neuron involved in the morphogenesis of the brain in the early developmental course disappear in neonates without apoptotic or degenerative changes in the neurons. This period corresponds to the first 1.5-2 years in humans. Thus, in Rett syndrome, the primary lesion appears in the brainstem NA and 5HT neurons which affects development of synaptogenesis of the cortex and also dysfunction of the PPN. The latter causes dysfunction of the DA neuron and the cholinergic neuron in the midbrain. The mutation of the MECP2 gene may cause early transcription of the genes which prune the axons of the aminergic neurons for the developmental morphogenesis of the central nervous system in early infancy.