Sleep disordered breathing and other sleep dysfunction in myotonic dystrophy type 2

Cerebral involvement and related aspects in myotonic dystrophy type 2

Myotonic dystrophy type 2 (DM2) is an autosomal dominant multisystemic disorder caused by CCTG repeats expansion in the first intron of the CNBP gene. In this review we focus on the brain involvement in DM2, including its pathogenic mechanisms, microstructural, macrostructural and functional brain changes, as well as the effects of all these impairments on patients' everyday life. We also try to understand how brain abnormalities in DM2 should be adequately measured and potentially treated. The most important pathogenetic mechanisms in DM2 are RNA gain-of-function and repeat-associated non-ATG (RAN) translation. One of the main neuroimaging findings in DM2 is the presence of diffuse periventricular white matter hyperintensity lesions (WMHLs). Brain atrophy has been described in DM2 patients, but it is not clear if it is mostly caused by a decrease of the white or gray matter volume. The most commonly reported specific cognitive symptoms in DM2 are dysexecutive syndrome, visuospatial and memory impairments. Fatigue, sleep-related disorders and pain are also frequent in DM2. The majority of key symptoms and signs in DM2 has a great influence on patients' daily lives, their psychological status, economic situation and quality of life.

Myotonic Muscular Dystrophy Type 2 in CT, USA: A Single-Center Experience With 50 Patients

ABSTRACT

Myotonic dystrophy type 2 (DM2) is an autosomal dominant disorder due to a (CCTG)n repeat expansion in intron 1 of the CNBP gene. In this article, we report the clinicopathologic findings in 50 patients seen at a single site over a 27 year period. DM2 was the fifth most common type of muscular dystrophy seen at our center with a 5-fold lower frequency as compared to DM1. Age of symptom onset ranged from 15 to 72 years, and the mean duration between symptom onset and diagnosis was 7.4 years. Weakness referable to the proximal lower extremities was the presenting symptom in 62% of patients. The degree of generalized weakness varied from severe in 30% to no weakness in 20% of patients. Clinical myotonia was noted in 18% and myotonic discharges on electromyography in 97% of patients. Pain symptoms were uncommon in our cohort. A significant correlation was noted between limb weakness and degree of muscle pathologic changes. There was no correlation between CCTG repeat size and other clinicopathologic findings. Six patients (12%) had cardiac abnormalities including one who developed progressive nonischemic dilated cardiomyopathy ultimately leading to cardiac transplantation. In 21 patients followed for 2 or more years, we noted a mean rate of decline in total Medical Research Council score of about 1% per year.

Biomolecular diagnosis of myotonic dystrophy type 2: a challenging approach

Myotonic dystrophy type 1 (DM1) and type 2 (DM2) are the most common adult form of muscular dystrophy, characterized by autosomal dominant progressive myopathy, myotonia, and multiorgan involvement. The onset and symptoms of the myotonic dystrophies are diverse, complicating their diagnoses and limiting a comprehensive approach to their clinical care. Diagnostic delay in DM2 is due not only to the heterogeneous phenotype and the aspecific onset but also to the unfamiliarity with the disorder by most clinicians. Moreover, the DM2 diagnostic odyssey is complicated by the difficulties to develop an accurate, robust, and cost-effective method for a routine molecular assay. The aim of this review is to underline by challenging approach the diagnostic limits and pitfalls that could results in failure to recognize the presence of DM2 disease. Understanding and preventing delays in DM2 diagnosis may facilitate family planning, improve symptom management in the short term, and facilitate more specific treatment in the long term.

Patient-Reported Impact of Symptoms in Myotonic Dystrophy Type 2 (PRISM-2)

OBJECTIVE

To determine the frequency and relative importance of the most life-affecting symptoms in myotonic dystrophy type 2 (DM2) and to identify the factors that have the strongest association with these symptoms.

METHODS

We conducted a cross-sectional study of adult patients with DM2 from a National Registry of DM2 Patients to assess the prevalence and relative importance of 310 symptoms and 21 symptomatic themes. Participant responses were compared by age categories, sex, educational attainment, employment status, and duration of symptoms.

RESULTS

The symptomatic themes with the highest prevalence in DM2 were the inability to do activities (94.4%), limitations with mobility or walking (89.2%), hip, thigh, or knee weakness (89.2%), fatigue (89.2%), and myotonia (82.6%). Participants identified the inability to do activities and fatigue as the symptomatic themes that have the greatest overall effect on their lives. Unemployment, a longer duration of symptoms, and less education were associated with a higher average prevalence of all symptomatic themes (p < 0.01). Unemployment, a longer duration of symptoms, sex, and increased age were associated with a higher average effect of all symptomatic themes among patients with DM2 (p < 0.01).

CONCLUSIONS

The lives of patients with DM2 are affected by a variety of symptoms. These symptoms have different levels of significance and prevalence in this population and vary across DM2 subgroups in different demographic categories.

Sleep and breathing disorders in myotonic dystrophy type 2

OBJECTIVES

In patients who exhibit myotonic dystrophy type 1 (DM1), sleep disorders and breathing impairments are common; however, in those with DM type 2 (DM2), limited studies on polysomnography (PSG) and none on phrenic compound motor action potential (CMAP) have been performed, which is the aim of this study.

MATERIALS AND METHODS

Sixteen patients with DM2 were questioned about respiratory symptoms. They underwent PSG with morning arterial gas analyses (AGA). Respiratory functions and phrenic CMAPs were studied. The data were compared to those of 16 healthy controls and 25 patients with DM1.

RESULTS

Daytime tiredness is the most common symptom, but orthopnea was reported in 13% of patients with DM2. A detailed sleep architecture analysis revealed a significantly greater proportion of time in stage 3 and REM sleep, and a shorter time in stage 2 in the DM2 than in controls. Lower respiratory volumes and pressures, abnormalities in AGA, night oxygen desaturation and higher EtCO2 are present in DM2, but are less pronounced than in the DM1 population. Small CMAP amplitudes were presented in 12% of patients with DM2, correlating with smaller respiratory functions and poorer sleep quality. AHI was abnormal in 38% of DM2, mainly due to obstructive apneas. PSG did not reveal hypoventilation.

CONCLUSIONS

Diaphragm weakness and sleep apneas might be present in patients with DM2; therefore, we suggest regular questioning about symptoms of respiratory insufficiency and monitoring of phrenic CMAP. PSG should be recorded, when patients have suggestive symptoms, abnormalities in AGA or higher BMI.

Neuroglia and their roles in central respiratory control; an overview

While once viewed as mere housekeepers, providing structural and metabolic support for neurons, it is now clear that neuroglia do much more. Phylogenetically, they have undergone enormous proliferation and diversification as central nervous systems grew in their complexity. In addition, they: i) are morphologically and functionally diverse; ii) play numerous, vital roles in maintaining CNS homeostasis; iii) are key players in brain development and responses to injury; and, iv) via gliotransmission, are likely participants in information processing. In this review, we discuss the diverse roles of neuroglia in maintaining homeostasis in the CNS, their evolutionary origins, the different types of neuroglia and their functional significance for respiratory control, and finally consider evidence that they contribute to the processing of chemosensory information in the respiratory network and the homeostatic control of blood gases.

Restless legs syndrome and daytime sleepiness are prominent in myotonic dystrophy type 2

OBJECTIVES

Although sleep disturbances are common in myotonic dystrophy type 1 (DM1), sleep disturbances in myotonic dystrophy type 2 (DM2) have not been well-characterized. We aimed to determine the frequency of sleep disturbances in DM2.

METHODS

We conducted a case-control study of 54 genetically confirmed DM2 subjects and 104 medical controls without DM1 or DM2, and surveyed common sleep disturbances, including symptoms of probable restless legs syndrome (RLS), excessive daytime sleepiness (EDS), sleep quality, fatigue, obstructive sleep apnea (OSA), probable REM sleep behavior disorder (pRBD), and pain. Thirty patients with DM2 and 43 controls responded to the survey. Group comparisons with parametric statistical tests and multiple linear and logistic regression analyses were conducted for the dependent variables of EDS and poor sleep quality.

RESULTS

The mean ages of patients with DM2 and controls were 63.8 and 64.5 years, respectively. Significant sleep disturbances in patients with DM2 compared to controls included probable RLS (60.0% vs 14.0%, p < 0.0001), EDS (p < 0.001), sleep quality (p = 0.02), and fatigue (p < 0.0001). EDS and fatigue symptoms were independently associated with DM2 diagnosis (p < 0.01) after controlling for age, sex, RLS, and pain scores. There were no group differences in OSA (p = 0.87) or pRBD (p = 0.12) scores.

CONCLUSIONS

RLS, EDS, and fatigue are frequent sleep disturbances in patients with DM2, while OSA and pRBD symptoms are not. EDS was independently associated with DM2 diagnosis, suggesting possible primary CNS hypersomnia mechanisms. Further studies utilizing objective sleep measures are needed to better characterize sleep comorbidities in DM2.