Report of the 95th European Neuromuscular Centre (ENMC) sponsored international workshop cognitive impairment in neuromuscular disorders, Naarden, The Netherlands, 13-15 July 2001

Executive functions and daily functioning in myotonic dystrophy type 1 ecological assessment with virtual reality

Central nervous system dysfunction is characteristic of patients with myotonic dystrophy type 1 (DM1). Although no consensus exists regarding the exact cognitive profile of these patients, executive dysfunction has been suggested to play a role. Due to the impact of executive functions on daily performance, this study aimed to describe executive functioning in an ecological manner and to analyze its impact - and that of other clinical variables - on the functional performance of DM1 patients. A Virtual Reality executive functioning test (Nesplora Ice Cream), the Wechsler Adult Intelligence Scale-Fourth Edition, and self-report questionnaires (AES, FSS, ESS and LIFE-H) were administered to 20 patients. Statistical analyses included correlation and multiple regression analyses to analyze the best predictors of daily performance. DM1 patients did not show major difficulties in the executive functioning tasks or in their overall performance on daily habits. However, both cold and hot executive functions still seem necessary for the correct accomplishment of life habits, since planning and level of apathy explained 47.6% of the total variance of daily functioning. This was the first study to assess executive functions in DM1 using Virtual Reality, and our findings open a debate about their actual impairment in this population.

267th ENMC International workshop: psychological interventions for improving quality of life in slowly progressive neuromuscular disorders

This workshop aimed to develop recommendations for psychological interventions to support people living with slowly progressive neuromuscular disorders (NMD). The workshop comprised clinicians, researchers, people living with NMD and their relatives. First, participants considered the key psychological challenges presented by NMD and the impact of NMD on relationships and mental health. Later, several psychological approaches for enhancing well-being in NMD were described. The results of randomised controlled trials of Cognitive Behaviour Therapy and Acceptance and Commitment Therapy for improving fatigue, quality of life, and mood in adults with NMD were examined. Then the group considered ways to adapt therapies for cognitive impairments or neurodevelopmental differences that occur in some NMD, alongside ways to support children and adolescents with NMD and their family members. Based on the evidence from randomised controlled trials, carefully conducted observational studies, and the coherence of these data with the experience of those living with NMD, the group recommends that psychological interventions should be embedded in the routine clinical care offered to people living with NMD.

Epidemiological study and genetic characterization of inherited muscle diseases in a northern Spanish region

Background

Inherited muscle diseases are a group of rare heterogeneous muscle conditions with great impact on quality of life, for which variable prevalence has previously been reported, probably due to case selection bias. The aim of this study is to estimate the overall and selective prevalence rates of inherited muscle diseases in a northern Spanish region and to describe their demographic and genetic features. Retrospective identification of patients with inherited muscle diseases between 2000 and 2015 from multiple data sources. Demographic and molecular data were registered.

Results

On January 1, 2016, the overall prevalence of inherited muscle diseases was 59.00/ 100,000 inhabitants (CI 95%; 53.35–65.26). Prevalence was significantly greater in men (67.33/100,000) in comparison to women (50.80/100,000) (p = 0.006). The highest value was seen in the age range between 45 and 54 (91.32/100,000) years. Myotonic dystrophy type 1 was the most common condition (35.90/100,000), followed by facioscapulohumeral muscular dystrophy (5.15/100,000) and limb-girdle muscular dystrophy type 2A (2.5/100,000).

Conclusions

Prevalence of inherited muscle diseases in Navarre is high in comparison with the data reported for other geographical regions. Standard procedures and analyses of multiple data sources are needed for epidemiological studies of this heterogeneous group of diseases.

Advances in imaging of brain abnormalities in neuromuscular disease

Brain atrophy, white matter abnormalities, and ventricular enlargement have been described in different neuromuscular diseases (NMDs). We aimed to provide a comprehensive overview of the substantial advancement of brain imaging in neuromuscular diseases by consulting the main libraries (Pubmed, Scopus and Google Scholar) including the more common forms of muscular dystrophies such as dystrophinopathies, dystroglycanopathies, myotonic dystrophies, facioscapulohumeral dystrophy, limb-girdle muscular dystrophy, congenital myotonia, and congenital myopathies. A consistent, widespread cortical and subcortical involvement of grey and white matter was found. Abnormalities in the functional connectivity in brain networks and metabolic alterations were observed with positron emission tomography (PET) and single photon emission computed tomography (SPECT). Pathological brain changes with cognitive dysfunction seemed to be frequently associated in NMDs. In particular, in congenital muscular dystrophies (CMDs), skeletal muscular weakness, severe hypotonia, WM abnormalities, ventricular dilatation and abnormalities in cerebral gyration were observed.

In dystroglycanopathy 2I subtype (LGMD2I), adult patients showed subcortical atrophy and a WM periventricular involvement, moderate ventriculomegaly, and enlargement of subarachnoid spaces. Correlations with clinical features have been observed with brain imaging characteristics and alterations were prominent in congenital or childhood onset cases. In myotonic dystrophy type 2 (DM2) symptoms seem to be less severe than in type 1 (DM1).

In Duchenne and Becker muscular dystrophies (DMD, BMD) cortical atrophy is associated with minimal ventricular dilatation and WM abnormalities.

Late-onset glycogenosis type II (GSD II) or Pompe infantile forms are characterized by delayed myelination. Only in a few cases of oculopharyngeal muscular dystrophy (OPMD) central nervous system involvement has been described and associated with executive functions impairment.

Brain pathology in myotonic dystrophy: when tauopathy meets spliceopathy and RNAopathy

Myotonic dystrophy (DM) of type 1 and 2 (DM1 and DM2) are inherited autosomal dominant diseases caused by dynamic and unstable expanded microsatellite sequences (CTG and CCTG, respectively) in the non-coding regions of the genes DMPK and ZNF9, respectively. These mutations result in the intranuclear accumulation of mutated transcripts and the mis-splicing of numerous transcripts. This so-called RNA gain of toxic function is the main feature of an emerging group of pathologies known as RNAopathies. Interestingly, in addition to these RNA inclusions, called foci, the presence of neurofibrillary tangles (NFT) in patient brains also distinguishes DM as a tauopathy. Tauopathies are a group of nearly 30 neurodegenerative diseases that are characterized by intraneuronal protein aggregates of the microtubule-associated protein Tau (MAPT) in patient brains. Furthermore, a number of neurodegenerative diseases involve the dysregulation of splicing regulating factors and have been characterized as spliceopathies. Thus, myotonic dystrophies are pathologies resulting from the interplay among RNAopathy, spliceopathy, and tauopathy. This review will describe how these processes contribute to neurodegeneration. We will first focus on the tauopathy associated with DM1, including clinical symptoms, brain histology, and molecular mechanisms. We will also discuss the features of DM1 that are shared by other tauopathies and, consequently, might participate in the development of a tauopathy. Moreover, we will discuss the determinants common to both RNAopathies and spliceopathies that could interfere with tau-related neurodegeneration.

Fatigue in neuromuscular disorders: focus on Guillain-Barré syndrome and Pompe disease

Fatigue accounts for an important part of the burden experienced by patients with neuromuscular disorders. Substantial high prevalence rates of fatigue are reported in a wide range of neuromuscular disorders, such as Guillain-Barré syndrome and Pompe disease. Fatigue can be subdivided into experienced fatigue and physiological fatigue. Physiological fatigue in turn can be of central or peripheral origin. Peripheral fatigue is an important contributor to fatigue in neuromuscular disorders, but in reaction to neuromuscular disease fatigue of central origin can be an important protective mechanism to restrict further damage. In most cases, severity of fatigue seems to be related with disease severity, possibly with the exception of fatigue occurring in a monophasic disorder like Guillain-Barré syndrome. Treatment of fatigue in neuromuscular disease starts with symptomatic treatment of the underlying disease. When symptoms of fatigue persist, non-pharmacological interventions, such as exercise and cognitive behavioral therapy, can be initiated.

Cognitive/personality pattern and triplet expansion size in adult myotonic dystrophy type 1 (DM1): CTG repeats, cognition and personality in DM1

BACKGROUND

Although central nervous system (CNS) involvement in adult myotonic dystrophy type 1 (DM1) was described long ago, the large number of variables affecting the cognitive and personality profile have made it difficult to determine the effect of DM1 on the brain. The aim of this study was to define the cognitive and personality patterns in adult DM1 patients, and to analyse the relationship between these clinical patterns and their association with the underlying molecular defect.

METHOD

We examined 121 adult DM1 patients with confirmed molecular CTG repeat expansion and 54 control subjects using comprehensive neuropsychological tests and personality assessments with the Millon Clinical Multiaxial Inventory (MCMI)-II. We used a multiple linear regression model to assess the effect of each variable on cognition and personality adjusted to the remainders.

RESULTS

Patients performed significantly worse than controls in tests measuring executive function (principally cognitive inflexibility) and visuoconstructive ability. In the personality profile, some paranoid and aggressive traits were predominant. Furthermore, there was a significant negative correlation between the CTG expansion size and many of the neuropsychological and personality measures. The molecular defect also correlated with patients' daytime somnolence.

CONCLUSIONS

Besides muscular symptomatology, there is significant CTG-dependent involvement of the CNS in adult DM1 patients. Our data indicate that the cognitive impairment predominantly affects the fronto-parietal lobe.

Event-related potentials (P300) and neuropsychological assessment in boys exhibiting Duchenne muscular dystrophy

OBJECTIVE: To examine auditory cognitive evoked potentials (P300 potentials) and neuropsychological dysfunction in patients with Duchenne muscular dystrophy (DMD). METHOD: P300 potentials and neuropsychological test results were obtained from 16 healthy control boys and 20 DMD patients. Full Intelligence Quotients (IQ) were estimated for patients and control group. Mean age was 9.5 years in the DMD patient group, and 10 years in the control group (p>0.05). RESULTS: The mean IQ values were 64.35 in the DMD patients and 82.68 in the control group (p=0.01). Mean P300 values were 347.6 in the DMD group and 337.4 in the control group (p=0.14). There was no significant correlation between parameters in each group. CONCLUSION: DMD patients showed a poor performance as evaluated by P300 potential compared to the control group, although the difference was not statistically significant. Systematic alterations in neuropsychological test results were found, the differences paralleling those detected in IQ.

Experienced and physiological fatigue in neuromuscular disorders

OBJECTIVE

Fatigue has been described as a typical symptom of neurological diseases. It might be caused both by changes at the peripheral and at the central level. This study measured the level of experienced fatigue and physiological correlates of fatigue in three genetically defined neuromuscular disorders.

METHODS

Sixty-five facioscapulohumeral dystrophy (FSHD), 79 classical myotonic dystrophy (DM), 73 hereditary motor and sensory neuropathy type I (HMSN) patients and 24 age-matched healthy controls made a 2-min sustained maximal voluntary contraction of the biceps brachii muscle. Experienced fatigue at the current moment was assessed with the abbreviated fatigue questionnaire just before the physiological measurement. Peripheral fatigue was quantified by comparing the amplitudes of an initial and a final stimulated force response during rest. Muscle fibre conduction velocity was determined from a 5-channel surface EMG recording in order to show peripheral changes during the contraction. Central aspects of fatigue were measured using superimposed electrical endplate stimulation.

RESULTS

Patients showed an increased level of experienced fatigue. Total physiological and peripheral fatigue were smaller in patients compared to controls, and central fatigue was normal. The most interesting result of this study was the presence of a large central activation failure (CAF) in all groups of neuromuscular patients; they showed CAF values of 36-41% already directly at the start of sustained contraction, whereas the control group showed only 12%. CAF slightly correlated with the level of experienced fatigue just before the test.

CONCLUSIONS

The cause of the large CAF in patients is unclear. Reduced concentration, motivation or effort can lead to lower central activation. In neuromuscular patients especially fear of physical activity or fear to damage the muscle or nerve tissue may contribute. Besides, also physiological feedback mechanisms or changes at the motocortical level may be a cause of reduced central activation.

SIGNIFICANCE

For the clinician it is important to know that experienced fatigue is part of the clinical spectrum of neuromuscular patients. Besides, the weakness in these patients is aggravated by reduced central activation. Potentially, both problems could be subject of an intervention.

Cognitive deficits and CTG repeat expansion size in classical myotonic dystrophy type 1 (DM1)

Background

This study was designed to investigate cognitive abilities and their correlations with CTG repeat expansion size in classical Myotonic dystrophy type 1 (DM1), given that earlier studies have indicated cognitive deficits, possibly correlating with blood CTG repeats expansion size.

Methods

A measurement of CTG repeat expansion in lymphocytes and an extensive neuropsychological examination was made in 47 patients (25 women and 22 men). Individual results in the examination were compared with normative data.

Results

A substantial proportion of patients with DM1 (> 40%) scored worse in comparison to normative collectives on tests measuring executive, arithmetic, attention, speed and visuospatial abilities. We found significant correlations between longer CTG repeat expansion size and lower results on most tests associated with these abilities. Furthermore, the association between executive (frontal) deficits and DM1 were strengthened when considering both test results and correlations with CTG repeat expansion size in lymphocytes.

Conclusion

This study showed deficits in several cognitive abilities when patients with DM1 are compared to normative collectives. Some of the neuropsychological tests associated with these abilities are correlated to CTG repeat expansion size in blood. These data highlight the importance of considering cognitive deficits when seeing patients with classical DM1 in clinical practice, but also the utility of using blood CTG repeat expansion size as a broad predictor of finding cognitive deficit in DM1.

Temperament and character in patients with classical myotonic dystrophy type 1 (DM-1)

This study was designed to investigate personality in classical Myotonic Dystrophy (DM-1). Forty-six patients with DM-1 (25 women and 21 men), 31 healthy controls and 37 subjects in a contrast group, consisting of patients with other muscle disorders (spinal muscular atrophy, facioscapulohumeral dystrophy and limb girdle muscular dystrophy), completed the Temperament and Character Inventory (TCI) (Cloninger, 1994). We aimed to establish whether CTG triplet repeat size correlated with ratings of personality dimensions in the TCI. The DM-1 patients scored significantly higher on the TCI dimension Harm avoidance and lower on Persistence, Self-directedness and Cooperativeness. Signs of a personality disorder were found in 20% of the DM-1 patients. No correlation was found between the number of CTG repeats and scores in the TCI. This study indicates deviant personality in classical DM-1 regarding temperament and character, both in comparison to healthy controls and to patients with other muscle disorders with no known brain disorder.

Changes in motor cortex excitability in facioscapulohumeral muscular dystrophy

Previous studies found that some patients with severe, early onset facioscapulohumeral muscular dystrophy (FSHD) present epilepsy and mental retardation. This suggests a functional involvement of central nervous system in severe FSHD. It is unknown whether minor functional changes of central nervous system are also present in less severe forms of FSHD. To investigate this, we examined the excitability of neuronal networks of the motor cortex with a range of transcranial magnetic stimulation paradigms in 20 FSHD patients with heterogeneous clinical severity and compared the data with that from 20 age-matched healthy individuals and from 6 age-matched patients with other muscle diseases. There was significantly less intracortical inhibition in FSHD patients (mean responses +/- SD reduced to 58.1+/-43.5% of the test size) than in controls (mean responses +/- SD reduced to 29.3+/-13.5% of the test size; P=0.025) and in patients with other muscle diseases (mean responses +/-SD, reduced to 30.6+/-11.7% of the test size; P=0.046). No significant difference was found between the control group and patients with other muscle diseases (P=0.970).