123rd ENMC International Workshop: Management and Therapy in Myotonic Dystrophy, 6–8 February 2004, Naarden, The Netherlands

MRI of trunk muscles and motor and respiratory function in patients with myotonic dystrophy type 1

Background

Myotonic Dystrophy 1 (DM1) causes progressive myopathy of extremity muscles. DM1 may also affect muscles of the trunk. The aim of this study was to investigate fat infiltration and muscle size in trunk muscles in DM1 patients, and in an age and gender matched control group. Further, explore how fat infiltration and degree of atrophy in these muscles are associated with motor and respiratory function in DM1 patients.

Method

We measured fat infiltration and trunk muscle size by MRI in 20 patients with genetically confirmed classic form of DM1, and compared these cases with 20 healthy, age and gender matched controls. In the DM1 group, we investigated correlations between MRI findings and clinical measures of muscle strength, mobility and respiration. We used sum scores for fat infiltration and muscle size in trunk flexors and trunk extensors in the analysis of group differences and correlations.

Results

Significant differences between cases and controls were present for fat infiltration in trunk flexors (p = 0.001) and trunk extensors (p = < 0.001), and for muscle size in trunk flexors (p = 0.002) and trunk extensors (p = 0.030). Fat infiltration in trunk flexors were significant correlated to back extension strength (rho = − 0.523 p = 0.018), while muscle size in trunk flexors was significantly correlated to trunk flexion strength (rho = 0.506 p = 0.023). Fat infiltration in trunk flexors was significantly correlated with lower general mobility (rho = − 0.628, p = 0.003), reduced balance (rho = 0.630, p < 0.003) and forced vital capacity (rho − 0.487 p = 0.040).

Conclusions

Trunk muscles in DM1 patients had significant higher levels of fat infiltration and reduced muscle size compared to age and gender matched controls. In DM1 patients, fat infiltration was associated with reduced muscle strength, mobility, balance and lung function, while muscle size was associated with reduced muscle strength and lung function. These findings are of importance for clinical management of the disease and could be useful additional outcome measures in future intervention studies.

Electronic supplementary material

The online version of this article (10.1186/s12883-019-1357-8) contains supplementary material, which is available to authorized users.

Major involvement of trunk muscles in myotonic dystrophy type 1

OBJECTIVES

The motor impairments in Myotonic Dystrophy 1 (DM1) are assumed to progress from distal toward proximal parts of the extremities in the Juvenile and Adult forms of DM1. On occasion and late in progress spine deformity is observed. In this study we have examined whether and to what extent trunk muscles are impaired in DM1, and if this impairment is correlated with the duration of the disorder, walking capacity, mobility, balance, and CTG-repeats.

MATERIALS & METHODS

Manual muscle testing (MMT) of skeletal muscle strength in trunk and extremities, reassessment of the mutation size, time since first symptom, the 6 min walk test (6MWT), Rivermead mobility index (RIM) and Timed up & go (TUG) were sampled in 38 adult DM1 outpatients.

RESULTS

We found significant impairment in trunk muscles. Trunk muscle strength decreased significantly with increasing mutation size (r = -0.64, P < 0.001). Reduced walking capacity, mobility and balance were significantly related to decreased trunk muscle strength.

CONCLUSION

DM1 affects trunk muscle groups. The trunk impairments seem to occur relatively early in disease progression. Awareness of trunk impairments may be of importance for everyday functioning and for understanding the risk of injuries due to falls reported among DM1 patients. It may also help in identification of DM1 patients and considered outcome measure in future clinical trials.

Effects of hand-training in persons with myotonic dystrophy type 1--a randomised controlled cross-over pilot study

PURPOSE

To investigate the effects of a hand-training programme on grip, pinch and wrist force, manual dexterity and activities of daily living, in adults with myotonic dystrophy type 1 (DM1).

METHOD

In this randomised controlled trial with a crossover design, 35 adults with DM1 were, after stratification for grip force, assigned by lot to two groups. Group A started with 12 weeks of hand training, while group B had no intervention. After a wash-out period of 12 weeks, where none received training, the order was reversed. The Grippit® was used as primary outcome measure and the hand-held Microfet2™ myometer, the Purdue Pegboard, the Canadian Occupational Performance Measure (COPM) and the Assessment of Motor and Process Skills (AMPS) were secondary outcome measures. Assessments were performed before and after training and control periods, i.e. four times altogether.

RESULTS

Ten persons dropped out and 13 had acceptable adherence. Intention-to-treat analyses revealed significant intervention effects for isometric wrist flexor force (p = 0.048), and for COPM performance (p = 0.047) and satisfaction (p = 0.027). On an individual level, improvements were in general showed after a training period.

CONCLUSION

The hand-training programme had positive effects on wrist flexor force and self-perception of occupational performance, and of satisfaction with performance. No evident detrimental effects were shown.

IMPLICATIONS FOR REHABILITATION

Myotonic dystrophy type 1 (DM1) is a slowly progressive neuromuscular disease characterised by myotonia and muscle weakness and wasting. People with DM1 are often concerned about their ability to carry out ADL and to participate in, e.g. work, sports and hobbies when they gradually become weaker. This pilot study showed that a hand-training programme improved wrist flexor force and self-perception and satisfaction of occupational performance. Resistance training of hand muscles with a silicon-based putty can be a therapy option for people with DM1 in clinical practise.

Clinical approach to the diagnostic evaluation of hereditary and acquired neuromuscular diseases

For diagnostic evaluation of a neuromuscular disease, the clinician must be able to obtain a relevant patient and family history and perform focused general, musculoskeletal, neurologic, and functional physical examinations to direct further diagnostic evaluations. Laboratory studies for hereditary neuromuscular diseases include the relevant molecular genetic studies. The electromyogram and nerve-conduction studies remain an extension of the physical examination, and help to guide further diagnostic studies such as molecular genetics and muscle and nerve biopsies. All diagnostic information needs are to be interpreted within the context of relevant historical information, family history, physical examination, laboratory data, electrophysiology, pathology, and molecular genetics.

Rasch-built myotonic dystrophy type 1 activity and participation scale (DM1-Activ)

We describe the development of an outcome measure of activity and participation for patients with myotonic dystrophy type 1 using the Rasch measurement model. A 49-item questionnaire was completed by 163 DM1 patients. Data were subsequently analyzed with Rasch software to design the item set to fit model expectations. Through systematic investigation of response category ordering, model fit, item bias, and local response dependency, we succeeded in constructing a 20-item unidimensional scale of activity and participation (DM1-Activ). High internal consistency (PSI=0.95) and good test-retest reliability values of item difficulty hierarchy and patient location were demonstrated. Patient measures had acceptable correlations with MRC sum scores and MIRS grades (ICC=0.69 and 0.71, respectively), indicating good external construct validity. DM1-Activ is a practical, reliable and valid outcome measure that fulfils all clinimetric requirements. Further evaluation of this scale is needed to provide a nomogram for clinical use.

Myotonic dystrophies type 1 and 2: a summary on current aspects

Myotonic dystrophies (DMs) encompass at least 2 forms: myotonic dystrophy type 1 and 2. In general, DMs are late-onset autosomal dominant disorders characterized by a variety of multisystemic features including myotonia, muscular dystrophy, cardiac conduction defects, dilated cardiomyopathy, posterior iridescent cataracts, frontal balding, insulin-resistance and disease-specific serological abnormalities such as gamma-glutamyltransferase and creatine kinase elevations, hyperglycemia, hypotestosteronism, and reduced immunoglobulin (Ig) G and IgM levels. Beyond the adult forms, in the classic DM1, a congenital form and an early-onset form is recognized. Here we summarize current aspects of the myotonic dystrophy pathogenesis and review the core features of both types of myotonic dystrophies, including the congenital DM1.

Nonmolecular treatment for muscular dystrophies

PURPOSE OF REVIEW

This review highlights emerging evidence on the management of patients with muscular dystrophies.

RECENT FINDINGS

New diagnostic modalities based on muscle biopsy and DNA analysis mean that diagnoses within the heterogeneous group of muscular dystrophies can be much more precise; also, as the phenotypes associated with these different disorders are clarified, new management implications can be recognized. At the same time, the spread of evidence based medicine into this area has led to an increase in clinical trial activity and the development of evidence based guidelines. Because many if not all muscular dystrophies are multisystem disorders, these guidelines relate not only to the limited number of interventions aimed at improving strength but also to the management of potentially life threatening complications.

SUMMARY

Because specific diagnoses carry specific management implications in many areas for these hitherto rather neglected disorders, a more proactive approach to patients with muscular dystrophies is needed. Complications involving, for example, the cardiovascular, respiratory and gastrointestinal systems may need to be sought and actively managed, whereas caution for complications of anaesthesia and other interventions may also be necessary. However, areas remain where there is little evidence from which practice guidelines can be developed and these will need to be addressed with well planned clinical trials.