Quantitative motor assessment in myotonic dystrophy

What Happened with Muscle Force, Dynamic Stability And Falls? A 10-Year Longitudinal Follow-Up in Adults with Myotonic Dystrophy Type 1

BACKGROUND

Individuals with myotonic dystrophy type 1 (DM1) are known to stumble and fall, but knowledge is scarce regarding dynamic stability in this disorder.

OBJECTIVE

To describe disease progress regarding muscle force, dynamic stability and patient reported unintentional falls during a ten-year period, in individuals with DM1.

METHODS

Quantification of isometric muscle force in four leg muscle groups and assessment of Timed 10-meter-walk in maximum speed (T10max), Timed Up&Go (TUG) and Step test (STEP) were performed at three occasions in a DM1 cohort, together with self-reported falls.

RESULTS

Thirty-four people (m/f:11/23, age:50.2 + /-9.4) participated. The muscle force loss after ten years was large in the distal ankle muscles. A steeper force decrease was seen in most muscles between year five and ten compared to the former five-year period. Males reported more falls than females, 91%vs 35%had fallen last year. A positive correlation, ρ= 0.633, p < 0.001, was shown between walking time (T10max) and number of falls. Frequent fallers were only seen among those with slower walk (T10max > 10seconds), and fewer steps in the STEP test (STEP≤5 steps).

CONCLUSIONS

A diminishing leg muscle strength and worse dynamic stability were seen in the group, with a steeper decrease in the latter five years. Weak ankle dorsiflexors, a slower walk and difficulties to lift the forefoot were related to frequent falls.

Assessment of muscular strength and functional capacity in the juvenile and adult myotonic dystrophy type 1 population: a 3-year follow-up study

INTRODUCTION

Myotonic dystrophy type 1 (DM1) is a progressive, multisystemic, and autosomal dominant disease. Muscle wasting and weakness have been associated with impaired functional capacity and restricted social participation in affected individuals. The disease's presentation is very heterogenous and its progression is still under-documented.

OBJECTIVE

The aim of the study was to document the progression of muscular strength and functional capacity in the DM1 population over a 3-year period.

METHODS

Twenty-three individuals with juvenile or adult phenotypes of DM1 were recruited to complete clinical assessments in 2016 and 2019. Maximal isometric muscle strength (MIMS) was evaluated with quantified muscle testing and functional capacity was evaluated with the Mini-BESTest, the 10-m walk test at comfortable and maximal speeds, the Timed Up and Go and the 6-min walk test. Participants also completed three questionnaires: DM1-Activ, Upper Extremity Functional Index and Lower Extremity Functional Scale (LEFS). Subgroup analyses were evaluated for sex, phenotype, and type of physical activity practiced during the 3-year period.

RESULTS

For the whole group, there was a significant decline in the scores of the Mini-BESTest and the LEFS. Also, MIMS significantly declined for prehension, lateral pinch as well as for hip abductors, knee extensors and ankle dorsiflexors muscle groups. Subgroups analyses revealed that men lost more MIMS than women, and that adult phenotype lost more MIMS than juvenile phenotype.

CONCLUSION

Quantified muscle testing is a better indicator of disease progression over a 3-year period than functional tests. Phenotype and sex are important factors that influence the progression of DM1.

Myopathies with finger flexor weakness: Not only inclusion-body myositis

Muscle disorders are characterized by differential involvement of various muscle groups. Among these, weakness predominantly affecting finger flexors is an uncommon pattern, most frequently found in sporadic inclusion-body myositis. This finding is particularly significant when the full range of histopathological findings of inclusion-body myositis is not found on muscle biopsy. Prominent finger flexor weakness, however, is also observed in other myopathies. It occurs commonly in myotonic dystrophy types 1 and 2. In addition, individual reports and small case series have documented finger flexor weakness in sarcoid and amyloid myopathy, and in inherited myopathies caused by ACTA1, CRYAB, DMD, DYSF, FLNC, GAA, GNE, HNRNPDL, LAMA2, MYH7, and VCP mutations. Therefore, the finding of finger flexor weakness requires consideration of clinical, myopathological, genetic, electrodiagnostic, and sometimes muscle imaging findings to establish a diagnosis.

Progressive Decline in Daily and Social Activities: A 9-year Longitudinal Study of Participation in Myotonic Dystrophy Type 1

OBJECTIVE

To describe and compare changes in participation over a 9-year period in women and men with myotonic dystrophy type 1 (DM1). To compare participation restrictions with available reference values from a typical aging population living in the community.

DESIGN

Descriptive longitudinal design comparing data from baseline (2002) with data from follow-up (2011).

SETTING

Neuromuscular clinic and participant's home.

PARTICIPANTS

Adults with DM1 participated in the follow-up study (N=115).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

The Assessment of Life Habits measured participation in 10 domains of daily and social activities. The minimal clinically important difference is 0.5 on a 10-point scale for participation accomplishment level.

RESULTS

A total of 62% of participants were women, and the mean age was 52.3±10.3 years. A decline (P<.01) was observed with increasing difficulty and assistance required in global participation (mean ± SD, -0.5±0.9), social activities subscore (-0.6±1.2), nutrition (-0.7±1.4), fitness (-1.0±1.6), personal care (-0.7±1.2), mobility (-0.5±1.9), community life (-0.8±1.9), and recreation (-1.5±3.0). More life areas are disrupted over time: 8 domains were below reference values from a population aged 55-64 years at follow-up compared with 2 domains at baseline. Satisfaction with participation remains high and stable over time.

CONCLUSION

As disease duration increases, global participation and more daily and social domains were restricted with increasing difficulty and assistance required. Adults with DM1 showed not only age-associated but disease-specific changes in participation. Description over time of participation could improve clinical assessment and guide interdisciplinary management of DM1, leading to higher rehabilitation success. Further investigation of the factors influencing changes in participation is required to support disease management and services planning.

Validation of the Nine Hole Peg Test as a measure of dexterity in myotonic dystrophy type 1

We aimed to validate the Nine Hole Peg Test as a measure of dexterity in myotonic dystrophy type 1 (DM1). Fifty patients with adult-onset, genetically confirmed DM1 were evaluated by Nine Hole Peg Test and re-evaluated at one week. Myotonia was not a limiting factor. The first test was compared with that performed by normal subjects (n = 28). Contextually, patients underwent handgrip and three-finger pinch assessments by handheld dynamometer. The Nine Hole Peg Test showed high intra-rater and inter-rater reliability in DM1 [ICC 0.86/0.83 for dominant and 0.90/0.88 for non-dominant hand, respectively]. Inverse correlation with handgrip and pinch strength values (r = -0.4; p < 0.01) and direct correlation with Muscular Impairment Rating Scale (r = 0.4; p < 0.01) were found for both DH and NDH. The test was able to differentiate severe DM1 patients, stratified by extent of muscle impairment, from mildly affected and normal controls, with a sensitivity of 97% and 95% for dominant hand and non-dominant hand, respectively (p < 0.0001). In conclusion, we showed that the Nine Hole Peg Test is a reliable, valid and sensitive test of dexterity in DM1, and that it can be considered as a candidate outcome measure to monitor natural history of disease and, possibly, therapeutic response in clinical trials.

Modified dynamic gait index and limits of stability in myotonic dystrophy type 1

INTRODUCTION

The purpose of this study was to describe and compare the performance of balance and walking tests in relation to self-reported fall history in adults with myotonic dystrophy type 1 (DM1).

METHODS

Twenty-two (13 male) participants with DM1 completed, a 6-month fall history questionnaire, the modified Dynamic Gait Index (mDGI), limits of stability (LoS) testing, and 10-m walking tests.

RESULTS

Mean (SD) falls in 6 months was 3.7 (3.1), and 19 (86%) participants reported at least 1 fall. Significant differences in mDGI scores (P = 0.006) and 10-m fast walking gait velocity (P = 0.02) were found between those who had been classified as "fallers" and those who had been classified as "nonfallers." Significant correlations were found between mDGI scores and 10-m walking time.

DISCUSSION

Falls are common in DM1, and the mDGI may have potential to distinguish fallers from nonfallers, whereas the LoS failed to detect such impairment. Future studies should further explore use of the mDGI in DM1. Muscle Nerve 58: 694-699, 2018.

Ankle Strength Impairments in Myotonic Dystrophy Type 1: A Five-Year Follow-up

BACKGROUND

In Myotonic Dystrophy type 1 (DM1) patients, ankle muscles are affected early and this impairment is reported to be a good biological marker for longitudinal studies.

OBJECTIVE

To characterize the ankle dorsiflexion (DF) and eversion (EV) maximal isometric muscle strength changes in adult DM1 patients over 5 years using a standardized handheld dynamometer protocol and the Myoankle method, compare the changes measured with both methods and to the standard error of measurement, and verify the relationship between ankle muscle strength and gait performance.

METHODS

The maximal isometric muscle strength of ankle DF and EV in DM1 patients from Quebec and Lyon was assessed at baseline, 18, 36 and 60 months using a handheld dynamometer (HHD) protocol and the MyoAnkle method.

RESULTS

There was a decrease of torque in DF/EV of 36.0% /31.3% and 27.7% /35.5% for the Quebec and Lyon cohorts respectively (p≤0.01), but not in a linear way. In most cases (82.5%), the changes observed were greater than the standard error of measurement. DF torque measures taken by the two methods (HHD and MyoAnkle) were highly correlated (rp = 0.97-0.98, p < 0.001).

CONCLUSION

Muscle strength ankle impairments are clinically meaningful in DM1 and can be accurately monitored using quantitative testing to measure the efficacy of therapeutic trials.

A 9-year follow-up study of quantitative muscle strength changes in myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is a neuromuscular disorder presenting with major muscle impairments. However, few studies have addressed muscle strength progression using quantitative methods. The aims of this study were to document muscle strength changes in eight muscle groups among adults with DM1 over a 9-year period, and to compare this progression between phenotypes (adult and late-onset) and sex. Patients with a genetic diagnosis of DM1 with the late-onset or the adult phenotype were recruited at baseline through the clinical registry of the Saguenay Neuromuscular Clinic. The maximum isometric muscle strength was measured at baseline and 9 years later using a standardized protocol of quantitative muscle testing. Muscle groups included were shoulder abductors, elbow flexors/extensors, wrist extensors, hip flexors, knee flexors/extensors, and ankle dorsiflexors. For the whole group, a mean loss of 24.5-52.8% was observed over the 9-year period for all muscle groups, except for hip flexors which remained stable. Generally, men were stronger and showed a significant greater rate of decline of muscle strength than women. The adult and late-onset phenotypes taken separately also showed a significant and similar decline over the 9-year period, except for the wrist and knee extensors where muscle strength of participants with the adult phenotype decreased faster than in the late-onset phenotype. The similar rate of decline of muscle strength loss observed between phenotypes highlights the need to develop interventions to prevent this decline, even for patients with the late-onset phenotype who are often considered as mildly impaired, and therefore neglected by the rehabilitation services.

Aceneuramic Acid Extended Release Administration Maintains Upper Limb Muscle Strength in a 48-week Study of Subjects with GNE Myopathy: Results from a Phase 2, Randomized, Controlled Study

Background: GNE Myopathy (GNEM) is a progressive adult-onset myopathy likely caused by deficiency of sialic acid (SA) biosynthesis.

Objective: Evaluate the safety and efficacy of SA (delivered by aceneuramic acid extended-release [Ace-ER]) as treatment for GNEM.

Methods: A Phase 2, randomized, double-blind, placebo-controlled study evaluating Ace-ER 3 g/day or 6 g/day versus placebo was conducted in GNEM subjects (n = 47). After the first 24 weeks, placebo subjects crossed over to 3 g/day or 6 g/day for 24 additional weeks (dose pre-assigned during initial randomization). Assessments included serum SA, muscle strength by dynamometry, functional assessments, clinician- and patient-reported outcomes, and safety.

Results: Dose-dependent increases in serum SA levels were observed. Supplementation with Ace-ER resulted in maintenance of muscle strength in an upper extremity composite (UEC) score at 6 g/day compared with placebo at Week 24 (LS mean difference +2.33 kg, p = 0.040), and larger in a pre-specified subgroup able to walk ≥200 m at Screening (+3.10 kg, p = 0.040). After cross-over, a combined 6 g/day group showed significantly better UEC strength than a combined 3 g/day group (+3.46 kg, p = 0.0031). A similar dose-dependent response was demonstrated within the lower extremity composite score, but was not significant (+1.06 kg, p = 0.61). The GNEM-Functional Activity Scale demonstrated a trend improvement in UE function and mobility in a combined 6 g/day group compared with a combined 3 g/day group. Patients receiving Ace-ER tablets had predominantly mild-to-moderate AEs and no serious adverse events.

Conclusions: This is the first clinical study to provide evidence that supplementation with SA delivered by Ace-ER may stabilize muscle strength in individuals with GNEM and initiating treatment earlier in the disease course may lead to better outcomes.

A More Efficient Transportable and Scalable System for Real-Time Activities and Exercises Recognition

Many people in the world are affected by muscle wasting, especially the population hits by myotonic dystrophy type 1 (DM1). Those people are usually given a program of multiple physical exercises to do. While DM1 and many other people have difficulties attending commercial centers to realize their program, a solution is to develop such a program completable at home. To this end, we developed a portable system that patients could bring home. This prototype is an improved version of the previous one using Wi-Fi, as this new prototype runs on BLE technology. This new prototype conceptualized induces great results.

French translation and cross-cultural adaptation of The Myotonic Dystrophy Health Index

INTRODUCTION

Validation studies of disease-specific instruments for myotonic dystrophy type-1 (DM1) are required prior to their global use in clinical trials involving different cultures and countries. Here we translate and culturally adapt the Myotonic Dystrophy Health Index (MDHI), a disease-specific patient-reported outcome (PRO) measure, for a French DM1 population.

METHODS

Using the International Society for Pharmacoeconomics and Outcomes Research Task Force method for translation and adaptation of PRO questionnaires, we created a French translation of the MDHI. We subsequently tested this instrument in a cohort of French-speaking patients with DM1.

RESULTS

The MDHI was forward and back translated and modified by consensus to create the most compatible translation. Cognitive interviews were conducted with 5 patients with DM1 to ensure the usability and understanding of the translation.

DISCUSSION

The French version of the MDHI is an optimal translation of the original instrument that is acceptable to native patients and ready for clinical trial use. Muscle Nerve 57: 686-689, 2018.

A 9-year follow-up study of the natural progression of upper limb performance in myotonic dystrophy type 1: A similar decline for phenotypes but not for gender

This study aimed to document and compare the decline of upper limb performance among adults with myotonic dystrophy type 1 according to phenotype and gender. A longitudinal descriptive design compared upper limb performance at baseline and follow-up of 70 women and 38 men with the late-onset or adult phenotypes. Grip strength and pinch strength as well as gross dexterity and fine dexterity were assessed. All four performance measures decreased significantly (p <0.001). The decline over time was similar for individuals with the late-onset and adult-onset phenotypes, but differed according to gender. For late-onset and adult-onset phenotypes respectively, women lost less grip strength than men: 0.4 and minus 0.8 kg (2.0% and -9.4%) in women vs. minus 7.4 and minus 3.1 kg (-19.2% and -30.7%) in men. A similar situation was found for gross dexterity: minus 3.0 and minus 3.2 blocks (-4.6% and -5.9%) in women vs. minus 12.4 and minus 8.7 blocks (-19.4% and -16.6%) in men. Pinch gauge had the smallest standard deviations and was one of the only measurement tools with significant detectable changes in relation to the standard error of measurement. Given these results, health professionals and researchers should consider phenotype and gender differently when planning health services or future studies. Indeed, as their upper limb strength and dexterity differed, even if their decline was similar, the phenotypes should not be pooled. Finally, the use of the pinch gauge to assess long-term change in upper limb ability seems preferable to the three other measurements.

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.

Lower limb muscle strength impairment in late-onset and adult myotonic dystrophy type 1 phenotypes

INTRODUCTION

Lower limb strength has never been characterized separately for late-onset and adult myotonic dystrophy type 1 (DM1) phenotypes.

METHODS

The purpose of this study was to: (1) describe and compare lower limb strength between the 2 DM1 phenotypes; and (2) compare the impairment profiles obtained from 2 assessment methods [manual (MMT) and quantitative (QMT) muscle testing] among 107 patients.

RESULTS

Both MMT and QMT showed more pronounced weakness in the adult phenotype. In the late-onset phenotype, although MMT showed normal strength, QMT revealed a loss of 11.7%-20.4%. Participants with grade 1 or 2 on the Muscle Impairment Rating Scale had weakness detected using QMT, which suggests earlier muscle impairment than MMT alone would suggest.

CONCLUSIONS

To avoid muscle wasting, physical activity recommendations should be made for the late-onset phenotype and in the early stages of the disease for the adult phenotype. MMT is not recommended for use in clinical trials. Muscle Nerve 56: 57-63, 2017.

Body composition and clinical outcome measures in patients with myotonic dystrophy type 1

Myotonic Dystrophy type 1 (DM1) is the most common form of adult onset muscular dystrophy. In this study we compared body composition in DM1 and matched controls and evaluated the relationship between these parameters and clinical outcome measures in DM1 patients. In addition we established the sensitivity to change of these measures in a prospective 18 month longitudinal study of the DM1 patient cohort. Clinical data, manual muscle testing (MMT), quantitative muscle testing (QMT) of ankle dorsiflexion, bilateral grip dynamometry, 6 minute walk test and a DM1 functional rating scale (DM1-Activ) were collected at baseline (n = 38) and 18 month follow-up (n = 36). The case-control analysis was performed comparing baseline data with 31 anthropometrically matched controls. Dual-energy X-ray absorptiometry (DEXA) was used to obtain regional measurements of fat-free mass index (FFMI) and fat mass index (FMI) and demonstrated significant reduction of FFMI in the legs (left p = 0.004; right p = 0.017) and trunk (p < 0.0001) and increased FMI localised to the trunk (p < 0.0001) in DM1 patients compared to controls. Regional left and right arm FFMI and FMI significantly positively and negatively correlated with grip strength and both total FFMI (p = 0.0009) and FMI (p = 0.02) decreased and increased by 0.38 kg/m² and 0.31 kg/m² respectively after 18 month follow-up. DEXA is likely to provide a useful secondary outcome measurement of disease progression in addition to muscle strength and timed functional tasks in clinical trials.

Lower limb muscle impairment in myotonic dystrophy type 1: the need for better guidelines

In myotonic dystrophy type 1 (DM1), leg muscle weakness is a major impairment. There are challenges to obtaining a clear portrait of muscle strength impairment. A systematic literature review was conducted on lower limb strength impairment in late-onset and adult phenotypes to document variables which affect strength measurement. Thirty-two articles were reviewed using the COSMIN guidelines. Only a third of the studies described a reproducible protocol. Only 2 muscle groups have documented reliability for quantitative muscle testing and only 1 total score for manual muscle testing. Variables affecting muscle strength impairment are not described in most studies. This review illustrates the variability in muscle strength assessment in relation to DM1 characteristics and the questionable validity of the results with regard to undocumented methodological properties. There is therefore a clear need to adopt a consensus on the use of a standardized muscle strength assessment protocol.

Muscle force, balance and falls in muscular impaired individuals with myotonic dystrophy type 1: a five-year prospective cohort study

Individuals with myotonic dystrophy type 1 (DM1) have progressive muscle weakness with gait and balance impairments. We explored prospectively the natural history of muscle force, gait, balance, balance confidence and walking ability in muscular affected individuals with DM1. After five years data from 43 individuals (m/f:18/25) were analysed. All measures of balance showed statistically significant deterioration (p < 0.001) with averaged yearly loss of function by 3-4%. In the group as a whole, loss of muscle force was statistically significant in all lower limb muscles measured after five years: changes relative to baseline force were median -6% to -18%. For males muscle force loss was statistically significant in all leg muscles, but only in hip flexors for women. After five years 100% of the men had fallen during the previous year and 67% three times or more, in contrast only 60% of the women had fallen in the previous year and 36% three times or more. The proportion of individuals seeking medical care the previous year, after falling, was more than doubled after five years, albeit the number of falls had not changed. Awareness of this increased risk of falls is important for caregivers and patients.

Natural history of skeletal muscle involvement in myotonic dystrophy type 1: a retrospective study in 204 cases

Myotonic dystrophy type 1 (DM1) is the most frequent muscular dystrophy in adult. The aim of this study was to investigate the natural history of skeletal muscle weakness in adults, in a cross-sectional, retrospective study. In a cohort of 204 adult DM1 patients, we quantified muscle impairment, handgrip force and physical disability. Muscle strength was similarly affected in the legs and in the arms, the right and left side, and distally more than proximally in patients. The earliest and the most affected skeletal muscles were the digit flexors, foot dorsiflexors and neck flexors; whereas the elbow and knee extensors and flexors were the least affected muscle groups. The rate of decline of the muscle strength was -0.111 units/year. The handgrip values were lower in DM1 patients than the normative values and the rate of decline in handgrip force per year was -0.24 kg. Limitation in mobility or walking is observed in 84 % of DM1 patients but requirement of wheelchair is infrequent (3 %). The decrease in muscle strength, handgrip force and the increase in physical disability were highly correlated with duration of the disease and the number of CTG repeats in the blood. Significant association was found between decline in muscle strength and the age at onset, physical disability and the age of patients at evaluation, handgrip force and gender. Decline in muscle weakness is very slow and although limitation when walking is a common manifestation of DM1 in patients, the requirement of wheelchair is infrequent.

Prevalence of Lifestyle Risk Factors in Myotonic Dystrophy Type 1

Background:

The prevalence of unhealthy lifestyle habits such as smoking has seldom been described in neuromuscular disorders, including myotonic dystrophy type 1 (DM1). However, it is essential to document the unhealthy lifestyle habits as they can exacerbate existing impairments and disabilities. The objectives are: 1) To determine the prevalence of risk factors among individuals with DM1; 2) To compare the prevalence among classic and mild phenotypes.

Method:

A survey was done on a sample of two-hundred (200) patients with DM1 as part of a larger study. Lifestyle risk factors included being overweight or obese, tobacco smoking, illicit drug use, excessive alcohol consumption and physical inactivity. A registered nurse administered the validated public health survey. Categorization of risk factors were based on national standards and compared with provincial and regional prevalences.

Results:

50% of DM1 patients were overweight or obese, 23.6% were regular smokers, and 76% were physically inactive. Except for overweight and obesity, significant differences were observed between patients with classic and mild phenotypes for all the other lifestyle risk factors: those with the classic phenotype being more often regular smokers, consuming more often illicit drugs and being less physically active.

Conclusions:

The results of this study will provide guidance for the development of better adapted and focussed health promotion interventions in the future.

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.

Isokinetic testing in patients with neuromuscular diseases: a focused review

OBJECTIVE

This literature review aimed to study the use of isokinetic testing in patients with neuromuscular diseases (NMDs) and to identify directions for future research of isokinetic testing.

DESIGN

The MEDLINE (January 1, 1965, to July 1, 2010), Cumulative Index to Nursing and Allied Health (1980 to May 2010), and Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 3, 2009) electronic databases were searched. The literature search was conducted using the keywords muscle assessment, muscle strength, evaluation, isokinetic, neuromuscular diseases, muscle fatigue, functional test, rehabilitation, and literature search. Relevant references cited in the selected articles were also considered, regardless of the year of publication.

RESULTS

The search strategy yielded 13 articles involving a variety of patients with known NMDs. All studies demonstrated that isokinetic dynamometry is appropriate and safe for ambulatory patients with NMDs. Isokinetic testing has proven to be reliable (intratest/intertest correlation coefficient ranged from 0.65 to 0.98), with the proximal muscles having the highest reliability, and sensitive to disease progression and to the effects of various therapeutic interventions. However, isokinetic testing has never gained wide acceptance, partly because of concerns about stabilizing the dynamometer and the subject during the test and of the lack of standardized protocols for isokinetic strength measurement.

CONCLUSIONS

Isokinetic testing is an important part of the comprehensive evaluation and rehabilitation of patients with NMD. Research has demonstrated its efficacy in providing clinically relevant information. When integrated with a complete history, physical examination, and functional evaluation, isokinetic testing and exercise can be a valuable tool for the clinician in the assessment, rehabilitation, and performance enhancement of patients with NMD. Such equipment, however, has several disadvantages, rendering it usually impractical in the clinical setting.

Quantitative assessment of skeletal muscle degeneration in patients with myotonic dystrophy type 1 using MRI

PURPOSE

To identify MRI biomarkers that could be used to follow disease progression and therapeutic efficacy in one individual muscle in patients with myotonic dystrophy type 1 (DM1).

MATERIALS AND METHODS

Lower limb MRI and maximal ankle dorsiflexor strength assessment, using a hand-held dynamometer, were performed in 19 DM1 patients and 6 control subjects. The volume of residual muscle tissue of Tibialis Anterior (TA) muscle was chosen as an index for muscle atrophy, and the T2-relaxation-time of the residual muscle tissue was measured to evaluate edema-like lesions. The fat-to-water ratio was assessed using three-point Dixon images to quantify fat infiltration in the entire muscle.

RESULTS

The intra-observer variability of MRI indices (∼5.2% for the residual muscle tissue volume and 2.5% for the fat-to-water ratio) was lower than that of the dorsiflexor torque measurement (∼11.5%). A high correlation (r = 0.91) was found between maximal ankle dorsiflexor strength and residual TA muscle tissue volume in DM1 patients. Increases in the fat-to-water ratio and T2-relaxation-time were associated with a decrease in maximal ankle dorsiflexor strength.

CONCLUSION

MRI appears as a noninvasive method which can be used to follow disease progression and therapeutic efficacy.

Aging with muscular dystrophy: pathophysiology and clinical management

Major advances in the fields of medical science and physiology, molecular genetics, biomedical engineering, and computer science have provided individuals with muscular dystrophy (MD) with more functional equipment, allowing better strategies for improvement of quality of life. These advances have also allowed a significant number of these patients to live much longer. As progress continues to change management, it also changes patients' expectations. A comprehensive medical and rehabilitative approach to management of aging MD patients can often fulfill expectations and help them enjoy an enhanced quality of life.

The use of muscle strength assessed with handheld dynamometers as a non-invasive biological marker in myotonic dystrophy type 1 patients: a multicenter study

Background

Myotonic dystrophy type 1 (DM1) is a multisystem disorder that demonstrates variable symptoms and rates of progression. Muscle weakness is considered one of the main problems with a clinical picture that is characterized by distal weakness of the limbs progressing to proximal weakness. The main objective of this study was to characterize the maximal strength of ankle eversion and dorsiflexion in DM1 patients. Manual and handheld dynamometer (HHD) muscle testing were also compared.

Methods

The maximal strength of 22 patients from Quebec (mean age = 41,1 ± 13,8) and 24 from Lyon (mean age = 41,6 ± 10,2) were compared to 16 matched controls.

Results

With the use of HHD, an excellent reproducibility of the torque measurements was obtained for both centers in eversion (R² = 0,94/Quebec; 0,89/Lyon) and dorsiflexion (R² = 0,96/Quebec; 0,90/Lyon). The differences between 3 groups of DM1 (mild, moderate, severe) and between them and controls were all statistically significant (p < 0,001). No statistical differences between sites were observed (p > 0.05). The degree of muscle strength decline in dorsiflexion (eversion) were 60% (47%), 77% (71%), and 87% (83%) for DM1 with mild, moderate, and severe impairments, respectively. The smallest mean difference between all DM1 patients taking together was 2.3 Nm, a difference about twice than the standard error of measurement. There was a strong relationship between eversion and dorsiflexion strength profiles (R² = 0,87;Quebec/0,80;Lyon). Using a 10-point scale, manual muscle testing could not discriminate between the 3 groups of DM1 patients.

Conclusions

The HHD protocol showed discriminative properties suitable for multicentre therapeutic trial. The present results confirmed the capacity of quantitative muscle testing to discriminate between healthy and DM1 patients with different levels of impairments. This study is a preliminary step for the implementation of a valid, reliable and responsive clinical outcome for the measurement of muscle impairments with this population.

Clinical features of spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy is an X-linked motor neuron disease caused by a CAG repeat expansion in the androgen receptor gene. To characterize the natural history and define outcome measures for clinical trials, we assessed the clinical history, laboratory findings and muscle strength and function in 57 patients with genetically confirmed disease. We also administered self-assessment questionnaires for activities of daily living, quality of life and erectile function. We found an average delay of over 5 years from onset of weakness to diagnosis. Muscle strength and function correlated directly with serum testosterone levels and inversely with CAG repeat length, age and duration of weakness. Motor unit number estimation was decreased by about half compared to healthy controls. Sensory nerve action potentials were reduced in nearly all subjects. Quantitative muscle assessment and timed 2 min walk may be useful as meaningful indicators of disease status. The direct correlation of testosterone levels with muscle strength indicates that androgens may have a positive effect on muscle function in spinal and bulbar muscular atrophy patients, in addition to the toxic effects described in animal models.

Usefulness of clinical and electrocardiographic data for predicting adverse cardiac events in patients with myotonic dystrophy

BACKGROUND

Myotonic dystrophy type 1 (DM1) has been associated with an increased risk of sudden death, either by heart block or malignant ventricular arrhythmias. Identifying patients at risk remains difficult and no consensus has been reached regarding the best approach for follow-up and prevention of sudden death.

OBJECTIVES

To identify noninvasive clinical and electrocardiographic predictors of adverse cardiac events in patients with DM1.

METHODS

Clinical and serial electrocardiographic data on 428 patients with a DNA-proven diagnosis of DM1, followed during a mean period of 11.7 years, were reviewed. Variables associated with adverse cardiac events were identified.

RESULTS

Eleven patients (2.6%) experienced sudden death and 13 (3.0%) required implantation of a pacemaker. On univariate analysis, adverse events were associated with advancing age, prolongation of the PR, QRS and corrected QT (QTc) intervals, as well as the degree of neuromuscular impairment. No such relationship was found with the extent of genetic anomaly (number of cytosine-thymine-guanine repeats). However, multivariate analysis using Cox proportional hazards models showed that only baseline PR and QTc intervals were significantly linked to the end points of sudden death or pacemaker implantation; the age-adjusted RR was 3.7 (95% CI 1.5 to 8.6) if baseline PR was 200 ms or longer (P=0.003), and 3.0 (95% CI 1.0 to 8.8) if the baseline QTc was 450 ms or longer (P=0.047).

CONCLUSIONS

In a large unselected cohort of 428 patients with DM1, the cumulative incidence of sudden death was relatively low, and the delayed conduction on surface electrocardiogram was found to be potentially helpful for identifying patients at risk for sudden death or pacemaker implantation.

Predictors of disrupted social participation in myotonic dystrophy type 1

OBJECTIVE

To identify personal and environmental predictors of the most disrupted participation domains in people with myotonic dystrophy type 1 (DM1).

DESIGN

Cross-sectional study.

SETTING

Outpatient neuromuscular clinic.

PARTICIPANTS

Adults (n=200; 121 women), age 18 years or older (mean age, 47 y), with a confirmed diagnosis of DM1 were selected from the registry of a neuromuscular clinic (N=416). Fifty-two participants had the mild phenotype and 148 the adult phenotype.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Social participation in mobility, housing, employment, and recreation was assessed with the Life Habits Measure. Disrupted participation was based on whether help was needed in performing most life habits because of incapacities or environmental barriers. Environmental factors were assessed by using the Measure of the Quality of the Environment. Personal factors were assessed with standardized instruments including the Berg Balance Scale, the Krupp Fatigue Severity Scale, and manual muscle testing.

RESULTS

A large proportion of participants (45%-61%) reported disrupted participation in all 4 domains. Lower-extremity strength (odd ratios [OR], 15.0-5.5; P<.050) and higher fatigue (OR, 6.0-2.6; P<.05) were present in participants with disrupted participation. With regard to environmental factors, family support (OR, 3.6-2.5; P<.05) and public services (OR, 2.8-2.2; P<.05) were perceived as barriers for participants with disrupted participation in most domains.

CONCLUSIONS

This study identified personal and environmental factors that may influence the trajectory toward disrupted participation in individuals with DM1. Fatigue, strength, family support, and public services were found to be independent predictors of disrupted participation.

Chronic pain in persons with myotonic dystrophy and facioscapulohumeral dystrophy

OBJECTIVE

To determine the nature and scope of pain in working-aged adults with myotonic muscular dystrophy (MMD) and facioscapulohumeral muscular dystrophy (FSHD).

DESIGN

Retrospective, cross-sectional survey.

SETTING

Community-based survey.

PARTICIPANTS

Convenience sample of subjects with MMD and FSHD.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Overall intensity and duration of pain, pain inference, pain sites, pain treatments, and relief provided by pain treatments.

RESULTS

More subjects with FSHD (82%) than with MMD (64%) reported pain. The most frequently reported pain sites for both diagnostic groups were lower back (66% MMD, 74% FSHD) and legs (60% MMD, 72% FSHD). Significant differences in pain intensity were found between the diagnostic groups in the hands, legs, knees, ankles, and feet, with patients with MMD reporting greater pain intensity at these sites than patients with FSHD. Age was related to the onset of pain (participants reporting pain were younger than those not reporting pain in the FSHD sample), but pain severity was not significantly associated with age in those reporting pain. Respondents with both diagnoses that reported mobility limitations and used assistive devices (eg, wheelchair, cane) reported more pain severity than those with mobility limitations who did not use assistive devices, who, in turn, reported more pain severity than respondents who reported no mobility limitations at all. The treatments that were reported to provide the greatest pain relief were not necessarily those that were the most frequently tried or still used.

CONCLUSIONS

The findings indicate that pain is a more common problem in persons with FSHD than in persons with MMD, although it is common in both populations. In addition, these pain problems are chronic, underscoring the need to identify and provide effective pain treatments for patients with these neuromuscular diseases.

The Change of Grip Strength in a Patient with Congenital Myotonic Dystrophy Over a 4-year Period

Myotonic dystrophy (MyD) is a neuromuscular disease that is autosomal dominant and the most common form of muscular dystrophy affecting adults. The clinical features of MyD include a multisystemic disorder characterized by myotonia, progressive muscle weakness and wasting, cataracts, premature balding and mental retardation. The most severe type of MyD is classified as congenital MyD (CMyD). The muscle weakness in CMyD is very severe, but muscle development can be observed in the period of growth. However, no clinical case of this type has been reported yet. Therefore, we report on a girl with CMyD who had an increase in muscle strength over a four-year period. The girl with CMyD participated in this study from the age of 9 to the age of 12. The measurement of muscle strength was recorded as the maximum score of grip strength with the use of dynamometers. Grip strength was assessed once a year by the same two physical therapists. Grip strength of CMyD for each year was markedly weak when compared with the normal controls, but muscle strength changed within some specific growth areas. The muscle weakness in CMyD was remarkable, but the result showed that specific muscle strength of CMyD in childhood was actually increased.

Towards an integrative approach to the management of myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is the most common type of muscular dystrophy in adults. Approximately 60% of individuals report either having difficulty performing or being unable to carry out some activities related to home management, mobility and transportation, work and leisure. Employment, educational level and income are, on average, lower than in the general population. The complexity and variability of disease manifestations in DM1 undoubtedly pose a challenge as regards anticipating all potential problems and developing a plan for health and community management. This article presents a conceptual model for DM1 management as well as a brief discussion of an approach for developing interdisciplinary health and community services.

Myotonic dystrophy: practical issues relating to assessment of strength

BACKGROUND

Myotonic dystrophy type 1 is a slowly progressive multisystem disease in which skeletal muscle involvement is prominent. As novel physical and pharmacological treatments become available, it is crucial to be able to measure their efficacy accurately.

METHODS

158 consecutive patients with myotonic dystrophy were assessed annually in a specialist muscle clinic. Strength was measured using both the Medical Research Council (MRC) scale and a hand-held dynamometer. Dynamometer readings were obtained from 108 normal subjects (controls).

RESULTS

The movements showing the greatest rate of change in strength were ankle dorsiflexion and pinch grip. Both of these showed a decline of only 0.06 points/year on the MRC scale. Using a hand-held dynamometer, a change in strength of 1.18 kgN/year for women and 1.61 kgN/year for men was detected.

CONCLUSIONS

The MRC scale is unsuitable for detecting the small changes in strength seen in a slowly progressive disease such as myotonic dystrophy. Dynamometry provides a simple alternative that can give meaningful data over the duration of a typical clinical trial.

The gross motor function measure™ is a valid and sensitive outcome measure for spinal muscular atrophy

Spinal muscular atrophy is a genetic disease of the anterior horn cell with high morbidity rate in childhood. Certain drugs may be of benefit and are in or under consideration for Phase II trials. Outcome measures that are age appropriate and representative of disease activity remain under study. Several have not yet been validated for spinal muscular atrophy. The Gross Motor Function Measure is a measure of motor function. We showed previously that the Gross Motor Function Measure is a reliable outcome measure to assess motor function in children with spinal muscular atrophy. By collating our data from 40 spinal muscular atrophy patients, ages 5 through 17 years, we now show the validity of the Gross Motor Function Measure when compared to Quantitative Muscle Testing and ambulatory status in children with spinal muscular atrophy. The median for Gross Motor Function Measure total scores for walkers was 237 (range: 197-261) and for non-walkers, 64 (range: 4-177; P<0.0001) with no distributional overlap. We conclude that the Gross Motor Function Measure is valid and sensitive as an outcome measure for clinical trials in pediatric spinal muscular atrophy.

Challenges in drug development for muscle disease: A stakeholders' meeting

Current treatment benefits for patients with muscle disease are limited, but progress in legislative and scientific initiatives have set the stage for the development of new therapies. The MD-CARE Act (Public Law 107-84), which allocates federal resources to muscular dystrophy, was approved by Congress and signed into law by the President of the United States in 2001. This has shifted the emphasis toward translational research. To facilitate a push toward therapy for muscle disorders, the Muscular Dystrophy Association (MDA) sponsored a meeting with representatives from industry, the Food and Drug Administration (FDA), the National Institutes of Health (NIH), and other government agencies and academia. Each contributed in different ways. The FDA helped define the necessary data to support investigational new drug (IND) applications including the design of proof-of-principle studies, outcome measures for clinical trials, and the pathway for developing surrogate measures for fast-tracking promising new drugs. The NIH, other government agencies, and the MDA described potential funding sources for translational research. Industry delineated a complementary role with academia, and academic investigators elucidated the current strengths and weaknesses of available clinical endpoints. The meeting provided a format for communication for diverse disciplines that usually have no common meeting ground, helping to lay the foundation for bringing products to market in a timely fashion.

Nutritional inadequacy in adults with muscular dystrophy

Patients with muscular dystrophy may be prone to nutrient deficiency due to mobility limitations or oropharyngeal weakness. Patients with myotonic muscular dystrophy (DM1) may be particularly prone to nutritional deficiencies from associated dysmotility of the entire gastrointestinal tract. We prospectively evaluated nutritional intake, body composition, and muscle strength in adult patients with DM1 (n = 29) and other muscular dystrophies (n = 22) on two occasions separated by approximately 6 months. Handgrip was significantly lower and knee extension higher for DM1 compared to other dystrophies, with no between-group differences in nutritional intakes. Many patients in both groups demonstrated inadequate nutrient intake of protein, energy, vitamins (water and fat soluble), and minerals (calcium and magnesium). Significant correlations were found between measures of strength and certain individual nutrients (e.g., copper and water-soluble vitamins). These data indicate that a substantial number of adults with muscular dystrophy do not meet current dietary intake recommendations. The potential clinical implications of these findings are discussed.