Strength Evaluation in Neuromuscular Disease

New Clinical and Immunofluoresence Data of Collagen VI-Related Myopathy: A Single Center Cohort of 69 Patients

Pathogenetic mechanism recognition and proof-of-concept clinical trials were performed in our patients affected by collagen VI-related myopathies. This study, which included 69 patients, aimed to identify innovative clinical data to better design future trials. Among the patients, 33 had Bethlem myopathy (BM), 24 had Ullrich congenital muscular dystrophy (UCMD), 7 had an intermediate phenotype (INTM), and five had myosclerosis myopathy (MM). We obtained data on muscle strength, the degree of contracture, immunofluorescence, and genetics. In our BM group, only one third had a knee extension strength greater than 50% of the predicted value, while only one in ten showed similar retention of elbow flexion. These findings should be considered when recruiting BM patients for future trials. All the MM patients had axial and limb contractures that limited both the flexion and extension ranges of motion, and a limitation in mouth opening. The immunofluorescence analysis of collagen VI in 55 biopsies from 37 patients confirmed the correlation between collagen VI defects and the severity of the clinical phenotype. However, biopsies from the same patient or from patients with the same mutation taken at different times showed a progressive increase in protein expression with age. The new finding of the time-dependent modulation of collagen VI expression should be considered in genetic correction trials.

Body composition, muscle strength, and physical function of patients with Bethlem myopathy and Ullrich congenital muscular dystrophy

OBJECTIVE

To determine the contributions of body mass, adiposity, and muscularity to physical function and muscle strength in adult patients with Bethlem myopathy (BM) and Ullrich congenital muscular dystrophy (UCMD).

MATERIALS AND METHODS

Evaluation involved one UCMD and 7 BM patients. Body composition was determined by body mass index (BMI) and dual-energy-X-ray-absorptiometry (DXA), muscle strength by dynamometry, physical function by the distance walked in 6 minutes (6MWD), forced vital capacity (FVC) by a spirometer.

RESULTS

Six participants were of normal weight and 2 overweight based on BMI; all were sarcopenic based on appendicular fat free mass index (AFFMI); and 7 were sarcopenic obese based on AFFMI and % fat mass. Average muscle strength was reduced below 50% of normal. The 6MWD was in BM patients 30% less than normal. FVC was reduced in 4 of the BM patients. Muscle strength had a good correlation with the physical function variables. Correlation between muscle strength and BMI was poor; it was very high with AFFMI. AFFMI was the best single explicator of muscle strength and physical function.

CONCLUSION

Muscle mass determined by DXA explains most of the variability of the measures of muscle strength and physical function in patients with BM and UCMD.

Musculoskeletal conditions of the foot and ankle: assessments and treatment options

Musculoskeletal conditions of the foot and ankle are an important public health challenge due to their increasing incidence combined with their substantial negative impact on patients' quality of life. Non-pharmacological treatments serve as the first line of treatment and are frequently used for patients with musculoskeletal conditions of the foot and ankle. This review provides a summary of the assessments and non-invasive treatment options based upon available evidence. Recent studies show that individuals with foot and ankle pain have multiple co-existing impairments in alignment, motion, load distribution and muscle performance that may be evident in static and/or dynamic tasks. In addition, both clinical and epidemiological studies support the inter-dependence between the foot and proximal joints. For instance, aberrant foot structure has been linked to foot osteoarthritis (OA), as well as OA and pain at the knee and hip. Most recently, advances in motion capture technology and plantar load distribution measurement offer opportunities for precise dynamic assessments of the foot and ankle. In individuals with musculoskeletal conditions of the foot and ankle, the chief objectives of treatment are to afford pain relief, restore mechanics (alignment, motion and/or load distribution) and return the patient to their desired level of activity participation. Given that most patients present with multiple impairments, combinational therapies that target foot-specific as well as global impairments have shown promising results. In particular, in individuals with rheumatoid arthritis and other rheumatic diseases, comprehensive rehabilitation strategies including early detection, foot-based interventions (such as orthoses) and wellness-based approaches for physical activity and self-management have been successful. While significant improvements have been made in the last decade to the assessment and treatment of foot and ankle conditions, few randomised clinical trials specifically have investigated patients with foot or ankle conditions to provide global insights into this area. Consequently, current recommendations vary based upon the scope of studies presented in this review as well as the strength of studies. This review indicates a need for more in-depth investigations into the components of assessment and treatment options for foot and ankle musculoskeletal conditions.

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.

Cyclosporine A in Ullrich congenital muscular dystrophy: long-term results

Six individuals with Ullrich congenital muscular dystrophy (UCMD) and mutations in the genes-encoding collagen VI, aging 5–9, received 3–5 mg/kg of cyclosporine A (CsA) daily for 1 to 3.2 years. The primary outcome measure was the muscle strength evaluated with a myometer and expressed as megalimbs. The megalimbs score showed significant improvement (P = 0.01) in 5 of the 6 patients. Motor function did not change. Respiratory function deteriorated in all. CsA treatment corrected mitochondrial dysfunction, increased muscle regeneration, and decreased the number of apoptotic nuclei. Results from this study demonstrate that long-term treatment with CsA ameliorates performance in the limbs, but not in the respiratory muscles of UCMD patients, and that it is well tolerated. These results suggest considering a trial of CsA or nonimmunosuppressive cyclosporins, that retains the PTP-desensitizing properties of CsA, as early as possible in UCMD patients when diaphragm is less compromised.

Duchenne muscle activity evaluation and muscle function preservation: is it possible a prophylactic strategy?

Duchenne muscular dystrophy yields pervasive and progressive muscle mass loss. In the current measures relating to the monitoring of disease progression the following are relevant (i): the type of scale used, (ii) the clinical significance of the attribute being measured and (iii) the mathematical properties of the data provided. The high prevalence of obesity at an early stage of this pathology could result not only from reduced physical activity, but also from low resting energy expenditure, abnormal nutrient utilization or overfeeding. This muscle weakness may be attenuated by regular low-intensity exercise. However, there is a critical lack of data to support appropriate exercise prescription. Because inappropriate activity may exacerbate the dystrophic process, a systematic analysis of muscle function to determine potential exercise load thresholds to avoid injury in dystrophic mice and dogs, and then in humans is recommended.

Development of a French Isometric Strength Normative Database for Adults Using Quantitative Muscle Testing

OBJECTIVE

To establish a normative database for isometric strength measured by quantitative muscle testing (QMT) for a French adult population.

DESIGN

Measurement of maximal voluntary isometric contraction.

SETTING

Four clinical centers involved in neuromuscular disorders.

PARTICIPANTS

A total of 315 healthy adults (147 men, 168 women) ages 20 to 80 years.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

Isometric torque values of 14 muscle functions (13 bilaterally and neck).

RESULTS

This study led to the development of a French isometric strength normative database for adults measured by QMT. For each muscle function, predictive regression models using age, sex, and weight are proposed. Some methodologic issues concerning strength measurement are discussed.

CONCLUSIONS

This database can be used to compute relative deficits in muscle strength for 27 muscle functions and also to estimate composite scores for follow-up of patients either during the natural history of their disease or during a therapeutic trial.

Force assessment in periodic paralysis after electrical muscle stimulation

OBJECTIVE

To obtain an objective measure of muscle force in periodic paralysis, we studied ankle dorsiflexion torque during induced paralytic attacks in hyperkalemic and hypokalemic patients. SUBJECTS, PATIENTS, AND METHODS: Dorsiflexor torque after peroneal nerve stimulation was recorded during provocative tests on 5 patients with hypokalemic or hyperkalemic disorders and on 2 control subjects (1995-2001). Manual strength assessment was simultaneously performed in a blinded fashion. Standardized provocation procedures were used.

RESULTS

The loss of torque in hyperkalemic patients roughly paralleled the loss of clinically detectable strength, whereas in the hypokalemic patients, pronounced torque loss occurred well before observed clinical effects. No dramatic changes occurred in the control subjects. Torque amplitude decreased more than 70% in all patients during the provocation tests; such decreases were associated with alterations induced in serum potassium concentrations.

CONCLUSIONS

Stimulated torque measurement offers several advantages in characterizing muscle dysfunction in periodic paralysis: (1) it is independent of patient effort; (2) it can show a definitely abnormal response early during provocative maneuvers; and (3) characteristics of muscle contraction can be measured that are unobservable during voluntary contraction. Stimulated torque measurements can characterize phenotypic muscle function in neuromuscular diseases.

The application of control limits analysis to the myometric assessment of motor performance in neuropathy patients

Measurement of muscle strength by myometry is used to monitor the natural course and treatment response of motor system diseases, both in individual patients and clinical trials. However, the practical usefulness of myometric data is reliant upon a statistical method for analysing serial strength measurements which distinguishes disease-related changes from random fluctuations in patient performance and operator/device dependent measurement errors. In this study we have applied control limits analysis to this problem. Using hand-held dynamometry, sets of baseline strength measurements were collected on two separate occasions during a period of clinical stability from up to four muscle groups in 22 patients with peripheral neuropathies. From these sets of data, 76 control limits were calculated and then used to describe the inter-measurement variation in muscle strength in individual muscles. The range of control limits was wide, varying from <10% of baseline (in 36% of muscles tested) to >50% (in 4% of muscles tested), with 88% of muscles falling within 30% of baseline. Follow-up data were also collected from all patients, including those undergoing treatment. Control limits analysis is a powerful and simple method for assessing the significance of motor performance changes in individual muscles in patients undergoing serial monitoring and can be easily applied to both single patients and clinical trials.

Strength measurements of the lumbrical muscles

This study was designed to measure the strength of the lumbrical muscles in the index and long fingers in patients with ulnar nerve paralysis. A hand-held dynamometer was used. The results show that in ulnar nerve damage the index and long fingers have a mean metacarpophalangeal (MCP) joint flexion strength of 0.8 kg (range 0.3-1.5), compared with 6.4 kg (range 4.6-7.9) in the noninvolved hand. Thus, the damaged fingers have only about 12% of the strength of those of the noninvolved hand. In the hand with ulnar paralysis, the loss of intrinsic strength (dorsal and palmar interosseous muscles) is considerable (almost 90%). The contribution of the interosseous muscles in maintaining the intrinsic position is considerably greater than that of the lumbricals. Comparing the Medical Research Council (MRC) scale (0-5) with the dynamometry measurements shows that MRC grade 3 correlates with about 0.8 kg, while grade 5 correlates with about 6.5 kg of MCP joint flexion strength.

Reliability of dynamic strength knee muscle testing in children

The isokinetic knee test is reliable in young individuals in a broad age range between 6 years of age to puberty, but not specifically in the youngest subgroup, in which cooperation may be less dependable. Hence, the purpose of this study was to investigate the reliability of isokinetic knee flexor/extensor muscle torque in a narrow age range: 6-8 years old. The sample consisted of 12 boys tested in three sessions with 3 days of rest between sessions. During each session, two tests were performed with each knee. Intrasession correlation coefficients ranged between .94 and .99 for quadriceps and between .78 and .96 for hamstrings. Interclass correlation coefficients, which express the reliability of a single test, were high (ranging from .85 to .95). Analysis of variance for repeated measurements showed that sixfold repetition of the test had no significant effect on peak torque measurements. These data suggest that the isokinetic knee flexion/extension torque is reliable in boys 6-8 years old.

Manual muscle strength testing: intraobserver and interobserver reliabilities for the intrinsic muscles of the hand

The reliability of manual muscle strength testing of the intrinsic muscles of the hand is reported. The muscle strengths of 28 patients who had neuropathies of the ulnar nerve or the ulnar and median nerves were graded by two physiotherapists to determine intraobserver and interobserver reliabilities. Muscle strength was graded using the numeric scale developed by the Medical Research Council (grades 0 to 5). Reliabilities were established for nine muscles or muscle groups. Intraobserver reliabilities ranged from 0.71 to 0.96 and interobserver reliabilities from 0.72 to 0.93. It is difficult to isolate, and hence grade, most of the intrinsic muscles of the hand. Therefore, it is suggested that specific movements be tested and graded when assessing and evaluating muscle or nerve function.

Isokinetic muscle testing (IMT) in neuromuscular diseases. Preliminary report

Isokinetic muscle testing (IMT) allows precise and reliable measurement of the force produced by the skeletal muscle during exercise at constant velocity and accommodating resistance. This study reports on some clinical situations that illustrate the difference between manual muscle testing (MMT) and IMT in neuromuscular patients. IMT was performed by a special method (continuous passive motion plus gravity compensation) which allowed the measurement of very weak forces, such as in the four patients described in this study. It is important to note that for the same MMT grading the corresponding isokinetic force values were very different. Therefore there is an obvious correspondence between the isokinetic measurement of muscle strength and the morphological change in the muscle on the CT scan of the thigh, which did not show up on MMT. IMT could be extremely important for research into neuromuscular disorders, where the detection of even the tiniest variations in strength is relevant.

Hand-held myometry: reference values

In thirteen major muscle groups of 50 healthy females and 50 males, aged 20-60 years, maximum voluntary contraction was measured with a hand-held dynamometer. The intrasession variation, the left-right variation, and the fifth and fiftieth centile values were calculated. The ratio of two observations within one session ranged from 0.85 to 1.18 and the ratio of left to right ranged from 0.82 to 1.22 (95% reference limits). In 20 volunteers the repeatability was tested after one week. The ratio of averages of three measurements in two successive weeks ranged from 0.82 to 1.23 (95% reference limits). There were only small differences between muscle groups concerning these ratios. A significant relation with age and weight/Quetelet Index could be demonstrated in some muscle groups. The mean strength of females is approximately two thirds of the strength of males. The data may be useful as reference values in the application of hand-held myometry.