Preserving function in Duchenne dystrophy with long-term pulse prednisone therapy

Associations between timing of corticosteroid treatment initiation and clinical outcomes in Duchenne muscular dystrophy

The long-term efficacy of corticosteroid treatment and timing of treatment initiation among Duchenne muscular dystrophy (DMD) patients is not well-understood. We used data from a longitudinal, population-based DMD surveillance program to examine associations between timing of treatment initiation (early childhood [before or at age 5 years], late childhood [after age 5 years], and naïve [not treated]) and five clinical outcomes (age at loss of ambulation; ages at onset of cardiomyopathy, scoliosis, and first fracture; and pulmonary function). Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using survival analysis. DMD patients who initiated corticosteroid treatment in early childhood had a higher risk of earlier onset cardiomyopathy compared to cases who initiated treatment in late childhood (HR = 2.0, 95% CI = [1.2, 3.4]) or treatment naïve patients (HR = 1.9, 95% CI = [1.1, 3.2]), and higher risk of suffering a fracture (HR = 2.3, 95% CI = [1.4, 3.7] and HR = 2.6, 95% CI = [1.6, 4.2], respectively). Patients with early childhood treatment had slightly decreased respiratory function compared with those with late childhood treatment. Ages at loss of ambulation or scoliosis diagnosis did not differ statistically among treatment groups. We caution that the results from our study are subject to several limitations, as they were based on data abstracted from medical records. Further investigations using improved reporting of disease onset and outcomes are warranted to obtain a more definitive assessment of the association between the timing of corticosteroid treatment and disease severity.

Developing standardized corticosteroid treatment for Duchenne muscular dystrophy

Despite corticosteroids being the only treatment documented to improve strength and function in boys with Duchenne muscular dystrophy (DMD) corticosteroid prescription is inconsistent and in some countries, corticosteroids are not prescribed. We are conducting a clinical trial that (1) compares the 3 most frequently prescribed corticosteroid regimes; (2) standardizes treatment of DMD complications; and (3) standardizes prevention of corticosteroid side effects. Investigators at 38 sites in 5 countries plan to recruit 300 boys aged 4-7 who are randomly assigned to one of three regimens: daily prednisone; daily deflazacort; or intermittent prednisone (10days on/10days off). Boys are followed for a minimum of 3years to assess the relative effectiveness and adverse event profiles of the different regimens. The primary outcome is a 3-dimensional variable consisting of log-transformed time to rise from the floor, forced vital capacity, and subject/parent satisfaction with treatment, each averaged over all post-baseline visits. The study protocol includes evidence- and consensus-based treatment of DMD complications and of corticosteroid side effects. This study seeks to establish a standard corticosteroid regimen for DMD. Since all new interventions for DMD are being developed as add-on therapies to corticosteroids, defining the optimum regimen is of importance for all new treatments.

Improving clinical trial design for Duchenne muscular dystrophy

BACKGROUND

Currently, the most promising therapies for Duchenne muscular dystrophy (DMD) are exon skipping and stop codon read-through, two strategies aimed at restoring the expression of dystrophin. A phase 3 clinical trial with drisapersen, a drug designed to induce exon 51-skipping, has failed to show significant improvement of the primary outcome measure, the six-minute walk test.

DISCUSSION

Here, we review some key points that should be considered when designing clinical trials for these new therapies. First, younger patients have more functional abilities and more muscle fibers to preserve than older patients and therefore are better subjects for trials designed to demonstrate the success of new treatments. Second, the inclusion of patients on corticosteroids both in the treatment and placebo groups is of concern because the positive effect of corticosteroids might mask the effect of the treatment being tested. Additionally, the reasonable expectation from these therapies is the slowing of disease progression rather than improvement. Therefore, the appropriate clinical endpoints are the prolongation of the ability to stand from the floor, climb stairs, and walk, not an increase in muscle strength or function. Hence, the time frames for the detection of new dystrophin, which occurs within months, and the ability to demonstrate a slowing of disease progression, which requires years, are strikingly different. Finally, placebo-controlled trials are difficult to manage if years of blindness are required to demonstrate a slowing of disease progression. Thus, accelerated/conditional approval for new therapies should be based on surrogate biochemical outcomes: the demonstration of de novo dystrophin production and of its beneficial effect on the functional recovery of muscle fiber. These data suggest that clinical trials for DMD patients must be adapted to the particular characteristics of the disease in order to demonstrate the expected positive effect of new treatments.

Corticosteroid Treatment Impact on Spinal Deformity in Duchenne Muscular Dystrophy

Duchenne muscular dystrophy is a progressive disease with loss of ambulation at around 9-10 years of age, followed, if untreated, by development of scoliosis, respiratory insufficiency, and death in the second decade of life. This review highlights the natural history of the disease, in particular, with regard to the development of the spinal deformity and how this complication has been modified by surgical interventions and overall by corticosteroid treatment. The beneficial effect of corticosteroids may have also an impact on the clinical trial design of the new emerging causative therapies.

Corticosteroids in Duchenne muscular dystrophy: major variations in practice

INTRODUCTION

In 2004, a Cochrane Review and AAN practice parameter concluded that prednisone 0.75 mg/kg/day is of short-term efficacy in Duchenne muscular dystrophy (DMD). Subsequent efforts to standardize care for DMD indicated wide variation in corticosteroid use.

METHODS

We surveyed physicians who follow patients with DMD, including: (1) clinics in the TREAT-NMD (Translational Research in Europe-Assessment and Treatment of Neuromuscular Diseases) network (predominantly Europe) and (2) U.S. MDA clinic directors. We also documented the co-administered corticosteroids in a trial of a putative treatment (ataluren) for DMD.

RESULTS

Of 105 Treat-NMD clinicians, corticosteroids were not used in 10 clinics, and 29 different regimens were used--the most frequent 0.75 mg/kg/day prednisone (61 centers); 10 days on/10 days off (36 centers); 0.9 mg/kg/day deflazacort (32 centers); and 5 mg/kg/day on weekends (10 centers). Similar diversity was identified in MDA clinics and in the ataluren trial.

CONCLUSIONS

Variability in corticosteroid use suggests uncertainty about risks/benefits of corticosteroid regimens for DMD.

Early corticosteroid treatment in 4 Duchenne muscular dystrophy patients: 14-year follow-up

INTRODUCTION

Corticosteroid treatment is the standard of care in Duchenne muscular dystrophy (DMD), but the optimal age to initiate treatment and dosage pattern remain a matter of discussion.

METHODS

We performed a long-term study of alternate-day corticosteroids in five 2- to 4-year-old DMD patients. The primary outcome measure was prolongation of the ability to walk.

RESULTS

One patient lost ambulation at age 10. Four patients, aged 16 to 18 were fully ambulant, and 3 of them could still climb stairs. Respiratory function was moderately reduced in 2. Left ventricular ejection fraction was > 45%. Short stature and delayed puberty were the most relevant side effects. Although the negative impact of corticosteroid treatment on growth rate remained their major concern, parents and patients stated that they preferred corticosteroid therapy.

CONCLUSIONS

Long-term corticosteroid treatment is effective in prolonging function but not in recovering lost function, and its early use seems appropriate.

Amplification of proinflammatory phenotype, damage, and weakness by oxidative stress in the diaphragm muscle of mdx mice

Duchenne muscular dystrophy (DMD) is a common and devastating type of childhood-onset muscular dystrophy, attributed to an X-linked defect in the gene that encodes dystrophin. Myopathy with DMD is most pronounced in the diaphragm muscle and fast-twitch limb muscles and is dependent upon susceptibility to damage, inflammatory cell infiltration, and proinflammatory signaling (nuclear factor-κB; NF-κB). Although recent papers have reawakened the notion that oxidative stress links inflammatory signaling with pathology in DMD in limb muscle, the importance of redox mechanisms had been clouded by inconsistent results from indirect scavenger approaches, including in the diaphragm muscle. Therefore, we used a novel catalytic mimetic of superoxide dismutase and catalase (EUK-134) as a direct scavenger of oxidative stress in myopathy in the diaphragm of the mdx mouse model. EUK-134 reduced 4-hydroxynonenal and total hydroperoxides, markers of oxidative stress in the mdx diaphragm. EUK-134 also attenuated positive staining of macrophages and T-cells as well as activation of NF-κB and p65 protein abundance. Moreover, EUK-134 ameliorated markers of muscle damage including internalized nuclei, variability of cross-sectional area, and type IIc fibers. Finally, impairment of contractile force was partially rescued by EUK-134 in the diaphragm of mdx mice. We conclude that oxidative stress amplifies DMD pathology in the diaphragm muscle.

Exacerbation of pathology by oxidative stress in respiratory and locomotor muscles with Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is the most devastating type of muscular dystrophy, leading to progressive weakness of respiratory (e.g. diaphragm) and locomotor muscles (e.g. gastrocnemius). DMD is caused by X-linked defects in the gene that encodes for dystrophin, a key scaffolding protein of the dystroglycan complex (DCG) within the sarcolemmal cytoskeleton. As a result of a compromised dystroglycan complex, mechanical integrity is impaired and important signalling proteins (e.g. nNOS, caveolin-3) and pathways are disrupted. Disruption of the dystroglycan complex leads to high susceptibility to injury with repeated, eccentric contractions as well as inflammation, resulting in significant damage and necrosis. Chronic damage and repair cycling leads to fibrosis and weakness. While the link between inflammation with damage and weakness in the DMD diaphragm is unresolved, elevated oxidative stress may contribute to damage, weakness and possibly fibrosis. While utilization of non-specific antioxidant interventions has yielded inconsistent results, recent data suggest that NAD(P)H oxidase could play a pivotal role in elevating oxidative stress via integrated changes in caveolin-3 and stretch-activated channels (SACs). Oxidative stress may act as an amplifier, exacerbating disruption of the dystroglycan complex, upregulation of the inflammatory transcription factor NF-B, and thus functional impairment of force-generating capacity.

Classification of the gait patterns of boys with Duchenne muscular dystrophy and their relationship to function

Corticosteroids have recently been shown to reduce expected loss of muscle strength in patients with Duchenne muscular dystrophy and extend the time they can walk. We evaluated 43 boys with the condition to determine whether taking corticosteroids is associated with differences in gait pattern, gross motor skills, energy efficiency, and timed motor performance. We used the gait deviation index to quantify the degree of gait pathology and a single measure of gait quality. There were minimal differences in gait pattern, gross motor skills, energy efficiency, or timed motor performance in boys who took corticosteroids compared with those who did not. Clustering by gait deviation index, however, revealed subtle differences between groups in gait patterns, gross motor skills, and energy efficiency. We conclude that, in boys with Duchenne muscular dystrophy, gait pattern deviations are related to function, which can provide further insight into the understanding of disease progression and treatment options to enhance function and maintain ambulation.

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.

Deflazacort use in Duchenne muscular dystrophy: an 8-year follow-up

Data reported here were collected over an 8-year period for 79 Duchenne muscular dystrophy patients, 37 of whom were treated with deflazacort. Mean length of treatment was 66 months. Treated boys stopped walking at 11.5 +/- 1.9 years, compared with 9.6 +/- 1.4 years for untreated boys. Cardiac function was better preserved with the use of deflazacort, as shown by a normal shortening fraction in treated (30.8 +/- 4.5%) vs untreated boys (26.6 +/- 5.7%, P < 0.05), a higher ejection fraction (52.9 +/- 6.3% treated vs 46 +/- 10% untreated), and lower frequency of dilated cardiomyopathy (32% treated vs 58% untreated). Scoliosis was much less severe in treated (14 +/- 2.5 degrees ) than in untreated boys (46 +/- 24 degrees ). No spinal surgery was necessary in treated boys. Limb fractures were similarly frequent in treated (24%) and untreated (26%) boys, but vertebral fractures occurred only in the treated group (7/37) (compared with zero for the untreated group). In both groups, body weight excess tripled between the ages of 8 and 12 years. All untreated patients grew normally (>4 cm/year), as opposed to only 15% of treated boys. Deflazacort improves cardiac function, prolongs walking, and seems to eliminate the need for spinal surgery, although vertebral fractures and stunted growth occur. The overall impact on quality of life appears positive.

Quantification of muscle strength and motor ability in patients with Duchenne muscular dystrophy on steroid therapy

OBJECTIVE: An assessment protocol was applied to quantify and describe muscular strength and motor abilities of 32 patients with Duchenne muscular dystrophy (DMD), aged between 5 and 12 years on steroid therapy. METHOD: Assessments were made monthly for the first six months and with intervals of two months thereafter until the 14-month end point. The tests employed included: the Medical Research Council (MRC) scale; the Hammersmith motor ability score; maximum weight lift; timed rise from floor and nine-meter walk. RESULTS: The results showed that loss of muscular strength and motor abilities were slowed in comparison to that observed in the natural evolution of the disease according to the literature. CONCLUSION: We conclude that a swift and objective assessment may be performed using the MRC scale for lower limbs and trunk, the Hammersmith motor ability score, timed nine-meter walk and weight lifts.

Cytoplasmic gamma-actin expression in diverse animal models of muscular dystrophy

We recently showed that cytoplasmic gamma-actin (gamma(cyto)-actin) is dramatically elevated in striated muscle of dystrophin-deficient mdx mice. Here, we demonstrate that gamma(cyto)-actin is markedly increased in golden retriever muscular dystrophy (GRMD), which better recapitulates the dystrophinopathy phenotype in humans. Gamma(cyto)-Actin was also elevated in muscle from alpha-sarcoglycan null mice, but not in several other dystrophic animal models, including mice deficient in beta-sarcoglycan, alpha-dystrobrevin, laminin-2, or alpha7 integrin. Muscle from mice lacking dystrophin and utrophin also expressed elevated gamma(cyto)-actin, which was not restored to normal by transgenic overexpression of alpha7 integrin. However, gamma(cyto)-actin was further elevated in skeletal muscle from GRMD animals treated with the glucocorticoid prednisone at doses shown to improve the dystrophic phenotype and muscle function. These data suggest that elevated gamma(cyto)-actin is part of a compensatory cytoskeletal remodeling program that may partially stabilize dystrophic muscle in some cases where the dystrophin-glycoprotein complex is compromised.

Cardiopulmonary support in duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked, rapidly progressive myopathy affecting the limb muscles, the respiratory muscles, the heart, the intestines, and the brain. Since about 90% of DMD patients die from muscular respiratory failure or cardiomyopathy, early and adequate therapy is essential. Ventilatory failure from muscle weakness requires mechanical support for ventilation and coughing as soon as there is symptomatic nocturnal hypoventilation. Today noninvasive positive-pressure ventilation (NIPPV) is the method of choice for supportive long-term mechanical ventilation in DMD. For assisted coughing, various methods are available, among which the mechanical in-exsufflator is the most widely used device. There is large nonrandomized clinical trial evidence that NIPPV improves quality of life and prolongs the lives of DMD patients if medical, social, economic, and ethical issues, raised by the availability of long-term NIPPV, are adequately addressed. Cardiac involvement in DMD manifests as impulse generation or impulse conduction abnormalities or cardiomyopathy. Cardiac abnormalities in DMD respond well to adequate therapy. Though DMD is ultimately a fatal disease, quality of life and life expectancy can be markedly improved if cardiopulmonary manifestations are adequately treated.

Corticosteroid Treatment and Functional Improvement in Duchenne Muscular Dystrophy

OBJECTIVE

To determine and compare the long-term effects of prednisone and deflazacort on the functional status of children with Duchenne muscular dystrophy.

DESIGN

A total of 49 boys with Duchenne muscular dystrophy, between the age of 12 and 15 yrs, who were observed over a 7-yr period were reviewed retrospectively. Eighteen had been treated with prednisone, 12 with deflazacort, and 19 had no drug treatment. All boys treated with steroids received medication for >2 yrs before losing their ambulation. Lower and upper limb motor functions, pulmonary function, prevalence of surgery for scoliosis, and side effects were compared.

RESULTS

Boys in the steroid groups were significantly more functional and performed better on all tests than boys not treated (P < 0.05). There was no significant difference between the deflazacort- and prednisone-treated groups (P > 0.05). The number of boys having scoliosis surgery in treated groups was significantly less than nontreated boys (P < 0.05). The control group's pulmonary capacity was decreasing and significantly less than both prednisone- and deflazacort-treated boys. Both deflazacort and prednisone had beneficial effect on pulmonary function and scoliosis. Cataracts, hypertension, behavioral changes, excessive weight gain, and vertebral fracture were noted as serious side effects.

CONCLUSIONS

Prednisone and deflazacort have a significant beneficial effect on slowing the disease progress. Their usage in Duchenne muscular dystrophy may prolong ambulation and upper limb function with similar potency. Both steroids also improve pulmonary function, in addition to delaying the need for spinal interventions, with similar therapeutic profiles.

Neuromuscular rehabilitation and electrodiagnosis. 4. Pediatric issues

This self-directed learning module highlights the physician's role in the diagnosis and treatment of neuromuscular disorders in pediatric populations. It is part of the chapter on neuromuscular rehabilitation and electrodiagnosis in the Self-Directed Physiatric Education Program for practitioners and trainees in physical medicine and rehabilitation. This article discusses both clinical and electrodiagnostic features of common neuromuscular disorders in pediatric populations. The diagnostic value of somatosensory evoked potential is reviewed in a case of traumatic spinal cord injury without radiographic abnormality. Therapeutic interventions of progressive muscular dystrophy are discussed, as well as the differential diagnosis of floppy infant syndrome, the most common pediatric electrodiagnostic referral.

OVERALL ARTICLE OBJECTIVES

(a) To become familiar with electrodiagnosis and rehabilitation for common neuromuscular disorders in the pediatric population, (b) to undrstand electrodiagnostic findings of Guillain-Barre syndrome corresponding to pathophysiology, (c) to become familiar with somatosensory evoked potentials, and (d) to be able to make differential diagnosis of floppy infant syndrome based on clinical findings as well as electrodiagnosis.

Effects of prednisone in canine muscular dystrophy

Glucocorticoid use may provide short-term functional improvement in boys with Duchenne muscular dystrophy (DMD). We report functional and histopathologic changes following a 4-month course of daily oral prednisone in a canine model of DMD, termed golden retriever muscular dystrophy (GRMD). Muscle extension forces in GRMD dogs treated daily with 1 and 2 mg/kg prednisone measured 2.349 +/- 0.92 and 3.486 +/- 0.67 N/kg, respectively, compared to 1.927 +/- 0.63 N/kg in untreated GRMD controls (p < 0.05 for 2 mg/kg group); GRMD muscle flexion forces measured 0.435 +/- 0.13 and 0.303 +/- 0.08 N/kg, respectively, compared to 0.527 +/- 0.01 N/kg in untreated GRMD controls (p < 0.05 for both groups). Although cranial sartorius hypertrophy and tibiotarsal joint angles also tended to improve, myofiber calcification increased and fetal myosin expression decreased following prednisone. Thus, functional data indicate benefit but histopathologic changes following prednisone treatment in GRMD suggest possible deleterious consequences.

Early prednisone treatment in Duchenne muscular dystrophy

The purpose of this long-term, open parallel-group, double-consent study of alternate-day, low-dose prednisone in 2-4-year-old patients with Duchenne muscular dystrophy (DMD) was to determine whether prednisone produces a beneficial effect when given earlier than usual. Muscle function was evaluated by timed tests, and muscle strength with a hand-held myometer. After 55 months of treatment, the five patients (mean age 8.3 years) in the prednisone group were still able to get up from the floor, whereas two of the three in the control group had lost this ability. Side effects included a decline in growth rate in the prednisone-treated patients and excessive weight gain in one control and three treated patients. Because steroids are effective in prolonging function, but not in recovering lost function, we propose that treatment be started with low-dose prednisone in DMD patients as soon as the diagnosis is definite.

Considerations to the policy of future clinical therapeutic trials in DMD

In spite of rapidly increasing insight into the molecular basis of neuromuscular diseases, treatment still relies on convention and clinical studies. Experience with a multicentre double blind treatment study in Duchenne muscular dystrophy and with consecutive steroid treatment documentation for up to 8 years enables us to identify a series of crucial points on which to focus while planning such clinical trials. The most important seem to be: a carefully structured, detailed study, clear-cut aims and objectives, expertise of investigators, sufficient training of examiners, and careful monitoring. If patients with neuromuscular diseases are treated outside structured studies, their course should be monitored comparably. Examples of the impact of such documentation are available from the ongoing German multicentre trial on the treatment of Duchenne muscular dystrophy.

Corticosteroids in Duchenne muscular dystrophy: a reappraisal

Duchenne muscular dystrophy is the most common and most severe form of childhood muscular dystrophies, resulting in early loss of ambulation between the ages of 7 and 13 years and death in the teens and twenties. Despite the phenomenal advances made in the understanding of the molecular genetics of the disease, no definitive cure has been found. Of all of the therapeutic drugs studied in Duchenne muscular dystrophy, only prednisone seems to have the potential for providing interim functional improvement for boys with Duchenne muscular dystrophy while they wait for a cure with gene or cell therapy. There is still no consensus regarding recommending corticosteroids as standard therapy for boys. This is an evidence-based review of all of the studies of corticosteroids (prednisone, deflazacort, and oxandrolone) in Duchenne muscular dystrophy. From this review, it is clear that until a definitive treatment for Duchenne muscular dystrophy is available, the use of deflazacort and prednisone with judicious dietary control and close clinical monitoring for side effects seems the best intervention for interim preservation of function in such a common devastating disorder of young growing boys.