Healthcare resource utilisation and direct medical cost for individuals with 5q spinal muscular atrophy in Sweden

BACKGROUND

Spinal muscular atrophy (SMA) is a rare, progressive, neuromuscular disorder. Recent advances in treatment require an updated assessment of burden to inform reimbursement decisions.

OBJECTIVES

To quantify healthcare resource utilisation (HCRU) and cost of care for patients with SMA.

METHODS

Cohort study of patients with SMA identified in the Swedish National Patient Registry (2007-2018), matched to a reference cohort grouped into four SMA types (1, 2, 3, unspecified adult onset [UAO]). HCRU included inpatient admissions, outpatient visits, procedures, and dispensed medications. Direct medical costs were estimated by multiplying HCRU by respective unit costs. Average annual HCRU and medical costs were modelled for SMA versus reference cohorts to estimate differences attributable to the disease (i.e., average treatment effect estimand). The trajectory of direct costs over time were assessed using synthetic cohorts.

RESULTS

We identified 290 SMA patients. Annualised HCRU was higher in SMA patients compared with reference cohorts. Highest risk ratios were observed for inpatient overnight stays for type 1 (risk ratio [RR]: 29.2; 95% confidence interval [CI]: 16.0, 53.5) and type 2 (RR: 23.3; 95% CI: 16.4,33.1). Mean annual direct medical costs per patient for each year since first diagnosis were greatest for type 1 (€114,185 and SMA-attributable: €113,380), type 2 (€61,876 and SMA-attributable: €61,237), type 3 (€45,518 and SMA-attributable: €44,556), and UAO (€4046 and SMA-attributable: €2098). Costs were greatest in the 2-3 years after the first diagnosis for all types.

DISCUSSION AND CONCLUSION

The economic burden attributable to SMA is significant. Further research is needed to understand the burden in other European countries and the impact of new treatments.

Low bone mineral density and reduced bone-specific alkaline phosphatase in 5q spinal muscular atrophy type 2 and type 3: A 2-year prospective study of bone health

AIM

Individuals with spinal muscular atrophy (SMA) are at risk of developing skeletal problems. This study investigated bone mineral density (BMD), bone turnover markers and motor function in children and adolescents with SMA type 2 and type 3 over a two-year period. The effect of nusinersen was studied in a subgroup.

METHODS

Single-centre study, including 20 patients, 2-18 years, of whom ten patients received nusinersen treatment. BMD was measured by dual-energy X-ray absorptiometry.

RESULTS

All patients had low BMD levels at baseline; mean Z-score -2.3 for total body less head (TBLH) and -2.9 for total hip left (THL). Significant correlations were found both at baseline and for the follow-up change for motor function and Z-scores (TBLH and THL). For the whole study group, reduced bone formation and unchanged bone resorption, assessed by bone-specific alkaline phosphatase (BALP) (p = 0.0006, ES = -0.83) and C-terminal cross-linking telopeptide of type I collagen (CTX), respectively, were found over the study period. However, BALP decreased less in the nusinersen treatment group, which suggests a positive development on bone mass in these patients.

CONCLUSION

Bone health evaluation is important in follow-up programmes for SMA patients. Further investigations are warranted for individuals on survival motor neuron-targeted treatments.

One in five patients with Duchenne muscular dystrophy dies from other causes than cardiac or respiratory failure

Duchenne muscular dystrophy (DMD) is a severe neuromuscular disorder with increasing life expectancy from late teens to over 30 years of age. The aim of this nationwide study was to explore the prevalence, life expectancy and leading causes of death in patients with DMD in Sweden. Patients with DMD were identified through the National Quality Registry for Neuromuscular Diseases in Sweden, the Swedish Registry of Respiratory Failure, pathology laboratories, neurology and respiratory clinics, and the national network for neuromuscular diseases. Age and cause of death were retrieved from the Cause of Death Registry and cross-checked with medical records. 373 DMD patients born 1970–2019 were identified, of whom 129 patients deceased during the study period. Point prevalence of adult patients with DMD on December 31st 2019 was 3.2 per 100,000 adult males. Birth prevalence was 19.2 per 100,000 male births. Median survival was 29.9 years, the leading cause of death being cardiopulmonary in 79.9% of patients. Non-cardiopulmonary causes of death (20.1% of patients) mainly pertained to injury-related pulmonary embolism (1.3 per 1000 person-years), gastrointestinal complications (1.0 per 1000 person-years), stroke (0.6 per 1000 person-years) and unnatural deaths (1.6 per 1000 person-years). Death from non-cardiopulmonary causes occurred at younger ages (mean 21.0 years, SD 8.2; p = 0.004). Age at loss of independent ambulation did not have significant impact on overall survival (p = 0.26). We found that non-cardiopulmonary causes contribute to higher mortality among younger patients with DMD. We present novel epidemiological data on the increasing population of adult patients with DMD.

Long term treatment with ataluren-the Swedish experience

Introduction

Ataluren is a relatively new treatment for male patients with Duchenne muscular dystrophy (DMD) due to a premature stop codon. Long-term longitudinal data as well as efficacy data on non-ambulant patients are still lacking. Here we present the results from a long-term follow-up study of all DMD patients treated with ataluren and followed at the Queen Silvia Children’s Hospital in Gothenburg, Sweden, with focus on the evolution of patients’ upper motor and respiratory function over time.

Methods

This is a retrospective longitudinal case-series study of all male DMD patients treated with ataluren and followed at the Queen Silvia Children’s Hospital in Gothenburg, Sweden, since 2008.

Results

Our eleven patients had a median exposure to ataluren of 2312 days which is almost a fourfold higher than previous studies. Loss of ambulation occurred at a median age of 13.2 years. Patients who lost ambulation prior to 13.2 years of age had received ataluren for 5 years, whereas patients who continued to be ambulatory after 13.2 years of age had received ataluren for 6.5 years until loss of ambulation or last follow-up if still ambulatory. Four of six non ambulatory patients had Performance of the Upper Limb scores above the expected mean values over time. All but one patient maintained a pulmonary decline above the expected over time. All ambulatory patients increased in their predicted forced vital capacity (FVC) with 2.8 to 8.2% annually. Following loss of ambulation, 5 of 6 patients declined in predicted FVC (%), with annual rate of decline varying from 1.8 to 21.1%. The treatment was safe and well tolerated throughout the follow-up period.

Conclusions

This is the first study to present long-term cumulative treatment outcomes over a median period of 6.3 years on ataluren treatment. Our results indicate a delay in loss of ambulation, as well as a slower decline in FVC and upper limb motor function even after loss of ambulation. We suggest that treatment with ataluren should be initiated as soon as the diagnosis is confirmed, closely monitored and, in case of sustainable benefit, continued even after loss of ambulation.

Cognitive and adaptive functioning in congenital and childhood forms of myotonic dystrophy type 1: a longitudinal study

AIM

To conduct a longitudinal follow-up of the development of global cognitive abilities and adaptive skills in individuals with congenital and childhood forms of myotonic dystrophy type 1 (DM1).

METHOD

Fifty-one participants (29 males, 22 females, mean age 19y 5mo, SD 4y 11mo, range 10y 10mo-28y 11mo) were divided into severe congenital (n=16), mild congenital (n=17), and childhood DM1 (n=18) subgroups. The average time between the first and second assessments was 7 years 8 months. Adaptive skills were evaluated using the Vineland Adaptive Behavior Scales and global cognitive functioning using Wechsler scales.

RESULTS

There was no statistically significant decline in cognitive abilities and adaptive behaviour. A tendency of decline regarding the level of intellectual disability was found in the congenital DM1 groups but not in the childhood group. In the congenital DM1 groups, the gap in relation to typically developing peers in cognitive and adaptive functioning increased. Predictors of change over time in adaptive skills were age and current level of intellectual disability: individuals with severe intellectual disability and younger individuals deteriorated the most. However, when raw scores were compared, no actual regression in adaptive functioning was found.

INTERPRETATION

The participants had not lost any important adaptive skills. Greater cognitive and adaptive development was found in the childhood group than in the congenital groups.

WHAT THIS PAPER ADDS

There is no absolute decline in cognitive and adaptive abilities in individuals with congenital and childhood myotonic dystrophy type 1. Pace of development is slow in comparison with normative data. The childhood group tended to show greater cognitive and adaptive development than the congenital groups.

NFL is a marker of treatment response in children with SMA treated with nusinersen

BACKGROUND

Recently, the anti-sense oligonucleotide drug nusinersen was approved for spinal muscular atrophy (SMA) and our aim was to find a response marker for this treatment.

METHODS

Twelve children with SMA type 1 and two copies of the SMN2 gene were included in a consecutive single-center study. The children were sampled for CSF at baseline and every time nusinersen was given intrathecally. The neuronal biomarkers NFL and tau and the glial biomarker GFAP were measured. Motor function was assessed using CHOP INTEND. Eleven similarly aged children, who were investigated to rule out neurological or infectious disease, were used as controls.

RESULTS

Baseline levels of NFL (4598 ± 981 vs 148 ± 39, P = 0.001), tau (939 ± 159 vs 404 ± 86, P = 0.02), and GFAP (236 ± 44 vs 108 ± 26, P = 0.02) were significantly higher in SMA children than controls. Motor function improved by nusinersen treatment in median 13 points corresponding to 5.4 points per month of treatment (P = 0.001). NFL levels typically normalized ( < 380 pg/ml) between the fourth and fifth doses [- 879.5 pg/mL/dose, 95% CI (- 1243.4, - 415.6), P = 0.0001], tau levels decreased [- 112.6 pg/mL/dose, 95% CI (- 206-7, - 18.6), P = 0.01], and minor decreases in GFAP were observed [- 16.9 pg/mL/dose, 95% CI (- 22.8, - 11.2), P = 0.02] by nusinersen treatment. Improvement in motor function correlated with reduced concentrations of NFL (rho = - 0.64, P = 0.03) and tau (rho = - 0.85, P = 0.0008) but not GFAP.

CONCLUSIONS

Nusinersen normalized the axonal damage marker NFL and correlated with motor improvement in children with SMA. NFL may, therefore, be a novel biomarker to monitor treatment response early in the disease course.

Health-related quality of life and orthosis use in a Swedish population with arthrogryposis

BACKGROUND

Joint contractures are the main characteristics for children with arthrogryposis multiplex congenita. Orthoses are often used to enable or facilitate walking.

OBJECTIVES

To describe health-related quality of life in children with arthrogryposis multiplex congenita and satisfaction with orthoses in those using orthoses.

STUDY DESIGN

Cross-sectional study.

METHODS

A total of 33 children with arthrogryposis multiplex congenita participated in the study. Questionnaires were used which measured health-related quality of life (Child Health Questionnaire-Parent Form and EQ-5D youth), mobility and self-care (Paediatric Evaluation of Disability Inventory) and satisfaction with orthoses (Quebec User Evaluation of Satisfaction with Assistive Technology 2.0). Children were divided into groups based on the use of orthoses: Ort-D were dependent on orthoses for walking, Ort-ND used orthoses but were not dependent on them for walking and Non-Ort did not use orthoses.

RESULTS

Children with arthrogryposis multiplex congenita had significantly lower Child Health Questionnaire scores in 9 of 12 subscales compared to healthy controls. The children's reported perceived health with EQ-5D youth did not show any difference between children using orthoses or children using only shoes. Paediatric Evaluation of Disability Inventory showed less mobility in Ort-D than in Non-Ort. In total, both orthosis groups were 'quite satisfied' with their orthoses.

CONCLUSION

Child Health Questionnaire-physical functioning was lowest in children who were dependent on orthoses (Ort-D) for walking. Both Ort-D and Ort-ND were similar satisfied with their orthoses. Clinical relevance This study contributes to knowledge about health-related quality of life in a group of ambulatory children with arthrogryposis multiplex congenita. For children using orthoses, it is relevant to capture their opinion about their orthoses but a questionnaire specifically for children should be developed.

Comparison of ambulatory capacity and disease progression of Duchenne muscular dystrophy subjects enrolled in the drisapersen DMD114673 study with a matched natural history cohort of subjects on daily corticosteroids

Duchenne muscular dystrophy is a rare genetic disorder with life-limiting pathology. Drisapersen induces exon 51 skipping, thereby producing a shorter but functional dystrophin protein. The longest available data are from an open-label extension study (PRO051-02) treating 12 boys with drisapersen (6 mg/kg/week subcutaneously). The median change (range) from baseline to week 177 in six-minute walking distance (6MWD) was 8 (-263, 163) metres. The current analysis aimed to put the results from PRO051-02 in the context of natural progression by comparing the functional trajectory of drisapersen-treated subjects to a matched natural history (NH) cohort, treated by standard of care. Subjects were matched individually by age and 6MWD, as the primary analysis, and by age and rise from floor (RFF), as sensitivity analysis. A total of 75 NH subjects were available for 6MWD analysis, of which matching was possible for 9 ambulant drisapersen-treated subjects. None of the 6 "stable" (baseline 6MWD ≥330 metres) drisapersen-treated subjects lost ambulation vs 4 out of 10 matched NH subjects over a comparable timeframe (~3.4 years), compared with 2 out of 3 ambulant "in decline" drisapersen-treated subjects vs all 6 matched NH subjects. A total of 79 NH subjects were available for RFF analysis. For continuous ambulatory subjects (N = 4), the RFF decline was more pronounced in the NH cohort than in the drisapersen-treated subjects. In conclusion, a comparison of ambulant drisapersen-treated subjects with matched NH subjects showed a difference in functional trajectories over a timeframe of up to 3.4 years in favour of drisapersen.

Long-Term Efficacy, Safety, and Pharmacokinetics of Drisapersen in Duchenne Muscular Dystrophy: Results from an Open-Label Extension Study

Background

Drisapersen induces exon 51 skipping during dystrophin pre-mRNA splicing and allows synthesis of partially functional dystrophin in Duchenne muscular dystrophy (DMD) patients with amenable mutations.

Methods

This 188-week open-label extension of the dose-escalation study assessed the long-term efficacy, safety, and pharmacokinetics of drisapersen (PRO051/GSK2402968), 6 mg/kg subcutaneously, in 12 DMD subjects. Dosing was once weekly for 72 weeks. All subjects had a planned treatment interruption (weeks 73–80), followed by intermittent dosing (weeks 81–188).

Results

Subjects received a median (range) total dose of 5.93 (5.10 to 6.02) mg/kg drisapersen. After 177 weeks (last efficacy assessment), median (mean [SD]) six-minute walk distance (6MWD) improved by 8 (-24.5 [161]) meters for the 10 subjects able to complete the 6MWD at baseline (mean age [SD]: 9.5 [1.9] years). These statistics include 2 subjects unable to complete the test at later visits and who scored “zero”. When only the 8 ambulant subjects at week 177 were taken into account, a median (mean [SD]) increase of 64 (33 [121]) meters in 6MWD was observed. Of 7 subjects walking ≥330 m at extension baseline, 5 walked farther at week 177. Of 3 subjects walking <330 m, 2 lost ambulation, while 1 declined overall but walked farther at some visits. Over the 188 weeks, the most common adverse events were injection-site reactions, raised urinary α₁-microglobulin and proteinuria. Dystrophin expression was detected in all muscle biopsies obtained at week 68 or 72.

Conclusion

Drisapersen was generally well tolerated over 188 weeks. Possible renal effects, thrombocytopenia and injection-site reactions warrant continued monitoring. Improvements in the 6MWD at 12 weeks were sustained after 3.4 years of dosing for most patients. For a small, uncontrolled study, the outcomes are encouraging, as natural history studies would anticipate a decline of over 100 meters over a 3-year period in a comparable cohort.

Trial Registration

ClinicalTrials.gov NCT01910649

Pain in adolescents with spinal muscular atrophy and Duchenne and Becker muscular dystrophy

BACKGROUND/PURPOSE

The purpose of this study was to explore the prevalence, nature and scope of pain in adolescents with spinal muscular atrophy and Duchenne and Becker muscular dystrophy and whether the pain differs between diagnostic groups or between adolescents with different ambulation status. Furthermore to study the consequences of pain and to identify pain-exacerbating and pain-relieving factors.

METHODS

In a national survey, fifty-five adolescents with spinal muscular atrophy and dystrophinopathy completed a questionnaire assessing pain frequency, duration, location using a body map, intensity and discomfort using visual analogue scales, pain interference using a modified version of Brief Pain Inventory and factors exacerbating and relieving pain.

RESULTS

Sixty-nine per cent of the adolescents reported pain during the past three months and 50% reported chronic pain. The pain prevalence did not differ significantly between diagnostic groups or between ambulators and non-ambulators. The average pain intensity was graded as mild and the worst pain as moderate. The pain typically occurred weekly, most frequently in the neck/back or legs. General activity and mood were the areas that were most affected by pain. Common pain-exacerbating factors were sitting, too much movement/activity and being lifted or transferred.

CONCLUSION

Pain is a frequent problem in adolescents with spinal muscular atrophy and dystrophinopathy. The assessments used enable an understanding both of the nature and scope of pain and of the impact of pain in everyday life. The study highlights the importance of assessing pain in a systematic manner and offering an individual approach to interventions designed to reduce pain in this population.

Distal arthrogryposis: clinical and genetic findings

AIM

Distal arthrogryposis is characterized by congenital contractures predominantly in hands and feet. Mutations in sarcomeric protein genes are involved in several types of distal arthrogryposis. Our aim is to describe clinical and molecular genetic findings in individuals with distal arthrogryposis and evaluate the genotype-phenotype correlation.

METHOD

We investigated 39 patients from 21 families. Clinical history, including neonatal findings, joint involvement and motor function, was documented. Clinical examination was performed including evaluation of muscle strength. Molecular genetic investigations were carried out in 19 index cases. Muscle biopsies from 17 patients were analysed.

RESULTS

A pathogenic mutation was found in six families with 19 affected family members with autosomal dominant inheritance and in one child with sporadic occurrence. In three families and in one child with sporadic form, the identified mutation was de novo. Muscle weakness was found in 17 patients. Ambulation was affected in four patients and hand function in 28. Fourteen patients reported pain related to muscle and joint affection.

CONCLUSION

The clinical findings were highly variable between families and also within families. Mutations in the same gene were found in different syndromes suggesting varying clinical penetrance and expression, and different gene mutations were found in the same clinical syndrome demonstrating genetic heterogeneity.

Bone mass development in patients with Duchenne and Becker muscular dystrophies: a 4-year clinical follow-up

AIM

To investigate the longitudinal development of bone mass in patients with Duchenne and Becker muscular dystrophies and to study the impact of muscle strength and motor function on bone mass in these patients.

METHODS

Eighteen patients with Duchenne muscular dystrophy (2.3-19.7 years at baseline) and six patients with the milder Becker muscular dystrophy (10.8-18.9 years at baseline) were followed during a 4-year period with respect to areal bone mineral density (BMD), motor function and muscle strength.

RESULTS

Greater bone mineral accretion was observed in the Becker patient group compared with the age-related Duchenne group above 10 years of age, and the older patients with Duchenne experienced decreased femoral neck BMD during the study period. In the study group, significant correlations were found between BMD in the lower extremities and muscle function parameters.

CONCLUSIONS

The differences in BMD between patients with Duchenne and Becker as well as between different bone measurement sites demonstrated in the present study point out the importance of preserving muscle strength and motor function in patients with muscular dystrophy. Moreover; it highlights the value of performing region-specific analysis of the bone quality in these patients.

A population-based study of genotypic and phenotypic variability in children with spinal muscular atrophy

AIMS

To describe the occurrence of spinal muscular atrophy (SMA) in childhood; to evaluate if any of the genes in the SMA region on chromosome 5q13 correlates with disease severity; to make genotype-phenotype correlations; to evaluate the variability of different disease alleles in carriers and the sensitivity of multiplex ligation-dependent probe amplification (MLPA) for detecting carriers.

METHODS

In a population-based study from Western Sweden MLPA was used to determine the copy-numbers of several genes in the SMA region (SMN1, SMN2, BIRC1, GTF2H2 and SERF1A) in SMA-patients and their parents.

RESULTS

We estimated the incidence of SMN1-related SMA in childhood at 1 in 11 800 live births and confirmed the relationship between the number of SMN2 copies and the severity of disease. No other direct relationships were found. All but one of the analysed parents were confirmed as carriers by MLPA analysis. A total of at least 30 different disease alleles were identified and no specific disease allele represented more than 15% of the total.

CONCLUSION

The childhood incidence of SMA in the Swedish population is around 1 in 12,000 live births and it is unlikely that there is any founder effect involved in SMA in western Sweden.

Embryonic myosin heavy-chain mutations cause distal arthrogryposis and developmental myosin myopathy that persists postnatally

BACKGROUND

Myosin is a molecular motor and the essential part of the thick filament of striated muscle. The expression of myosin heavy-chain (MyHC) isoforms is developmentally regulated. The embryonic isoform encoded from MYH3 (OMIM *160720) is expressed during fetal life. Recently, mutations in MYH3 were demonstrated to be associated with congenital joint contractures, that is, Freeman-Sheldon and Sheldon-Hall syndromes, which are both distal arthrogryposis syndromes. Mutations in other MyHC isoforms cause myopathy. It is unknown whether MYH3 mutations cause myopathy because muscle tissue has not been studied.

OBJECTIVES

To determine whether novel MYH3 mutations are associated with distal arthrogryposis and to demonstrate myopathic changes in muscle biopsy specimens from 4 patients with distal arthrogryposis and MYH3 mutations.

DESIGN

In a cohort of patients with distal arthrogryposis, we analyzed the entire coding sequence of MYH3. Muscle biopsy specimens were obtained, and in addition to morphologic analysis, the expression of MyHC isoforms was investigated at the protein and transcript levels.

RESULTS

We identified patients from 3 families with novel MYH3 mutations. These mutations affect developmentally conserved residues that are located in different regions of the adenosine triphosphate-binding pocket of the MyHC head. The embryonic (MYH3) isoform was not detected in any of the muscle biopsy samples, indicating a normal developmental downregulation of MYH3 in these patients. However, morphologic analysis of muscle biopsy specimens from the 4 patients revealed mild and variable myopathic features and a pathologic upregulation of the fetal MyHC isoform (MYH8) in 1 patient.

CONCLUSIONS

Distal arthrogryposis associated with MYH3 mutations is secondary to myosin myopathy, and postnatal muscle manifestations are variable.

Low bone mineral density and decreased bone turnover in Duchenne muscular dystrophy

This cross-sectional study examined bone mineral density, bone turnover, body composition and calciotropic hormones in 24 boys with Duchenne muscular dystrophy (DMD) (2.3-19.7 years), most of whom were being treated with prednisolone, and 24 age-matched healthy boys. Our study demonstrated lower bone mineral density in the DMD group for total body, spine, hip, heel and forearm measurements. These differences between DMD patients and controls increased with increasing age. Biochemical markers of both bone formation and resorption revealed reduced bone turnover in DMD patients. The fracture rate was not higher in DMD patients. The DMD group had low vitamin D levels but high leptin levels in comparison with the control group. Muscle strength correlated with bone mineral density assessed at the hip and heel in the DMD group. Interventions that increase bone formation should be considered, as DMD patients have reduced bone turnover in addition to their low bone mineral density.

Isometric Muscle Torque in Children 5 to 15 Years of Age: Normative Data

OBJECTIVE

To establish reference values of arm and leg muscle strength as measured by isometric torque production in healthy children.

DESIGN

Measurement of isometric muscle strength in healthy children.

SETTING

Public school.

PARTICIPANTS

Healthy children (N=149; 76 boys, 73 girls) ages 5 to 15 years.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Isometric torque values of 12 arm and leg muscle groups of healthy children as measured by a handheld dynamometer.

RESULTS

Normative data were obtained for children 5 to 15 years of age. There was an increase in torque with age and weight and a strong correlation with both age and weight. There were few differences between boys and girls. Equations for predicted torque taking into account age, weight, and sex were calculated. The agreement between examiners was excellent.

CONCLUSIONS

Studies on growing children require comparison to healthy (normal) children to assess the amount of deviation from normal and to be able to draw conclusions of change over time. The reference values for torque in combination with a predicted value based on the child's age, weight, and sex make it possible to compare over time and between subjects and provide a tool for evaluation of physical status and efficacy of therapy.

Muscle involvement and motor function in amyoplasia

The most common form of arthrogryposis multiplex congenita (AMC) is amyoplasia. Diagnostic criteria are highly specific, with decreased muscle mass, typical contractures and limb positioning at birth. Intellectual development is normal. The aims of this study were to investigate how muscle strength and contractures affect motor function in amyoplasia, and to relate current functional status to joint positions at birth. Medical records were reviewed and a clinical examination was performed, with investigation of muscle strength, range of motion, and motor function. Thirty-five patients with amyoplasia participated and were divided into three functional groups: 11 community ambulators, 11 household ambulators, and 7 non-ambulators. Six children less than 2 years old were not categorized. Community ambulators had the best muscle strength and none had knee flexion contractures extending 20 degrees. Household ambulators had severe contractures in the lower limbs, but good muscle strength in the upper limbs. Non-ambulators had most severe contractures and most severely reduced muscle strength. Most of the non-ambulators were born with hips in severe abduction, flexion and external rotation. Good and very good correlations were found between muscle strength and motor function, and only moderate correlations between range of motion and motor function. We conclude that more attention should be paid to developing muscle strength, with early stimulation of active movement, and that periods of immobilization should be minimized. Further, ultrasound or MRI of muscle tissue in the newborn period would be useful to evaluate prerequisites for future development of muscle strength and thereby anticipate response to therapy.

Myotonic dystrophy: muscle involvement in relation to disease type and size of expanded CTG-repeat sequence

This study aimed to: classify a cohort of children and adolescents with myotonic dystrophy (dystrophia myotonica: DM) into congenital and childhood onset forms; estimate CTG expansion size; and quantify muscle strength, contractures, and motor function in children with DM and compare results with those of controls. Participants were clinically examined, medical records were reviewed, and isometric muscle strength, contractures, and motor function were measured. Participants were: 42 children with DM (18 females, 24 males; mean age 8y 9mo [SD 4y 7mo], range 10mo to 17y) and 42 age- and sex-matched, healthy controls. Children with DM were divided into three groups: severe congenital (n=13), mild congenital (n=15), and childhood (n=14). Children with childhood DM were significantly weaker than controls (wrist and ankle dorsiflexors [p=0.0044, p=0.0044 respectively]; hip abductors and flexors [p=0.0464, p=0.0217]; and knee flexors and extensors: [p=0.0382, p=0.0033]). Children with mild congenital DM were significantly weaker than controls in all assessed muscle groups. Contractures and skeletal deformities were more frequent at time of investigation than at birth, suggesting that foot and spine deformities in particular increase over time. Motor function score was significantly lower for children with DM than for controls. Children with severe congenital DM had the lowest motor function, with correlation between motor function and size of CTG repeat (p=-0.743). Children found jumping, heel standing, and head lifting the most difficult items to perform but few had difficulty walking, running, or stair climbing. DM in children is a heterogeneous disorder with a wide spectrum of muscle involvement, and owing to increased risk of contractures and skeletal deformities, regular follow-ups are recommended.

Myotonic dystrophy: muscle involvement in relation to disease type and size of expanded CTG-repeat sequence

This study aimed to: classify a cohort of children and adolescents with myotonic dystrophy (dystrophia myotonica: DM) into congenital and childhood onset forms; estimate CTG expansion size; and quantify muscle strength, contractures, and motor function in children with DM and compare results with those of controls. Participants were clinically examined, medical records were reviewed, and isometric muscle strength, contractures, and motor function were measured. Participants were: 42 children with DM (18 females, 24 males; mean age 8y 9mo [SD 4y 7mo], range 10mo to 17y) and 42 age- and sex-matched, healthy controls. Children with DM were divided into three groups: severe congenital (n=13), mild congenital (n=15), and childhood (n=14). Children with childhood DM were significantly weaker than controls (wrist and ankle dorsiflexors [p=0.0044, p=0.0044 respectively]; hip abductors and flexors [p=0.0464, p=0.0217]; and knee flexors and extensors: [p=0.0382, p=0.0033]). Children with mild congenital DM were significantly weaker than controls in all assessed muscle groups. Contractures and skeletal deformities were more frequent at time of investigation than at birth, suggesting that foot and spine deformities in particular increase over time. Motor function score was significantly lower for children with DM than for controls. Children with severe congenital DM had the lowest motor function, with correlation between motor function and size of CTG repeat (p=-0.743). Children found jumping, heel standing, and head lifting the most difficult items to perform but few had difficulty walking, running, or stair climbing. DM in children is a heterogeneous disorder with a wide spectrum of muscle involvement, and owing to increased risk of contractures and skeletal deformities, regular follow-ups are recommended.

Multiple congenital contractures: birth prevalence, etiology, and outcome

OBJECTIVES

We wanted to estimate the birth prevalence of multiple congenital contractures (MCC), determine the cause of the MCC according to the primary level of involvement of the developing motor system, and compare the different groups in terms of inheritance, mortality, and morbidity.

STUDY DESIGN

A retrospective epidemiologic study through the screening of registers, reviews of medical records, and clinical re-examinations was performed in western Sweden to identify all the children with MCC born between 1979 and 1994.

RESULTS

The birth prevalence of MCC on the basis of 68 cases was 1 in 5100 live births. The majority of cases with cerebral involvement (n = 23), spinal involvement (n = 16), or mechanical restriction (n = 3) were sporadic, whereas most cases with neuromuscular (n = 12) or connective tissue involvement (n = 9) were inherited. The cerebral group was more severely affected compared with the other groups in terms of mortality, joint contractures at birth, feeding difficulties during infancy, and independent walking at follow-up. In 8 cases with myopathy, the joint contractures were normalized on follow-up.

CONCLUSION

A search for a specific etiology in each case is important for genetic counseling, prognosis, and therapy because inheritance, mortality, and morbidity differ between the groups.

Longitudinal data analysis: an application to construction of a natural history profile of Duchenne muscular dystrophy

A 30-month prospective study of 27 Scandinavian boys with confirmed diagnosis of Duchenne muscular dystrophy was carried out to construct profiles of the natural history of the disease. Assessments which included measures of voluntary muscle strength and function were done at 3 monthly intervals except for the first and second which were separated by 1 month. Recently developed statistical methods for analysis of longitudinal data with repeated observations on the same individual were used avoiding the problem of induced serial correlations. This allowed for the construction of both reference and prediction profiles for the variables %MRC, motor ability, walking time for 10 m and the sum of myometry of seven muscle groups.

Muscle strength and motor function in children and adolescents with spinal muscular atrophy II and III

The aim of this study was to quantify isometric muscle strength and motor function in children and adolescents with spinal muscular atrophy (SMA) and to analyse the impact of reduced muscle strength on motor function. Six children and adolescents with SMA II and eight with SMA IlI were assessed regarding isometric muscle strength and motor function. Isometric muscle strength was tested with a myometer and the values obtained were compared with normative data. Motor function was videotaped and 20 movements were scored according to a three-point scale. All of the assessed children and adolescents with SMA II and SMA III showed reduced muscle strength, but there were great differences within the group. The typical pattern of muscle weakness in SMA, with proximal weakness greater than distal and the lower limbs more affected than the upper, was also seen in these children. The muscle weakness affected motor function in all assessed children. Walking, transfer from lying or sitting to the standing position and stair-climbing were possible in some of the children, despite marked reduction of muscle strength. The study increases our knowledge concerning the degree of muscle weakness in children with SMA and the impact of muscle weakness on motor function. The results increase our possibilities of understanding the prerequisites for everyday life in these children and planning therapeutic interventions. Repeated assessments with the methods used in this study may be used to monitor the course of the disease and to evaluate the efficacy of treatment.

A randomized comparative study of two methods for controlling Tendo Achilles contracture in Duchenne muscular dystrophy

A 30-month prospective randomized study of 27 Scandinavian boys with confirmed diagnosis of Duchenne muscular dystrophy was done to compare the effect of passive stretching combined with the use of night splints (group A) or passive stretching (group B) on the evolution of Tendo Achilles contractures. Assessments were based on the methodology of Scott et al. (Muscle Nerve 1982;5:291-301)Analysis of the pattern and mechanism of dropout was done to eliminate bias between the two groups. Logistic regression showed that Tendo Achilles contracture was the most important variable (P=0.0020) for dropout. Methods of statistical analysis for longitudinal data avoiding induced serial correlations were used in the analysis. The expected annual change in Tendo Achilles contracture was found to be 23% less in group A than in group B after equalization for total muscle strength (%MRC).