Proximal spinal muscular atrophy: current orthopedic perspective

Diving into progress: a review on current therapeutic advancements in spinal muscular atrophy

Spinal muscular atrophy (SMA) is an uncommon disorder associated with genes characterized by the gradual weakening and deterioration of muscles, often leading to substantial disability and premature mortality. Over the past decade, remarkable strides have been made in the field of SMA therapeutics, revolutionizing the landscape of patient care. One pivotal advancement is the development of gene-targeted therapies, such as nusinersen, onasemnogene abeparvovec and risdiplam which have demonstrated unprecedented efficacy in slowing disease progression. These therapies aim to address the root cause of SMA by targeting the survival motor neuron (SMN) gene, effectively restoring deficient SMN protein levels. The advent of these innovative approaches has transformed the prognosis for many SMA patients, offering a glimmer of hope where there was once limited therapeutic recourse. Furthermore, the emergence of small molecule compounds and RNA-targeting strategies has expanded the therapeutic arsenal against SMA. These novel interventions exhibit diverse mechanisms of action, including SMN protein stabilization and modulation of RNA splicing, showcasing the multifaceted nature of SMA treatment research. Collective efforts of pharmaceutical industries, research centers, and patient advocacy groups have played an important role in expediting the translation of scientific discoveries into visible clinical benefits. This review not only highlights the remarkable progress achieved in SMA therapeutics but also generates the ray of hope for the ongoing efforts required to enhance accessibility, optimize treatment strategies, rehabilitation (care and therapies) and ultimately pave the way for an improved quality of life for individuals affected by SMA.

Multidisciplinary physical rehabilitation program of individuals with spinal muscular atrophy in an inclusive school setting

Spinal muscular atrophy (SMA) is a neuromuscular ailment that leads to the deprivation of motor neurons in the spinal cord, producing denervation and muscle weakness. This case report explains how a patient with type 2 SMA used a therapeutic exercise rehabilitation program in a school environment. Motor functions were assessed by Gross Motor Function Measure-88 (GMFM-88), Manual Muscle Testing (MMT), and Hammersmith Functional Motor Scale (HFMS), which is validated and reliable. This study employed a repeated pre-test post-test measures design. During a year of treatment sessions, the child underwent twice weekly 45-minute physical therapy sessions for 48 weeks. The research was carried out between March 2022 and February 2023. The purpose of the intervention, which comprised a variety of therapeutic workouts, was to enhance physical function and gross motor abilities in an age-appropriate manner. The intervention utilized in this study led to improvements in GMFM-88, HFMS, and MMT total scores. The results of this case study showed that a child with type 2 SMA aged nine had successfully improved their gross motor skills and muscle strength.

Association between spinal muscular atrophy type and delayed diagnosis and the risk of spinal deformity in Indonesian patients

BACKGROUND

Spinal muscular atrophy (SMA) is a genetic disease that causes muscle weakness and atrophy. Delayed diagnosis can lead to loss of motoric functions, which may then progress to deformities such as thoracolumbar scoliosis, pelvic obliquity, and hip subluxation/dislocation. The lack of information or limited experience among healthcare providers and costly genetic tests can cause delayed diagnosis. The current study aimed to assess the characteristics of patients with SMA. Moreover, the association between SMA type and delayed diagnosis and the risk of spinal deformity in the Indonesian SMA Community was evaluated.

METHODS

This was a cross-sectional study performed on 53 patients diagnosed with SMA. Data about patients' characteristics were obtained from the Indonesian SMA Community using a questionnaire in August 2019. The information included age, sex, SMA type, age at suspicion and definite diagnosis of SMA, and presence of spinal deformities. Then, descriptive analysis and logistic regression analysis were performed, and the Kruskal-Wallis test and the Chi-square test were utilized.

RESULTS

The median age of patients suspected of SMA was 24 months. A definitive diagnosis of SMA was obtained at 36 months. Further, 43% of patients presented with SMA type 2 and 58% with spinal deformities. Results showed a positive correlation between time interval between suspicion and definite diagnosis of SMA and the risk of spinal deformities (B = 0,07; p > 0.05). Delayed diagnosis was more common in SMA type 3 than in SMA types 1 and 2, and SMA type 2 was correlated with a twofold risk of spinal deformities (p = 0.03; prevalence ratio = 2.09).

CONCLUSIONS

SMA type 2 is associated with a twofold risk of spinal deformities. Delayed diagnosis is more common in SMA type 3 than in SMA types 1 and 2. Moreover, there was an association between the time interval between suspicion and definite diagnosis of SMA and the risk of spinal deformities in patients with SMA.

Experience and Perspectives in the US on the Evolving Treatment Landscape in Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a rare, progressive neuromuscular disorder that, until recently, was the most common inherited cause of infant mortality. Since 2016, three disease-modifying therapies have emerged, nusinersen, onasemnogene abeparvovec-xioi, and risdiplam, leading to a transformation in the SMA treatment landscape, changes in disease trajectories, and a profound impact on clinical care. This environment poses a challenge to making informed treatment decisions, including initial treatment choice, treatment changes, and potential use of combination therapies as new data emerge. To better understand factors that influence physician-patient decision-making, a roundtable discussion was convened by Biogen (sponsor) with a panel of four US SMA experts. This report shares the panel’s opinions and clinical experiences, with the goals of helping clinicians and people with SMA and their families to better understand the factors influencing real-world treatment decisions and stimulating a broader discussion in the SMA community. The panelists highlighted that patients are often heavily involved in treatment decisions, and physicians must be aware of current data to guide patients in making the best decisions. Thus, in the absence of data from head-to-head treatment comparisons, physicians’ roles include reviewing treatment options and describing what is known of the benefits, challenges, and potential side effects of each therapy with patients and families. For infants and young children, the panelists expressed a sense of urgency for early intervention to minimize motor function loss, whereas the goal for adults is long-term disease stabilization. In the panelists’ experience, factors that influence patients’ decisions to change to an alternative therapy include convenience, administration route, novelty of therapy, and hope for improved function, while reasons for returning to a previous therapy include a perception of decreased efficacy and side effects. Ongoing clinical trials and analyses of real-world experiences should further inform treatment decisions and optimize patient outcomes.

Management of arthrofibrosis in neuromuscular disorders: a review

Arthrofibrosis, or rigid contracture of major articular joints, is a significant morbidity of many neurodegenerative disorders. The pathogenesis depends on the mechanism and severity of the precipitating neuromuscular disorder. Most neuromuscular disorders, whether spastic or hypotonic, culminate in decreased joint range of motion. Limited range of motion precipitates a cascade of pathophysiological changes in the muscle-tendon unit, the joint capsule, and the articular cartilage. Resulting joint contractures limit functional mobility, posing both physical and psychosocial burdens to patients, economic burdens on the healthcare system, and lost productivity to society. This article reviews the pathophysiology of arthrofibrosis in the setting of neuromuscular disorders. We describe current non-surgical and surgical interventions for treating arthrofibrosis of commonly affected joints. In addition, we preview several promising modalities under development to ameliorate arthrofibrosis non-surgically and discuss limitations in the field of arthrofibrosis secondary to neuromuscular disorders.

Treatment preference among patients with spinal muscular atrophy (SMA): a discrete choice experiment

OBJECTIVE

To examine patient/caregiver preference for key attributes of treatments for spinal muscular atrophy (SMA).

BACKGROUND

In the rapidly evolving SMA treatment landscape, it is critically important to understand how attributes of potential treatments may impact patient/caregiver choices.

DESIGN/METHODS

A discrete choice experiment survey was developed based on qualitative interviews. Patients with SMA (≥ 18 years) and caregivers of patients were recruited through a U.S. patient organization. Respondents made choices in each of 12 sets of hypothetical treatments. The relative importance of five treatment characteristics was compared (measured by regression coefficients [RC] of conditional logit models): (1) improvement or stabilization of motor function, (2) improvement or stabilization of breathing function, (3) indication for all ages or pediatric patients only, (4) route of administration [repeated intrathecal (IT) injections, one-time intravenous (IV) infusion, daily oral delivery] and (5) potential harm (mild, moderate, serious/life threatening).

RESULTS

Patient ages ranged from less than 1 to 67 years (n = 101, 65 self-reported and 36 caregiver-reported) and 64 were female. Total SMA subtypes included: type 1 (n = 21), type 2 (n = 48), type 3 (n = 29), other (n = 3). Prior spinal surgery was reported in 47 patients. Nusinersen and onasemnogene abeparvovec-xioi use were reported in 59 and 10 patients, respectively. Improvement in motor and breathing function was highly valued [RC: 0.65, 95% confidence interval (CI): 0.47-0.83 and RC: 0.79, 95% CI: 0.60-0.98, respectively]. Oral medication and one-time infusion were strongly preferred over repeated IT injections (RC: 0.80, 95% CI: 0.60-0.98 and RC: 0.51, 95% CI: 0.30-0.73, respectively). Patients least preferred an age-restricted label/approved use (≤ 2 years of age) (RC: - 1.28, 95% CI: - 1.47 to - 1.09). Cross-attributes trade-off decision suggested a lower willingness for a high-risk therapy despite additional efficacy gain. For some patients, there may be willingness to trade off additional gains in efficacy for a change in route of administration from repeated intrathecal administration to oral medication.

CONCLUSIONS

Improvements in motor/breathing function, broad indication, oral or one-time infusion, and minimal risk were preferred treatment attributes. Treatment decisions should be made in clinical context and be tailored to patient needs.

Scoliosis Surgery Significantly Impacts Motor Abilities in Higher-functioning Individuals with Spinal Muscular Atrophy1

BACKGROUND

Weakness affects motor performance and causes skeletal deformities in spinal muscular atrophy (SMA). Scoliosis surgery decision-making is based on curve progression, pulmonary function, and skeletal maturity. Benefits include quality of life, sitting balance, and endurance. Post-operative functional decline has not been formally assessed.

OBJECTIVE

To assess the impact of scoliosis surgery on motor function in SMA types 2 and 3.

METHODS

Prospective data were acquired during a multicenter natural history study. Seventeen participants (12 type 2, 5 type 3 with 4 of the 5 having lost the ability to ambulate) had motor function assessed using the Hammersmith Functional Motor Scale Expanded (HFMSE) performed pre-operatively and at least 3 months post-operatively. Independent t-tests determined group differences based on post-operative HFMSE changes, age, and baseline HFMSE scores.

RESULTS

Three participants had minimal HFMSE changes (±2 points) representing stability (mean change = -0.7). Fourteen participants lost >3 points, representing a clinically meaningful progressive change (mean change = -12.1, SD = 8.9). No participant improved >2 points. There were no age differences between stable and progressive groups (p = 0.278), but there were significant differences between baseline HFMSE (p = 0.006) and change scores (p = 0.001). Post-operative changes were permanent over time.

CONCLUSIONS

Scoliosis surgery has an immediate impact on function. Baseline HFMSE scores anticipate post-operative loss as higher motor function scores were associated with worse decline. Instrumentation that includes fixation to the pelvis reduces flexibility, limiting the ability for compensatory maneuvers. These observations provide information to alert clinicians regarding surgical risk and to counsel families.

Management and current status of spinal muscular atrophy: a retrospective multicentre claims database analysis

Introduction

The interest in patient demographics and disease management has increased in the past years due to their utility in developing measures that allow healthcare providers to reflect disease complexity.

Objective

To revise the current status of spinal muscular atrophy in the region of Catalonia, and to validate the utility of the database for this aim.

Methods

Five hundred twenty-four patients diagnosed with a spinal muscular atrophy were identified in the region of Catalonia via the novel program of data analysis for research and innovation in health (PADRIS). Patient records included in the analysis corresponded to primary care, hospital, emergency room, extended care and mental health admissions between 2007 and 2017.

Results

58.02% of patients with a SMA diagnosis were males while 40.84% were females. Average age of diagnosis was 38.31 ± 24.49 years ±SD. Significantly lower was the age of diagnosis of spinal muscular atrophy type I, 1.81 ± 3.01 years. An average of 22 patients died per year during the study period, with a mean decease age of 62.96 ± 25.41 years. Patients were generally attended in hospitals, and the use of healthcare resources was focused on resolving respiratory issues and scoliosis. The highest ratio of admissions per patient was registered in those aged 0 to 4 years. Patients presented a higher risk than the general population and a higher frequency of multimorbidites.

Conclusions

Patients exhibited similar characteristics to prior European studies. Multiple admissions in younger patients, mostly due to respiratory issues, have a central role in increasing medical costs of SMA. Equally, the higher risk of patients and increased number of multimorbidity groups translate in an elevated number of admissions in health centres and ER, deriving in higher expenses.

Incidence of complications in the management of non-ambulatory neuromuscular early-onset scoliosis with a rib-based growing system: high- versus low-tone patients

PURPOSE

The purpose of this study is to evaluate whether patients with high-tone neuromuscular early-onset scoliosis have different surgical outcome and complication rate, when compared to patients with low-tone neuromuscular early-onset scoliosis treated with a rib-to-pelvis rib-based dual growing system.

METHODS

This is a retrospective cohort study of 67 neuromuscular early-onset scoliosis patients, collected from a multicenter database, treated with a rib-to-pelvis rib-based dual growing system. All patients were divided into two groups: high tone and low tone. Pre-, intra- and postoperative data were compared between both groups. Complications were reported by a standardized system.

RESULTS

Twenty-six high-tone and 41 low-tone patients were found homogeneous regarding gender, age at surgery, weight, height, estimated blood loss and surgery time. High-tone group (19/26 = 73.1%) experiences more postoperative complications than low-tone group (22/41 = 53.7%). Most common complications were infection, device migration, death and hardware failure. Permanent abandonment of rib-based growing technique and device removal was required in 21% of high-tone patients (P < 0.001). None of the low-tone patients required abandonment.

CONCLUSION

High-tone patients had more complications than those with low tone in management of neuromuscular early-onset scoliosis treated with a rib-to-pelvis rib-based dual growing system. A different surgical approach may be required to treat the high-tone neuromuscular early-onset scoliosis.

Patient characteristics and hospitalisation costs of spinal muscular atrophy in Spain: a retrospective multicentre database analysis

OBJECTIVES

To analyse the characteristics of patients diagnosed with spinal muscular atrophy in Spain, and to revise data on disease management and use of resources in both public and private healthcare centres.

DESIGN

A retrospective multicentre database analysis.

SETTING

870 admission records registered between 1997 and 2015 with a diagnosis of spinal muscular atrophy were extracted from a Spanish claims database that includes hospital inpatient and outpatient admissions from 313 public and 192 private hospitals in Spain.

RESULTS

Admission files corresponded to 705 patients; 61.99% were males and 38.01% females. Average patient age was 37 years. Disease comorbidities registered during the admission consistently included hypertension, scoliosis and respiratory failures, all associated with the standard disease course. Regarding disease management at the hospital level, patients were mostly admitted through scheduled appointments (58.16%), followed by emergency admissions (41.72%), and into neurology services in 17% of the cases. Mean hospitalisation time was 10.45 days and in-hospital mortality reached 5.29%. The overall direct medical costs of spinal muscular atrophy were €291 525, excluding medication. The average annual cost per admission was €6274, with large variations likely to reflect disease complexity and that increases with length of stay.

CONCLUSIONS

The rarity of the disease difficulties the study of demographics and management; yet, an analysis of patient characteristics provides necessary information that can be used by governments to establish more efficient healthcare protocols. This study reflects the impact that individual needs and disease severity can have in disease burden calculations. Forthcoming decision-making policies should take into account medical costs and its variability, as well as pharmaceutical expenses and indirect costs. To our knowledge, this is the first study evaluating the use of healthcare resources of patients with spinal muscular atrophy in Spain.

Cost Effectiveness of Nusinersen in the Treatment of Patients with Infantile-Onset and Later-Onset Spinal Muscular Atrophy in Sweden

BACKGROUND

Spinal muscular atrophy is a rare neuromuscular disorder with a spectrum of severity related to age at onset and the number of SMN2 gene copies. Infantile-onset (≤ 6 months of age) is the most severe spinal muscular atrophy and is the leading monogenetic cause of infant mortality; patients with later-onset (> 6 months of age) spinal muscular atrophy can survive into adulthood. Nusinersen is a new treatment for spinal muscular atrophy.

OBJECTIVE

The objective of this study was to evaluate the cost effectiveness of nusinersen for the treatment of patients with infantile-onset spinal muscular atrophy and later-onset spinal muscular atrophy in Sweden.

METHODS

One Markov cohort health-state transition model was developed for each population. The infantile-onset and later-onset models were based on the efficacy results from the ENDEAR phase III trial and the CHERISH phase III trial, respectively. The cost effectiveness of nusinersen in both models was compared with standard of care in Sweden.

RESULTS

For a time horizon of 40 years in the infantile-onset model and 80 years in the later-onset model, treatment with nusinersen resulted in 3.86 and 9.54 patient incremental quality-adjusted life-years and 0.02 and 2.39 caregiver incremental quality-adjusted life-years and an incremental cost of 21.9 and 38.0 million SEK (Swedish krona), respectively. These results translated into incremental cost-effectiveness ratios (including caregiver quality-adjusted life-years) of 5.64 million SEK (€551,300) and 3.19 million SEK (€311,800) per quality-adjusted life-year gained in the infantile-onset model and later-onset model, respectively.

CONCLUSIONS

Treatment with nusinersen resulted in overall survival and quality-adjusted life-year benefits but with incremental costs above 21 million SEK (€2 million) [mainly associated with maintenance treatment with nusinersen over a patient's lifespan]. Nusinersen was not cost effective when using a willingness-to-pay threshold of 2 million SEK (€195,600), which has been considered in a recent discussion by the Dental and Pharmaceutical Benefits Agency as a reasonable threshold for rare disease. Nonetheless, nusinersen gained reimbursement in Sweden in 2017 for paediatric patients (below 18 years old) with spinal muscular atrophy type I-IIIa.

High Healthcare Resource Use in Hospitalized Patients with a Diagnosis of Spinal Muscular Atrophy Type 1 (SMA1): Retrospective Analysis of the Kids' Inpatient Database (KID)

BACKGROUND

Patients with spinal muscular atrophy (SMA) have high healthcare resource use (HRU) due to respiratory and nutritional complications resulting from progressive muscle atrophy. While previous studies estimate the direct costs to be US$113,000 to US$121,682 per year in the US, they potentially understate costs for type 1 SMA (SMA1). This study analyzed HRU in hospitalizations with a diagnosis of SMA1 and compared it with hospitalizations with complex chronic conditions (CCC) other than SMA1 or those with no CCC.

METHODS

This retrospective analysis of a defined subset of the 2012 Kids' Inpatient Database (KID) compared a nationally estimated number of hospitalizations of children (aged < 3 years) categorized into three groups: (1) SMA1 (n = 237 admissions), (2) no CCC (n = 632,467 admissions), and (3) other CCC (n = 224,953 admissions).

RESULTS

Mean total charges were higher for SMA1 admissions compared with admissions with no CCC (US$150,921 vs US$19,261 per admission, respectively; costs: US$50,190 vs $5862 per admission, respectively; both p < 0.0001). A larger proportion of SMA1 admissions were billed for one or more procedure codes (81.9%) than in the no CCC group (39.4%) or other CCC group (70.1%; both p ≤ 0.0003). SMA1 admissions had a longer length of stay compared with admissions with no CCC (15.1 vs 3.4, respectively; p < 0.0001).

CONCLUSIONS

The average total charges for a single SMA1 admission were higher than those of the no CCC group. Because most infants with SMA1 require multiple hospitalizations per year, previous estimates may dramatically underestimate the direct costs associated with HRU. Further studies are required to determine the indirect costs and societal impacts of SMA1.

Spinal Muscular Atrophy and Ependymoma

Spinal muscular atrophy (SMA) is an autosomal recessive disorder, characterized by a progressive degeneration of anterior horn cells of the spinal cord resulting in hypotonia, skeletal muscle atrophy and weakness. We report the case of a 33-year-old female with SMA type IV (SMA4) who presented with symptoms of spinal cord lesion that was initially missed. Further evaluation resulted in the diagnosis of ependymoma. To the best of our knowledge, this is the first time that the coexistence of SMA4 and ependymoma has been reported.

Spinal Muscular Atrophy

Spinal muscular atrophy is an autosomal-recessive disorder characterized by degeneration of motor neurons in the spinal cord and caused by mutations in the survival motor neuron 1 gene, SMN1. The severity of SMA is variable. The SMN2 gene produces a fraction of the SMN messenger RNA (mRNA) transcript produced by the SMN1 gene. There is an inverse correlation between SMN2 gene copy number and clinical severity. Clinical management focuses on multidisciplinary care. Preclinical models of SMA have led to an explosion of SMA clinical trials that hold great promise of effective therapy in the future.

Spinal muscular atrophy: diagnosis and management in a new therapeutic era

Spinal muscular atrophy (SMA) describes a group of disorders associated with spinal motor neuron loss. In this review we provide an update regarding the most common form of SMA, proximal or 5q-SMA, and discuss the contemporary approach to diagnosis and treatment. Electromyography and muscle biopsy features of denervation were once the basis for diagnosis, but molecular testing for homozygous deletion or mutation of the SMN1 gene allows efficient and specific diagnosis. In combination with loss of SMN1, patients retain variable numbers of copies of a second similar gene, SMN2, which produces reduced levels of the survival motor neuron (SMN) protein that are insufficient for normal motor neuron function. Despite the fact that understanding of how ubiquitous reduction of SMN protein leads to motor neuron loss remains incomplete, several promising therapeutics are now being tested in early-phase clinical trials.