Course Of Spinal Muscular Atrophy Research Articles

Expert consensus on newborn screening for spinal muscular atrophy (2023 edition)

Spinal muscular atrophy (SMA) is a common degenerative neurological disease characterized by progressive muscle weakness and atrophy. In recent years, disease-modifying therapies have emerged and changed the natural course of SMA, with pre-symptomatic diagnosis and treatment being superior to post symptom treatment. Therefore, in order to standardize and guide the current newborn screening work of SMA, we organized national experts from related fields across the country to reach the following consensus: the SMA newborn screening process and related issues, the SMA post-screening diagnosis process and related issues, and the disease management of screened and confirmed SMA newborns, etc.

P.48 The impact of newborn screening and early therapy on the course of spinal muscular atrophy: a retrospective analysis of a single center experience

P.48 The impact of newborn screening and early therapy on the course of spinal muscular atrophy: a retrospective analysis of a single center experience

Spinal muscular atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive disease caused by biallelic mutations in the SMN1 (survival motor neuron1) gene on chromosome 5q13.2, which leads to aprogressive degeneration of alpha motor neurons in the spinal cord and in motor nerve nuclei in the caudal brainstem. It is characterized by progressive proximally accentuated muscle weakness with loss of already acquired motor skills, areflexia and, depending on the phenotype, varying degrees of weakness of the respiratory and bulbar muscles, although the facial muscles and eye muscles are not affected. The previously purely symptom-oriented treatment has undergone asignificant expansion since 2017 with the approval of three drugs (nusinersen, onasemnogene abeparvovec and risdiplam) that modify the course of the disease at the gene expression level and have led to achange in the natural disease course of SMA. The effect of these new forms of treatment can only be fully assessed in the coming years. New aspects and challenges in this context are discussed in this article.

Treatment with nusinersen in a girl with spinal muscular atrophy type 1 - Case report

We report the case of a girl with spinal muscular atrophy (SMA) type 1, who is the first patient with SMA in Slovenia treated with nusinersen, the first disease modifying therapy available for these patients. SMA is an autosomal recessive neuromuscular disorder characterized by muscle weakness, atrophy and paralysis due to the degeneration of the anterior horn cells, leading to premature death, most commonly due to respiratory infections. Nusinersen, an antisense oligonucleotide, was clinically approved based on clinical trials showing dramatic improvement in the natural course of infantile-onset SMA. After the genetic confirmation of SMA, our girl was the first child in Slovenia to receive nusinersen, which was provided through an expanded access programme. She received intrathecal applications of nusinersen according to the protocol. No serious adverse events were observed. Assessment of her motor skills was performed using The Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP – INTEND) before the beginning of treatment and after completing the first 7 applications of nusinersen. She scored 21/64 points before the introduction of treatment and 32/64 after the completion of treatment. In conclusion, nusinersen improved the CHOP – INTEND motor function score and has been effective in delaying the expected natural course of SMA in our patient.

Recommendations for gene therapy of spinal muscular atrophy with onasemnogene abeparvovec-AVXS-101 : Consensus paper of the German representatives of the Society for Pediatric Neurology (GNP) and the German treatment centers with collaboration of the medical scientific advisory board of the German Society for Muscular Diseases (DGM)

Spinal muscular atrophy (SMA) is asevere, life-limiting neurodegenerative disease. Adisease-modifying and approved therapy with nusinersen has been available in Germany since July 2017. Gene therapies offer another promising treatment option through a once in a lifetime administration. In May 2019 agene replacement therapy for the treatment of SMA was approved for the first time by the U.S. Food and Drug Administration (FDA). An application for approval in Europe has been submitted and is currently pending. This consensus paper was compiled at the invitation of the German Society for Muscular Diseases (DGM) with the participation of all potential German neuromuscular treatment centers, the German section of the Society for Pediatric Neurology (GNP) and with the involvement of the medical scientific advisory board of the DGM. The aim was to define and establish the necessary prerequisites for asafe and successful application of the new gene replacement therapy in clinical practice. Gene replacement therapy with onasemnogene abeparvovec has the potential to significantly influence the course of SMA. Long-term data on sustainability of effects and possible adverse effects of gene replacement therapy are not yet available. The application of this innovative therapy must be carried out in specialized and appropriately qualified treatment centers under strict safety conditions. This article makes suggestions for the necessary framework conditions and gives recommendations for asystematic pretreatment and posttreatment assessment schedule under gene therapy. The effectiveness and safety of the therapy should be systematically documented in an industry-independent and disease-specific register.

Drug treatment for spinal muscular atrophy type I.

Background Spinal muscular atrophy (SMA) is caused by degeneration of anterior horn cells of the spinal cord, which leads to progressive muscle weakness. Children with SMA type I will never be able to sit without support and usually die by the age of two years. There are no known efficacious drug treatments that influence the course of the disease. This is an update of a review first published in 2009. Objectives To evaluate whether drug treatment is able to slow or arrest the disease progression of SMA type I, and to assess if such therapy can be given safely. Drug treatment for SMA types II and III is the topic of a separate updated Cochrane review. Search methods We searched the Cochrane Neuromuscular Disease Group Specialized Register (8 March 2011), CENTRAL (The Cochrane Library 2011, Issue 1), MEDLINE (January 1991 to February 2011), EMBASE (January 1991 to February 2011) and ISI Web of Knowledge (January 1991 to 8 March 2011). We searched the Clinical Trials Registry of the U.S. National Institute of Health (www.ClinicalTrials.gov) (8 March 2011) to identify additional trials that had not yet been published. Selection criteria We sought all randomised or quasi-randomised trials that examined the efficacy of drug treatment for SMA type I. Participants had to fulfil the clinical criteria and have a deletion or mutation of the SMN1 gene (5q11.2-13.2) confirmed by genetic analysis.The primary outcome measure was time from birth until death or full time ventilation. Secondary outcome measures were development of rolling, sitting or standing within one year after the onset of treatment, and adverse events attributable to treatment during the trial period. Data collection and analysis Two authors (RW and AV) independently reviewed and extracted data from all potentially relevant trials. For included studies, pooled relative risks and standardised mean differences were to be calculated to assess treatment efficacy. Main results One small randomised controlled study comparing riluzole treatment to placebo for 10 SMA type 1 children was identified and included in the original review. No further trials were identified for the update in 2011. Regarding the primary outcome measure, three of seven children treated with riluzole were still alive at the ages of 30, 48 and 64 months, whereas all three children in the placebo group died; but the difference was not statistically significant. Regarding the secondary outcome measures, none of the children in the riluzole or placebo group developed the ability to roll, sit or stand, and no adverse effects were observed. For several reasons the overall quality of the study was low, mainly because the study was too small to detect an effect and because of baseline differences. Follow-up of the 10 included children was complete. Authors' conclusions No drug treatment for SMA type I has been proven to have significant efficacy.

Magnetic resonance imaging of the cervical spinal cord in spinal muscular atrophy.

ObjectiveIn this study we investigated the potential value of magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) in characterizing changes in the cervical spinal cord and peripheral nerve roots in vivo in patients with spinal muscular atrophy (SMA).MethodsWe developed an MRI protocol with 4 sequences to investigate the cervical spinal cord and nerve roots on a 3 Tesla MRI system. We used 2 anatomical MRI sequences to investigate cross-sectional area (CSA) at each spinal segment and the diameter of ventral and dorsal nerve roots, and two diffusion tensor imaging (DTI) techniques to estimate the fractional anisotropy (FA), mean (MD), axial (AD) and radial diffusivity (RD) in 10 SMA patients and 20 healthy controls.ResultsThere were no significant differences in CSA (p > .1), although an 8.5% reduction of CSA in patients compared to healthy controls was apparent at segment C7. DTI data showed a higher AD in grey matter of patients compared to healthy controls (p = .033). Significantly lower MD, AD and RD values were found in rostral nerve roots (C3-C5) in patients (p < .045).ConclusionsWe showed feasibility of an advanced 3 T MRI protocol that allowed differences to be determined between patients and healthy controls, confirming the potential of this technique to assess pathological mechanisms in SMA. After further development and confirmation of findings in a larger sample, these techniques may be used to study disease course of SMA in vivo and evaluate response to survival motor neuron (SMN) augmenting therapy.

PTEN Depletion Decreases Disease Severity and Modestly Prolongs Survival in a Mouse Model of Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is the second most common genetic cause of death in childhood. However, no effective treatment is available to halt disease progression. SMA is caused by mutations in the survival motor neuron 1 (SMN1) gene. We previously reported that PTEN depletion leads to an increase in survival of SMN-deficient motor neurons. Here, we aimed to establish the impact of PTEN modulation in an SMA mouse model in vivo. Initial experiments using intramuscular delivery of adeno-associated vector serotype 6 (AAV6) expressing shRNA against PTEN in an established mouse model of severe SMA (SMNΔ7) demonstrated the ability to ameliorate the severity of neuromuscular junction pathology. Subsequently, we developed self-complementary AAV9 expressing siPTEN (scAAV9-siPTEN) to allow evaluation of the effect of systemic suppression of PTEN on the disease course of SMA in vivo. Treatment with a single injection of scAAV9-siPTEN at postnatal day 1 resulted in a modest threefold extension of the lifespan of SMNΔ7 mice, increasing mean survival to 30 days, compared to 10 days in untreated mice. Our data revealed that systemic PTEN depletion is an important disease modifier in SMNΔ7 mice, and therapies aimed at lowering PTEN expression may therefore offer a potential therapeutic strategy for SMA.

Mechanisms involved in spinal cord central synapse loss in a mouse model of spinal muscular atrophy.

Motoneuron (MN) cell death is the histopathologic hallmark of spinal muscular atrophy (SMA), although MN loss seems to be a late event. Conversely, disruption of afferent synapses on MNs has been shown to occur early in SMA. Using a mouse model of severe SMA (SMNΔ7), we examined the mechanisms involved in impairment of central synapses. We found that MNs underwent progressive degeneration in the course of SMA, with MN loss still occurring at late stages. Loss of afferent inputs to SMA MNs was detected at embryonic stages, long before MN death. Reactive microgliosis and astrogliosis were present in the spinal cord of diseased animals after the onset of MN loss. Ultrastructural observations indicate that dendrites and microglia phagocytose adjacent degenerating presynaptic terminals. Neuronal nitric oxide synthase was upregulated in SMNΔ7 MNs, and there was an increase in phosphorylated myosin light chain expression in synaptic afferents on MNs; these observations implicate nitric oxide in MN deafferentation and suggest that the RhoA/ROCK pathway is activated. Together, our observations suggest that the earliest change occurring in SMNΔ7 mice is the loss of excitatory glutamatergic synaptic inputs to MNs; reduced excitability may enhance their vulnerability to degeneration and death.

Temporal requirement for high SMN expression in SMA mice

Spinal muscular atrophy (SMA) is caused by loss of the survival motor neuron 1 gene (SMN1) and retention of the SMN2 gene, resulting in reduced SMN. SMA mice can be rescued with high expression of SMN in neurons, but when is this high expression required? We have developed a SMA mouse with inducible expression of SMN to address the temporal requirement for high SMN expression. Both embryonic and early postnatal induction of SMN resulted in a dramatic increase in survival with some mice living greater than 200 days. The mice had no marked motor deficits and neuromuscular junction (NMJ) function was near normal thus it appears that induction of SMN in postnatal SMA mice rescues motor function. Early postnatal SMN induction, followed by a 1-month removal of induction at 28 days of age, resulted in no morphological or electrophysiological abnormalities at the NMJ and no overt motor phenotype. Upon removal of SMN induction, five mice survived for just over 1 month and two female mice have survived past 8 months of age. We suggest that there is a postnatal period of time when high SMN levels are required. Furthermore, two copies of SMN2 provide the minimal amount of SMN necessary to maintain survival during adulthood. Finally, in the course of SMA, early induction of SMN is most efficacious.

Observational Study of Spinal Muscular Atrophy Type 2 and 3

To characterize the short-term course of spinal muscular atrophy (SMA) in a genetically and clinically well-defined cohort of patients with SMA. A comprehensive multicenter, longitudinal, observational study. The Pediatric Neuromuscular Clinical Research Network for SMA, a consortium of clinical investigators at 3 clinical sites. Sixty-five participants with SMA types 2 and 3, aged 20 months to 45 years, were prospectively evaluated. We collected demographic and medical history information and determined the SMN 2 copy number. Clinical outcomes included measures of motor function (Gross Motor Function Measure and expanded Hammersmith Functional Motor Scale), pulmonary function (forced vital capacity), and muscle strength (myometry). Participants were evaluated every 2 months for the initial 6 months and every 3 months for the subsequent 6 months. We evaluated change over 12 months for all clinical outcomes and examined potential correlates of change over time including age, sex, SMA type, ambulatory status, SMN2 copy number, medication use, and baseline function. There were no significant changes over 12 months in motor function, pulmonary function, and muscle strength measures. There was evidence of motor function gain in ambulatory patients, especially in those children younger than 5 years. Scoliosis surgery during the observation period led to a subsequent decline in motor function. Our results confirm previous clinical reports suggesting that SMA types 2 and 3 represent chronic phenotypes that have relatively stable clinical courses. We did not detect any measurable clinical disease progression in SMA types 2 and 3 over 12 months, suggesting that clinical trials will have to be designed to measure improvement rather than stabilization of disease progression.

Pulmonary function and scoliosis in children with spinal muscular atrophy types II and III.

The objectives were to evaluate the clinical course of spinal muscular atrophy (SMA) types II and III patients necessitating scoliosis surgery at the National University Hospital, Singapore. A retrospective review of SMA types II and III patients, born over a 10-year period between 1983 and 1992, was conducted. There were eight patients: four with SMA type II and four with SMA type III. The mean age at scoliosis surgery was 9 years 7 months (range 7 years 6 months-12 years 4 months). The mean preoperative Cobb angle was 65.4 degrees (range 43-90 degrees ) and the mean postoperative Cobb angle was 22.6 degrees (range 12-45 degrees ), with a mean correction of 64.8% (range 47.7-77.8%). The decline in percentage predicted forced vital capacity (FVC) was 7.7% (95% CI: 12.4% to 3.0%) per year preoperatively and this was reduced to 3.8% (95% CI: 5.8% to 1.9%) per year postoperatively. The mean length of preoperative and postoperative lung function follow-up was 6.3 months (range 0.03-31 months) and 44 months (range 0-110 months), respectively. This study suggests that pulmonary function in SMA types II and III continues to decline after scoliosis surgery, though the rate of decline is less marked. Overall, the combined results from this study and all other previously published studies are conflicting in regard to the effect of scoliosis surgery on pulmonary function in SMA types II and III, though half of the studies (3 of 6) did demonstrate a continued decline in lung function postoperatively. This decline in pulmonary function despite spinal stabilization is likely secondary to the progressive neuromuscular weakness of the disease.

Riluzole attenuates spinal muscular atrophy disease progression in a mouse model.

Spinal muscular atrophy (SMA) is a motor neuron disease caused by mutations of the survival motor neuron 1 gene (SMN1). No curative treatment is available. Mutant mice carrying homozygous deletion of Smn exon 7 directed to neurons display a degenerative process of motor neurons similar to that found in human SMA. To test whether riluzole, which exhibits neurotrophic properties, might have a protective role in SMA, mutant mice were treated with it after the onset of the degenerative process. Riluzole improved median survival and exerted a protective effect against aberrant cytoskeletal organization of motor synaptic terminals but not against loss of proximal axons. These results demonstrate that the disease course of SMA can be attenuated after the onset of neuromuscular defects and may warrant further investigation in a therapeutic trial in SMA.

Function changes in spinal muscular atrophy II and III. The DCN/SMA Group.

The course of spinal muscular atrophy (SMA) is not well established except for those patients whose age of onset is before 6 months and who achieve only "sit with support" as their maximum function (Werdnig-Hoffmann disease or SMA I). This study shows that there is another group of SMA patients whose age of onset and maximum function achieved can be used as prognostic guides. Fifty percent of SMA patients who could walk without assistance and whose onset was prior to age 2 years lost the ability to walk independently by age 12. Fifty percent of SMA patients who walked and whose onset was between 2 and 6 years of age lost walking ability by age 44 years. Fifty percent of SMA patients who could walk with assistance as their best function ever achieved lost this ability by age 7 years, unrelated to age of onset; none could walk with assistance after age 14 years. Seventy-five percent of SMA patients who developed the ability to sit independently as their best function were still sitting after age 7 years independent of age of onset; 50% of this group could sit independently after age 14 years. Eighty-five percent of SMA patients who could walk could not negotiate stairs without holding onto a rail. They could raise their hands above the head; however, as they lost walking ability, they lost this function as well. Only one SMA patient whose maximum function was sitting independently could get to the sitting position on his own. Only two of these patients could hold their hands above their heads. All patients with SMA lose function over time. This function loss occurs slowly and is related primarily to maximum function achieved; knowledge of age of onset provides helpful information, especially for predicting the loss of independent walking.

Natural history in proximal spinal muscular atrophy. Clinical analysis of 445 patients and suggestions for a modification of existing classifications.

To describe the natural history in all types of proximal spinal muscular atrophy (SMA) and to propose a modified classification scheme that takes the long-term course of SMA into account. Patients with proximal SMA were studied prospectively and retrospectively in a genetic study that was based on clinical and family data. Four hundred forty-five patients with SMA were ascertained since 1985 through various departments of neurology and neuropediatrics, institutes of human genetics, and the German muscular dystrophy association (Deutsche Gesellschaft für Muskelkranke, Freiburg, Germany). The study group was subdivided into patients with four types of SMA (ie, SMA types I, II, III, and IV) on the basis of achieved motor development and age at onset. Survival probabilities at 2, 4, 10, and 20 years of age were 32%, 18%, 8%, and 0%, respectively, in patients with SMA type I (those who were never able to sit) and 100%, 100%, 98%, and 77%, respectively, in patients with SMA type II (those who were able to sit but were unable to walk). Nineteen of 104 patients with SMA type II lost the ability to sit; this inability to sit was not of prognostic relevance. Patients with SMA type III (those who were able to walk [age at onset, younger than 30 years]) were subdivided into those with an age at onset before (SMA type IIIa) and after (SMA type IIIb) 3 years. The probabilities of being ambulatory at 10, 20, and 40 years after onset were 73%, 44%, and 34%, respectively, in patients with SMA type IIIa, and they were 97%, 89%, and 67%, respectively, in patients with SMA type IIIb. The definition of long-term characteristics of SMA is helpful in providing medical care to families with members who have SMA and also in providing important information for future genotype-phenotype studies and therapeutic trials of patients with SMA. Our data indicate that the widely used classification schemes did not consider the broad spectrum of SMA so a practical modification was suggested.

Neuromuscular diseases of childhood

This review covers three areas. First, dramatic progress in the discovery of abnormal loci on certain chromosomes associated with several motor unit diseases eventually will obviate the need for more invasive testing. Second, new information about the natural course of spinal muscular atrophy is beginning to clarify the nature of this disease. Third, changes in the treatment of the acute and chronic polyneuropathies has shortened hospital stays.