No products in the cart.
Spinal Muscular Atrophy: Understanding Causes, Symptoms, and Treatment Options
What is Spinal Muscular Atrophy?
Spinal muscular atrophy affects motor neurones in the spinal cord, leading to muscle weakness and atrophy.
Spinal muscular atrophy (SMA) is a genetic neuromuscular condition in which specialised nerve cells—motor neurones in the spinal cord and brainstem—gradually fail. These motor neurones control voluntary movements, such as head control, crawling, walking, and swallowing. When they deteriorate, the muscles they supply become weak and waste away (muscular atrophy).
SMA most commonly results from changes in the survival motor neurone 1 (SMN1) gene. The SMN1 gene makes the SMN protein, which motor neurones need to survive and function. Reduced SMN protein causes the characteristic muscle weakness of SMA.
There is a related gene, SMN2, that produces a small amount of working SMN protein and influences how severe the condition is. In practice, the number of SMN2 copies, together with clinical assessment and genetic testing, helps clinicians decide on prognosis and the most suitable treatment approach.
Symptoms and progression vary widely — from early infantile weakness (for example, an infant with a weak cry and difficulty feeding) to milder, later-onset muscle weakness in adults. Advances in diagnosis and treatments mean the outlook for many people with SMA is changing.
Types of Spinal Muscular Atrophy
Spinal muscular atrophy is described using SMA types that reflect the usual age of onset and typical clinical features. These classifications (SMA types 0–4) help clinicians and families understand likely patterns of muscle weakness, guide genetic testing, and inform treatment decisions—especially when considered alongside the number of SMN2 gene copies.
| SMA Type | Age of Onset | Key Features | Clinical course / management notes |
| Type 0 (Prenatal) | Before birth | Reduced fetal movements; very low tone and severe weakness at birth; respiratory compromise | Often requires immediate specialist respiratory and feeding support; early genetic testing and specialist input are essential. |
| Type 1 (Werdnig‑Hoffmann) | 0–6 months | Marked hypotonia, poor head control, difficulty swallowing and breathing; never sit independently | Early multidisciplinary care and disease‑modifying treatment can change the expected clinical course; respiratory and nutritional support are key. |
| Type 2 (Dubowitz) | 6–18 months | Able to sit but not to stand or walk independently; progressive proximal muscle weakness | Orthopaedic monitoring, respiratory assessment, and timely therapy optimise function; the SMN2 copy number and treatment affect outcomes. |
| Type 3 (Kugelberg‑Wanderer) | > 18 months (childhood/early adolescence) | Can stand and walk initially but may experience gradual loss of ambulation over time | Physiotherapy, mobility aids and regular review help maintain independence; treatment access and individual courses vary. |
| Type 4 (Adult‑onset) | Adulthood (typically 20s–30s) | Mild motor impairment with slow progression; primarily proximal weakness | Management focuses on symptom control, occupational adaptation and maintaining activity. |
Note: these categories (SMA types) are descriptive. Modern treatments and the number of SMN2 gene copies can alter the clinical course for many people with SMA. For personalised information about the prognosis, treatment options, and management, consult a neuromuscular specialist or genetics service.
Signs and Symptoms of Spinal Muscular Atrophy
Children with SMA type 1 or 2 often show significant muscle weakness and hypotonia (low muscle tone).
The main features of spinal muscular atrophy are progressive muscle weakness and loss of motor function, but how and when symptoms appear varies by SMA type. Below are typical signs to watch for at different ages and why they matter for care and treatment.
Early infancy (Types 0–1)
- Severe hypotonia — a “floppy baby” with very low muscle tone
- Poor or absent head control
- Weak cry and weak cough
- Difficulty feeding and swallowing, leading to poor weight gain
- Breathing problems and paradoxical breathing (abdomen moves outward on inhalation)
- Failure to reach motor milestones (e.g., rolling, sitting)
- Typically normal cognition and alertness despite marked muscle weakness
Later onset (Types 2–4)
- Progressive proximal muscle weakness affecting shoulders and hips
- Difficulty rising from the floor (Gowers’ manoeuvre may be absent in SMA) and trouble climbing stairs
- Frequent falls and early fatigue on exertion
- Tremor of the hands or fingers in some people
- Orthopaedic issues such as scoliosis and joint contractures
- Respiratory insufficiency can occur, especially with weakened intercostal muscles
- Preserved cognitive function is typical
Why respiratory problems matter
Respiratory complications are a major concern in SMA because weakness of the chest wall muscles (intercostal muscles) can lead to an ineffective cough and difficulty clearing secretions. This increases the risk of chest infections. Regular respiratory assessment, airway clearance techniques and, when needed, cough-assist devices or non-invasive ventilation form core elements of care.
Orthopaedic and functional consequences
Muscle weakness and imbalance commonly lead to scoliosis (spinal curvature), hip problems and contractures. These issues can limit mobility and affect activities of daily living. Early physiotherapy, positioning, orthoses and timely orthopaedic review help reduce complications and maintain function.
How SMA differs from muscular dystrophy
Unlike many muscular dystrophies, SMA is primarily a motor neurone disorder: creatine kinase levels are often normal or only mildly elevated, and cognitive development is usually preserved. Genetic testing distinguishes SMA from other neuromuscular conditions and guides management.
Spotting Symptoms Early Is Always Best: Red Flags
Example: A baby who is three months old, having a weak cry, cannot control their head, and has issues logging on to a feed in a timely manner shows signs of needing immediate help. Jumping and recognising the signs, in addition to genetic testing and having a specialist, permits efficient care and help.
Worried about SMA symptoms?
Intervention is the key to decreasing the effect and impact it can have. If you notice weakness in the muscles, lagging behind in their milestones, or problems with their breathing and feeding, reach out to a GP or a specialist team. Ask about newborn screening if relevant in your area.
Causes and Genetics of Spinal Muscular Atrophy
Autosomal recessive inheritance pattern of SMA – both parents must be carriers for a child to inherit the condition.
Genetic basis
Spinal muscular atrophy (SMA) is usually caused by changes in the survival motor neurone 1 (SMN1) gene on chromosome 5q. The SMN1 gene makes the SMN protein, which motor neurones need to function and survive. When both copies of the SMN1 gene are absent or non-functional, SMN protein levels fall, and motor neurones degenerate, producing the progressive muscle weakness and muscular atrophy that characterise SMA.
The role of SMN2 and gene copies
Most people have a similar gene called SMN2 that can produce some working SMN protein, although it makes less full‑length protein than SMN1. The number of SMN2 gene copies a person has partly determines how severe their symptoms are: more SMN2 copies generally mean more SMN protein and a milder clinical course. Clinicians use SMN2 copy number together with clinical findings to guide treatment decisions.
Inheritance pattern
SMA is inherited in an autosomal recessive way. This means both parents must be carriers of a pathogenic change in an SMN1 gene for a child to be affected. Typical outcomes when both parents are carriers are:
- 25% chance the child will have SMA
- 50% chance the child will be a carrier like the parents
- 25% chance the child will neither have SMA nor be a carrier
Carrier frequency and testing
Carrier screening and genetic testing are available for people planning a family or who have a family history of SMA. Carrier frequency estimates and incidence figures vary by population; genetic counselling helps interpret results and discuss options. If one parent is known to be a carrier, targeted testing of the other parent and early genetic testing of infants at risk are recommended.
Genetic testing not only identifies changes in the SMN1 gene but can also determine SMN2 copy number, which is increasingly important in treatment planning. If you are considering testing, ask your GP for a referral to a genetics service or specialist neuromuscular clinic for personalised advice.
Diagnosing Spinal Muscular Atrophy
Genetic testing is the gold standard for diagnosing SMA, identifying mutations in the SMN1 gene.
Early diagnosis of spinal muscular atrophy (SMA) allows timely access to genetic testing, specialist care and disease‑modifying treatments. The diagnostic pathway usually combines clinical assessment with genetic testing; other investigations can support management and rule out alternative causes of muscle weakness.
Clinical assessment — what clinicians look for
A healthcare professional will take a detailed history (including family history) and perform a focused neurological and developmental examination. Key features that prompt further testing include hypotonia, delayed motor milestones, weak cry or feeding difficulties, and progressive muscle weakness or reduced reflexes.
Genetic testing — what it checks
Genetic testing is the definitive test for SMA. A blood sample is used to look for changes in the SMN1 gene and to count copies of the SMN2 gene. Results typically show:
- Homozygous deletion or mutation of the SMN1 gene (the commonest finding in SMA)
- SMN2 gene copy number, which helps predict likely severity and guide treatment choices
Supporting investigations
Other tests may be used to assess severity, monitor problems or exclude other conditions:
- Electromyography (EMG): may show denervation patterns
- Nerve conduction studies: typically normal in SMA but help exclude peripheral neuropathies
- Creatine kinase (CK): usually normal or mildly raised (helps differentiate from many muscular dystrophies)
- Imaging and pulmonary function tests: for orthopaedic and respiratory assessment as needed
Newborn screening and early testing
Many countries and regions are introducing newborn screening for SMA. This involves a small blood-spot test shortly after birth to detect SMN1 deletions before symptoms develop. Early detection through screening enables pre‑symptomatic treatment in eligible infants, which can substantially improve motor outcomes. Check with your local NHS or newborn-screening programme for availability in your area.
What families can expect — a short checklist
- Referral to a genetics service or neuromuscular clinic after an abnormal screen or clinical suspicion
- Discussion with a genetic counsellor about testing implications and family planning
- Timing: simple genetic tests are often processed within days to a few weeks; specialist appointments may take longer
- Follow-up planning for respiratory, nutritional and physiotherapy assessments if SMA is confirmed
Need support after diagnosis?
If you or your child receives a diagnosis of SMA, contact your specialist centre or SMA UK for information, emotional support and practical advice about tests, treatment options and local services.
Treatment Options for Spinal Muscular Atrophy
Disease-modifying therapies have revolutionised SMA treatment, significantly improving outcomes.
The treatment landscape for spinal muscular atrophy (SMA) has changed rapidly with the arrival of disease‑modifying therapies. Current care combines these therapies with multidisciplinary supportive management to maximise function, participation and quality of life for people with SMA.
Disease‑modifying therapies — overview
Several licensed treatments now target the genetic mechanisms of SMA. They do not cure the condition but can substantially improve motor function, especially when started early. Below are the principal therapies in clinical use; eligibility, age limits and commissioning vary by country and centre, so always discuss options with a specialist neuromuscular team.
Nusinersen (Spinraza®)
An antisense oligonucleotide that modifies SMN2 gene splicing to increase production of functional SMN protein. It is delivered by intrathecal injection into the spinal fluid on a scheduled dosing regimen.
Approved for a wide range of ages
Onasemnogene abeparvovec (Zolgensma®)
A one‑time gene replacement therapy that delivers a functional copy of the SMN1 gene using an AAV9 viral vector via intravenous infusion. It is currently provided to eligible infants and young children in line with national guidance.
Primarily for very young children — local guidance applies
Risdiplam (Evrysdi®)
An oral SMN2 splicing modifier taken daily that increases levels of functional SMN protein throughout the body. It is appropriate for many ages and can be used where oral administration is preferred or when intrathecal access is challenging.
Licensed for infants and older patients in many jurisdictions
Who may benefit? Early treatment, ideally before substantial motor neurone loss, tends to produce the most marked gains; however, people across the SMA spectrum may experience improvements in strength, motor skills or respiratory needs depending on age, baseline function and SMN2 copy number.
How to access treatment
- Referral to a specialist neuromuscular or paediatric centre is required for assessment and prescribing.
- Eligibility and funding are determined by national health services or commissioning bodies; your local specialist team can advise on pathways in your area.
- Genetic testing (SMN1 mutation and SMN2 copy number) is usually required to guide decisions.
Supportive care and symptom management
Alongside disease‑modifying treatments, comprehensive supportive care is essential to manage respiratory, nutritional and orthopaedic complications and to help maintain mobility and independence.
Respiratory management
- Regular respiratory assessment and monitoring
- Airway clearance techniques and physiotherapy
- Cough‑assist devices and non‑invasive ventilation when needed
- Preventive measures such as vaccinations
Nutritional and feeding support
- Swallowing assessment and feeding strategies
- Dietary advice and supplements where required
- Consideration of gastrostomy for safe prolonged feeding in some cases
Orthopaedic and neuromuscular care
- Scoliosis surveillance and timely intervention
- Contracture prevention through stretching and positioning
- Bracing, orthoses and surgical options when indicated
Mobility, assistive technology and rehabilitation
- Individualised physiotherapy programmes to maintain range of motion and function
- Customised wheelchairs, standing aids and mobility devices
- Adaptive equipment for daily living and augmentative communication where needed
Gene therapy — more detail
Gene therapy using an AAV9 vector delivers a working copy of the SMN1 gene to motor neurones. When given early, trials have shown marked improvements in motor milestones and reduced ventilatory support needs for many infants. Important considerations include eligibility criteria, immune response risks, the need for liver monitoring and high treatment costs — discuss benefits and risks with a specialist centre.
Practical points and monitoring
- Treatment decisions are personalised: specialists consider age, SMA type, current function and SMN2 copy number.
- Ongoing monitoring (liver tests, growth, motor skills, respiratory function) is part of standard care after starting disease‑modifying therapy.
- Combination approaches and clinical trials may be options; speak to your clinical team about research and registries.
Explore treatment options
For detailed information about specific treatments, eligibility and how to access them in the UK, contact your neuromuscular specialist centre or visit SMA UK’s treatment pages.
Gene Therapy for Spinal Muscular Atrophy
Gene therapy works by delivering a functional copy of the SMN1 gene to motor neurones.
Gene therapy has been a major advance in SMA care. By delivering a functional SMN1 gene, the treatment aims to increase SMN protein production and preserve motor neurone function. Evidence shows the greatest benefit when given pre‑symptomatically or early in the disease course.
How it works and what to expect
- Given as a single intravenous infusion using an AAV9 vector that can cross into the nervous system.
- Does not integrate into the patient’s DNA; rather, the introduced gene exists as an episome in the cell nucleus.
- Requires pre‑treatment assessment and close follow‑up, including liver function monitoring and immunological screening.
Outcomes and limitations
Clinical studies report meaningful motor gains and reduced need for ventilatory support in many treated infants. Limitations include current age eligibility policies in some regions, potential immune reactions, the need for monitoring and variable long‑term durability data. Economic and commissioning considerations also affect access; speak with your specialist centre for the latest guidance.
Therapy Interventions for Spinal Muscular Atrophy
Physiotherapy is essential for maintaining mobility and preventing complications in SMA
Therapies such as physiotherapy, occupational therapy and speech and language therapy are vital parts of SMA management. They support mobility, independence, feeding and communication and reduce complications associated with progressive muscle weakness.
Physiotherapy approaches
- Regular stretching and range‑of‑motion work to prevent contractures
- Tailored strengthening and conditioning within safe limits
- Respiratory physiotherapy and airway clearance training
- Hydrotherapy/aquatic sessions to exploit buoyancy for movement
StandSure Therapy Aid
The StandSure system is an example of standing support used in physiotherapy programmes. It provides stable, adjustable support to promote weight‑bearing, posture and bone health while allowing therapists to guide movement safely.
Occupational and speech therapy
Occupational therapy helps people adapt everyday activities and maintain independence with assistive equipment and environmental changes. Speech and language therapy supports safe swallowing, nutrition and alternative communication options when needed.
Explore StandSure for Physiotherapy
Discover how standing aids and tailored therapy programmes can form part of a rehabilitation plan to preserve mobility and support respiratory health.
Clinical Trials and Research Developments
Ongoing research continues to advance our understanding and treatment of spinal muscular atrophy.
Research into spinal muscular atrophy (SMA) is active and evolving. Clinical trials explore new treatments, refine existing therapies and investigate approaches that may benefit people across different SMA types and ages.
Current research focus areas
Key directions under investigation include:
Next‑generation SMN‑enhancing therapies
New compounds and delivery methods aim to increase production of SMN protein more effectively or with fewer side effects than current options.
Combination approaches
Some trials study whether combining gene therapy, SMN2 splicing modifiers and other treatments provides additive benefits compared with single therapies.
Non‑SMN strategies
These approaches target muscle health or motor neurone function independently of SMN protein, with the goal of complementing SMN‑targeted treatments.
Considering trial participation
Joining a clinical trial can offer access to novel treatments and helps advance knowledge, but it also involves commitments and potential risks. Discuss the following with your clinical team:
- Eligibility criteria (age, SMA type, previous treatments)
- Study design and whether a placebo or external control is used
- Visit frequency, procedures and possible side effects
- Expected benefits and burdens, informed consent and withdrawal rights
How to find trials
- Search registries such as ClinicalTrials.gov and national trial registries
- Contact your specialist neuromuscular centre or genetics clinic for local opportunities
- Join patient registries (for example via SMA UK) to receive notifications about suitable studies
The SMA research landscape changes quickly. If you are interested in research participation, speak to your healthcare team and consider registering with reputable patient registries to stay informed about new trial openings.
Explore Clinical Trial Opportunities
Join the SMA registry to stay informed about clinical trials and research opportunities that may be suitable for you or your loved one.
Support Resources for Individuals with SMA
Support groups provide valuable information, resources, and emotional support for families affected by SMA
Living with spinal muscular atrophy (SMA) involves medical care, practical adjustments and emotional support. A range of organisations, services and community networks exist to help people with SMA and their families access healthcare, equipment, education and peer support to maintain quality of life.
SMA UK support services
SMA UK offers specialist support across the UK for people affected by spinal muscular atrophy. Their services commonly include:
- Information and support helpline staffed by experienced advisors
- Outreach support workers who provide personalised guidance and signposting
- Peer support networks to link families with similar experiences
- Educational resources about managing SMA and accessing treatments
- Advocacy for improved care, treatment access and funding
- Financial grants or advice to help with equipment and home adaptations
SMA UK support groups
SMA UK runs both in‑person and online support groups. These groups help people and carers to:
- Connect with others who understand day‑to‑day challenges
- Share practical tips for equipment, therapies and daily care
- Receive updates on treatments, research and services
- Access emotional and peer support during difficult times
Groups are accessible regardless of location or mobility and can be an important source of community and resilience.
Additional support resources
Beyond SMA‑specific organisations, a network of healthcare and social services can support people with SMA and their families.
Healthcare coordination
- Neuromuscular care centres and specialist clinics
- Care coordinators and specialist nurses
- Respiratory and palliative care teams for complex needs
Education and employment
- Educational Health and Care Plans (EHCPs) and school accessibility support
- Assistive technology and adaptations for learning
- Career counselling and workplace adjustments under disability legislation
Financial and practical assistance
- Disability benefits advisors and appeals support
- Housing adaptation grants and mobility equipment funding
- Respite care and carer support services
Quick help — who to contact
- GP or paediatrician for initial concerns and referrals
- Local neuromuscular or genetics clinic for diagnosis, management and treatment access
- SMA UK for practical support, peer networks and funding advice (see links above)
Practical tips for home and daily life
- Start with a simple home‑adaptation checklist: access routes, bathroom aids, bed and seating options
- Consider a referral to an occupational therapist to assess daily living equipment
- Explore assistive technology (environmental controls, communication aids) to increase independence
- Plan for coordinated care: bring together therapy, medical, educational and social services
Emotional wellbeing and peer support
Psychological support, counselling and peer groups help people and families cope with the emotional impact of a long‑term condition. Accessing local or online support groups can reduce isolation and provide practical strategies for day‑to‑day management.
Connect with SMA UK
SMA UK provides information, support and signposting for people with SMA and their carers. Their advisors can help you find local services, apply for grants and connect with peer support.
Living with Spinal Muscular Atrophy
With appropriate support and adaptations, people with SMA can lead fulfilling, independent lives
Many people with spinal muscular atrophy lead full and rewarding lives with appropriate care, rehabilitation and access to assistive technology. A holistic approach that includes medical management, therapy, education and social support helps maximise participation and independence.
Daily life and independence
Strategies that commonly support independence include:
- Customised mobility equipment and regular review to match changing needs
- Home modifications such as ramps, widened doorways and accessible bathrooms
- Smart home technology and environmental controls to reduce physical barriers
- Consideration of adapted driving options where appropriate
- Personal assistance and community care services when required
Education and employment
With suitable adjustments, people with SMA can access education and work opportunities:
- Educational accommodations such as individual learning plans and assistive technology
- Workplace adjustments and flexible working, including remote options
- Vocational guidance and career counselling to align roles with strengths and accessibility
Supporting emotional wellbeing
Access to counselling, peer mentoring and stress‑management techniques can support psychological health. Celebrating achievements and focusing on capabilities helps families and individuals maintain resilience.
With improvements in treatments, management and social support, many people with SMA pursue education, careers and personal goals while maintaining quality life.
Understanding and Managing Spinal Muscular Atrophy
Spinal muscular atrophy (SMA) covers a spectrum of presentations, but with timely diagnosis, access to specialist care and modern treatment options, many people with SMA can achieve meaningful improvements in function and participation. Advances in disease‑modifying therapies, combined with coordinated supportive care, have changed expectations for treatment and management in recent years.
Effective SMA management is multidisciplinary: medical therapies, physiotherapy and occupational therapy, respiratory and nutritional care, and connection with social and educational services all play a part. Collaborating with a neuromuscular or genetics centre helps ensure personalised decisions about treatment, monitoring and rehabilitation that aim to maximise quality of life and independence.
If you are concerned about possible symptoms, contact your GP or local paediatrician for a referral to a specialist neuromuscular or genetics clinic. After diagnosis, ask about genetic counselling, treatment options and patient registries — and consider registering with support organisations to receive updates on treatments, trials and practical resources.
Get Comprehensive Support for SMA
Whether you are newly diagnosed or seeking further information, SMA UK can help with practical advice, peer support and signposting to specialist care. Subscribe to their updates or contact your local specialist centre to stay informed.
