Information & Support

Spinal Muscular Atrophy Type 1

This information sheet briefly explains the cause, effects, and management of Spinal Muscular Atrophy (SMA) Type 1. It includes sources of further information and support. It is for the families of children diagnosed with SMA Type 1. It may also be useful for healthcare and other professionals.

More information on caring for your baby on a daily basis is available in the leaflet ‘Looking After Your Baby’.

Further information on SMA Type 1 and sources of support is available from SMA Support UK’s route map for SMA Type 1.

SMA Type 1 is a complex condition; there is a lot of information to take in, and every child with SMA is different. Your child’s medical team will always be happy to go over any of this with you.

What is Spinal Muscular Atrophy ?

Spinal Muscular Atrophy (SMA) is a rare, genetically inherited neuromuscular condition. SMA may affect crawling and walking ability, arm, hand, head and neck movement, breathing and swallowing. SMA is often grouped into ‘Types’. Types of SMA are based on the age at which symptoms first appear and what physical ‘milestones’ a baby or child is likely to achieve. Milestones can include the ability to sit, stand, or walk.

There are four main types of SMA: Types 1, 2 and 3 appear in childhood. Type 4 appears in adulthood and is also known as Adult Onset SMA.

These ‘Types’ are not rigid categories. There is a wide spectrum of severity between the different types of SMA and between children, young people, and adults within each type.

There are also other, even rarer, forms of SMA with different genetic causes including SMA with Respiratory Distress (SMARD), Spinal and Bulbar Muscular Atrophy (SBMA), and Distal SMA (DSMA).

Usually, electrical signals from our brain are sent down our spinal cord along our nerve cells and through to our muscles. This makes it possible for us to consciously contract our muscles and to make them move.

SMA affects a particular set of nerve cells called the lower motor neurons 1 which run from the spinal cord out to our muscles. The lower motor neurons carry messages that make it possible for us to move the muscles we use to crawl and walk, to move our arms, hands, head, and neck, and to breathe and swallow.

For our lower motor neurons to be healthy, we need to produce an important protein called the Survival Motor Neuron (SMN) protein. Our ability to do this is controlled by a gene called Survival Motor Neuron 1 ( SMN1 ) 2.

We all have two copies of this SMN1 gene. one from each parent. People who have two faulty copies of the SMN1 gene have SMA. People who have one faulty copy of the SMN1 gene are carriers of SMA. Carriers usually do not have SMA or any symptoms of SMA. People who have two healthy copies of the SMN1 gene do not have SMA and are not carriers.

SMA is passed from parents to their children through their SMN1 genes. When two people who are carriers have a child together, their child may inherit two faulty SMN1 genes, one from each parent. If this happens, then their child will have SMA.

Having two faulty SMN1 genes means that a child is only able to produce very low amounts of the SMN protein. This causes their lower motor neurons in their spinal cord to deteriorate. Messages from their spinal cord do not efficiently get through to their muscles, which makes movement difficult. Their muscles waste due to lack of use and this is known as muscular atrophy.

For more information on ‘The Genetics of Spinal Muscular Atrophy ’ please click here.

SMA Type 1 is the most severe form of SMA. It accounts for between 50 – 70% of cases of childhood onset SMA. It is sometimes called Werdnig-Hoffman Disease or severe infantile SMA.

Each baby with SMA Type 1 is different. The symptoms of SMA Type 1 usually appear within the first few months of life. In some cases SMA can affect babies even before birth and mothers may remember that their baby had become less active towards the end of their pregnancy. Generally, the earlier the onset of symptoms, the more severe the condition. The most severely affected babies may die before, during, or very shortly after birth. This is sometimes referred to as SMA Type 0.

Sometimes doctors try to indicate the degree of severity within SMA Type 1 by using a decimal classification 3. for example, 1.1, 1.2, 1.5, 1.9. If you have any queries regarding this please speak to your child’s medical team.

SMA Type 1 is a life-limiting condition. Though it is not possible to accurately predict, for the majority of children (approximately 95%) life expectancy is less than 18 months. In general, babies diagnosed within the first few weeks or months of life have a significantly shorter life expectancy.

How is SMA Type 1 diagnosed?

A doctor will diagnose SMA Type 1 after taking a medical history, physically examining your child, and by taking a blood sample for DNA testing. The blood sample is tested for a deletion mutation in the Survival Motor Neuron 1 ( SMN1 ) gene on chromosome 5. The result of this test is usually available within 2 – 4 weeks.

If there is any uncertainty about the diagnosis. further muscle tests such as an electromyogram ( EMG ) or a muscle biopsy may be discussed, but these are not usually needed to confirm SMA.

Is there a treatment or cure?

At present there is no cure for SMA, and no treatment that will repair the damage to the lower motor neurons or reverse the weakening of the muscles. However there is a range of options aimed at managing symptoms, reducing complications of weakness and maintaining the best quality of life for as long as possible.

What are the effects of SMA Type 1?

This section describes the effects of SMA Type 1 in general terms. But, it’s important to remember that each child with SMA Type 1 is affected differently and the severity of the condition varies from child to child.

Babies with SMA Type 1 are often described as ‘floppy’ babies, due to their low muscle tone ( hypotonia ) and severe muscle weakness. The muscle weakness affects movement, swallowing and breathing. Babies with SMA Type 1 are unable to lift their heads, have difficulty rolling over and are unable to sit unsupported. They may also have a weak cry.

Children’s muscle weakness is usually the same on both sides of their body ( symmetrical ). The muscles closest to the centre of their body ( proximal muscles) are usually more severely affected than the muscles furthest away from the centre of their body ( distal muscles). Generally, babies with SMA Type 1 have weaker legs than arms. Babies have difficulty lifting their arms and legs, while still being able to use their hands and fingers.

Weakness of the respiratory muscles can cause severe difficulties with breathing and coughing. It can also increase the chance of respiratory infections which can be life-threatening.

The muscles used for sucking and swallowing are also affected and this may cause difficulty with feeding and weight gain. Difficulty with swallowing can increase the risk of fluids or food passing into the lungs ( aspiration ) which can cause choking and, in some cases, pneumonia.

The brain is unaffected and babies affected by SMA Type 1 are often described as bright, alert and responsive. The muscles of the face are not usually affected so babies can smile and frown.

What healthcare and support is needed for SMA Type 1?

Your baby should receive care from a multidisciplinary healthcare team, which can feel like an overwhelming number of people but they all have an important role to play. You may have contact with specialists in neuromuscular conditions, palliative care. respiratory medicine, orthopaedics, physiotherapy. occupational therapy. speech and language therapy, dietetics and a hospital or community consultant paediatrician. If possible one of the team should be your keyworker whose job it is to help co-ordinate services for your family. You can find out more about how these people help in our information sheet ‘Who’s Who of Professionals’.

At every appointment with your baby’s medical team you should be given time to ask questions and then jointly decide what support is best for your baby.

Good respiratory management is important to provide comfort and reduce complications of muscle weakness. An overview of respiratory management in SMA can be found in the booklet ‘Standards of Care for Spinal Muscular Atrophy – the family guide’ published by TREAT-NMD. This booklet can be obtained from Spinal Muscular Atrophy Support UK or downloaded from the TREAT-NMD website.

There are a number of options for respiratory support. Not all options will be appropriate for all babies with SMA Type 1.

The options may include:

  • Chest physiotherapy to maintain comfort
  • Suction to remove secretions
  • Medications to reduce secretions
  • Pain relief to reduce any distress caused by breathlessness
  • Non-invasive ventilation ( NIV ) with mechanical ventilation to increase comfort, in the management of acute infection or to correct night time hypoventilation .

Non-invasive ventilation may not be appropriate for some babies, for example, babies with severe weakness of the muscles around the mouth and throat ( bulbar muscles ), and in babies aged less than 6 months. For others though it may help to relieve respiratory distress or facilitate discharge home from hospital

Invasive ventilation – mechanical ventilation via an endotracheal tube (a flexible plastic tube passed through the mouth or nose into the trachea ) or a tracheostomy. Mechanical ventilation via an endotracheal tube may sometimes be used as a short term measure in a medical emergency. However, until there is an effective treatment to prevent the progression of muscle weakness, the use of tracheostomy with long term invasive ventilation remains an ethical dilemma

Choosing the most appropriate management involves very difficult decisions. You should have time and support to ask questions and discuss the different options, to help decide which is most appropriate for your baby. These discussions will be with your medical team who have knowledge of your baby’s condition and possible progression. You may also wish to seek emotional support from sources outside your medical team, for example, family, community and spiritual leaders.

Your baby may have difficulties with feeding and swallowing due to their muscle weakness. Feeding can become a tiring process for babies with SMA Type 1 and as a result they may lose weight. Babies with a weak swallow are also at risk of inhaling (aspirating) their feed which can cause respiratory (chest) infections.

Advice and support on feeding, swallowing and nutrition is available from a number of healthcare professionals. These may include your health visitor, consultant, speech and language therapist, dietitian and community nurse. Occupational therapists and physiotherapists may also advise you on positioning

and seating to assist with feeding.

At this time there is no clear evidence that babies with SMA Type 1 need a therapeutic feed or one with an increase or decrease in particular nutrients.

If swallowing becomes unsafe, or if your baby is not gaining enough weight, alternative ways of feeding may be suggested. These may include feeding through a nasogastric (NG) tube, a nasojejunal (NJ) tube or a gastrostomy (G) tube.

You should have the opportunity to discuss the reasons for these suggestions and have time to ask questions in order to understand the possible benefits and risks to your baby. Whichever option is chosen, you will be provided with training and support to enable you to feed your child safely at home.

Constipation is a common problem with babies with SMA Type 1. It can cause discomfort and respiratory distress. Some babies may also experience reflux. To reduce discomfort and prevent complications the management of these symptoms should be discussed with your baby’s medical team.

Options for care and support

You should have the opportunity to discuss in depth the range of care options available for your baby. Your baby’s medical team will help you to decide what support is most appropriate for your individual circumstances. These discussions are important for developing an advance care plan to record the treatment you wish your baby to receive when his/her health deteriorates or in an emergency situation. This plan can be reviewed and you can change your mind at any time.

Ideally the goal of care is to enable your child to enjoy a good quality of life at home with their family for as long as possible, with a minimum of hospital admissions.

In addition to medical interventions available for breathing and feeding, additional support is available to improve your baby’s health and wellbeing and to provide emotional support for you and your family. When your baby is at home this may be provided by your General Practitioner (G.P.), community nursing or palliative care team. Children’s hospices also offer a wide range of services and support to children with life-limiting conditions and their families throughout the UK. Details of local children’s hospice and palliative care services are available from Together for Short Lives. Helpline: 0808 8088 100.

Physiotherapy can provide passive exercises to enable movement that babies are unable to make independently. You can be taught these techniques so that you can do these with your baby at home. Passive exercises are also good for babies’ circulation and help prevent stiffening of the joints (contractures).

Physiotherapists may suggest performing stretches and exercises when your baby is in the bath, swimming or hydrotherapy pool. Building these exercises into play can make them fun and babies often enjoy the additional freedom of movement provided by warm water.

Chest physiotherapy is also very important to help clear the chest when babies have difficulty coughing.

Good posture management can improve comfort. An occupational therapist can advise on seating which will help to provide appropriate support for your baby. This will also make it easier for them to play.

Sleep systems may sometimes be provided to increase comfort and support your baby’s limbs in a good position at night time. Your occupational therapist will be able to provide you with advice on this.

What other help is available?

The impact of a diagnosis of SMA Type 1 on families is enormous. It’s important for you to have emotional support and plenty of time to talk and ask questions. This can be with members of your baby’s medical team, your General Practitioner (G.P.), health visitor, social worker, psychologist or a counsellor.

In addition to the care and support provided by your baby’s medical team, Spinal Muscular Atrophy Support UK’s support services team can provide information and support to families in the UK affected by SMA. Our outreach workers are able to visit you at home. They offer personalised support and information, and are available to answer questions. They can discuss with you the support you and your family can access. We can also put you in touch with our peer support volunteers who have personal experience of living with SMA Type 1. Multisensory toy packs are also available free of charge for babies in the UK diagnosed with SMA Type 1.

Information about these services is available on our website or please phone us on 01789 267 520 or email: supportservices@smasupportuk.org.uk.

Muscular Dystrophy UK also provide information, support, advocacy services and grants towards specialist equipment for people affected by a range of neuromuscular conditions. You can visit their website or you can phone them on 0800 652 6352 or e-mail: info@musculardystrophyuk.org.

Regional care advisors, and sometimes neuromuscular nurse specialists, are attached to NHS neuromuscular clinics in various regions of the UK. They provide support and information to children and adults with muscle diseases and their families. They link up with other professionals and services so that people receive the local health and social support they need. Regional care advisors’ contact details are available on Muscular Dystrophy UK’s website.

Families living in the UK may be eligible for a number of financial benefits to help towards the cost of providing the extra care their child may need. This does depend on your individual circumstances.

For further information about financial benefits, visit the Gov.UK website and look at the sections ‘Benefits’ and ‘Carers and Disability Benefits’. The Department of Work and Pensions (DWP) can be contacted on: 0345 608 8545.

Contact a Family provide information and support to families who have a child with a disability. This includes information on benefits and grants. They can be contacted on 0808 808 3555 or through their website.

Disability Rights UK publishes free factsheets on a range of benefits and the ‘Disability Rights Handbook’ annually. For further information, please click here.

Together for Short Lives provide information and support to families who have a child with a life-limiting condition. They can be contacted on 0808 8088 100 or through their website.

Turn2Us is a charity which helps people access money available to them through welfare benefits, grants, and other help. They can be contacted on 0808 802 2000 or through their website.

Your health visitor, community nurse, neuromuscular care advisor, family support worker, social worker or outreach worker may be able to help you with applications for financial benefits.

There are also a number of charities that may assist you with the cost of general household goods, specialist equipment and holidays / days out. Please contact SMA Support UK for more information or see the SMA type 1 route map.

As a parent with a child with SMA you should be offered a referral for genetic counselling. You can also request a referral from your General Practitioner (G.P.).

Genetic counselling takes place with a healthcare professional who has expert training in genetics. They will help you to understand how SMA is passed on and what the chances are of other people in your family being affected. Genetic counselling also provides you with the opportunity to discuss your choices for any future pregnancies. You will be able to go back to your genetic counsellor at a later date if you have more questions.

For more information on the genetics of SMA, the chances of having a child with SMA and the tests that can be carried out, please see our leaflet ‘The Genetics of Spinal Muscular Atrophy ’.

For information on ‘Future Options in Pregnancy’ please click here.

What does the future hold?

To find out more about SMA research, please click here.

As new treatments for SMA are being developed they need to be tested in clinical trials but because SMA is a rare condition it can sometimes take years to find enough patients for a clinical trial. The UK SMA Patient Registry is a database of genetic and clinical information about people affected by SMA which aims to speed up this process. The Registry also helps specialists gain more knowledge about the condition and the number of people affected by SMA. This information helps to develop and improve worldwide standards of care for people with SMA. You can find out more by looking at their website. e-mailing: registry@treat-nmd.org.uk or phoning: 0191 241 8605.

Author: SMA Support UK Information Production Team

Version: 2.4. Last reviewed: October 2015. Next full review due: October 2016

  1. Lunn, M.R. and Wang, C.H. (2008) ‘ Spinal muscular atrophy ’, The Lancet. 371(9630), pp. 2120-2133.
  2. Lefebvre, S. Bürglen, L. Reboullet, S. Clermont, O. Burlet, P. Viollet, L. Benichou, B. Cruaud, C. Millasseau, P. Zeviani, M. Le Paslier, D. Frézal, J. Cohen, D. Weissenbach, J. Munnich, A. and Melki, J. (1995) ‘Identification and characterization of a spinal muscular atrophy -determining gene ’, Cell. 80(1), pp. 155-165.
  3. Dubowitz, V. (1999) ‘Very severe spinal muscular atrophy (SMA Type 0): an expanding clinical phenotype ’, European Journal of Paediatric Neurology. 3(2), pp. 49-51.
  4. Commission of the European Communities (2008) Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee to the Regions on Rare Diseases: Europe’s challenges. Available at: http://ec.europa.eu/health/ph_threats/non_com/docs/rare_com_en.pdf.

Other sources used:

Aton, J. Hurst Davis, R. Jordan, K.C. Scott, C.B. and Swoboda, K.J. (2014) ‘Vitamin D intake is inadequate in spinal muscular atrophy type 1 cohort: correlations with bone health’, Journal of Child Neurology. 29(3), pp. 374-380.

Bush, A. Fraser, J. Jardine, E. Paton, J. Simonds, A. and Wallis, C. (2005) ‘ Respiratory management of the infant with type 1 spinal muscular atrophy ’, Archives of Disease in Childhood. 90(7), pp. 709-711.

Chatwin, M. Bush, A. and Simonds, A.K. (2011) ‘Outcome of goal-directed non-invasive ventilation and mechanical insufflation/exsufflation in spinal muscular atrophy type 1’, Archives of Disease in Childhood. 96(5), pp. 426-432.

Nadeau, A. D’Anjou, G. Debray, G. Robitaille, Y. Simard, L.R. and Vanasse, M. (2007) ‘A newborn with Spinal Muscular Atrophy Type 0 presenting with a clinicopathological picture suggestive of myotubular myopathy ’, Journal of Child Neurology. 22(11), pp. 1301-1304.

Roper, H. and Quinlivan, R. on behalf of workshop participants (2010) ‘Implementation of “the consensus statement for the standard of care in spinal muscular atrophy ” when applied to infants with severe type 1 SMA in the UK’, Archives of Disease in Childhood. 95(10), pp. 845-849.

Swoboda, K.J. Kissel, J.T. Crawford, T.O. Bromberg, M.B. Acsadi, G. D’Anjou, G. Krosschell, K.J. Reyna, S.P. Schroth, M.V. Scott, C.B. and Simard, L.R. (2007) ‘Perspectives on clinical trials in spinal muscular atrophy ’, Journal of Child Neurology. 22(8), pp. 957-966.

TREAT-NMD Neuromuscular Network (2008) Standards of Care for Spinal Muscular Atrophy. Available at: www.treat-nmd.eu/care/sma/family-guide

Wang, C.H. Finkel, R.S. Bertini, E.S. Schroth, M. Simonds, A. Wong, B. Aloysius, A. Morrison, L. Main, M. Thomas, M.A. Crawford, T.O. Trela, A. and participants of the International Conference on SMA Standard of Care (2007) ‘Consensus statement for Standard of Care in Spinal Muscular Atrophy ’, Journal of Child Neurology. 22(8), pp. 1027-1049.

In this section

Category: Disease

Similar articles: