There are several different types of spinal muscular atrophy (SMA), which start at different ages.

They can all cause weakness and difficulty moving, but how bad these problems are varies.

Intelligence and learning ability aren't affected by any type of SMA.

Type 1 SMA (young babies)

Children with type 1 SMA show symptoms in the first 6 months of life.

Babies with the condition:

• have very weak and floppy arms and legs (hypotonia)
• have problems moving, eating, breathing, and swallowing
• are unable to raise their head or sit without support

Most babies with type 1 SMA die during the first few years of life, usually as a result of serious breathing difficulties.

Spinal Muscular Atrophy UK has more information about type 1 SMA.

Type 2 SMA (older babies and toddlers)

Children with type 2 SMA usually show symptoms when they're 7-18 months old. The symptoms are less severe than type 1.

Children with the condition may:

• be able to sit up without help, but not stand or walk
• have weak arms or legs
• have shaking (tremors) in their fingers and hands
• later develop problems with their joints, such as an unusually curved spine (scoliosis)
• have weak breathing muscles and difficulty coughing – this can put them at risk of chest infections

Type 2 SMA can shorten life expectancy, but most children with it survive into adulthood and can have long, fulfilling lives.

Spinal Muscular Atrophy UK has more information about type 2 SMA.

Type 3 SMA (children and young adults)

People with type 3 SMA usually develop symptoms after 18 months of age, but this is very variable and sometimes it may not appear until late childhood or early adulthood.

People with the condition:

• are able to stand and walk without help, although they may find walking or getting up from a sitting position difficult
• may have balance problems, difficulty running or climbing steps, and a slight shaking in their fingers
• may find walking gets gradually harder over time, and they may eventually lose the ability to walk when they're older

Type 3 SMA doesn't usually affect life expectancy.

Spinal Muscular Atrophy UK has more information about type 3 SMA.

Type 4 SMA (adults)

Type 4 SMA, also called adult-onset SMA, usually begins in early adulthood.

Someone with the condition may have:

• weakness in the hands and feet
• difficulty walking 
• shaking and twitching muscles

Type 4 SMA gets slowly worse over time, but doesn't normally cause problems with breathing or swallowing. It doesn't affect life expectancy.

Spinal Muscular Atrophy UK has more information about type 4 SMA.

Other types of SMA

There are several other types of SMA, including:

• spinal muscular atrophy with respiratory distress (SMARD) – a type of SMA that's usually diagnosed during a baby's first year of life and can cause serious breathing problems
• Kennedy's disease, or spinobulbar muscular atrophy (SBMA) – a rare type of SMA that only affects men and usually starts in middle age; it doesn't usually affect life expectancy
• distal spinal muscular atrophy (DSMA) – a type of SMA that mainly affects the hands, feet, lower arms, and lower legs

Tests can be carried out to check if you or your child has spinal muscular atrophy (SMA), or if you're at risk of having a child with the condition.

Tests before getting pregnant

Speak to your GP if you're planning a pregnancy and:

• you've had a child with SMA before
• you have a history of the condition in your family
• your partner has a history of the condition in their family

Your GP may refer you for genetic counselling to help you understand the risk of your child having SMA. You can have a blood test to see if you have the faulty gene linked to the condition.

If you're at risk of having a child with SMA, talk to your genetic counsellor about your options.

These may include:

• getting pregnant and waiting to see if your child is born with SMA, or having tests during pregnancy to see if they will have it
• using donated sperm or eggs to get pregnant
• pre-implantation genetic diagnosis (PGD) – where a woman's eggs are fertilised in a laboratory and the resulting embryos are tested for SMA before being put in the womb

Tests during pregnancy

If you're pregnant and there's a risk you could have a child with SMA, tests can be carried out to check for the condition.

The 2 main tests are:

• chorionic villus sampling (CVS) – a sample of cells from the placenta are tested, usually during weeks 11 and 14 of pregnancy
• amniocentesis – a sample of amniotic fluid is tested, usually during weeks 15-20 of pregnancy

Both these tests can slightly increase your chances of a miscarriage.

If tests show your baby is likely to have SMA, talk to your doctor about what this means and what your options are.

Tests after birth

If you or your child has typical symptoms of SMA, a genetic blood test can be done to confirm the condition.

You may also be asked if anyone in your family has a condition that affect the nerves and muscles in your family.

A physical examination may be done to look for signs of SMA or similar conditions.

Very occasionally, other tests may be needed, too. For example:

• electromyography – thin needles are inserted into a muscle to detect how well it's working
• muscle biopsy – a small sample of muscle is taken for analysis

The charity Spinal Muscular Atrophy UK provides more information and advice if your child has recently been diagnosed with SMA.

It's not currently possible to cure spinal muscular atrophy (SMA), but research is ongoing to find new treatments.

Treatment and support is available to manage the symptoms and help people with the condition have the best possible quality of life.

A team of different healthcare professionals will be involved in your or your child's care. They'll help come up with a care plan outlining the support and treatments you may need.

Feeding and diet help

It's important for people with SMA, especially children, to get the right nutrients. This will help with healthy growth and development.

A dietitian can offer advice about feeding and diet.

If you or your child has difficulty feeding or swallowing, a feeding tube may sometimes be needed.

Several types of tube can be used, such as a tube attached directly to the stomach through the skin of the tummy (gastrostomy tube), or a tube passed through the nose and down the throat (nasogastric tube).

Breathing help

There are several treatments for the breathing problems that can affect people with SMA.

These include:

• breathing exercises to strengthen the breathing muscles and make coughing easier
• a suction machine to help clear the throat if needed – this involves passing a thin, plastic tube to the back of the throat to suck away any mucus
• in more severe cases, a special machine that provides air through a mask or tube

You may be advised to have vaccinations against flu and pneumonia to reduce your risk of becoming seriously ill from these infections.

Assistive equipment

If you or your child have difficulty moving, an occupational therapist or physiotherapist can provide advice and support.

For example, they can advise you about things such as:

• mobility equipment – including walking frames and wheelchairs
• supports for the arms or legs (splints or braces)
• shoe inserts that make walking easier (orthotics)

Find out more about getting the right care equipment.

The Spinal Muscular Atrophy UK charity also has more advice about day-to-day living with SMA

Exercises and stretches

Exercises and stretches can help maintain strength and stop joints becoming stiff.

A physiotherapist can suggest some exercises to try.

The amount of exercise you or your child can do will depend on your condition, but it's best to try to stay as active as possible.

Treatments for spine problems

Some children with SMA develop an unusually curved spine (scoliosis).

Treatments for this include:

• a specially made back brace to help support the back and encourage the spine to grow correctly
• spinal surgery – where the spine is straightened using metal hooks and rods, before being fused into place with pieces of bone

Read more about treatments for scoliosis in children.

Research into new treatments

Research is being carried out into possible new treatments for SMA.

You can ask your medical team about ongoing clinical trials into new treatments. You can also check the database of clinical trials for SMA to see what research is happening at the moment.

Previous research has suggested a new medicine called nusinersen (Spinraza) can help some people with SMA.

It was recently approved in the US and by the European Medicines Agency, but will be assessed by the National Institute for Health and Care Excellence (NICE) before it can be made routinely available in England.

For more information, see:

• Spinal Muscular Atrophy UK: nusinersen