Causes of ataxia 

Ataxia is caused by damage to a part of the brain known as the cerebellum, and sometimes damage to part of the spinal cord or peripheral nerves.

The spinal cord is a long bundle of nerves that runs down the spinal column and connects the brain to all other parts of the body.

The cerebellum is located at the base of the brain and is responsible for controlling:

  • walking and sitting balance
  • limb co-ordination
  • eye movements
  • speech 

Damage can occur as a result of injury or illness (as is the case with acquired ataxia) or because the cerebellum or spinal cord degenerates (as is the case with hereditary ataxia).

In a minority of cases, there's no clear reason why the cerebellum and spinal cord become damaged, as with idiopathic late onset cerebellar ataxia (ILOA).

Acquired ataxia

Acquired ataxia can have a wide range of potential causes, including:

  • severe head injury – for example, the type of injury that can occur during a car crash or a fall
  • bacterial brain infection, such as meningitis or encephalitis (an infection of the brain itself)
  • viral infection – some viral infections, such as chickenpox or measles, can spread to the brain, although this is very rare 
  • conditions that disrupt the supply of blood to the brain, such as a stroke, haemorrhage (bleeding in or around the brain) or a transient ischaemic attack (TIA)
  • cerebral palsy – a series of conditions that can disrupt a child's normal growth and development
  • multiple sclerosis – a long-term condition that damages the nerve fibres of the central nervous system
  • sustained long-term alcohol misuse
  • underactive thyroid gland
  • cancer 
  • certain toxic chemicals, such as mercury, lead, solvents and some types of pesticides – these can trigger ataxia if a person is exposed to enough of them
  • medications such as benzodiazepines can occasionally trigger ataxia as a side effect
  • autoimmune conditions, such as lupus, where the immune system attacks healthy tissue

Hereditary ataxia

Hereditary ataxia is caused by a genetic mutation (faulty gene). Genes are units of DNA that determine a particular characteristic, such as the sex of a baby or eye colour. A baby receives two copies of every gene – one from their mother and one from their father.

Ataxia can be inherited in two possible ways:

  • autosomal recessive – such as the mutations responsible for Friedreich's ataxia and ataxia-telangiectasia
  • autosomal dominant  – such as the mutations responsible for some cases of spinocerebellar ataxia

These are described in more detail below.

Autosomal recessive

When ataxia is autosomal recessive, it means the affected person has inherited the mutated gene from both their mother and their father.

If they only received one mutated gene, the other normal gene will cancel out the effects of the mutation and they will just be a carrier of the condition.

It's estimated that around 1 in 75 people are carriers of the mutated gene that causes Friedreich's ataxia, and around 1 in 100 people are carriers of the mutated gene that causes ataxia-telangiectasia.

The likelihood of two carriers meeting by chance is very low, which explains why these types of ataxia are so rare.

If two carriers of the mutated gene were to have a baby, there would be a:

  • one in four chance the baby would receive a pair of normal genes
  • one in two chance the baby would receive one normal gene and one mutated gene (be a carrier)
  • one in four chance the baby would receive a pair of mutated genes and develop ataxia

If you have autosomal recessive ataxia and your partner is a carrier, there is a:

  • one in two chance your baby will receive one normal gene and one mutated gene and will be a carrier
  • one in two chance your baby will receive a pair of mutated genes and develop ataxia

If you have autosomal recessive ataxia and your partner doesn't and they aren't a carrier, there's no risk of any of your children developing ataxia. This is because your mutated gene will be cancelled out by your partner's normal gene. However, your children will be carriers.

Autosomal dominant

When ataxia is autosomal dominant (as is the case for spinocerebellar ataxia), you can develop the condition if you receive a single mutated gene, either from your mother or father. This is because the mutation is strong enough to override the other normal gene.

If you have autosomal dominant ataxia, any children you have will have a one in two chance of developing ataxia, regardless of sex.

Being a parent with a disability

Reesha has two daughters Ria, 14 and Lea, 8. She also has cerebral palsy, a condition that affects movement and co-ordination. Reehsa describes the challenges she faces as a parent with a disability.

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Ataxia research

Identifying the genes responsible for the different types of ataxia and establishing how they cause symptoms is vital for developing effective treatments.

According to Ataxia UK, so far 28 genes linked to spinocerebellar ataxia have been discovered. More than 30 other types of inherited ataxias have also been identified.

Research is currently being carried out to identify other genes that cause inherited cerebellar ataxias.

The Ataxia UK website has more information about the latest developments in ataxia research.

Genetics

Find out how you inherit your physical and behavioural characteristics, and about testing for genetic conditions

Page last reviewed: 04/07/2013

Next review due: 04/07/2015