Ataxia is a condition that causes a loss of physical co-ordination due to underlying damage to the nervous system and brain.
Ataxia can affect every part of the body including:
- the legs,
- the arms,
- the mouth and tongue, and
- the eyes.
Therefore, ataxia can cause a wide range of symptoms such as:
- difficulty walking,
- difficulty speaking,
- difficulty swallowing (dysphagia), and
- difficulty performing tasks that require a high degree of physical control, such as writing and eating.
Types of ataxia
There are two main types of ataxia:
- hereditary ataxia - where the symptoms develop slowly over many years and are caused by underlying problems with the genes, and
- acute ataxia - where the symptoms develop suddenly due to a related trauma, injury, or health condition, such as a stroke.
Hereditary ataxia
Hereditary ataxias are caused by defects in the genes that a person inherits from their parent(s). These defects are known as genetic mutations.
There are over 70 different types of hereditary ataxia, which can be broadly classified into how the genetic mutation that is responsible for the condition is passed down through families. This is usually done in one of two ways:
- autosomal recessive ataxia - where the genetic mutation can only be passed down if both parents have a copy of the mutated gene, and
- autosomal dominant ataxia - where the genetic mutation can be passed down if only one parent has a copy of the mutated gene.
The two types of inherited ataxia share a broadly similar pattern of symptoms, except cases of autosomal recessive ataxia usually develop earlier in life than autosomal dominant ataxia.
See the causes section for a more detailed explanation about the genetics of ataxia.
Autosomal recessive ataxia
Examples of autosomal recessive ataxia include:
- Friedreich’s ataxia - where the symptoms of ataxia usually begin between the 5-20 years of age, and
- ataxia-telangiectasia - where the symptoms of ataxia begin in infancy or early childhood.
Autosomal dominant ataxia
Examples of autosomal dominant ataxia include:
- spinocerebellar ataxia - where the symptoms usually begin between 30-40 years of age, and
- episodic ataxia - which is a rare type of ataxia that usually begins during the teenage years and causes episodes of ataxia symptoms with symptom-free periods in between.
It is now known that there are 29 different sub-types of spinocerebellar ataxia, each caused by a different genetic mutation.
Acute ataxia
Acute ataxia can have a wide range of causes. These include:
- cancers - such as a brain tumour,
- health conditions that interrupt the supply of blood to the brain - such as a stroke, or a brain haemorrhage (bleeding in or around the brain),
- alcohol or drug overdose,
- toxins (poisons) - such as mercury,
- health conditions that damage the
- nervous system - such as multiple sclerosis,
- health conditions where the immune system attacks healthy tissue (autoimmune conditions), such as lupus, and
- infections - such as meningitis, measles, and rubella.
How common is ataxia?
Acute ataxia can be a relatively common complication of conditions such as stroke, encephalitis (infection of the brain), and multiple sclerosis.
Hereditary ataxia is rare. For example, in England, Friedreich’s ataxia, which is the most common type of hereditary ataxia, is estimated to develop in 1-2 people out of 50,000. Men and women are equally affected.
Both ataxia-telangiectasia and spinocerebellar ataxia are estimated to develop in 1 out of every 100,000 people in England, although higher rates of ataxia-telangiectasia have been reported in other countries.
Outlook
The outlook for acute ataxia will depend on the underlying cause. For example, ataxia that is being caused by an infection will often resolve once the infection has passed.
However, if you have ataxia that is caused by a condition such as multiple sclerosis, you are likely to experience repeated episodes of ataxia.
The outlook for hereditary ataxia is fairly poor. There is currently no cure for most of the hereditary ataxias, and the symptoms become progressively worse over time.
For example, many people with hereditary ataxia will eventually require a wheelchair due to a loss of their ability to walk.
In addition, 50% of people with Friedreich’s ataxia also experience thickening of their heart muscle, which can increase their risk of heart disease and shorten their natural life expectancy.
On the whole, the life expectancy for people with ataxia is highly variable. For example, some people with Friedreich’s ataxia die in their thirties, while others live well into their seventies.
