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What is motor neurone disease?

Motor neurone disease (MND) is a term used to describe a group of diseases that affect nerve cells called 'motor neurons'.

Motor neurons carry messages from the brain to the muscles via the spinal cord. These messages allow us to make movements like walking, swallowing, talking and breathing.

In motor neurone disease, the nerves become damaged and start to die. When this happens, muscles start to weaken and waste away. Currently, there is no cure for MND and it is life-limiting.

The speed at which MND progresses varies for each person. Survival time also varies, but the average life expectancy is 2 to 3 years from diagnosis.

A coordinated care approach can help people with MND live better for longer. Known as multidisciplinary care, this involves engaging with a team of health professionals from a range of disciplines.

Every day in Australia, two people are diagnosed with MND and two people die from the disease. More than 2,300 Australians are thought to be living with MND at any one time.

The lifetime risk of MND is about 1 in 300 by the age of 85. The risk grows as people get older. Yet many people have not heard of MND before they themselves, or someone they know, has been diagnosed.

Slightly more men than women are diagnosed with MND. Research has shown that MND is more common in people over 50. However, around half of people with MND are diagnosed under the age of 60.

MND affects people from every country and ethnicity in the world.

Early signs of physical problems or other symptoms of MND can be mild. Symptoms also vary from person to person. Where the weakness in the body starts depends on which motor neurons are affected first.

Some of the signs are:

  • stumbling due to weakness of the leg or foot muscles     
  • trouble holding objects due to weakness in the shoulder or the hand muscles
  • slurring of speech or swallowing problems due to weakness of the tongue and throat muscles. 

The signs and symptoms will worsen over time.

There is no single test for MND. This means diagnosing motor neurone disease can be a lengthy process.

Doctors usually watch a person's health over time before confirming they have MND. A GP may notice issues with your muscles, the brain, or the nervous system. They then refer you to a neurologist, a specialist in brain and nervous system disorders.

Other neurological conditions have similar symptoms to MND, especially in the early stages. Because of this, doctors need to rule out other diseases.

Reaching an MND diagnosis can take a long time. It can take several months, and sometimes up to a year. This may be frustrating and confusing. While diagnosing MND may be complex, getting the correct diagnosis is crucial. A confirmed diagnosis of MND is the first step towards receiving the right care, support, and treatments.

The diagnosis of MND can be assisted through a range of tests. Two key tests are:

  • nerve conduction studies (NCS), which involve figuring out how the nervous system works by studying electrical stimulation of nerves and recording muscle activity
  • electromyography (EMG), a process of inserting a needle electrode into various muscles to measure their electrical activity.

In the majority of cases the cause of MND is unknown.

In up to 15% of cases a genetic mutation is thought to be the cause of the disease. Inherited MND is also known as “familial MND”.

There are many theories about the causes of MND. Theories include:

  • exposure to toxins and chemicals in the environment
  • viral infection
  • immune related damage
  • premature ageing of motor neurons
  • genetic factors.

It is thought that any of these potential causes may act individually or in combination to contribute to the development of MND. Recent research suggests a six-step process with genes, environment and ageing all involved.

Research focused on environmental causes understandably often provokes intense media and community interest. Some studies may report an association, but it is important to note that association is very different from cause.

The causes and disease mechanisms section from the UK's MND Association research blog provides an overview of recent research.

You inherit your genes from your biological mother and father and they determine things like the colour of your eyes, how tall you will be, the colour of your skin and a whole host of other things. Genes can also influence the kinds of illnesses you may develop.

Researchers can now test for the presence of mutations in a number of newly identified genes that increase your risk of developing the disease. Some of these are the SOD1, TDP43, FUS and C9orf72 genes.

When a “faulty” MND gene is identified in someone, their children, siblings and parents have a 50% chance of having the same fault.

Within the families affected, the disease may present at different ages, affect different parts of the body and progress at different rates despite family members carrying the same fault. In families, there may be individuals who carry the “faulty” gene but never actually develop the disease.

Scientists think that there are a series of events that need to happen before the disease process begins and that these events can interact with the faulty gene and start the disease process off.

It is hoped that research may lead to treatments that prevent or delay the onset of MND in someone with an MND-related genetic mutation. Clinical trials of therapies targeting SOD1 and C9orf72 mutations are under way.

Some people with a family history of MND may be interested in genetic testing. Others may not. If you are thinking of getting tested, talk to your doctor. They can refer you to a genetic counselling service.

The MND Decision Support Tool is designed to help people discuss their choices with their doctor or genetic counsellor and this short animation provides a visual overview about genetics and MND.