Motor neurone disease (MND)

MND happens when special nerve cells called motor neurones, found in the brain and spinal cord, gradually stop working. Doctors still do not fully understand why this happens.

Genetic causes

One known cause of MND is a fault in a person's genes. About 20% of cases are linked to genetic causes. Half of these genetic cases happen in people who have a family history of MND, while the other half happen in people with no family history at all.

Having a family history of frontotemporal dementia can also raise the chance of inheriting MND.

The faulty gene affects how well the nerve cells can function and survive.

If you have a genetic form of MND, there is a chance you could pass on the risk of the condition to your child. How likely they are to actually develop it depends on many factors, including age.

Not everyone who carries the genetic mutation will go on to develop MND during their lifetime. In general, the longer a person lives, the greater the chance the condition will appear.

If one of your parents had MND but there is no other family history of the disease, your own risk is only slightly raised, to about 1.4%. For comparison, the risk in the general population is about 0.3%.

Other possible causes of motor neurone disease

It is still not clear exactly why motor neurones start to lose their function. Most experts think it is caused by a combination of factors affecting either the motor neurones themselves or the cells that support them. Researchers are looking into several possible processes.

Aggregates are unusual clumps of protein that build up inside motor neurones. They are seen in almost every case of MND and may interfere with how these nerve cells normally work. Their presence can also be a sign that the cell is under stress.

The protein most often found in these clumps is called TDP-43. It plays a role in processing the cell's genetic instructions through a molecule called RNA. Changes in the gene that codes for this protein, known as TARDBP, can cause some genetic cases of MND.

Every cell has systems that carry nutrients and other chemicals in and move waste products out. Research suggests that these transport systems become disrupted inside motor neurones. Over time, toxic waste can build up in cells simply as a natural result of normal activity and ageing.

The body normally clears this toxic waste through its own disposal systems, but these can be affected by both ageing and outside environmental factors.

Glial cells surround and support motor neurones, supplying them with nutrients. When glial cells stop working properly, motor neurones no longer get the support and nourishment they need to function normally. Scientists are still studying exactly how glial cells are involved in MND.

Nerve cells communicate using chemical messengers called neurotransmitters. One of these, glutamate, excites neurones, and one theory suggests that too much glutamate activity may damage them over time.

Riluzole, a medicine used to treat MND, works by reducing nerve cell activity, blocking the action of glutamate.

Mitochondria act as the batteries of the cell, providing the energy needed for it to work normally. In people with MND, the mitochondria inside motor neurones may not function as they should.

Diagnosing motor neurone disease

Speak to your GP if you experience the initial symptoms of MND.

After hearing about your symptoms and an initial exam, your GP might refer you to a neurologist (a doctor who specialises in conditions affecting the brain and nervous system).

Diagnosing MND can be difficult during the early stages. This is because many of the first symptoms can be caused by other more common health conditions like:

• a trapped nerve – wear and tear of the bones in the spine can sometimes cause nerves to become trapped under the spine
• peripheral neuropathy – where part of the nervous system is damaged by another condition, like type 2 diabetes
• swallowing difficulties caused by narrowing or inflammation of the gullet
• speech difficulties due to problems with the voice box
• damage to the brain by stroke or other neurological conditions like multiple sclerosis (MS) in younger people

Initial testing

MND is usually diagnosed by a neurologist based on the symptoms and a physical examination.

There’s no single test for MND. Various tests might be used to rule out other possible causes of the your symptoms. Tests might include:

• blood tests – these can be used for several reasons, like checking that organs are working, or to look for a marker of muscle damage (creatinine kinase)
• magnetic resonance imaging (MRI) scan – to give a detailed picture of your brain and spinal cord
• electromyography (EMG) – measures the electrical activity in your muscles, which shows how well your motor neurones are working and connecting to the muscles
• nerve conduction test – similar to an EMG but measures how quickly your nerves can conduct an electrical signal
• lumbar puncture – a sample of spinal fluid might be tested to exclude an inflammatory or nerve condition caused by an infection
• muscle biopsy – in rare cases, a small sample of muscle might be removed for testing to determine whether the problem lies in the muscles

Gene tests can be used to support the diagnosis in some individuals. They might provide an explanation of why they’ve developed the disorder. Your GP can give you more information about specialists who can help with genetic testing.

Confirming the diagnosis

There are many reasons why there may be delays in diagnosis. The initial symptoms might not appear to be serious. Or symptoms might not be recognised as being related to the nervous system so a neurologist isn’t consulted at first.

Sometimes, the diagnosis of MND is clear without the need for further tests. Confirming a diagnosis can sometimes be time-consuming even for an experienced neurologist. They might need a period of observation to be sure, particularly in cases where the condition progresses slowly. MND can only be diagnosed if the symptoms are clearly getting worse (progressive).

Receiving the diagnosis

Being told you have MND can be devastating and the news can be difficult to take in at first.

After you’re diagnosed you should be provided with contact details of an MND care specialist. These are healthcare professionals with specialist experience caring for people with MND. They’ll be able to give you (and your family) extra support after the diagnosis and during your time with the illness.

Talking to a counsellor or a trained clinical psychologist might help with feelings of depression and anxiety.

It’s not unusual to have thoughts of taking your own life, although very few people with MND go on to do this. You should discuss these thoughts with your doctor.

Taking antidepressants or medicines to reduce anxiety may help. Your care team will be able to tell you about this.

Although there is no cure for MND, treatments are available to help relieve the symptoms.

A team of healthcare professionals will work together to help care for you. This multidisciplinary team typically includes:

• a neurologist and an MND care specialist
• a specialist in breathing (respiratory specialist)
• physiotherapists to advise on mobility aids
• occupational therapists to assess the need for adaptations to living environments
• speech and language therapist to provide help with communication and swallowing
• dieticians to support nutrition

As the condition advances, you might also need palliative care.

Riluzole

Riluzole is the only licensed medication in the UK that has shown a survival benefit for people with MND. Riluzole is thought to slow down the damage to the motor neurone cells by reducing their sensitivity to the nerve transmitter glutamate.

In medical research, riluzole extended survival by 2 to 3 months on average.

Side effects of riluzole are usually mild and can include nausea, tiredness and, less commonly, a rapid heartbeat.

Very rarely, riluzole has been known to cause liver damage. If you are prescribed riluzole you will need to have blood tests for the first few months to check your liver is working properly. If you have had significant liver disease, riluzole may not be suitable for you.