Motor Neurone Disease (MND) is the name of a group of diseases that cause the death of the nerve cells (neurones) that control the muscles that enable us to move, speak, swallow and breathe.
With no nerves to activate them, these muscles gradually weaken and waste away. This causes progressive loss of mobility in the limbs, and difficulties with speech, swallowing and breathing. The progression varies significantly from person to person.
The most common type of MND is Amyotrophic Lateral Sclerosis, or ALS. In some countries, including North America, MND is called ALS.
Incidence: The number of people who are newly diagnosed with MND every year
International figures predict that approximately two in every 100,000 people are diagnosed with MND each year. In New Zealand that means about 100 people are diagnosed with MND each year – about two every week.
Prevalence: The total number of people who have MND at any time
About 300 people in New Zealand are living with MND, or 1 in 15,000 New Zealanders. Worldwide, more than 450,000 people are currently living with MND.
Mortality rate: The number of deaths due to MND per year
Each year MND causes the deaths of over 100 people in New Zealand. In 2011, one in every 202 deaths in New Zealand was caused by MND.
Lifetime risk: The average risk of developing MND over the course of your life
A person’s lifetime risk of developing MND is up to one in 300 (reference: Table 2, Johnston 2006).
Early symptoms are mild and may include stumbling due to weakness of the leg muscles, difficulty holding objects due to weakness of the hand muscles, and slurring of speech or swallowing difficulties due to weakness of the tongue and throat muscles.
Cramps and muscle twitching are also common symptoms.
Emotional responses may be more easily triggered and the person with MND may be aware of laughing and crying more readily than previously.
For some people, the symptoms are widespread from the onset. However MND usually begins by affecting a single limb or aspect of motor function, becoming more generalised as the disease progresses.
There is no specific test for MND. Diagnosis requires eliminating other possible conditions.
Diagnosing MND is difficult because:
If your general practitioner (GP) suspects a neurological problem, you will be referred to a neurologist who does the diagnosis. To improve timely referrals MND NZ has a Red Flag tool to help GPs.
If your neurologist believes there is cause for concern you may be sent for a series of diagnostic tests which may include the following:
This test is sometimes called the needle test, because fine needles are used to record the naturally-occurring nerve impulses within certain muscles. Muscles that have lost their nerve supply can be detected because their electrical activity is different from normal healthy muscles. Recordings are usually taken from each limb and the bulbar (throat) muscles. The EMG can be shown as abnormal even if that particular muscle is as yet unaffected.
An electrical impulse is applied through a small pad on the skin, which measures the speed at which your nerves carry electrical signals. This test may be carried out at the same time as the EMG.
This procedure is designed to measure the activity of the upper motor neurones; its findings can help in the diagnostic process. It may be carried out at the same time as a nerve conduction test.
This involves lying flat in an MRI scanning machine. An MRI scan will not diagnose MND, because the damage caused by MND does not show up on this scan. It is a tool for eliminating other conditions that can mimic symptoms of MND.
A blood test will be looking to see if there is a rise in levels of creatine kinase. This is produced when muscle breaks down and can occasionally be found in the blood of people with MND. It is not specific for MND and may also be an indicator of other medical conditions.
There are several other tests your neurologist may request if the clinical findings indicate they could be useful.