What is MND?
Motor Neurone Disease (MND) is a rapidly progressive neurodegenerative condition in which the damage and death of motor neurones causes a loss of connection between the brain and the voluntary muscles. Progressive muscle weakness and wasting eventually affects the muscles controlling movement of the limbs, speech, swallowing and breathing. A key feature of the disease is the speed of progression in most affected patients.
There are four main types of MND, each affecting people in different ways.
Amyotrophic lateral sclerosis (ALS)
This is the most common form, with both upper and lower motor neurone involvement. This form of the disease is characterised by weakness and wasting in the limbs as well as increased muscle tone. Average life expectancy is from two to five years from onset of symptoms.
Progressive bulbar palsy (PBP)
This type of MND affects about a quarter of people diagnosed. Symptoms start with slurring of speech and may progress to cause difficulty in swallowing. Life expectancy is between six months and three years.
Progressive muscular atrophy (PMA)
Affects only a small proportion of people, mainly causing damage to the lower motor neurones in the spinal cord. Early symptoms may be noticed as weakness or clumsiness of a hand or a foot. Life expectancy is similar to that of ALS.
Primary lateral sclerosis (PLS)
A rare form of MND involving the upper motor neurones only, causing stiffness and clumsiness of the limbs which usually starts in the legs. Speech and swallowing may also be affected. This is the most slowly progressive form of MND and patients commonly have a life expectancy of more than 10-15 years.
What are the symptoms of MND?
The symptoms of MND start in different parts of the body in individual patients and the speed of progression of symptoms also varies between individuals. The disease usually begins very gradually and people often just feel tired to start with. Clumsy fingers, a weak grip, foot-drop, difficulty in walking, or slurring of speech are often the first symptoms of muscle problems. Although thinking and reasoning aren’t usually noticeably affected, around five percent of people diagnosed with MND will have some level of intellectual difficulty or a change in personality.
Testing for MND
There is no single diagnostic test for MND. The diagnosis is usually made based on symptoms and what a neurologist finds on examining the person. It is important to carefully exclude more treatable conditions which may mimic MND.
Tests to help diagnose MND include:
• Electromyography (EMG) - this test uses fine needles to measure the electrical activity of muscles
• Nerve conduction tests - an electrical impulse is applied through a small pad on the skin - this measures the speed at which nerves carry electrical signals
• Magnetic resonance imaging (MRI) scan - this uses a magnetic signal to produce images of the inside of the body including the nervous system
• Various blood tests to check for other conditions which may mimic MND
The causes of MND
About 95% of cases of MND are "sporadic", occurring as a one off condition within the family. The risk is greater in men and increases with age. No definite cause for sporadic MND has been established, but it is suspected that a high level of physical activity may be a risk factor. Research done by Professor Adriano Chio in Turin made the headlines in 2008, when he looked into a link between MND and football players, finding that there was a seven times higher incidence in footballers compared to the rest of the population.
Approximately five per cent of cases are “familial MND”, defined either by a family history of MND or by testing positive for a known genetic mutation associated with the disease. Several genes which can cause familial MND have now been identified including changes in the SOD1, TDP-43 and FUS genes.