Motor neurone disease is a rare progressive disorder that affects special nerves in the brain and spinal cord called motorneurons.
These nerves control muscle movement and their degeneration leads to severe weakness, muscle wastage and eventually complete debilitation. The motorneurons control important muscle movements such as walking, speaking, swallowing, breathing and gripping. As the disease progresses, these actions become increasingly difficult and eventually the sufferer loses the ability to carry them out altogether.
The exact cause of motor neurone disease is unclear and it is not thought that race, ethnicity or lifestyle factors play a role. However, genes are thought to contribute to the condition in some cases. In around 5% of cases, there is a family history of either motor neurone disease or a similar condition called frontotemporal dementia and in the majority of these cases, defective genes have been identified as contributors to the disease.
There are several subtypes of motor neurone disease. The onset of symptoms is slightly different with each subtype of the condition but as the disease progresses, symptoms tend to overlap.
The most common form of motor neurone disease is amyotropic lateral sclerosis or ALS. This condition usually develops between the ages of 50 and 70 years and rarely affects those under the age of 40. The majority of ALS occurs as a sporadic or noninherited disease but around 1 in 20 cases are due to an inherited form of the condition. In most commonwealth countries, ALS is also referred to as motor neurone disease and in the United States it is also called Lou Gehrig’s disease.
The term amyotrophic lateral sclerosis is derived from several Greek terms. The term “amyotrophic” can be broken down into three parts – “a” meaning absent, “myo” referring to muscles and “trophic” referring to nourishment or nutrition. Together, this can be interpreted as a lack of muscle nourishment. The term “lateral” refers to the areas around the spinal cord where the affected nerve cells are found. The degeneration of these nerves leads to hardening or “sclerosis” in these areas.
Reviewed by Sally Robertson, BSc