Motor neurone disease is a progressive degenerative disorder affecting specialist nerve cells called motor neurons that control muscle movement.
Motor neurons are vital in controlling the various activities of the body that involve muscle movement including walking, running, speaking, swallowing, breathing and gripping. As the disease progresses, these actions become difficult and eventually the person is unable to carry them out at all.
The skeletal muscles are muscles that are voluntarily controlled such as those in the legs used for walking. There muscles are innervated by a group of nerves called the lower motor neurones. The lower motor neurons are found in the ventral horn of the spinal cord and are responsible for all voluntary movements. The lower motor neurons are activated by the release of glutamate form the upper motor neurones in the brain stem.
In motor neurone disease, damage to the ventral horns of the spinal cord leads to atrophy of the ventral roots. Neurons in the frontal and temporal lobes also degenerate. Studies looking at the nerve damage caused by motor neuron disease have revealed the presence of sponge-like deformities called spongiosis, skein like inclusions and bunina bodies as well as the formation of vacuoles.
In around 5% of people who suffer from motor neurone disease, defective genes are thought to play a role in contributing to the disease. A number of genes have been identified that cause the inherited form of this disease and these include: SOD1, TDP-43, FUS,VCP, C90RF72, SQSTM1 and Profilin1.
Reviewed by Sally Robertson, BSc