Motor neurone disease is a debilitating condition caused by degeneration of the nerve cells that control muscle movement.
Exactly what leads to the loss of these specialist motor neuron is not understood, although genetic predisposition has been identified as a factor in a small proportion of sufferers. In around 5% of cases, the patient has a family member who also developed either motor neurone disease or a similar condition called frontotemporal dementia. In most of these individuals, gene mutations have been identified as contributors to the condition. In cases where there seems to be no family history, the condition is referred to as sporadic.
Hypothesized causes of motor neurone disease
Although it is not clear why the motor neuron become damaged, researchers think a combination of various interrelating factors may play a role and some of these include:
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, SQSTM1and Profilin1.
Disruption of the nerve cells
All cells have a transport system for moving nutrients into the cell and waste materials out of the cell. It is speculated that in motor neurone disease, the transport systems in motor neuron becomes defective, causing loss of normal nerve function.
Proteins sometimes clump together and form aggregates in motor neurone disease. The clumps may interrupt the usual function of the neuron.
Build up of toxic wastes
Normal cell activity can eventually lead to the build up of toxic products inside cells. Antioxidiants produced by the body usually combat this toxic waste but some experts believe that in the case of motor neurone disease, the affected nerve cells are deficient in antitoxidants.
All nerve cells communicate using special chemical messengers called neurotransmitters. One of these is called glutamate. Some studies suggest that an increased sensitivity to glutamate in motor neuron may be responsible for the damage caused to the cells in people with motor neurone disease. This has not been linked to dietary intake of glutamate.
Studies have demonstrated that the mitochondria or power houses of the cells that provide the cell’s energy, are abnormal in the motor neuron of people with the condition.
Deficiency of neurotrophic factors
Motor neuron are provided with nutrients by neurotrophic factors. Research has shown that these factors are not correctly produced in motor neurone disease, which may weaken the nerves and leave them susceptible to damage.
Reviewed by Sally Robertson, BSc