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Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics
in 2 minutes or less.
In this installment I will discuss amyotrophic lateral sclerosis, or ALS.
Also known as Lou Gehrig’s disease in the US and motor neuron disease in the UK, ALS
is characterized both by muscle spasticity and a progressive weakening of the muscles.
As the disease progresses, patients may lose hand and arm function, and experience difficulty
walking, speaking, and even breathing.
Respiratory failure is often the cause of death, and the average survival time from
diagnosis is around 3-5 years.
Although some cases of ALS are inherited, in the vast majority of cases the cause of
ALS is unknown.
ALS is a neurodegenerative disorder, meaning it is characterized by the degeneration and
death of neurons.
Specifically, the affected neurons in ALS are called upper and lower motor neurons.
Upper motor neurons extend from the cerebral cortex or brainstem and carry motor information
down to the spinal cord.
Lower motor neurons extend from the spinal cord or brainstem to skeletal muscle to cause
movement.
Degeneration of upper motor neurons often is responsible for spasticity and modest weakness,
but degeneration of lower motor neurons causes more disabling weakness.
As the motor neurons stop working, muscles also begin to atrophy.
Mutations in several genes have been linked to the development of ALS, but the effects
of the mutations are not completely clear and the mechanism that causes neurodegeneration
in ALS is still not understood.
Similar to other neurodegenerative diseases like Alzheimer’s disease, ALS is characterized
by the accumulation of dysfunctional proteins within neurons.
Although the impact of these protein groups or aggregates is unclear, it is hypothesized
that they could impair neuronal function.
There also are a number of other mechanisms proposed to play a role in neurodegeneration
in ALS and it is likely more than one is involved.