Amyotrophic Lateral Sclerosis (ALS), also known as Lou Gehrig’s Disease, is the most famous form of motor neuron disease.
It is a chronic progressive neurodegenerative condition that affects only motor neurons.
In ALS the alpha motor neurons in the spinal cord (also known as lower motor neurons) are lost, as well as the upper motor neurons of the corticospinal tracts.
This results in the gradual loss of the ability to move. The paralysis is a spastic paralysis due to the loss of the upper motor neurons but the muscle tissue also atrophies away due to the loss of the lower motor neurons. This gives the classical clinical picture of ALS which is spastic cachexia.
The cause of the disease is very poorly understood. Our present understanding is that it can hit anybody. Once it begins it progresses, gradually making the individual more and more neurologically disabled. They eventually cannot walk or talk or swallow.
Whilst they loose all these functions, cognition remains completely intact, as the disease is very specific and only effects the motor neurons and not the rest of the brain. So the individual remains completely with it as they become more physically disabled.
The condition will eventually result in death as the motor neurons that control the diaphragm will degenerate and breathing will fail. Individuals often die of aspiration pneumonia long before this happens however due to the problems with swallowing resulting in aspiration of saliva and phlegm.
In this video we discuss in detail the neuropathophysiology of ALS and how it results in paralysis. We then towards the end of the video discuss what little is known about the pathogenesis of the neurodegeneration seen in ALS.