Amyotrophic lateral sclerosis (ALS) is called Lou Gehrig’s disease because the famous baseball player developed and died of this serious and progressive neurological disease.
ALS is yet another disease of the nervous system for which no cause has yet been discovered. A small percentage, about 5 to 10 percent of the cases, are familial, and the causative gene has been pinpointed in some of these cases to a particular chromosome. However, most cases of ALS are sporadic, meaning they occur in people randomly with no family history of the condition. There are some Pacific islands, Guam and Papua New Guinea, where the inhabitants have a much greater chance of developing ALS than in most of the world, but whether this is because of an inherited factor or some other local factor is not known.
ALS affects only motor neurons the nerve cells that originate in the brain or the spinal cord and run to muscle cells to stimulate them to contract. Brain cells that are involved in thought, vision, hearing and other brain functions are not affected. Therefore consciousness, and the ability to see, hear and think clearly are maintained throughout the course of ALS. Steven Hawking, one of the great theoretical physicists of our time has been afflicted with a slowly progressive variant of ALS for many years and continues to do theoretical physics.
The nerve cells that transmit sensations from our body into our brain are also not affected by ALS, and therefore someone with the disease does not have numbness, or abnormal sensations that people frequently have with multiple sclerosis, a more common neurological condition.
Studies of the brain and spinal cord in ALS simply show a reduction in the number of motor neuron cells. There is no sign of inflammation, which would indicate an infection or inflammatory disease.
Because the disease causes the loss of motor neurons both in the brain (upper motor neurons), and in the spinal cord (lower motor neurons) the signs of the condition may vary in different parts of the body and between different people afflicted with it. An arm that has lost lower motor neurons will be weak and flaccid, with a decrease in size of the muscles and loss of reflexes. A leg which has lost upper motor neurons will also be weak, but the muscles will still have some size and tone and the reflexes will be exagerrated. As the disease progresses weakness and loss of muscle tone and reflexes usually is present in both arms and legs.
Particularly dangerous is the weakness that develops in the muscles that allow us to breathe and swallow. Inability to eat and frequent choking on food that is aspirated into the lungs is a terrible complication of the condition, and respiratory problems are usually the cause of death at the end.
There is no specific treatment for ALS and the average survival of the typical case is about three to five years from the time of diagnosis. There are some variants of the disease that may have longer survival. Physical therapy and measures to prevent infection and aspiration of food and secretions into the lungs are very important to prevent complications, but in most cases the loss of the motor neurons is relentless and ultimately fatal.