Amyotrophic lateral sclerosis (ALS), sometimes called Lou Gehrig’s disease, is a rapidly progressive, invariably fatal neurological disease that attacks the nerve cells (neurons) responsible for controlling voluntary muscles. The disease belongs to a group of disorders known as motor neuron diseases, which are characterized by the gradual degeneration and death of motor neurons.
Motor neurons are nerve cells located in the brain, brainstem, and spinal cord that serve as controlling units and vital communication links between the nervous system and the voluntary muscles of the body. Messages from motor neurons in the brain (upper motor neurons) are transmitted to motor neurons in the spinal cord (lower motor neurons) and from them to particular muscles. In ALS, both the upper motor neurons and the lower neurons degenerate or die, ceasing to send messages to muscles. Unable to function, the muscles gradually weaken, waste away (atrophy), and twitch. Eventually, the ability of the brain to start and control voluntary movement is lost.
Types of ALS:
- Sporadic: the most common form of ALS in the U.S. These cases occur randomly, without any identifiable cause, and there is no association with persons in the family with the disease.
- Familial: suggests that the disease is inherited and accounts for a very small number of cases in the United States.
- Guamanian: an extremely high incidence of ALS has been observed in Guam and the Trust Territories of the Pacific.
What causes ALS?
The cause of ALS is not known, and scientists do not yet know why ALS strikes some people and not others. In 1993, scientists discovered that mutations in the gene that produces the SOD1 enzyme were associated with some cases of familial ALS. This enzyme is a powerful antioxidant that protects the body from damage caused by free radicals. Free radicals are highly reactive molecules produced by cells during normal metabolism. If not neutralized, free radicals can accumulate and cause random damage to the DNA and proteins within the cells. Although it is not yet clear how the SOD1 gene mutation leads to motor neuron degeneration, researchers have theorized that an accumulation of free radicals may result from faulty functioning of this gene.
Studies also have focused on the role of glutamate in motor neuron degeneration. Glutamate is one of the chemical messengers or neurotransmitters in the brain. Scientists have found that, compared to healthy people, ALS patients have higher levels of glutamate in the serum and spinal fluid. Laboratory studies have demonstrated that neurons begin to die when, over long periods of time, they are exposed to excessive amounts of glutamate.
Symptoms:
- twitching and cramping of muscles, especially in the hands and feet
- loss of motor control in hands and arms
- impairment in the use of the arms and legs
- tripping and falling
- dropping things
- persistent fatigue
- uncontrollable periods of laughing or crying
- slurred or thick speech and difficulty in projecting the voice
As the disease progresses, symptoms may include:
- difficulty breathing
- difficulty swallowing
- paralysis
Treatment:
No cure has yet been found for ALS. However, the Food and Drug Administration (FDA) has approved the first drug treatment for the disease riluzole (Rilutek). Riluzole is believed to reduce damage to motor neurons by decreasing the release of glutamate. Clinical trials with ALS patients showed that riluzole prolongs survival by several months, mainly in those persons experiencing difficulty in swallowing.
For most people with ALS, primary treatment may involve the management of symptoms, and may include physical, occupational, speech, respiratory, and nutritional therapies. Some medications and/or heat or whirlpool therapy may help to relieve muscle cramping. Exercise, although recommended in moderation may help to maintain muscle strength and function.
Statistics:
- Most people who develop ALS are between the ages of 40 and 70, although the disease can occur at any age.
- ALS occurs throughout the world with no racial, ethnic, or socioeconomic boundaries.
- ALS affects as many as 30,000 Americans, with 5,600 new cases diagnosed in the U.S. each year.
