What Is Amyotrophic Lateral Sclerosis?
Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is a rapidly progressive, invariably fatal neurological disease. This disease attacks the nerve cells (neurons) responsible for controlling voluntary muscles. ALS belongs to a group of disorders known as
motor neuron diseases, which are characterized by the gradual degeneration and death of motor neurons.
Understanding Motor Neurons
Motor neurons are nerve cells located in the brain, brainstem, and spinal cord. These nerve cells serve as controlling units and provide vital communication links between the nervous system and the voluntary muscles of the body. Messages from motor neurons in the brain (called upper motor neurons) are transmitted to motor neurons in the spinal cord (called lower motor neurons). From here, they are transmitted to particular muscles.
The Link Between Motor Neurons and Amyotrophic Lateral Sclerosis
In amyotrophic lateral sclerosis, both the upper motor neurons and the lower motor neurons degenerate or die, ceasing to send messages to the muscles. Unable to function, the muscles gradually weaken, waste away, and twitch. Eventually, the ability of the brain to start and control voluntary movement is lost.
Because amyotrophic lateral sclerosis affects only motor neurons, the disease does not impair a person's:
- Mind
- Personality
- Intelligence
- Memory.
Nor does it affect a person's ability to:
- See
- Smell
- Taste
- Hear
- Recognize touch.
People with this condition usually maintain control of eye muscles and bladder and bowel functions.
Symptoms of Amyotrophic Lateral Sclerosis
Individuals with amyotrophic lateral sclerosis lose their strength and the ability to move their arms, legs, and body. When muscles in the diaphragm and chest wall fail, individuals lose the ability to breathe without ventilator support.
In most cases, ALS does not impair a person's mind, memory, or senses. However, a small percentage of people may experience problems with memory or decision making, and there is growing evidence that some people may develop a form of
dementia.
(Click ALS Symptoms for more information, including early symptoms.)
What Causes Amyotrophic Lateral Sclerosis?
The cause of amyotrophic lateral sclerosis is not known, and scientists do not know why the disease strikes some people and not others.
ALS research scientists are investigating a number of possible causes, including:
- Genetics
- Glutamate
- Autoimmune responses
- Environment.
Diagnosing Amyotrophic Lateral Sclerosis
Although there is no single test that can provide a definitive diagnosis, the presence of upper and lower motor neuron signs in a single limb is strongly suggestive. However, a diagnosis of amyotrophic lateral sclerosis is primarily based on the signs and symptoms and on a series of tests to rule out other diseases.
Scientists have not yet found a cure for amyotrophic lateral sclerosis. However, the U.S. Food and Drug Administration (FDA) has approved the first drug treatment for ALS, which is called riluzole (Rilutek®). Riluzole is believed to reduce damage to motor neurons and prolong survival by several months (mainly in those with difficulty swallowing).
Other treatments are designed to relieve symptoms and improve the quality of life. Drugs are also available to help individuals with:
Individuals with amyotrophic lateral sclerosis may eventually consider forms of mechanical ventilation (respirators).
Prognosis With Amyotrophic Lateral Sclerosis
Regardless of the part of the body that is first affected by amyotrophic lateral sclerosis, muscle weakness and atrophy spread to other parts of the body as the disease progresses. Individuals with this condition will have increasing difficulties with moving, swallowing, and speaking or forming words.
Eventually, people with amyotrophic lateral sclerosis will not be able to:
- Stand or walk
- Get in or out of bed on their own
- Use their hands and arms.
In later stages, individuals will have difficulty breathing as the muscles of the respiratory system weaken. Although ventilation support can ease problems with breathing and prolong survival, it will not affect the progression of the disease.
Most people with amyotrophic lateral sclerosis will die from respiratory failure within three to five years from the start of their symptoms. However, about 10 percent of people with the condition will survive for ten or more years.
Statistics on Amyotrophic Lateral Sclerosis
In the United States, approximately 20,000 people have amyotrophic lateral sclerosis, and an estimated 5,000 are diagnosed each year.
In 90 to 95 percent of all cases, the disease occurs randomly with no clearly associated risk factors, and about 5 to 10 percent of all ALS cases are inherited
(see Familial Amyotrophic Lateral Sclerosis.).
Familial ALS usually results from a pattern of inheritance that requires only one parent to carry the gene responsible for the disease
(see ALS and Who It Affects).
Sunday, May 2, 1939, will be forever remembered in the annals of baseball as the day New York Yankees' first baseman Lou Gehrig voluntarily benched himself, ending a streak of 2,130 consecutive games.
For months, the once-great player's game had been in decline. His reflexes were off. He stumbled, fumbled, and struggled to hit or catch the ball. No one understood why.
A few days after Gehrig benched himself, doctors diagnosed his illness as amyotrophic lateral sclerosis. This is a progressive disease of the central nervous system that remains incurable to this day.
Two years later, on June 2, 1941, Gehrig died at the age of 37. The disease that took his life became known to Americans as Lou Gehrig's disease.
