Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease or motor neuron disease, is a progressive, degenerative disease that destroys the nerve cells that control voluntary muscle movement. These cells, called "motor neurons," run from the brain through the brainstem or spinal cord to muscles that control movement in the arms, legs, chest, throat and mouth. In people with ALS, these cells die off, causing the muscle tissues to waste away. ALS does not affect a person's sensory functions or mental faculties. Other, nonmotor neurons, such as sensory neurons that bring information from sense organs to the brain, remain healthy.
Generally, ALS is categorized in one of two ways: Upper motor neuron disease affects nerves in the brain, while lower motor neuron disease affects nerves coming from the spinal cord or brainstem. In both cases, motor neurons are damaged and eventually die. ALS is fatal. The average life expectancy after diagnosis is two to five years, but some patients may live for years or even decades. (The famous physicist Stephen Hawking, for example, lived for more than 50 years after he was diagnosed.) There is no known cure to stop or reverse ALS.
Each person with ALS experiences a different proportion of upper and lower motor neurons that die. This results in symptoms that vary from person to person. The disease progresses, affecting more nerve cells as time goes on. As muscle tissues deteriorates, the muscles become weaker and atrophy (wither) and the person's limbs may begin to look thinner. However, the muscles can also become spastic (moving involuntarily) and this may lead to increased muscle tone in some parts of the body.
The initial symptoms of ALS can vary considerably from person to person, as can the rate at which ALS progresses. Not all individuals with ALS develop the same symptoms or the same sequences or patterns of progression. However, all people with ALS will experience progressive muscle weakness and paralysis.
In the early stages of ALS, the symptoms may be so minor that they are overlooked. Common symptoms include:
In more advanced stages, ALS causes shortness of breath and difficulty in breathing and swallowing, which is what eventally lead to a person's death.
Based on US population studies, a little more than 5,600 people in the United States are diagnosed with ALS each year – approximately 15 new cases per day. It is estimated that as many as 30,000 Americans have the disease at any given time. About 60% of the people reported to have ALS in the United States are men, and 93% of patients are caucasian.
Most people develop ALS between the ages of 40 and 70, with an average age of 55 at the time of diagnosis. However, rare cases of the disease do occur in persons in their 20s and 30s. Approximately 50% of people diagnosed with ALS live at least three or more years after diagnosis. About 25% live five years or more and up to 10% live more than 10 years.
Although the cause of ALS is not completely understood, recent research suggests that multiple complex factors contribute to the death of motor neurons. Specific risk factors for ALS have not been conclusively identified, but ongoing research is exploring the possible role of genetics and/or environmental factors. Research published in 2009 suggests that smoking tobacco may heighten a person's risk for ALS.
Any one or more of the following factors may be responsible for the disease:
It is also likely that specific gene mutations and/or heredity modifies the disease and the likelihood of developing it.
Diagnosing ALS is difficult because there is no single medical test for it. Also, since many neurologic diseases cause similar symptoms, these other conditions must be ruled out first, through clinical examinations and medical tests. A comprehensive diagnostic workup includes most, if not all, of the following tests and procedures:
Individula doctors will determine which of the above tests to conduct, usually based on the physical exam and the results of previous medical tests the patient has had.
Currently there is no known cure or treatment that halts or reverses the progression of ALS. However, the FDA-approved medications riluzole (brand names Rilutek, Teglutik) and edaravone (Radicava) have been shown to modestly slow the progression of ALS. In addition, there are several promising clinical trials being conducted worldwide that are yielding important information on how to combat this disease.
While the search for an effective treatment and cure continues, multidisciplinary teams across the globe are assisting patients and their families to adjust to the many challenges of living with ALS. These teams of specialists use devices and therapies to help patients manage their ALS symptoms and to allow people with the disease to maintain their independence and quality of life. This multidisciplinary approach has also been shown to prolong survival of people who have ALS.
Treatments and interventions may include:
Many people with ALS and other neuromuscular diseases decide to take part in research studies to help test new medications and treatments aimed at treating the disease. To learn more about these studies, visit the US National Institutes of Health Clinical Trials Registry.
Learn more about ALS from the additional content below, and by visiting Hospital for Special Surgery's ALS Program.