Amyotrophic lateral sclerosis (ALS) is a rapidly progressing neurodegenerative disease that attacks the nerve cells in the brain and spinal cord that control voluntary muscle movement. As these nerve cells, called motor neurons, decline, they stop sending messages to the muscles. This causes the muscles to weaken, twitch, and atrophy (lose muscle mass and deteriorate). ALS was once referred to as “Lou Gehrig’s disease” after the New York Yankees baseball player who retired in 1939 because of the disease.
Age range most commonly affected by ALS
Percentage of cases that are sporadic (not hereditary)
Average survival in years
ALS most commonly affects people between the ages of 40 and 70, though younger and older people can also develop the disease. According to the National Institutes of Health, men are slightly more likely to develop the disease than women, though as age increases, this difference is reduced. Some studies suggest that military veterans also have an increased risk of the disease. The reason for this is unknown but may be due to exposure to lead, pesticides, and other environmental toxins during their service. Ongoing research in this area is looking into the impact of environmental, behavioral, and occupational factors on the development and progression of this disease.
While the disease is caused by a decline in motor neuron function, scientists don’t yet know why it occurs in some people and not others. In 5 to 10 percent of cases, the disease is inherited from a parent with the disease-causing gene. Researchers have identified more than a dozen genetic mutations that cause the hereditary form of ALS. However, for 90 to 95 percent of cases, the disease is sporadic, meaning it happens without any clear cause, risk factor, or family history of the disease. The family members of individuals with sporadic ALS do not have an increased risk of developing the disease.
The main symptoms of ALS include muscle weakness, stiffness, and atrophy. Early signs, such as muscle twitches, cramps, stiffness, or weakness in one body part, can be subtle. Symptoms usually first appear in a hand or arm. This might look like difficulty with tasks including buttoning a shirt, turning a lock, or writing. In some cases, the disease begins by affecting one leg, causing trouble with walking or more frequent stumbling.
As the disease progresses, people with ALS have difficulty standing, moving, walking, swallowing, and speaking. Eventually, they lose their ability to breathe without the support of a ventilator.
The disease is not known to be associated with cognitive impairment, but recent studies suggest some people with ALS may develop a form of dementia that affects memory and decision-making.
ALS is ultimately fatal, typically due to respiratory failure when the muscles needed to breathe become too weak. On average, people with ALS survive about three to five years while about 10 percent will live 10 years or more.
There is not a specific test to diagnose ALS. Doctors typically diagnose the disease by reviewing a person’s medical history and performing physical and neurologic exams. They may also use electromyography (EMG) to test nerve and muscle function and conduct other tests, such as blood and urine tests, a spinal tap, and magnetic resonance imaging (MRI), to rule out other conditions.
There is no cure for ALS or treatment to reverse its damage. However, medications can help slow the disease’s progression and manage symptoms such as muscle cramps, spasticity, pain, and excess saliva. Two FDA-approved medications for ALS have been shown to prolong survival. People with ALS may also experience sleep disturbances and depression, which can be treated with medication and therapy.
As the disease progresses, physical and occupational therapy, speech therapy, communication devices, and special equipment can help people with ALS remain mobile and independent for as long as possible. Later on, when symptoms worsen, people with ALS may require help from a caregiver as well as a feeding tube or a ventilator.
Current research efforts are working to identify potential risk factors, understand the disease’s progression, and develop better ways to diagnose, assess, and treat ALS.
Additional research projects are investigating the disease mechanism of ALS to identify new targets for treatment, the mutations that occur in motor neurons and cause this disease, and whether metabolic changes and nutrition impact disease progression.
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