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What is Amyotrophic Lateral Sclerosis (ALS)?

Amyotrophic lateral sclerosis (ALS) (sometimes called Lou Gehrig’s disease or classical motor neuron 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, brain stem, 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 (called upper motor neurons) are transmitted to motor neurons in the spinal cord (called lower motor neurons) and from them to particular muscles.

In ALS, both the upper motor neurons and the lower motor neurons degenerate or die, ceasing to send messages to 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.

What are the symptoms?

The onset of ALS may be so subtle that the symptoms are overlooked. The earliest symptoms may include fasciculations (tiny muscle twitches), cramps, tight and stiff muscles (spasticity), muscle weakness affecting an arm or a leg, slurred and nasal speech, or difficulty chewing or swallowing. These general complaints then develop into more obvious weakness or atrophy that may cause a physician to suspect ALS.

The parts of the body showing early symptoms of ALS depend on which muscles in the body are affected. Many individuals first see the effects of the disease in a hand or arm as they experience difficulty with simple tasks requiring manual dexterity such as buttoning a shirt, writing, or turning a key in a lock. In other cases, symptoms initially affect one of the legs, and people experience awkwardness when walking or running or they notice that they are tripping or stumbling more often. When symptoms begin in the arms or legs, it is referred to as “limb onset” ALS. Other individuals first notice speech problems, termed “bulbar onset” ALS.

Regardless of the part of the body first affected by the disease, muscle weakness and atrophy spread to other parts of the body as the disease progresses. Individuals may develop problems with moving, swallowing (dysphagia), and speaking or forming words (dysarthria). Symptoms of upper motor neuron involvement include spasticity and exaggerated reflexes (hyperreflexia) including an overactive gag reflex. An abnormal reflex commonly called Babinski’s sign (the large toe extends upward as the sole of the foot is stimulated in a certain way) also indicates upper motor neuron damage. Symptoms of lower motor neuron degeneration include muscle weakness and atrophy, muscle cramps, and fasciculations.

When muscles in the diaphragm and chest wall fail to function properly, individuals lose the ability to breathe without ventilatory support.

The disease does not affect a person’s ability to see, smell, taste, hear, or recognize touch. Although the disease does not usually impair a person’s mind or personality, several recent studies suggest that some people with ALS may develop cognitive problems involving word fluency, decision-making, and memory. The cause of ALS is not known, and scientists do not yet know why ALS strikes some people and not others.

Who gets ALS?

More than 12,000 people in the U.S. have a definite diagnosis of ALS, for a prevalence of 3.9 cases per 100,000 persons in the U.S. general population, according to a report on data from the National ALS Registry. ALS is one of the most common neuromuscular diseases worldwide, and people of all races and ethnic backgrounds are affected. ALS is more common among white males, non-Hispanics, and persons aged 60–69 years, but younger and older people also can develop the disease. Men are affected more often than women.

In 90 to 95 percent of all ALS cases, the disease occurs apparently at random with no clearly associated risk factors. Individuals with this sporadic form of the disease do not have a family history of ALS, and their family members are not considered to be at increased risk for developing it.

About 5 to 10 percent of all ALS cases are inherited. The familial form of ALS usually results from a pattern of inheritance that requires only one parent to carry the gene responsible for the disease. Mutations in more than a dozen genes have been found to cause familial ALS.

Is there any treatment?

What is the prognosis?

What research is being done?

The National Institute of Neurological Disorders and Stroke (NINDS) conducts research in its laboratories at the National Institutes of Health (NIH) and also supports additional research through grants to major medical institutions across the country. The goals of this research are to find the cause or causes of ALS, understand the mechanisms involved in the progression of the disease, and develop effective treatments.