Amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS), also known as motor neurone disease (MND) or Lou Gehrig's disease, is a specific disease that causes the death of neurons controlling voluntary muscles. Some also use the term motor neuron disease for a group of conditions of which ALS is the most common. ALS is characterized by stiff muscles, muscle twitching, and gradually worsening weakness due to muscles decreasing in size. It may begin with weakness in the arms or legs, or with difficulty speaking or swallowing. About half of the people affected develop at least mild difficulties with thinking and behavior and most people experience pain. Most eventually lose the ability to walk, use their hands, speak, swallow, and breathe. The cause is not known in 90% to 95% of cases, but is believed to involve both genetic and environmental factors. The remaining 5–10% of cases are inherited from a person's parents. About half of these genetic cases are due to one of two specific genes. The underlying mechanism involves damage to both upper and lower motor neurons. The diagnosis is based on a person's signs and symptoms, with testing done to rule out other potential causes. No cure for ALS is known. The goal of treatment is to improve symptoms. A medication called riluzole may extend life by about two to three months. Non-invasive ventilation may result in both improved quality and length of life. Mechanical ventilation can prolong survival but does not stop disease progression. A feeding tube may help. The disease can affect people of any age, but usually starts around the age of 60 and in inherited cases around the age of 50. The average survival from onset to death is two to four years, though this can vary. About 10% survive longer than 10 years. Most die from respiratory failure. In Europe, the disease affects about two to three people per 100,000 per year. Rates in much of the world are unclear. In the United States, it is more common in white people than black people. Descriptions of the disease date back to at least 1824 by Charles Bell. In 1869, the connection between the symptoms and the underlying neurological problems was first described by Jean-Martin Charcot, who in 1874 began using the term amyotrophic lateral sclerosis. It became well known in the United States in the 20th century when in 1939 it affected the baseball player Lou Gehrig and later worldwide following the 1963 diagnosis of cosmologist Stephen Hawking. The first ALS gene was discovered in 1993 while the first animal model was developed in 1994. In 2014, videos of the Ice Bucket Challenge went viral on the Internet and increased public awareness of the condition. ALS is a motor neuron disease, also spelled 'motor neurone disease', which is a group of neurological disorders that selectively affect motor neurons, the cells that control voluntary muscles of the body. Motor neuron diseases include amyotrophic lateral sclerosis (ALS), primary lateral sclerosis (PLS), progressive muscular atrophy (PMA), progressive bulbar palsy, pseudobulbar palsy, and monomelic amyotrophy (MMA). ALS itself can be classified a few different ways: by how fast the disease progresses (slow vs fast progressors), by whether it is inherited or sporadic, and by where it starts. In about 25% of cases, muscles in the face, mouth, and throat are affected first, because motor neurons in the part of the brain stem called the medulla oblongata (formerly called the 'bulb') start to die first along with lower motor neurons. This form is called 'bulbar onset'. In about 5% of cases muscles in the trunk of the body are affected first. In most cases the disease spreads and affects other spinal cord regions. A few people with ALS have symptoms that are limited to one spinal cord region for at least 12 to 24 months before spreading to a second region; these regional variants of ALS are associated with a better prognosis. ALS can be classified by the types of motor neurons that are affected. Typical or 'classical' ALS involves neurons in the brain (upper motor neurons) and in the spinal cord (lower motor neurons). Primary lateral sclerosis (PLS) involves only upper motor neurons, and progressive muscular atrophy (PMA) involves only lower motor neurons. There is debate over whether PLS and PMA are separate diseases or simply variants of ALS. Classic ALS accounts for about 70% of all cases of ALS and can be subdivided into spinal-onset and bulbar-onset ALS. Spinal-onset ALS, also called limb-onset ALS, begins with weakness in the arms and legs and accounts for about two-thirds of all cases of classic ALS. Bulbar-onset ALS begins with weakness in the muscles of speech, chewing, and swallowing and accounts for about one-third of all cases of classic ALS. It is associated with a worse prognosis than spinal-onset ALS; a population-based study found that bulbar-onset ALS has a median survival of 2.0 years and a 10-year survival rate of 3%, while spinal-onset ALS has a median survival of 2.6 years and a 10-year survival rate of 13%.