The Motor neurone disease reference article from the English Wikipedia on 24-Jul-2004
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Motor neurone disease

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Motor Neurone Disease (MND) is a term used to cover a number of illnesses of the motor neurone. Amyotrophic Lateral Sclerosis (ALS), Progressive Muscular Atrophy (PMA), Progressive Bulbar Palsy (PBP) and Progressive Lateral Sclerosis (PLS) are all types of MND. MND is the term used internationally whilst ALS is often used in the USA (where it is also known as Lou Gehrig's disease) to cover all forms of MND. It was first described by Jean-Martin Charcot, a French neurologist, in 1869 and in France the disease is also known as Maladie de Charcot.

Overview

The disorder is characterized by the progressive loss of voluntary muscle contraction due to the destruction of nerve cells in the brain and the spinal cord that are responsible for the stimulation of the voluntary muscles.

The muscles are simply stimulated by a group of neurons located on the frontal portion of the spinal cord projecting to the muscle cells (second motor neurons) and these nerve cells are stimulated by a group of nerve cells that project from a specific region called the motor area, located on the frontal lobe (first motor neurons). The latter projection is called the corticospinal tract. The nerve cells of both pathways shrink and die for some unknown reason giving rise to muscle weakness, muscle cramps, speech impairment, difficulty swallowing and breathing. The international support organization uses the abbreviation ALS/MND to refer to the disease.

History

Lou Gehrig brought national and international attention to the disease in 1939 when he abruptly retired from baseball after being diagnosed with ALS/MND. Theoretical physicist Stephen Hawking and the ex-Glasgow Celtic football player Jimmy Johnstone also suffer from the disease.

Incidence

ALS/MND is indeed the most frequently observed member of a family of disorders called motor neuron diseases. This family has three major subgroups called primary lateral sclerosis (only the first motor neurons are affected), spinal muscular atrophy (only the second motor neurons are affected) and ALS (both are affected).

The incidence of ALS/MND is approximately 1 out of 100,000 people, and men are affected slightly more than women. The onset of symptoms is usually after the 5th or 6th decade and there are also familial forms of the disease.

Causes

Some cases with familial forms of the disease were shown to have a mutation on their superoxide dismutase (SOD) 1 genes, which produces an enzyme that reduces the oxidative stress of the nerve cells. Similar findings led the researchers to assume that the nerve cell death was caused by an excess of free radicals in the cell. This hypothesis is one of many others developed to describe the etiology of ALS/MND and is waiting to be reliably proven. Meanwhile, some experimental drugs are used to reduce the oxidative stress of the cells with very limited success.

Diagnosis

The diagnosis is established on both clinical grounds and an electromyography (EMG) examination, which is obligatory to demonstrate the diffuse loss of nervous stimulation of muscles of extremities, face and abdomen. Neuroimaging examinations can be performed for some occasional cases especially for a mass lesion of upper parts of spinal cord to exclude some disorders that may mimic the symptoms of ALS/MND. The disease has always a grave prognosis and the patients usually die within 2 to 10 years (although there are documented cases of people living 35 years or more; Hawking has lived for more than 40 years since his diagnosis). There is no cure and the treatment is usually supportive and symptomatic.

Treatment

Some current promising research towards a cure has focused on gene therapy and the use of stem cells, though the ethical and legal difficulties surrounding the harvesting of stem cells have slowed progress, particularly in the United States.

Etymology

Amyotrophic comes from the Greek language. A- means "no", myo refers to muscle, and trophic means nourishment; amyotrophic therefore means "no muscle nourishment," which describes the characteristic atrophication of the sufferer's disused muscle tissue. Lateral identifies the areas in a person's spinal cord where portions of the nerve cells that are affected are located. As this area degenerates it leads to scarring or hardening ("sclerosis") in the region.

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