Motor Neuron Diseases

Below is a list of Motor Neuron Diseases:

Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS), sometimes called Lou Gehrig's 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, brainstem, 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 (atrophy), and twitch (fasciculations). Eventually, the ability of the brain to start and control voluntary movement is lost.

ALS causes weakness with a wide range of disabilities (see section titled "What are the symptoms?"). Eventually, all muscles under voluntary control are affected, and patients lose their strength and the ability to move their arms, legs, and body. When muscles in the diaphragm and chest wall fail, patients lose the ability to breathe without ventilatory support. Most people with ALS die from respiratory failure, usually within 3 to 5 years from the onset of symptoms. However, about 10 percent of ALS patients survive for 10 or more years.

Although the disease usually does not impair a person's mind or intelligence, several recent studies suggest that some ALS patients may have alterations in cognitive functions such as depression and problems with decision-making and memory.

ALS does not affect a person's ability to see, smell, taste, hear, or recognize touch. Patients usually maintain control of eye muscles and bladder and bowel functions, although in the late stages of the disease most patients will need help getting to and from the bathroom.

The cause of ALS is not known, and scientists do not yet know why ALS strikes some people and not others.

Spinal Muscular Atrophy

Spinal Muscular Atrophy (SMA) Types I, II, and III belong to a group of hereditary diseases that cause weakness and wasting of the voluntary muscles in the arms and legs of infants and children. The disorders are caused by an abnormal or missing gene known as the survival motor neuron gene (SMN1), which is responsible for the production of a protein essential to motor neurons. Without this protein, lower motor neurons in the spinal cord degenerate and die.

The type of SMA (I, II, or III) is determined by the age of onset and the severity of symptoms. Type I (also known as Werdnig-Hoffman disease, or infantile-onset SMA) is evident at birth or within the first few months.

Symptoms include floppy limbs and trunk, feeble movements of the arms and legs, swallowing difficulties, a weak sucking reflex, and impaired breathing.

Type II (also known as juvenile SMA, intermediate SMA, or chronic SMA, has an onset between 6 and 18 months. Legs tend to be more impaired than arms.

Children with Type II are usually able to sit without support if placed in position. Some may be able to stand or walk with help.

Type III (also called Wolhlfart-Kugelberg-Welander disease, or mild SMA) can begin as early as the toddler years or as late as adolescence. Children can stand alone and walk, but may have difficulty getting up from a sitting position.

Post-Polio Syndrome

Post-polio syndrome (PPS) is a condition that affects polio survivors anywhere from 10 to 40 years after recovery from an initial paralytic attack of the poliomyelitis virus.

PPS is characterized by a further weakening of muscles that were previously affected by the polio infection.

Symptoms include fatigue, slowly progressive muscle weakness and, at times, a decrease in muscle size (muscular atrophy). Joint pain and increasing skeletal deformities such as scoliosis are common.

Some patients experience only minor symptoms, while others develop spinal muscular atrophy, and very rarely, what appears to be, but is not, a form of amyotrophic lateral sclerosis (ALS), also called Lou Gehrig's disease. PPS is rarely life-threatening.

Primary Lateral Sclerosis

Primary lateral sclerosis (PLS) is a rare neuromuscular disease with slowly progressive weakness in voluntary muscle movement. PLS belongs to a group of disorders known as motor neuron diseases.

In motor neuron diseases, the nerve cells that control voluntary muscle movement degenerate and die. In PLS, the corticospinal motor neurons (often called "upper motor neurons") in the brain are affected. There is no evidence of degeneration of lower motor neurons in the spinal cord or brainstem and there is little muscle wasting (what doctors call "amyotrophy").

Symptoms include weakness, muscle stiffness and spasms (spasticity), clumsiness, slowing of movement, and problems with balance. Onset of PLS usually occurs after age 40. The symptoms often begin with problems in the legs, but may also start with hand clumsiness or changes in speech. PLS progresses gradually over a number of years, or even decades.

Scientists do not believe PLS has a simple hereditary cause. There are similar, but rare, hereditary childhood disorders termed "juvenile PLS." The diagnosis of PLS requires extensive testing to exclude other diseases. When symptoms begin, PLS may be mistaken for amyotrophic lateral sclerosis or ALS (Lou Gehrig's disease) and the diagnosis of PLS can be delayed for several years.

Monomelic Amyotrophy

Monomelic amyotrophy (MMA) is characterized by progressive degeneration and loss of motor neurons, the nerve cells in the brain and spinal cord that are responsible for controlling voluntary muscles. It is characterized by weakness and wasting in a single limb, usually an arm and hand rather than a foot and leg.

There is no pain associated with MMA. While some physicians contend that mild sensory loss may be associated with this disease, many experts suggest that such symptoms actually indicate a cause other than MMA. MMA occurs in males between the ages of 15 and 25. Onset and progression are slow.

MMA is seen most frequently in Asia, particularly in Japan and India; it is much less common in North America.

In most cases, the cause is unknown, although there have been a few published reports linking MMA to traumatic or radiation injury. There are also familial forms of MMA.

Diagnosis is made by physical exam and medical history. Electromyography (EMG), a special recording technique that detects electrical activity in muscles, shows a loss of the nerve supply, or denervation, in the affected limb; MRI and CT scans may show muscle atrophy. People believed to have MMA should be followed by a neuromuscular disease specialist for a number of months to make certain that no signs of other motor neuron diseases develop.