What are the symptoms of Motor Neuron Diseases?

By  ,  National Institute of Health
Jan 07, 2013

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A brief description of the symptoms of some of the more common MNDs follows.

Amyotrophic lateral sclerosis (ALS), also called Lou Gehrig's disease or classical motor neuron disease, is a progressive, ultimately fatal disorder that eventually disrupts signals to all voluntary muscles. In the United States, doctors use the terms motor neuron disease and ALS interchangeably. Both upper and lower motor neurons are affected. Approximately 75 percent of people with classic ALS will also develop weakness and wasting of the bulbar muscles (muscles that control speech, swallowing, and chewing).


Symptoms are usually noticed first in the arms and hands, legs, or swallowing muscles. Muscle weakness and atrophy occur disproportionately on both sides of the body. Affected individuals lose strength and the ability to move their arms, legs, and body. Other symptoms include spasticity, exaggerated reflexes, muscle cramps, fasciculations, and increased problems with swallowing and forming words. Speech can become slurred or nasal. When muscles of the diaphragm and chest wall fail to function properly, individuals lose the ability to breathe without mechanical support. Although the disease does not usually impair a person's mind or personality, several recent studies suggest that some people with ALS may have alterations in cognitive functions such as problems with decision-making and memory. ALS most commonly strikes people between 40 and 60 years of age, but younger and older people also can develop the disease. Men are affected more often than women. Most cases of ALS occur sporadically, and family members of those individuals are not considered to be at increased risk for developing the disease. (There is a familial form of ALS in adults, which often results from mutation of the superoxide dismutase gene, or SOD1, located on chromosome 21.) A rare juvenile-onset form of ALS is genetic. Most individuals with ALS die from respiratory failure, usually within 3 to 5 years from the onset of symptoms. However, about 10 percent of affected individuals survive for 10 or more years.


Progressive bulbar palsy, also called progressive bulbar atrophy, involves the bulb-shaped brain stem —the region that controls lower motor neurons needed for swallowing, speaking, chewing, and other functions. Symptoms include pharyngeal muscle weakness (involved with swallowing), weak jaw and facial muscles, progressive loss of speech, and tongue muscle atrophy. Limb weakness with both lower and upper motor neuron signs is almost always evident but less prominent. Affected persons have outbursts of laughing or crying (called emotional lability). Individuals eventually become unable to eat or speak and are at increased risk of choking and aspiration pneumonia, which is caused by the passage of liquids and food through the vocal folds and into the lower airways and lungs. Stroke and myasthenia gravis each have certain symptoms that are similar to those of progressive bulbar palsy and must be ruled out prior to diagnosing this disorder. In about 25 percent of ALS cases early symptoms begin with bulbar involvement. Some 75 percent of individuals with classic ALS eventually show some bulbar involvement. Many clinicians believe that progressive bulbar palsy by itself, without evidence of abnormalities in the arms or legs, is extremely rare.


Pseudobulbar palsy, which shares many symptoms of progressive bulbar palsy, is characterized by upper motor neuron degeneration and progressive loss of the ability to speak, chew, and swallow. Progressive weakness in facial muscles leads to an expressionless face. Individuals may develop a gravelly voice and an increased gag reflex. The tongue may become immobile and unable to protrude from ...

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