AMYOTROPHIC LATERAL SCLEROSIS

(ALS) also called Lou Gehrig's Disease, degenerative nervous-system disorder that causes muscle wasting and paralysis. The disease usually occurs after age 40, more often in men than in women; prognosis is gravealmost always negativeand victims usually die within two to five years. ALS affects the motor neuronsi.e., those neurons that control muscular movements. The muscles innervated by the degenerating neurons become weak and eventually atrophy. The disease has an insidious onset. The early signs are usually weakness of the hands, along with muscle atrophy. The muscular weakness and atrophy slowly creep up the forearms to the shoulders. The lower limbs also become weak and spastic. Fibrillation (rapid twitching) is almost always present. Weakness and spasticity may be present for months before actual atrophy is evident. Death generally results from atrophy of the respiratory muscles. A variety of ALS in which the neuron degeneration is most pronounced in the spinal cord is termed progressive muscular atrophy. Its symptoms are similar to the above, except that, instead of spasticity in the feet and legs, atrophy and weakness may be present. Victims of progressive muscular atrophy generally survive longer than those suffering from classic ALS. In progressive bulbar palsya variety of ALS in which the degeneration is centred on the neurons of the cranial nerves and brainstemchewing, talking, and swallowing are difficult. Often there are involuntary outbursts of laughing and crying; tongue fibrillation and atrophy are common. The prognosis is especially bleak in this form of ALS, with death commonly occurring within one to three years of onset. About 510 percent of cases of ALS are the result of genetic inheritance. In 1993 researchers discovered the defective gene responsible for the hereditary form of ALS. The gene produces the enzyme superoxide dismutase, which eliminates free radicals from the body's cells. Free radicals are molecular by-products of normal cell metabolism that can destroy cells if allowed to accumulate in them. In persons with the defective version of this gene, the superoxide dismutase produced is somehow ineffective in neutralizing free radicals, which go on to selectively destroy motor neurons. The discovery of the mutated gene enabled genetic screening to determine potential carriers in families with a history of ALS.