If a neuron dies, the nerve fiber dies, and ultimately the muscle cell will atrophy. The rate and location of neuron death varies. Both types of neurons are eventually destroyed in ALS, but the course of their destruction may vary. Therefore, the patient may have stiffness in some muscles and paralysis in others. The disease, however, will continue to progress until all motor neurons are involved and the patient is totally paralyzed.
Most patients die as a result of respiratory failure.
To date, research has identified a gene abnormality in 20 percent of those with the FALS form. The incidence of ALS is 1.5 per 100,000, and the prevalence is 4 to 5 per 100,000. Over 25 percent live 10 years with the disease, and another 15 percent survive longer than 15 to 20 years. No significant progress in understanding the pathogenesis of ALS occurred until the 1990s. In recent years, new insights from research have brought potential new drugs to clinical trial.