Motor Neuron Diseases

The motor neuron disorders are a clinically diverse group of diseases that share a pathologic loss of the motor neurons. The most common adult-onset disorder is amyotrophic lateral sclerosis (ALS). Other forms include the spinal muscular atrophies, infectious motor neuronopathies, and rare focal forms of anterior horn cell loss.Overall, the incidence rate of ALS is believed to be 1.5 to 2.0 cases per 100,000 person-years, and the prevalence rate is 4 to 6 cases per 100,000 population. Other than in sparsely populated geographic clusters (eg, Guam and the Kii Peninsula of Japan), the incidence rate seems consistent across ethnic and geographic boundaries.