What is the definition or description of: amyotrophic lateral sclerosis?

Neurodegenerative: ALS is a neurodegenerative disease of the upper and lower motor neurons. There is a male predominance, and occurs most frequently between the ages of 50 - 60 years. While the most frequent form has a dire prognosis, it does have several variants, with different prognoses that can be prolonged with respect to survival. The diagnosis is based on the clinical findings and robust NCV/EMG studies.