Amyotrophic lateral sclerosis (ALS) is a debilitating neurodegenerative disorder characterized by a progressive loss of motor function. ALS affects upper motor neurons and lower motor neurons. As these motor neurons stop working, muscles also begin to atrophy; this can eventually lead to respiratory failure, which is often the cause of death in ALS patients. The pathophysiology of ALS is not completely understood, but similar to other neurodegenerative diseases like Alzheimer's disease it is characterized by clusters of dysfunctional proteins within neurons. In this video, I discuss ALS symptoms and pathophysiology.