Lou Gehrig's disease, clinically known as amyotrophic lateral sclerosis, is a progressive neurodegenerative disorder of the motor neurons resulting in the loss of muscle function. Lou Gehrig's disease is characterized by the deterioration of motor neurons, which initiate voluntary muscle contractions in the brain and allow muscle movement and locomotion, explains the ALS Society. The progressive deterioration of motor neurons inhibits the ability of the brain to send neural impulses to muscle fibers and initiate movement. This progressive degeneration of motor neurons leads first to muscle weakness, then to paralysis, and then to atrophy of the chest muscles, resulting in respiratory failure and eventually death for most. ALS is the most severe, debilitating motor neuron disease, but there are several others.
Primary Lateral Sclerosis
Primary lateral sclerosis is a progressive neurodegenerative disease affecting the upper motor neurons in the brain. This disease is characterized by progressive, involuntary muscle tension and spasms as a result of the deterioration of upper motor neurons, which control the activity of the lower motor neurons, according to the ALS Society of Canada. Primary lateral sclerosis usually affects the lower extremities first, resulting in stiffness and pain due to diminished motor neuron function. As the disease progresses, individuals experience clumsiness, lower back and neck pain and loss of balance due to spasticity in the legs, which also produces slowness and stiffness of movement.
Progressive Bulbar Palsy
Progressive bulbar palsy, also known as progressive bulbar atrophy, is a progressive neurodegenerative disease that involves the brain stem--the region of the brain that regulates lower motor neurons needed for speaking, swallowing and other functions, the National Institute of Neurological Disorders and Strokes explains. The degeneration of the lower motor neurons within the brain stem leads to progressive loss of speech, tongue muscle atrophy, difficulty swallowing and muscle weakness, as well as limb weakness. About 75 percent of patients with classic Lou Gehrig's disease eventually show disease involvement in the brain stem and about 25 percent of initially show symptoms characteristic of bulbar involvement.
Spinal Muscular Atrophy
Spinal muscular atrophy is a group of motor neuron diseases that lead to progressive muscle degeneration, weakness and eventually death, as the muscles of the chest atrophy, resulting in respiratory failure, according to the University of Maryland Medical Center. Spinal muscular atrophy is the second leading cause of neuromuscular disorders, and it affects four out of every 100,000 people. Type 1 spinal muscular atrophy, also known as Werdnig-Hoffman disease, is the most severe form of the disease. Infants born with type 1 spinal muscular atrophy often have very little muscle tone, breathing problems and corresponding muscle weakness. Symptoms commonly include a loss of muscle tone resulting in poor posture, an increase of respiratory infections, and nasal speech.
