Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s Disease or motor neuron disease, is a rare, progressive, group of neurological diseases that impact the nerve cells (neurons) responsible for controlling voluntary muscle movement (e.g. muscles involved in swallowing, walking, etc.). The affected motor neurons in ALS can be divided into upper and lower motor neurons. Upper motor neurons are neurons sending messages from the brain to spinal cord and lower motor neurons are neurons sending messages from the spinal cord to particular muscles. The muscles progressively weaken as these neurons deteriorate (degenerate) and die resulting in the brain’s inability to communicate with muscles.
ALS can be classified as sporadic or familial (inherited). Sporadic causes of ALS can be subclassified into 4 groups: classical ALS, primary lateral sclerosis (PLS), progressive bulbar palsy (PBP), and progressive muscular atrophy (PMA). Although the causes of ALS are not completely understood, multiple complex factors may contribute to the degeneration of motor neurons. Researchers over the years found several genetic mutations and cellular defects that may play a role in motor neuron degeneration. Environmental factors such as exposure to toxins or infectious agents, viruses, physical trauma, diet, military service, and occupational factors may also be involved in the development of ALS.