Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder involving the neurons of the motor system in the brain and spinal cord. The disorder was first described by Ran in 1850. This description was then expanded in 1873 by Charcot, who emphasized the involvement of the corticospinal tracts. In the United States, ALS is often referred to as Lou Gehrig's Disease, after the famous ball player who was stricken by the disease in the midst of his career. In Europe the term Motor Neuron Disease is preferred, although this term can also be used to designate the class of disorders of which ALS is only one entity. Other disorders which fall under the category of motor neuron disease include primary lateral sclerosis, spinal muscular atrophy, and progressive bulbar palsy guide.