Unfortunately the most common motor neuron disease, amyotrophic lateral sclerosis,is the most severe. It begins at 40 to 70 years of age with men outnumbering women. Initially there may be focal weakness and atrophy in a limb, such as a shoulder or leg (foot drop), which subsequently spreads and becomes bilateral. Other patients may first have dysarthria, hoarseness, or impaired swallowing (bulbar ALS).