http://www.merck.com/mrkshared/mmanual_home/sec6/70.jsp Section 6. Brain and Nerve Disorders Chapter 70 Peripheral Nerve Disorders Symptoms Amyotrophic lateral sclerosis is a progressive disease that begins with weakness, often in the hands, less frequently in the feet. Weakness may progress more on one side of the body than the other and generally proceeds up the arm or leg. Cramps are common as well and may precede the weakness, but sensation remains intact. Over time, in addition to increased weakness, spasticity intervenes: Muscles become tight, spasms ensue, and tremors may appear. The muscles of speech and swallowing may weaken, leading to difficulty in speaking (dysarthria) and swallowing (dysphagia). Eventually the disease may weaken the diaphragm, leading to breathing problems; some people may need a respirator to breathe. Amyotrophic lateral sclerosis is always progressive, though the rate of progression may vary. About 50 percent of people with the disease die within 3 years of the first symptoms, 10 percent live 10 years or more, and occasionally a person survives for as long as 30 years. [/url]Other Neuromuscular Junction Disorders Many drugs, certain insecticides (organophosphates), and the nerve gases used in chemical warfare can affect the neuromuscular junction. Some of these substances prevent the natural breakdown of acetylcholine after the nerve impulse has been transmitted to the muscle. Very high doses of some antibiotics can cause weakness in a similar way.