Stiffness, Cramps and Twitching Neuromuscular diseases can cause a variety of symptoms other than muscle weakness. Not all of these symptoms are painful, but some can be inconvenient or annoying. Learning the medical names and natures of these symptoms can lead to better discourse between you and your doctor, and sometimes better management of symptoms. The classic muscle cramp is neural in origin, meaning the contractions are caused by abnormal nerve activity rather than abnormal muscle activity. This type of contraction problem usually has a sudden onset and may be ended by stretching the muscle passively.
True cramps can occur in anyone, particularly after exercise or at night.
A second kind of cramp, which doesn't involve abnormal nerve activity, occurs when a muscle is temporarily locked in a contracted state. This sensation can be painful and is often described as a cramp. Like classic cramps, fasciculations are caused by abnormal nerve activity, but they tend to involve only a small portion of the affected muscle and aren't generally painful. Neurologist Valerie Cwik of the University of Arizona Health Sciences Center in Tucson says that everyone gets fasciculations now and then, particularly around the eye, in the small muscle of the back of the hand between the thumb and index finger, and in the feet. Fasciculations are made worse by stress, lack of sleep and caffeine.