Muscle pain and cramps are neuromuscular symptoms of diverse etiology. When these symptoms are associated with exercise, a biochemical defect in glycolytic or lipid metabolism, a mitochondrial myopathy, or defect in muscle contraction is frequently suspected. Diagnosis is usually established when such defect is demonstrated histochemically or by NMR. In some neuromuscular disorders, these symptoms may not necessarily be induced by exercise and they are usually part of a wide constellation of symptoms. Some of them are distinct enough to be recognized clinically or electrophysiologically, as in peripheral neuropathies, myotonias, or syndromes of continuous muscle activity. However, despite modern histochemical techniques, a number of muscle disorders remain, characterized primarily by muscle pain and cramps, where light microscopy or electrophysiologic studies show either normal or nonspecific findings.
Polysomnography in idiopathic muscle pain syndrome (fibrositis)