Muscle spasm as a cause of somatic pain.

Pains which seem predominantly to affect the muscles are extremely common and many hypotheses regarding their genesis have been developed, but most of them have lost support in time. The concept of "fibrositis", so popular 20 years ago, is now almost universally suspect, and few would claim that any sound basis for it has been discovered. But the destruction of a hypothesis, such as "fibrositis", does not eradicate the condition it was designed to explain. As has often been pointed out in discussion: "the pain is very real". Other theories are still current and should undergo the same critical treatment as did "fibrositis". For example, it is frequently suggested that muscle spasm is the cause of pain in a variety of disorders ranging from prolapsed intervertebral disk (Rose, 1954) to psychoneurosis (Holmes and Wolff, 1952). It is such common knowledge that a sustained muscular contraction can be painful that it is not surprising that an involuntary muscular contraction -a muscle spasm-should be invoked as a cause of pain in disease. Indeed, this idea has led to the therapeutic use of muscle relaxants, such as d-tubocurarine (Schlesinger, 1946) and myanesin (Schlesinger, Drew, and Wood, 1948), but the results have not been very impressive. It is important to examine the evidence on which the concept of muscular spasm as a common cause of pain is based. There is, of course, the clinical observation that some painful muscles are both tender and firm to the touch. Such observations may well be misleading and there have been many attempts to prove the existence of the postulated muscular spasm by instrumental methods. Of these, electrical devices, as in electromyography, have been chiefly used, and one of the most frequently quoted contributions is that of Elliott (1944a). Elliott examined the electrical activity in muscles of fourteen patients who were later proved surgically to be suffering from prolapsed intervertebral disks. He inserted needle electrodes and