Muscle cramps are a common complaint encountered by both neurologists and primary care physicians. In more recent studies of elderly outpatients, the prevalence of cramps was 35–60%. Forty percent reported having cramps more than three times per week. The prevalence of “true” muscle cramps was reported to be 95% in a group of young students recently enrolled in an exercise class. The word “cramp” is most likely derived from “cram”, whose old High German and Norse roots suggest squeezing, pressing uncomfortably. Cramps are characterized by a sudden, painful, involuntary contraction of the muscle, lasting from seconds to minutes, often with a palpable hard knot in the affected muscle. This painful muscle contraction, associated with electrical activity, is termed a “true cramp”. Several studies suggest that cramps arise from spontaneous discharges of the motor nerves, not from the muscle itself and must be distinguished from other muscle pain or spasm.
True muscle cramps occur also in disease of the lower motor neuron; in certain metabolic disorders; following acute extracellular volume depletion, inherited syndromes; as a side-effect of medications; and in many patients – especially the elderly, for unknown reasons.
Medical history, physical examination, and a limited laboratory screen help to determine the various causes of muscle cramps. Treatment options are guided both by experience and by a number of therapeutic trials. Quinine sulfate is an effective medication, but the side-effect profile is worrisome, and other membrane-stabilizing drugs are probably just as effective.