Exercise effect on creatine phosphokinase elevation in motor neuron disease.
Creatine phosphokinase (CPK) is usually elevated in inflammatory and degenerative muscle disease but is usually reported as normal in neuropathic diseases. A review of the literature indicates, however, that it is elevated in 50 to 75% of patients who have motor neuron diseases, and that these elevations are usually 5 to 6 times normal. The effect of bedrest and moderate exercise on serial CPK values in a patient with motor neuron disease is assessed. Bedrest for 24 hours decreased his CPK to 0.58 of the baseline value; 5 hours following moderate exercise it increased to 1.71 of the basal value. This phenomenon appears to be a response to exercise stimuli rather than to the disease process itself. CPK values up O 1000 IU/L are compatible with the diagnosis of amyotrophic lateral sclerosis (ALS). In patients whose CPK values seem atypical, it is best to have them rest 48 hours before repeating the test.