CPK (creatine phosphokinase )is used to measure muscle damage. It must be broken down to isoenzymes to differentiate it from skeletal, brain, and heart involvement. If you had a fall, it would be elevated. If you had and heart attack it would also be elevated, so isoenzymes are a must. In neuro, it is used to see if you are having muscle breakdown caused by any of many diseases that cause atrophy and myositis. It is also useful in siezure, stroke, brain injury diagnoses.

CPK is a test that is repeated to show a trend in the progression of a problem.

Here is a link:
http://www.nlm.nih.gov/medlineplus/e...cle/003504.htm