Electromyogram (EMG) And Nerve Conduction Studies: What To Think About

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What To Think About

• The levels of some enzymes in the blood, such as aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and creatine phosphokinase (CPK), may rise when muscle tissue is damaged. An electromyogram can cause higher levels of these enzymes for up to 10 days after the EMG, so blood tests for these enzymes should not be done for 5 to 10 days after an EMG.
• Special types of electromyograms (EMG) may also be done:
  • Single-fiber EMG is a special type of EMG test. For this test, very small needles are inserted into a muscle to see how a single muscle fiber contracts. It is a useful test for myasthenia gravis, a disease that affects the nerve-muscle (neuromuscular) junctions.
  • Repetitive nerve stimulation is a useful test for myasthenia gravis and Lambert-Eaton syndrome. In this test, small, repeated shocks are given to measure how the muscle reacts to repeated nerve stimulation.
  • External sphincter electromyogram measures the electrical activity of the external urinary sphincter to help find urination problems. The urinary sphincter is a ringlike band of muscles around the urethra that helps control urination. The electrical activity can be measured by skin electrodes, by needle electrodes inserted through the skin, or by electrodes in an anal plug.

Last updated:	July 29, 2008
Author:	Monica Rhodes
Reviewed By:	Anne C. Poinier, MD - Internal Medicine, Colin Chalk, MD, CM, FRCPC - Neurology
Editors:	Maria Essig, Tracy Landauer