If you have pain, weakness, or numbness in your back, neck, or hands, measuring the speed and degree of electrical activity in your muscles and nerves can help your doctor make a proper diagnosis. This process is called electrodiagnostic testing. Two tests are commonly used: Electromyography (EMG) and Nerve Conduction Studies (NCS).
These tests can accurately determine injuries to the nerves or nerve roots, as well as diseases of the nerves and muscles. In some conditions, however, it may take several weeks for changes to become apparent. Additionally, the tests cannot determine the existence or extent of pain. A person may still feel pain or exhibit symptoms even though electrodiagnostic tests show that the nerves are functioning normally. In these cases, your orthopaedist will recommend a course of treatment for you.
Electromyography (EMG) is a diagnostic procedure that evaluates the health condition of muscles and the nerve cells that control them. These nerve cells are known as motor neurons. They transmit electrical signals that cause muscles to contract and relax. An EMG translates these signals into graphs or numbers, helping doctors to make a diagnosis. A doctor will usually order an EMG when someone is showing symptoms of a muscle or nerve disorder. These symptoms may include tingling, numbness, or unexplained weakness in the limbs. EMG results can help the doctor diagnose muscle disorders, nerve disorders, and disorders affecting the connection between nerves and muscles.
NCS are often done along with the EMG to determine if a nerve is functioning normally.The doctor conducting the test will tape wires (electrodes) to the skin in various places along the nerve pathway. Then the doctor stimulates the nerve with an electric current. As the current travels down the nerve pathway, the electrodes placed along the way capture the signal and time how fast the signal is traveling. In healthy nerves, electrical signals can travel up to 120 miles per hour. If the nerve is damaged, however, the signal will be slower and weaker. By stimulating the nerve at various places, the doctor can determine the specific site of the injury. Nerve conduction studies also may be used during treatment to test the progress being made.
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