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EEG/EMG/Evoked Potential Lab

Nerve Conduction Studies and Electromyography (EMG)

What are nerve conduction studies and EMGS?
You have been referred to the Neurophysiology Laboratory for evaluation of a possible nerve or muscle disorder associated with complaints of numbness, pain, abnormal sensations, weakness, fatigue or cramps. The studies to be conducted will record electrical signals from nerves and muscles to help the physician arrive at a diagnosis. There are two main procedures: Nerve Conduction Studies and Electromyography.
  • Nerve conduction studies:
    In these studies, nerves are stimulated over the skin by brief electrical stimuli and the responses are recorded using small electrodes placed on the skin. These stimuli will cause a momentary tingling sensation and may cause a muscle supplied by the nerve to twitch. The strength of the stimuli applied will be varied but they generally cause only mild momentary discomfort. The responses provide information about how well nerve impulses are conducted along the nerve.


  • Electromyography (EMG):
    Electrical signals are generated from muscles in the EMG studies by inserting a fine needle electrode directly into selected muscles. The signals, displayed on a screen and audible through a loudspeaker, are recorded from muscle at rest and with muscle contraction. No electrical shocks are applied in the study. EMG is well tolerated by most patients. The fine needle causes only momentary discomfort on insertion; generally less than a needle stick to draw blood.
What preparation is involved?
There is no preparation involved for Nerve Conduction Studies or EMG. You should eat normally and take your usual medication. There is no need to restrict your activities before or after the test.

Avoid applying lotions or ointments to the skin prior to the study.

If you are taking blood-thinning medications, such as Coumadin, or have a bleeding disorder, please inform the examining physician. It may not be advisable to have an EMG, although Nerve Conduction Studies are permissible.

If you are referred for a diagnosis of Myasthenia Gravis, your physician may have to temporarily stop a drug called Mestinon to avoid interfering with the studies.

If you have a cardiac pacemaker or defibrillator, inform the examining physician, as certain precautions will be required in performing Nerve Conduction Studies.

In general, the study will take about 30 minutes, although a complicated study may exceed an hour. A mild bruise may occur infrequently with EMG examination. The study should not cause any permanent after-affects.

Registration for the tests:
You will need to register approximately 15 minutes prior to your appointment time in Neurophysiology Lab, located on the third floor of the East Medical Building. You should check with your insurance company in advance as to whether you need a referral from your primary care doctor, in order to ensure that the costs of the test(s) will be covered.

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St. Luke's Hospital - 232 South Woods Mill Road - Chesterfield, MO 63017 Main Number: 314-434-1500 Emergency Dept: 314-205-6990 Patient Billing: 888-924-9200
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