Explanation of Tests

NCV, EMG, EP, EEG

Your doctor may have ordered one or more of the following tests for you: NCV (nerve conduction velocity). Needle EMG (electromyograph), EP (evoked potential), EEG (electroencephalogram). These are diagnostic tests (not treatments) which can help determine whether any damage has occurred in nerve, muscle or brain tissue, or in the pathways leading from various organs to the brain.

General Information: Nerve cells carry tiny electrical charges which signal the muscles to contract. Special machines can measure this electricity, including how fast the signal is “conducted” along the nerve fibers and how well the muscles respond to the electrical stimulation. Evoked potential machines record the brain waves produced by electrical, visual, or auditory stimulation of the appropriate organs. If the response of the muscles is slow, or the brain waves are delayed, these tests will help your doctor to pin-point the problem and begin necessary treatment. EEG machines measure brainwave activity.

What to expect for EMG/NCV: These procedures are harmless.  We ask that you not wear lotion on your body the day of the tests.  The physician or technician will ask you some questions about medical history and present complaints.  He/ she will then ask you to lie down on an examination table or bed.  You may be asked to remove some articles of clothing, depending on the area to be tested.  In the testing room there will be one or more machines with screens which the examiner will watch as your test proceeds; he will also be listening to the clicks or static-like sounds produced by the machine.

What to expect for EEG:  You will need to arrive about ten minutes prior to your appointment time.  We ask that you do not wear hair spray, gel, mousse, ect. in your hair for this test.  You will be asked to sit in a recliner chair and the technician will place electrodes on your scalp using a gel paste.  This paste will wash out of your hair with regular shampoo.  The electrodes will monitor your brainwave activity.

Nerve Conduction Velocity (NCV): This test measures how fast the nerve impulse travels along the nerve. Electrodes will be taped to your skin and you will feel tiny electrical shocks which may make your arm or leg “jump.” These will be slightly uncomfortable, but are not usually painful, and they are very brief. They have been compared to the “shock” you feel on a cold day when you walk across a carpet and touch a metal object.

With the Needle EMG Test we are studying how your muscles react to your commands. The doctor will cleanse your skin and insert a very fine, flexible needle directly into the affected muscles. The insertion of the needle is ordinarily not very painful, but may feel quite uncomfortable, depending upon the sensitivity of the area being tested. This part of the test is usually brief also.

Evoked Potential Tests: These are generally painless, although they take longer to perform than either the NCV or EMG. Electrodes will be attached to your scalp with electrode paste, and you will either lie on a bed or sit in a chair as you listen to clicks (Brainstem Auditory Evoked Potential, BAEP), watch a changing pattern on a TV screen (Visual Evoked Potential, VEP), or receive small electrical charges on your arms or legs (Somato-sensory Evoked Potential, SEP). These tests may require one hour or more to complete.

With the EEG Test we are recording brain waves. Electrodes are attached to the scalp with an adhesive agent, and you are asked to relax and even sleep. This test is painless.

Importance of Relaxation: The best advice your doctor can give you during these tests is to try to relax. Make yourself think of something else, breathe regularly and deeply, and let your muscles relax. If you are tense and your muscles are taut, the tests will take longer and be more difficult for both you and your examiner.

Report of Findings: The information obtained from the tests performed in the Electrodiagnostic Laboratory will be analyzed and sent to your doctor. He will explain to you the results as they apply in your particular case.

Other Questions: If you have any further questions regarding the tests or other matters, make a note of them and someone will attempt to answer them during your visit. If you cannot keep the appointment arranged for you, please call our office between 8:30 and 4:30, Monday through Friday, to reschedule your tests.

Parking and Directions: We are located on the 7th floor of Jackson Hospital Goode Building.  A cross-walk on the 4th floor of the parking deck to our office, Suite 700.