(NCV) Nerve Conduction Studies and (EMG) Electromyography
An Electromyography (EMG) and Nerve Conduction Study (NCV) are complementary electro diagnostic tests that, if possible, should be performed at the same appointment.
(NCV)
A NCV is a test that measures the ability of a specific nerve to transmit an electrical signal. The NCV test is performed by placing electrodes on the surface of the skin over a specific muscle that is predominate innervated by one or two nerve roots. Then the nerve is stimulated with a small electrical charge, similar to the static electrical shock you may get from walking across a carpet. The electrical stimulation moves along the nerve and is measured at the electrodes. The speed and the amplitude are recorded and help determine if the nerve is compressed, diseased, or non-functioning. The test is performed for motor (muscle) nerves as well as sensory (nerves that give sensation like numbness, burning, cold, etc...) nerves. If muscle weakness is caused by a muscular disease, the nerve conduction speed remains normal. If a muscle weakness is caused by a neurological disease or nerve compression, the nerve conduction speed is usually slowed. If a sensory nerve is caused by a disease process it maybe
small in amplitude or non-existent. The findings should be correlated with an EMG and a neurological interpretation.
(EMG)
An EMG is an electro diagnostic test performed by neurologists. This test measures the electrical activity of the specific muscle being tested. This test is performed with very fine needles (close to the diameter of your eyelash) placed into a muscle and records the electrical activity your body produces in that muscle. No external electricity is used. The neurologist views the activity of the muscle on the computer screen as well as listens to the activity on the computer speakers. A normal resting muscle is quit and displays no electrical activity. An active or contracting muscle produces electrical activity that increases as the muscle contraction increases. Abnormal or absent electrical activity in a muscle is an indication of peripheral nerve disease or spinal motor neuron disease.
By utilizing a NCV study and an EMG study the neurologist can better detect the existence, the extent, and the location of a disease process (i.e. muscular dystrophy or amytrophic lateral sclerosis) or nerve injury.
How to Prepare for Your Test
Please bathe the day of your appointment, if possible. This helps to remove your body's natural oils and makes the test easier for you and the technician.
Do not apply oils or lotions to your skin the day of your test. These make testing more difficult for the technician and you, because they make the skin less conductive.
Do not wear tight fitting clothes.
If you are having testing on your hands, wrists, or arms, please wear a loose top that will allow the sleeve to be pulled up to the top of your arm. If you forget we will have a gown for your convenience.
If you are having testing on your feet or legs, please wear loose fitting shorts or pants that will allow the pant legs to be pulled up 3 or 4 inches above the knees. If you forget we will have a gown or disposable shorts for your convenience.