Nerve Conduction Studies (NCS) are often done at the same time as an electromyogram (EMG) to diagnose neurological diseases. An EMG measures the electrical activity of muscles at rest and during contraction. NCS measures how well and how fast the nerves can send electrical signals.
Peripheral Nerves exit spinal cord and control the muscles in the body with electrical signals. These electrical signals produce impulses and make the muscles react in specific ways. Nerve and muscle problems can cause the muscles to react in abnormal ways.
If you have pain, numbness, tingling, burning or weakness in the arms or legs your doctor may conduct these tests to find out what nerves are involved. These tests check to see how well your spinal cord, nerve roots, nerves and muscles that control your legs, are working.
In this test, electrodes are attached to your skin with tape or a paste. A shock-emitting electrode is placed directly over the nerve, and a recording electrode is placed over the muscles controlled by that nerve. Several electrical pulses are sent to the nerve, and the time it takes for the muscle to contract in response to the electrical pulse is recorded. The speed of the response is called the “conduction velocity.” There are established norms and conduction speeds for each nerve in the body. The results from your test are compared to these norms to help determine if there any nerve conduction abnormalities.
Reduced conduction velocities in a nerve may indicate a nerve injury. PLEASE NOTE: Conduction speeds generally get slower with age.
A Motor NCS is performed on the motor portion of the nerve while a Sensory NCS is performed on the sensory portion of the peripheral nerve.
Nerve conduction studies are done before an EMG – if both tests are being done. Nerve conduction tests may take from 15 minutes to 1 hour or more, depending on how many nerves and muscles are being studied.
The results of the test are used as an aid for the doctor in his/her approach to formulate a thorough and comprehensive treatment plan.
The nerve conduction velocity tests can be used to detect true nerve disorders like peripheral neuropathy or conditions whereby nerves are affected by mechanical compression injury carpal tunnel or nerve entrapments.