Nerve Conduction Studies (NCS)
What are Nerve Conduction Studies?
Nerves control the muscles in the body by sending electrical signals called impulses. These impulses make the muscles react in specific ways. When nerve and muscle disorders are present, the disorders cause the muscles to react in abnormal ways.
Nerve conduction studies measure how well and how fast nerves send electrical signals to the muscles.
Nerve conduction studies are often performed along with an electromyogram or EMG study to provide more in-depth information to the physician.
Why are Nerve Conduction Studies Performed?
Nerve conduction studies are performed to:
Assess disorders of the peripheral nervous system which includes the nerves that lead away from the brain and spinal cord and the smaller nerves that branch off from those nerves. Nerve conduction studies are often used to help diagnose nerve disorders such as pinched nerves, carpal tunnel syndrome or Guillain-Barr syndrome.
Procedure for Nerve Conduction Studies
In this test, several flat metal disc electrodes are attached to your skin with tape or a special paste. A shock-emitting electrode is placed directly over the nerve and a recording electrode is placed over the muscles under control of that nerve. Several quick electrical pulses are sent to the nerve. The time it takes for the muscle to contract in response to the electrical pulse is then recorded. The speed of muscle contraction response is called the conduction velocity.
Nerve conduction studies are done before an EMG if both tests are being performed. Nerve conduction tests may take from 15 minutes to 1 hour or more, depending on how many nerves and muscles are studied.
There are no risks associated with nerve conduction studies. Since it is a non-invasive procedure, there is no chance of infection. The voltage associated with the electrical pulses is not high enough to cause an injury.