NERVE CONDUCTION STUDIES

A nerve conduction study (NCS) is a test commonly used to evaluate the function, especially the ability of electrical conduction, of the motor and sensory nerves of the human body. Nerve conduction velocity (NCV) is a common measurement made during this test. The term NCV often is used to mean the actual test, but this is improper use of the term since velocity is only one measurement out of the entire test.

Nerve conduction studies are used mainly for evaluation of paresthesias (numbness, tingling, burning) and/or weakness of the arms and legs. The type of study is determined by the problem. Some of the common disorders which can be diagnosed by nerve conduction studies include:

• Peripheral neuropathy
• Carpal tunnel syndrome
• Ulnar neuropathy
• Guillain-Barré syndrome

The interpretation of nerve conduction studies is complex, but in general, different pathological processes result in changes in latencies, motor and/or sensory amplitudes, or slowing of the conduction velocities to differing degrees. For example, slowing of the NCV usually indicates there is damage to the myelin. Another example, slowing across the wrist for the motor and sensory latencies of the median nerve indicates focal compression of the median nerve at the wrist, called carpal tunnel syndrome. On the other hand, slowing of all nerve conductions in more than one limb indicates generalized sick nerves, or generalized peripheral neuropathy. People with diabetes mellitus often develop generalized peripheral neuropathy.

Risks
Nerve conduction studies are very helpful to diagnose certain diseases of the nerves of the body. The test is not invasive, but can be a little painful due to the electrical shocks. However, the shocks are associated with such a low amount of electrical current that they are not dangerous to anyone. Patients with a permanent pacemaker or other such implanted stimulators such as deep brain stimulators or Spinal Cord Stimulators must tell the examiner prior to the study. This does not prevent the study, but special precautions are taken.

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