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 may be misleading, since velocity is only one measurement in the test suite.
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 required is dependent in part by the symptoms presented. A physical exam and thorough history also help to direct the investigation.
Some of the common disorders that can be diagnosed by nerve conduction studies are:
• Peripheral neuropathy
• Carpal tunnel syndrome
• Ulnar neuropathy
• Guillain-Barré syndrome
• Facioscapulohumeral muscular dystrophy
• Spinal disc herniation
• Cubital Tunnel Syndrome
• Tarsal Tunnel Syndrome
• Guyon Canal Syndrome
• Peroneal neuropathy
INTERPRETATION OF NERVE CONDUCTIONS
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 diseased nerves, or generalized peripheral neuropathy. People with diabetes mellitus often develop generalized peripheral neuropathy.