A nerve conduction velocity test measures nerve conduction velocity. In this test, an electrical stimulus is applied to a peripheral nerve and the length of time it takes for the corresponding muscle...

A nerve conduction velocity test measures nerve conduction velocity. In this test, an electrical stimulus is applied to a peripheral nerve and the length of time it takes for the corresponding muscle to contract is measured. Because the length of the nerve from stimulus point to muscle and the time it takes for the muscle to contract are both known, NCV can be calculated.

This test result is helpful in distinguishing between different types of pathologies. For example, a patient with muscle weakness is being tested by a physician. There are three possible sources of the weakness:

• Disease of the muscle itself such as
  muscular dystrophy.
  
  In this condition, normal muscle tissue is replaced by adipose tissue and the muscle becomes incapable of contraction.


• Disease at the neuromuscular junction (NMJ) such as
  myasthenia gravis
  . This condition is described in the Skeletal Muscle Histology exercise and results from damage to the acetylcholine receptors on the muscle end plate.


• Disease of the nerve such as
  Guillain-Barré syndrome
  . This condition is poorly understood, but appears to involve the immune system attacking and destroying the myelin sheath of peripheral nerves.

There are three possible outcomes of the NCV test: normal NCV and muscle contraction with repeated muscle stimulation; normal NCV but muscle becomes increasingly fatigued with repeated stimulation; and a slow NCV.

Match each potential NCV test result to its pathology and describe why you made your decision.