Nerve Conduction Studies(NCS)/Electromyographic Studies(EMG)

What are NCS/EMG studies?

An electromyogram (EMG) measures the electrical activity of muscles at rest and during contraction. Nerve conduction studies measure how well and how fast the nerves can send electrical signals.


Nerve conduction study (NCS)

There are several types of nerves but generally speaking, the two major types are motor and sensory nerves. Motor nerves carry signals from the brain to the muscle to enable contraction and movement, and sensory nerves relay information to the brain. When the nerve is stimulated with metal electrodes (metallic patch/es that can conduct signals), a response can be measured by surface (on the skin) electrodes some distance away in sensory nerves overlying the nerve itself. For the motor nerves, the response is usually detected over the muscle that is activated by that nerve. In this fashion, results can reveal information about the size and speed of the electrically conducted impulse. The size usually reveals the number of nerve fibres present and the speed, the integrity of the myelin (insulating membrane around the nerve 'axon' or cable). This is why the word 'conduction' is used.

Electromyogram (EMG)

The second part of this test is an EMG, which studies your muscles. First, a small metal disc (about the size of a fifty-cent piece) will be taped to your skin. Then, the EMG doctor will insert a small needle into your muscle in order to record your muscle’s electrical activity. EMG testing may be done on several different muscles but each muscle is tested one at a time. During the test, you will hear a crackling speaker sound. This is the electrical activity from your muscles, which has been changed into sound waves.
You do not receive any electrical stimulation for this part of the test.
The EMG can be somewhat uncomfortable because of the small needle sticks.
For a day or two after the test, you may feel some tenderness or notice a small bruise around the sites where the needle was inserted.

The tests focus on the somatic nerves, these nerve fibres transmit sensations and control muscles.


Info on the nervous system
The central nervous system is made up of the spinal cord and brain.
The spinal cord runs from the base of the brain down the middle of the back and ends just above the waist. It is made up of nerve cells (neurons) and long nerve fibers called axons that relay all incoming information from the rest of the body to the brain and all outgoing information from the brain to the rest of the body.
Unlike the nerves of the peripheral nervous system, those in the central nervous system do not regenerate once they have been injured. So when the spinal cord is injured, a patient will suffer varying degrees of paralysis if these axons become destroyed.

The test can identify potential for recovery, identify recovery already taken place and establish an opinion on what is less likely to recover.

Here is some further reading for those who like the technical info...my intention was to read it, understand it and the translate into easy understanding but its complex and can't really be explained any better than this:
jnnp.bmj.com/content/76/suppl_2/ii32.full