Definition: an electromyogram (EMG) looks at the function of the nerve roots that leave the spinal column.
This is done by observing how electrical currents are transmitted from the nerves to the muscles.
The pressure on the nerves or damage to them, changes the way in which the electrical current is transmitted by the muscles, as they react on the information that is sent to them from the brain by the nerves.
By ordering this test to diagnose problems in the spine, it is combined with a test that shows the electrical signals that go from the body to the brain.
Why is it done?
In search of abnormal electrical signals in the muscles, the EMG can tell your doctor if a nerve is irritated or pinched.
For example, if a bulb is placed on the lamp and illuminated, it can be assumed that the wiring is OK, but if the bulb does not turn on you might consider that something is probably wrong with the wiring.
The EMG is able to determine the state of the nerves that innervate the muscles, which is why your doctor may consider that these should be found pinching or compressing somewhere.
How is an Electromyogram done?
Small electrodes are inserted into the muscles of the legs, where the nerve that goes to each muscle is stimulated to then observe how long it takes the electrical signal to reach the muscle and cause it to contract. The procedure takes about 2 to 3 hours to complete.
What are the limitations?
An Electromyogram does not show the reason why there is a problem with the nerves in the spine or what is causing it. The test mainly looks at how your muscles are reacting to the nerve problem, including determining that they can not be in the same place.
Another limitation of the EMG is that the result of the test may be normal when the nerve is actually damaged. This is called a “false positive”, that is, the results of the tests look positive even though the nerve is actually negative.
What are the risks?
There are few risks associated with an Electromyogram test . Every time a needle is inserted in its day there is a small possibility of infection. However, it is practically non-existent in a test like this.