An electromyogram (EMG) gauges the electrical activity of muscles at rest and during contraction. Nerve conduction studies (NCS) measure how well and how fast the nerves can send electrical signals.
The nervous system is a complex, sophisticated system that regulates and coordinates body activities. It is made up of two major divisions including the central nervous system; which is the brain and spinal cord, and the peripheral nervous system; which are all other neural elements. The brain sends out signals through electrical signals—called impulses—that control the muscles of the body. Unfortunately, nerve and muscle problems cause the muscles to react in abnormal ways.
The purpose of EMG/NCS is to localize where your symptoms are coming from. That can be pain, any kind of numbness and tingling, as well as weakness and the test is also good at assessing the severity of your symptoms. Typically, these studies are ordered when a patient is having some type of nerve symptom such as pain, numbness and tingling or a burning sensation, as well as any type of weakness where a person can feel a change in muscle strength.
An EMG is performed for two primary reasons. Firstly, it can be used to locate diseases that damage muscle tissue, nerves, or the junctions between the two. These problems may include a herniated disc, amyotrophic lateral sclerosis (ALS), or myasthenia gravis (MG). Secondly, it can be used to detect the origin of weakness, paralysis, or muscle twitching. Problems in a muscle, the nerves supplying a muscle, the spinal cord, or the area of the brain controlling a muscle can all be the source of these symptoms. However, the EMG does not show brain or spinal cord diseases.
EMG is a simple outpatient procedure taking no more than an hour. A needle electrode attached by wires to a recording machine is inserted into a muscle. Then, the electrical activity in that muscle is recorded while the muscle is at rest. Next, you will be asked to contract the muscle slowly and steadily. This electrical activity is recorded. You may have electrical activity recorded in many locations.
NERVE CONDUCTION STUDIES (NCS)
A Nerve conduction Study is performed in order to isolate damage to the peripheral nervous system, which includes all the nerves leading away from the brain and spinal cord, as well as the smaller nerves branching out from those nerves.
NCS is also a simple outpatient procedure taking no more than an hour or could take as little as 15 minutes. If you are having both tests completed, Nerve conduction studies will be completed first. In this test, several flat metal discs are attached to your skin using tape. A shock-emitting electrode is placed directly over the nerve, and a recording electrode is placed over the muscles controlled by that nerve. Several quick electrical pulses are given to the nerve, and the time it takes for the muscle to contract in reply is recorded.
Both tests are valuable techniques for diagnosing nerve damage. If damage exists, these can help define the source of the damage and can assist in guiding treatments.