Electromyogram (EMG)

The Electromyogram (EMG) is a test that is done to measure changes in nerve function, which may be negatively affected by long-term compression or irritation of the nerve root. The peripheral nerves, which supply information to the muscles, skin, and organs of our body, arise from the nerve roots that exit through the sides of the spine. The nerves of the body are part of the central nervous in our spine, and they become part of the peripheral nervous system after the exit the spine, though the openings known as the intervertebral foramina.

The nerves may become constricted where they exit the spine through these openings, or they may become constricted as they pass through the body, due to muscle tension or systemic diseases. When the nerves become irritated or constricted for short periods of time, the electrical signals that pass through them may remain normal. When these nerves become damages for longer periods of time, the electrical signal conduction may become abnormal. Examples of abnormal electrical activity include muscle weakness and the loss of feeling in the affected section of the body supplied by that nerve. The size of the muscle on that side of the body may diminish as the muscle atrophies.



The affects of these changes in the functioning of that nerve may become permanent if the cause of the nerve compression is not treated. The Electromyogram (EMG) is one type of electrodiagnostic test that may be performed to confirm the diagnosis of nerve compression. This test may tell doctors a lot about the physical state of individual nerves and their level of functioning, but they will not indicate why that nerve has become injured. For that, additional tests may be done.

Electromyogram (EMG): there are two types of electrodiagnostic tests that may be performed when patients complain of pain that radiates down one or both legs. One such test is called a Nerve Conduction Velocity (NCV) study. With this study, various electrodes are connected to sensor pads that stick to the foot and leg. The speed of the nerve signals are measured from one electrode to the other, to compare those signal velocities to ones that would occur in a normal patient. The speed of conditioning will be diminished in nerves that have become irritated or compressed for more than 1 week's time.

The EMG test, involves the placement of needles through the skin and directly into the muscles. This test measures the signal strength of the muscles as the patient flexes and relaxes them. This is one of the most painful tests associated with back pain diagnostics, but it is one that doctors consider to be important enough that its diagnostic quality outweighs the temporary side effects (pain).

When the nerves become injured for a period of 1 week or longer, abnormalities may occur in them that present as back pain, radiculopathy, or other neurologic impairments. The electrical signal activity in these nerves may change. These nerve changes become more likely to become permanent the longer the nerve has become damaged. Due to the nerve damage, the number of nerve fibers supplying that muscle diminishes. If the cause of the nerve compression is removed, the functioning of that nerve may or may not return to normal, depending on how long it was affected. This EMG test will be performed to measure the changes in the nerve function, as measured by the amount of electrical activity in that nerve when the patient activates it by flexing the muscles supplied by that nerve. This diagnostic procedure may last for up to 60 minutes, which is a long period of time to have needles threaded directly into the belly of your muscles.

tests don't tell doctors what the cause of the back pain or leg pain is, but they help to identify the location of the nerve damage. Nerve Conduction Velocity studies differentiates between peripheral nerve disorders and spinal cord problems. When doctors are able to identify the exact location of nerve damage, it helps them in later surgical procedures, such as spine surgery and therapeutic injections.

An Electromyogram (EMG) study is also known as Electromyography. Degenerative changes to the muscles which may be represented by this test as decreases in the action potential amplitude and the duration of the action potentials. These action potentials will be created by the muscles as the patient attempts to flex them with as much force as they can.