Electromyography | EMG | Electromyogram | Electromyograph


Electromyography Definition

Electromyography (EMG) is a medical procedure for measuring the responses of muscle to nervous stimulation.

The instrument used to perform electromyography is called an electromyograph, which produces a record called an electromyogram.

An electromyograph detects the electrical potential generated by muscle cells when these cells contract.

Benefits Of Electromyography

Electromyography can help to distinguish primary muscle conditions from muscle weakness caused by neurologic disorders including muscular dystrophy, inflammation of muscles, peripheral nerve damage (damage to nerves in the arms and legs), strained nerves, myasthenia gravis, amyotrophic lateral sclerosis (ALS), disc herniation, and others.

Electromyography can be used to differentiate between true weakness and reduced use due to pain or lack of motivation. It is helpful in finding the causes of weakness, involuntary twitching, paralysis, and abnormal levels of muscle enzymes.

Neuromuscular disorders such as Motor Neurone Disease, neuropathy, nerve damage and muscle damage can be diagnosed with the help of Electromyography. Electromyography is also used in biofeedback studies and training.

Electromyography training is a kind of biofeedback in which patients study to control muscle tension in the face, neck, and shoulders. For example, such training is sometimes given to migraine patient.

Types Of Electromyography

There are two types of Electromyography: the surface EMG and the intramuscular EMG Intramuscular EMG involves inserting a needle electrode through the skin into the muscle whose electrical activity is to be measured. .

Surface EMG (SEMG) involves placing the electrodes on the skin overlying the muscle to detect the electrical activity of the muscle. In both types of Electromyography, the electrical activity is displayed visually on an oscilloscope and may also be displayed audibly through a microphone.

Electromyography Test

The electrical activity in nerves and muscles can be measured with electromyography. This test is helpful to determine if abnormalities exist in the way nerves transmit electrical impulses or abnormalities to the muscles themselves. 

The Electromyography test consists of two parts:

  • Electromyography study which looks at electrical activity in muscles at rest and also when they are tensed up or contracted (if possible) to determine if the pattern of activity is normal
  • Nerve Conduction Study / NCS which evaluates the speed and amount of electrical activity along a nerve

You can get the information about the integrity of the muscles and the nerves in your body with the help of electromyography. An Electromyography examination is typically ordered by a physician to evaluate for muscle or nerve damage as part of a medical workup.

Using a monitor, amplifier, loudspeaker, computer, stimulator and high tech filters the examiner actually sees and hears how your muscles and nerves are working.

As part of the Electromyography a very small needle is inserted into different muscles in the arm, leg, neck or back where you are having symptoms. In many cases the examination will include areas far from where you are having symptoms because nerves can be very long.

In each test, a new clean new needle is used, and the needle is thrown out after the test is complete. There is virtually no chance to catch any diseases from having an Electromyography.

Also, the chance of infection is minimal, because the needle used is sterilized. An Electromyography is only one part of nerve testing; another part is called the nerve conduction study.

The examining physician must analyze the data and combine all the information into a report after Electromyography testing. The electro diagnostic examination report will be added to your medical record and a copy sent to the referring physician. Be sure to follow up with your health care provider.


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