What is an Electromyogram?

This test helps to evaluate the functioning of two types of nerves:

• Sensory. These nerves send information about touch, pain, temperature and vibration to the spinal cord and from there to the brain. These nerves also help in recognising physical positioning and identifying the shape of an object.
• Motor. These nerves send signals from the brain so that the muscles contract and move voluntarily.

When is Electromyography necessary?

A health professional requests this test when it is suspected that a nerve is not working well. The patient may note this in one of the following ways:

• Numbness in a part of the body
• Loss of strength in an extremity
• Pain not explained by other causes
• Difficulty swallowing or walking
• Double vision
• Hoarseness or loss of voice

It may also be used to diagnose other situations, such as:

• Nerve entrapment injuries, such as carpal tunnel syndrome
• Nerve root injury due to a herniated disc
• Trauma or other injuries to the nerves
• Facial paralysis
• Nerve damage or neuropathy
• Muscle diseases or myopathies
• Neuromuscular junction problems, such as myasthenia gravis or Lambert-Eaton syndrome

How should I prepare for Electromyography?

Patients do not have to come on an empty stomach and can continue taking their usual medication on the day of the test, except in specific cases explained at the time of the appointment. The patient must not apply any type of cream to the part of the body where the test will be performed.

How is Electromyography performed?

To study nerve function, the patient is asked to sit in a reclining chair or lie down on a bed and expose the part of the body to be examined.

Electrodes and a receiver are placed on the clean surface of the skin to record and analyse the nerve response. Afterwards, an electric current is applied at certain points. Depending on the results obtained, it may be necessary to investigate further: by assessing more nerves in the same limb; those in the same limb on the opposite side; or those in other parts of the body.

If muscle activity needs to be studied, the healthcare professional inserts an electrode with a very fine needle into the muscle. During the process, the patient receives instructions on how to relax and contract the muscle to record electrical activity. No type of drug or electrical current is administered through the needle.

Who performs the Electromyography?

The test is performed by a technician with specific training in neurological diagnosis together with a specialist doctor. The latter is responsible for supervising the results and deciding if any additional studies are needed.

How long does Electromyography take?

The test duration is about 30 minutes per scan. This time may vary depending on the nerves to be studied, the reason for the request, the accessibility of the nerve and whether a needle study needs to be done.

What will I feel during Electromyography?

Some discomfort may be noticed during the application of the electric current (a prick or spasm); however, this usually subsides when stopped. It is administered with the minimum intensity necessary for its proper implementation; health personnel will indicate where and when the electrical currents will be felt.

When a needle electrode is used to study the muscle, some patients report discomfort when the needle is inserted and when they have to contract the muscle to perform the test.

In both cases, you can talk to health professionals to take a short break during the test.

Special situations

Health professionals should be informed if you have a pacemaker or any other electronic device (e.g., spinal cord or deep brain stimulators). Also, if you have any illness or are taking medication that may interfere with blood clotting (e.g., Sintrom, heparin, aspirin, other anticoagulants or antiplatelets).