Electromyography (EMG)

1 What is an Electromyography (EMG)?

A diagnostic procedure that assesses the nerve cells which controls the motor neurons and the health of muscles is called electromyography (EMG).

The motor neurons transmit electrical signals that can cause our muscles to contract and these signals are translated by the EMG into graphs, numerical values or sounds that a specialist interprets.

Electrodes which are tiny devices are used to detect or transmit electrical signals.

A needle electrode will be inserted directly into the muscle and will record the electrical activity in that particular muscle during a needle EMG while in nerve conduction study uses electrodes taped to the skin or surface electrodes to measure the strength and aped of signals that are travelling between two or more points.

EMG results can reveal muscle dysfunction, problems with nerve-to-muscle signal transmission or nerve dysfunction.

2 Reasons for Procedure

Here are the most common reasons to receive an electromyography (EMG).

If you have signs and symptoms which indicate a muscle or nerve disorder, your doctor may order an EMG for you.

Some of the possible symptoms include numbness, tingling, muscle cramping or pain, certain types of limb pain and muscle weakness.

EMG results sometimes rule out other conditions such as:

  • muscle disorders such as polymyositis or muscular dystrophy
  • disorders of the peripheral nerves such as peripheral neuropathies or carpal tunnel syndrome
  • diseases affecting the connection between the muscle and the nerve such as myasthenia gravis
  • disorders that affect the nerve root such as herniated disk in the spine
  • disorders that affect the motor neurons in the spinal cord or in the brain such as amyotrophic lateral sclerosis or polio
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3 Potential Risks

In electromyography, complications are rare and it is a low-risk procedure such as bleeding, nerve injury where a needle electrode is inserted or infection.

There is a very small risk which can cause air to leak into the area between the chest wall and the lungs that can cause lungs to collapse (pneumothorax) when a muscle along the chest wall are examined with a needle electrode.

4 Preparing for your Procedure

To prepare for an electromyography, the neurologist who is a nervous system specialist will interview you if you have other medical conditions such as:

  • if you have hemophilia which is a blood-clotting disorder that causes prolonged bleeding
  • if you are taking blood-thinning medications
  • if you have a pacemaker or any other electrical medical device

Some of the questions that you can ask include:

  • What is the time should I arrive?
  • What is the best way to find the EMG lab?
  • Do I need to stop taking my prescription medications before the exam?
  • Can I bring a relative?

Take a bath or shower first before the exam to remove oils from your skin and do not apply creams and lotions.

5 What to Expect

Here you can find out what to expect from your electromyography procedure.

During your EMG, you will be asked to change into a hospital gown and lie down on the examination table.

The following explanations will help you understand about the exam: electrodes – the technician or neurologist will place electrodes at various areas on your skin or they will insert a needle electrodes at different areas based on where you are experiencing the symptoms; sensations – a tiny electrical current that you may feel as a spasm or twinge that sometimes will be transmitted by electrodes.

The needle electrode sometimes can cause pain or discomfort that will end after the removal of the needle, but if you are bothered by the pain you can ask your neurologist to take a short break during the exam; instructions – your neurologist will tell you if there is an electrical activity when the muscle is at rest or when the muscle contracts.

He will give you instructions on contracting and resting a muscle, he may also ask you to change positions depending on what the nerve or muscle he is examining.

After the EMG, you might experience some minor and temporary bruising where the needle is inserted but it should fade after several days. Consult your doctor if the bruising persists.

6 Procedure Results

The result of your electromyography exam will be interpreted by your neurologist and he will prepare a report.

He will also discuss the result with you and about your follow-up appointments.

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