What Is Electromyography?
is a diagnostic procedure that evaluates the health condition of muscles and
the nerve cells that control them. These nerve cells are known as motor neurons. They transmit electrical
signals that cause muscles to contract and relax. An EMG translates these
signals into graphs or numbers, helping doctors to make a diagnosis.
A doctor will usually order an EMG when someone is showing symptoms
of a muscle or nerve disorder. These symptoms may include tingling, numbness, or
unexplained weakness in the limbs. EMG results can help the doctor diagnose
muscle disorders, nerve disorders, and disorders affecting the connection
between nerves and muscles.
There are two components to an EMG test: the nerve conduction
study and needle EMG. The nerve
conduction study is the first part of the procedure. It involves placing small
sensors called surface electrodes on the skin to assess the ability of the
motor neurons to send electrical signals. The second part of the EMG procedure,
known as needle EMG, also uses sensors
to evaluate electrical signals. The sensors are called needle electrodes, and
they are directly inserted into muscle tissue to evaluate muscle activity when
at rest and when contracted.
During each part of the EMG procedure, one electrode releases a
very mild electrical signal while the other electrodes measure how long it
takes for the signal to reach them. This mimics the natural electrical signals
sent by the nerves to the muscles. The distance between the electrodes and time
it takes for a signal to reach them is used to determine the speed at which the
nerves are able to send and receive signals. An abnormal speed usually
indicates a muscle or nerve disorder.
Some doctors may refer to electromyography as an electrodiagnostic
Why Is an Electromyography Performed?
Your doctor may perform an EMG if you’re experiencing symptoms
that may indicate a muscle or nerve disorder. Some symptoms that may call for
an EMG include:
pain or cramping
muscle twitching (or tics)
The results of an EMG can help your doctor determine the underlying
cause of these symptoms. Possible causes could include:
How Do I Prepare for an Electromyography?
Make sure to notify your doctor about any over-the-counter or
prescription medications you may be taking. It’s also important to tell your
doctor if you have a bleeding disorder, or if you have a pacemaker or
implantable defibrillator. You may not be able to have an EMG if you have any
of these medical conditions or devices.
If you are able to have an EMG, you should do the following
smoking for at least three hours before the procedure.
or take a shower to remove any oils from the skin. Don’t apply any lotions or
creams after washing.
comfortable clothing that doesn’t obstruct the area that your doctor will be
evaluating. You may be asked to change into a hospital gown right before the
What Happens During an Electromyography?
You will be asked to lie down on an examination table or to sit
in a reclined chair. Your doctor may ask you to move into different positions
during the procedure.
An EMG has two parts: the nerve conduction study and the needle
EMG. The nerve conduction study is performed first. During this portion of the
procedure, your doctor will apply several electrodes to the surface of your
skin, usually in the area where you are experiencing symptoms. These electrodes
will evaluate how well your motor neurons communicate with your muscles. Once
the test is complete, the electrodes are removed from the skin.
After the nerve conduction study, your doctor will perform the
needle EMG. Your doctor will first clean the affected area with an antiseptic.
Then, they will use a needle to insert electrodes into your muscle tissue. You
may feel slight discomfort or pain while the needle is being inserted.
The needle electrodes will evaluate the electrical activity of
your muscles when contracted and when at rest. These electrodes will be removed
after the test is over.
During both parts of the EMG procedure, the electrodes will deliver
tiny electrical signals to your nerves. A computer will translate these signals
into graphs or numerical values that can be interpreted by your doctor. The
entire procedure should take between 30 and 60 minutes.
What Are the Risks of an Electromyography?
An EMG is a very low-risk exam. However, you may feel sore in the
area that was tested. The soreness may last for a few days and can be relieved
with an over-the-counter pain reliever, such as ibuprofen.
In rare cases, you may experience tingling, bruising, and
swelling at the needle insertion sites. Make sure to tell your doctor if the
swelling or pain becomes worse.
What Do My Electromyography Results Mean?
Your doctor may review the results with you right after the procedure.
However, if another health care provider ordered the EMG, then you may not know
the results until you attend a follow-up appointment with your doctor.
If your EMG shows any electrical activity in a resting muscle,
then you may have:
- a muscle disorder
- a disorder affecting the nerves that connect to
- inflammation caused by an injury
If your EMG shows abnormal electrical activity when a muscle
contracts, then you may have a herniated disc or a
nerve disorder, such as ALS or carpal tunnel syndrome.
Depending on your results, your doctor will talk to you about any
additional tests or treatments that might be needed.