What is Electrodiagnostic testing?
Electrodiagnostic testing helps to figure out if there is a problem with involved muscles or nerves or if it is a problem with both.
Procedures can be run to see if the nerves are moving information slowly or nerves are even really connected to muscles.
Procedures can also tell if there is a problem with the muscle that is unrelated to the nerve. Electrodiagnosis is a term test includes a variety of tests which includes needle Electromyography (EMG), nerve conduction studies (NCS), brainstem auditory evoked response (BAER) and other types of interoperative monitoring (which occur during neurosurgery).
Procedures that involve surface EMG are not considered part of electrodiagnostic medicine.
What Is Electromyography?
Electromyography (EMG) is a procedure used to assess muscle health and their controlling nerve cells (motor neurons).
EMG results can find problems with nerve-to-muscle signal transmission, as well as nerve or muscle dysfunction.
Symptoms can include:
- Weakness in muscles
- Atrophy or wasting of muscle
- Cramping, or other muscle pain
- Poor Reflexes
- Certain other kinds of limb pain
Electrodiagnostic testing like EMG is used to help figure out the correct diagnosis and where the problem actually is. Is the leg pain coming from sciatica or is it actually a hip problem?
Is the shoulder pain from a rotator cuff issue or from a herniated cervical disc. Or is it both?
That is something that EMG can help with. It can also be used to determine if someone should have surgery and they can also be done occasionally after injury to objectively document recovery or deterioration.
An EMG consists of two parts the Nerve Conduction Studies (NCS) and the electromyography (EMG). These two parts are almost always done together to many people refer to the entire thing as an EMG. The test results help diagnose muscle disorders and problems with nerves conducting signals to the muscles in the body.
The first part of the test is the Nerve Conduction Studies (NCS), which is also known as a nerve conduction velocity (NCV). , An electric stimulator is placed on the skin along with 3 electrode stickers. The stimulator applies a small electric stimulation to the skin and the specialized stickers record the how fast your nerves conduct the signal.
Dr. Royer may perform the test in multiple areas during one testing session to determine if there is any nerve damage and may compare with the other limb.
In the second part of an EMG test, Dr. Royer places a small, specialized needle into the muscle in the affected limb.
The needle has special sensors in it to monitor the muscle activity and is connected by a wire to a computer to measure the nerve transmissions. Multiple muscles are testing in the affected limb and usually the affected limb is the only that has muscles tested using the needle.
During the test, the patient may contract and release the muscle to compare the different types of signals sent by the motor neurons.
What Happens During an Electromyography Test?
Typically, an EMG is an outpatient procedure but sometimes happens during a hospital stay. The patient must remove all jewelry, hairpins, eyeglasses, or any other pieces of metal. A patient should avoid lotion the affected area before the procedure as this can negatively affect the test.
After the skin is cleaned, Dr. Royer will locate the nerve and place the needle or the electrode in the proper position.
The patient moves and contracts muscles following Dr. Royer’s instructions.
Is the EMG Test Painful?
An EMG test is accompanied by some discomfort but is not necessarily painful. Inserting the needles into the skin and the small electric stimulation administered can make the muscles sore for a day or two after the procedure.
If there is pain during the procedure, it is important to tell the doctor performing the test and possibly take a short break between tests. While it is not typically a test that patients love having, most report that testing is tolerable.
Are There Risks to Having an EMG?
An EMG is a very low-risk procedure. The area that was tested may be sore for a few days and occasionally there is bruising or swelling at the site. Any time the skin is punctured, there is a risk of infection.
Patients with bleeding disorders or those that are undergoing anti-coagulation therapy may be at risk for excessive bleeding. Another complication is accidentally penetrating something other than the intended muscle, like a nerve or the lungs but these complications are extremely rare.
What Can an EMG Test Determine?
An EMG determines what is causing a patient’s symptoms. Some underlying causes shown in an EMG include:
- Pinched nerves
- Cervical or Lumbar Radiculopathy
- Carpal Tunnel Syndrome
- Ulnar Neuropathy
- Radial Neuropathy
- Fibular Neuropathy
- Tarsal Tunnel Syndrome
- Disorders that affect nerves away from the spinal cord (i.e. carpal tunnel)
- Muscle disorders (i.e. muscular dystrophy)
- Nerve disorders (i.e. amyotrophic lateral sclerosis [ALS] or polyneuropathy from diabetes)
- Disorders that affect the electrical signals sent by the motor neurons to the muscles (i.e. myasthenia gravis)
There is some overlap between diagnostic imaging, like MRIs, and EMG/NCV. The best way to think about is it to picture an area affected by a natural disaster liker a hurricane or tornado.
If you were to fly over the area in a helicopter, you would be able to see some house that obviously do not have power.
You might see downed powerlines outside the house and assume that they do not have power.
Flying overhead gives you an idea of the structure and is similar to the information that you get from an MRI.
Going into the house and flipping the lights on to see if they work is like doing an EMG.