Electrical Diagnostic Testing
What is Electro Diagnostic Testing?
Electro diagnostic testing is a diagnostic test that measures electrical activity within muscle fibers & nerves. It is an important tool that can help a doctor diagnose nerve damage. This test can detect and identify the specific location and cause of a patient’s impaired peripheral nervous system. It can also help a doctor formulate an effective treatment plan that is best for a patient. This type of testing is usually performed by a neurologist or pain management doctor.
This testing is particularly effective in evaluating the numbness and tingling a patient can experience down the arms and legs, known as radiculopathy. These unpleasant sensations are common in patients with herniated and bulging spinal discs. Electrical Diagnostic Test usually includes both electromyography (EMG) and nerve conduction velocity (NCV) testing performed during the same testing session.
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What is an EMG Electrical Diagnostic Test?
Our bodies are able to move and feel different sensations because of the complex interaction between our muscles and brain. This interaction is made possible by a system of nerves known as the peripheral nervous system. This system, which is essentially the wiring that carries electrical impulses to and from the brain, can be damaged in any number of ways including in an accident. When this system is damaged, an EMG/NCV study can help diagnose the problem.
EMG or electromyography is a type of electrical diagnostic testing that measures muscle electrical activity. This form of electrical diagnostic testing is commonly used to assess muscle weakness, paralysis, twitching, and impaired motor ability. It is also very helpful in investigating unexplained pain, numbness associated with carpal tunnel syndrome, as well as the tingling associated with herniated and bulging discs.
This type of electrical diagnostic testing provides helpful information concerning abnormalities in the speed of nerve impulses to those muscles being tested. Normal muscles demonstrate a specific amplitude and response pattern not seen in those with nerve damage.
Electromyography can distinguish between true muscle weakness, pain-induced weakness, or weakness due to lack of motivation. This form of electro diagnostic testing can disclose whether the muscle disorder is caused either by nerve damage or the muscle itself.
The EMG test ranges between 30 to 90 minutes, depending on the suspected condition and the findings throughout the study.
How Is EMG Testing Conducted?
EMG testing requires the insertion of a small needle into the affected muscle which acts as an electrode. The patient then contracts the muscle for evaluation. The strength of the patient’s electrical impulses are analyzed both at rest and after contraction of the muscle tested.
During this type of electro diagnostic testing, a muscle’s electrical activity can be displayed graphically on a computer screen, or oscilloscope, as well as audibly via a speaker. This information reflects the capability of the muscle to react to nervous stimulation. Both NCV and EMG studies should include proximal and distal muscles and at least involve one upper and lower limb. Most EMG studies include the testing of two extremities.
What is An NCV test?
A Nerve Conduction Velocity study (NVC) is another type of electro diagnostic testing. NCV and EMG studies are both usually performed during the same electro diagnostic testing session. The NCV, usually performed first, can provide useful information regarding the health and function of sensory and motor neurons. It measures the transmission speed of impulses through the nerve and helps identify the location, nature, and extent of nerve injury.
The myelin sheath is an insulating layer that covers nerves and influences the speed of impulse conduction. A faster nerve conduction reflects healthy nerves and adequate myelin insulation. Most neuropathies are caused by axonal damage rather than damage to the myelin sheath. Further, given that NCV investigates nerve conduction and not electrical activity within muscles, NCV is normal in most patients with muscle disorders which is helpful in diagnosing the problem.
NCV testing usually takes between 15 minutes to an hour, depending on how many regions are being studied.
How is An NCV Study Performed?
Your doctor will position an electrode on your skin over each nerve tested. Your doctor will then activate a small electric current to test each nerve. The examination’s testing results are recorded by electrodes and either printed in graph form or projected onto a screen.
Generally, most NCV and EMG tests are performed from areas further from the center of your body known as distal regions, to areas closer to the center of your body known as proximal regions. This allows your doctor to test longer nerves before shorter ones.
Is Electrical Diagnostic Test Uncomfortable?
Complication risks with NCV and EMG examinations are rare. Electrical stimulation seldom causes any temporary or permanent damage to nerves. As with any procedure involving needles, there is a slight risk of infection and bleeding upon needle insertion during EMG testing. However, this risk is minimal with appropriate pressure techniques and antiseptic practices.
EMG testing does involve slight discomfort upon needle insertion. There may be some muscle tenderness or bruising experienced for a few days after the examination. With NCV testing, you may experience some manageable discomfort because the electrical stimulus is small and often minimally felt. Nonetheless, only a small proportion of patients find it intolerable. Patients with an informed understanding of these examinations usually readily tolerate the testing.
Preparation For Electro Diagnostic Testing
Prior to any diagnostic study, your doctor should complete a review of your clinical course as well as your medical history. Patients should bathe or otherwise ensure that the skin is clean prior to the examination. You should also avoid lotion or cream application before the testing. On the day of the testing itself, you will be asked to wear a gown for easier access to the extremities.