Electromyogram, commonly referred to as an EMG, literally means an electrical study of muscle. It is a type of electrodiagnostic testing used to help determine if there is evidence of nerve or muscle injury contributing to your symptoms. The spinal cord is a thick bundle of nerves and other tissue that extends from the brain through the spinal column. As the spinal cord descends, there are spinal nerves that branch off and go to various parts of the body. It is very important to be able to evaluate the nerves when dealing with spinal problems or other musculoskeletal issues. Specialized nerve tests called Electromyography and Nerve Conduction Studies are designed to diagnose abnormalities in the functioning of nerves.
The EMG test helps to clarify the cause of symptoms by confirming and any nerve or muscle damage. This is especially helpful when exam findings or other diagnostic tests are not clear. Electrodiagnostic testing cannot tell you the cause of nerve or muscle damage, it only confirms details of the damage. An EMG test for the upper extremities may tell if there is a cervical radiculopathy or other nerve irritation such as ulnar or median nerve damage from cubital or carpal tunnel syndrome. An EMG test for the lower extremities may tell if there is a lumbar radiculopathy or peripheral neuropathy from a condition such as diabetes. Generally speaking, nerve damage or irritation must be present for at least 6-8 weeks to show changes on an EMG test. The EMG results determine the exact location of nerve damage, the severity of damage and if damage is ongoing or chronic. Severity is usually classified as mild, moderate or severe and damage is noted as acute or chronic. Acute damage refers to ongoing nerve irritation and suggests that intervention would be helpful in reducing or eliminating symptoms. Chronic nerve damage is unlikely to resolve. The longer a nerve is irritated, the harder it is to return to normal function. This information is very useful when deciding if injection therapy may be helpful, evaluating expectations from treatment options, understanding if there is a more urgent need for surgical intervention, and potentially guiding which surgical levels may need to be addressed.
Dr. Bharara performs both electromyography and nerve conduction study tests at the Virginia Spine Institute. The test is performed on clean, dry, and preferably warm skin. A stimulating device is used to deliver an electrical impulse along the nerve being tested. The delivered shock will feel similar to being stung by static electricity; the signal amplitude and waveform is recorded and displayed on a computer screen for analysis. After nerve conductions are performed, there is a needle analysis of several individual muscles in your arm, leg and/or along the spine. The needle is similar to an acupuncture needle and is specially designed to pick up electrical signals from muscle tissue. You will see and hear this electrical activity on the computer screen during the test. The activity is analyzed to determine if there has been any damage to muscles or the nerve supply to the muscle. Combining the information from both the nerve conductions and needle electromyography provides great insight into the health of the peripheral nervous system.
In general, the test may be a little uncomfortable. There is no risk of serious injury to the nerve or muscles from this test. The vast majority of patients who experience an increase in their pain after the test do very well with simple pain management strategies such as rest, ice, and anti-inflammatory medications.