Electromyography (EMG)
An Important Tool in Diagnosing Neuromuscular Pain
An EMG study is actually composed of two portions: electromyography (EMG) and nerve conduction study (NCS). An EMG/NCS study is a diagnostic tool used to evaluate disease and injury in muscles and nerves, including herniated disc, sciatica, spinal stenosis, neuropathy, and other painful conditions. Often used to evaluate symptoms of numbness, tingling, pain, weakness, or muscle cramping, this study can help physicians determine, confirm, or rule out a diagnosis.
How does an EMG/NCS study help?
Nerves control and move muscles by sending electrical signals. Each signal causes a very specific reaction. Disease and injury can influence or disrupt this signal, causing the muscle to have an abnormal reaction. An EMG/NCS study is used to measure the electrical activity between nerves and muscles. The NCS portion of the exam is usually done first and evaluates how well the nervous system is conducting electrical signals. The EMG portion of the exam complements the NCS portion by evaluating muscle function.
How does an EMG/NCS study work?
For the NCS portion of the test, flat electrodes are attached to the skin with special paste over the affected nerve and over the muscles controlled by that nerve. Several small electrical pulses are given to the nerve, and the time it takes for the muscle to contract in response is recorded. These small electrical pulses cause a quick tingling or mild shock-like sensation and may cause the muscle to twitch. Depending on the symptoms, several nerves may be tested.
For the EMG section of the test, a small, thin needle electrode attached by wires to a recording machine is inserted into the muscle tissue. Because medication is not injected, there is less discomfort than with shots. The electrode may be moved a number of times to record the activity in different areas of the muscle or in different muscles.
During the EMG, patients are asked to relax and contract the targeted muscles. The needle acts as an electrical probe conveying information to the recording machine. The doctor can hear and see how the muscles and nerves are working by watching the EMG monitor.
How long does it take?
The exact number of nerves and muscles tested may vary based on the clinical symptoms being addressed. The NCS portion may take from 15 minutes to one hour or more, depending on how many nerves and muscles are studied. The EMG portion may take 30-60 minutes.
What are the expected results?
At Capitol Spine & Pain Centers, EMG/NCS studies are safely performed in a sterile, office-based setting. The risk of infection is miniscule. There can sometimes be bruising or soreness over the areas penetrated by the needle, but patients typically return to work or normal activities following the test. The information provided by this important diagnostic tool can help determine the most effective treatment approach for many causes of acute and chronic pain..
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