The test can confirm normal function or estimate the degree of nerve damage.įigure 1.
1).Īn EMG or NCS may be ordered if you have pain, tingling, numbness, or unexplained weakness in the arms or legs. So, like the car buyer who looks beyond appearance and requests a test-drive, your doctor will look beyond the structure on a CT/MRI scan and test function before making a decision regarding treatment.Īn EMG/NCS is the equivalent of a test drive: It evaluates how well the nerves from the spine transmit information to and from the arms, legs, and paraspinal muscles (Fig. The nerve could have been damaged with swelling, but now the swelling is less. It cannot tell if the nerve was more severely pinched three weeks ago or how tightly the nerve is being pinched right now. It only shows narrowing when the MRI was taken, at one point in time. MRI scans show us details about disc herniation, or narrowing (stenosis) of the nerve canals.Īn MRI may show nerve entrapment, but it has limitations. X-rays tell us about bony alignment (scoliosis) or bony spurs (arthritis).
In a similar manner, X-ray, MRI or CT myelogram all take a look at spinal structure - the bones, discs and nerves. You first look at the car’s structure: Is there any body damage or leaking oil? No matter how good it looks, you do not make an offer to buy without driving the car to test its function: How does it steer or brake? How does the engine sound? This structural exam is expanded by imaging tests that look inside the body at the skeleton, muscles and nerves (X-rays, MRIs, and/or CT myelograms).Ī good analogy is shopping for a used car. The tests add valuable information to what your doctor already knows from your history, physical exam, and imaging scans.įor example, during the physical exam the doctor looks for clues as to the underlying spinal problem (loss of muscle or “atrophy,” loss of reflexes, weakness, and/or areas of numbness). While an MRI or X-ray of the spine can provide clues about its structure, EMG and NCS tests provide data about how the muscles and nerves function. The presence or absence of injury can be helpful in determining further treatment. The tests can help identify nerve injury or muscle disease such as carpal tunnel syndrome, a pinched spinal nerve, peripheral neuropathy, myositis, or ALS. Electromyography (EMG) & nerve conduction studies (NCS) OverviewĮMG and NCS are tests that measure the electrical activity of the muscles and nerves of the body, usually to an arm or a leg.
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