EMG vs. Nerve Conduction Study: What’s the Difference?

The nerves in your body play several roles, controlling autonomic functions like breathing and heartbeat, delivering sensory information like touch, hearing, and sight, and controlling muscle movement. 

As with other systems in the body, nerves can suffer from dysfunctions that require medical assessment. Electromyography (EMG) and nerve conduction studies (NCS) are two tests used to measure aspects of nerve performance, though they’re usually performed together. 

At 360 Orthopedics in Sarasota, Venice, and Lakewood Ranch, Florida, we may order EMG or NCS testing for our patients to diagnose nerve issues. These two tests, however, evaluate different aspects of nerve performance. 

Let’s look at both EMG and NCS testing to help you better understand the purposes of these important neuromuscular assessment tools. 

EMG

EMG testing measures the electrical activity in muscles when they’re both contracted and relaxed. This helps us determine if muscles are responding the way they should or if you have myopathy, a disorder that affects how muscles respond to nerve signals. 

The test uses a fine, needle-like electrode inserted into a muscle being assessed for trouble. The electrode provides information on the tiny electrical signals provided by nerves that trigger muscular responses. 

While the insertion of the electrode produces a pinching sensation typical of any procedure involving a needle, the test itself produces no sensation, as the electrode simply records data from muscle movement. You may have some minor muscle soreness in the first few days after your test. 

NCS

A nerve conduction study uses surface electrodes, both transmitters and receivers, to measure the efficiency and speed of electrical signals along the nerve being assessed. Conditions like peripheral neuropathy and pinched nerves can be diagnosed using NCS testing. 

There’s no discomfort with the electrodes placed on your skin, though you’ll feel a series of mild electrical sensations, usually described as tingling or similar to the feeling of a static discharge. The data generated measures both the strength of the signal conducted by the nerve and the speed at which the signal travels. 

Safety

EMG testing may cause minor swelling or bruising around the electrode insertion site, and there’s a theoretical risk of infection due to the skin being pierced. However, this risk is of the same order as procedures like allergy shots or blood samples. 

NCS testing is even safer. The electrodes remain on the surface of your skin, and the strength of the electrical signals transmitted into your body is too small to damage any tissue. 

Results

EMG and NCS tests are performed together, as they can help determine whether a problem is caused by muscle dysfunction (EMG) or nerve damage (NCS), or both. Together, these tests provide a more comprehensive overview of muscle and nerve function than either test can offer on its own, offering complementary diagnostic information for our physicians.

Call or click to book a consultation for muscle and nerve assessments at the nearest 360 Orthopedics location today.