Electromyography (EMG) is used to measure electrical activity or muscle response based on the way the nerve stimulates the muscle. Electroneuronography (ENoG) is another test of facial nerve function that can establish how badly nerves are disrupted as a way to determine potentially necessary surgeries in the future.
For individuals with nerve problems, one of these tests will often be done. It’s important to understand the differences between the two and how each of them works.
What is an EMG?
A facial EMG is a test that looks at the integrity and health of the facial nerve. In most cases, it is used after at least six months of identified facial nerve paralysis.
The procedure involves small needles being inserted into specific facial muscles. While this occurs, the patient is asked to contract those muscles. Simultaneously, a record is made of nerve signals. This gives a physician more information about how healthy the muscles and nerves in these areas are.
A muscle that is reinnervating will show wave and spike activity as well as action potentials. If the muscles are not reinnervating, random electrical noise and fibrillation baselines or potentials may be seen. This shows that the muscles are living and searching for a nerve signal, but that the nerve is not providing one.
Full electrical silence during the test indicates a denervated nerve that is irreversibly damaged. This means that it cannot be reinnervated now or in the future.
What Is ENoG?
A professional will do an ENoG test as a way to determine how healthy a facial nerve may be.
During the process, an electrode will be placed on each side of the face with tape. One will be near the nasolabial fold, while the other is over the stylomastoid foramen under and behind the ear.
Each of the electrodes is responsible for a different function. The one behind the ear will put out an electrical pulse, while the other electrode works to pick up any of the signals coming from the nerve fibers in the face.
A comparison of the strength, speed, and size of the transmitted signals allows for a measurement of the integrity of a nerve in the face. Tests are performed and compared on different sides of the face to determine how large the difference is between an unhealthy and healthy nerve.
Sometimes, several ENoGs will be taken on separate days. This offers a way to determine if a nerve is improving or getting worse as time goes on.
What to Know Before an EMG or ENoG
If you are scheduled for an ENoG or EMG, the physician will explain what is about to happen and answer all your questions. In most cases, no fasting is needed. Restrictions on tobacco and caffeine may be required depending on the physician.