An electronystagmography can provide insight to the sensory system.
Electronystagmography (ENG) is a test performed on individuals with vertigo, a condition that results in the illusion of experiencing spinning motion that can cause dizziness. Involving the strategic placement of electrodes, an ENG may also be recommended for patients with other hearing-related issues. Specifically, various ENG tests evaluate the functioning of:
- The acoustic (vestibulocochlear) nerve that links the inner ear to the brain to control balance and hearing
- The oculomotor nerve, which connects to eye muscle
Reasons for an Electronystagmography
An ENG is typically performed to evaluate patients with suspected issues affecting the vestibular (sensory) system, which affects balance and orientation. The test may also be done to diagnose or assess the extent of conditions like Usher syndrome that can affect both hearing and vision, or various inner ear disorders, such as Ménière’s disease and inner ear inflammation (labyrinthitis). ENG testing may also be recommended for patients with:
- Hearing loss without a clear source
- Benign tumors on the acoustic nerve (acoustic neuroma)
- Suspected lesions in one or both ears
Types of ENG Tests
There are different types of ENG tests. During a caloric test, electrodes stimulate the balance system with cool and warm air or water. Eye movements and reactions to temperatures are recorded. With an oculomotor test, the head is kept still as the eyes follow a light that’s moved across and beyond a patient’s field of vision. During a positional test, patients are asked to make certain rapid movements, such as moving the head from side-to-side or standing up and sitting down. Additional ENG tests include:
- Calibration test: A light that’s six to ten feet away is followed with the eyes to check for a condition where pupils overshoot their target (ocular dysmetria)
- Pendulum-tracking test: Eyes follow a light that’s directed in a pendulum-like motion
- Gaze nystagmus test: Patients are instructed to focus on a fixed object to determine how well focus can be maintained
Preparing for an ENG
Adults having an electronystagmography are usually advised to avoid caffeine and alcohol 24 to 48 hours prior to the test. Before the test is done, ears will be checked for earwax and signs of inflammation and other issues that may interfere with the tests. Certain medications, especially sedatives and tranquilizers, may also need to be temporarily stopped.
During and After Testing
During the test, electrodes are placed above and below the eye to allow electrical activity to be recorded. A standard electronystagmography is three parts: a caloric, oculomotor, and positional test. The electrodes are attached with a special paste around each eye. Patients may be asked to look in various directions as the various ENG tests are performed. With a caloric test, water or air is placed into the ear as eye movements are recorded. The electrodes are attached to a recorder that will chart the results from all tests performed.
Results from an electronystagmography will determine how hearing or related vision problems are treated. Testing can also identify specific diseases or injuries affecting the acoustic nerve, including inner ear damage, viral infections, and blood vessel or movement disorders. In some instances, additional testing my be recommended to rule out or confirm other suspected problems. There are minimal risks associated with any of the various types of ENG tests that may be performed.