What is electronystagmography?

Electronystagmography (ENG) is a diagnostic procedure used to assess the functionality of specific nerves in the brain. It evaluates the nerves responsible for eye movements, hearing, and balance coordination. Your doctor may order an ENG if you suspect or are diagnosed with a condition that impacts your sense of balance.

What nerves does an ENG test?

An ENG checks for quick involuntary eye movements, known as nystagmus. It also checks the condition of four cranial nerves:

• The Oculomotor nerve connects your eye muscles to your brain, enabling eye movement.
• The trochlear nerve is also responsible for ocular muscles and helps shift the gaze from the nose to the right or left.
• The abducens nerve, which facilitates lateral gaze by the eye, innervates the eyeball's lateral rectus muscle.
• The vestibular nerve connects your inner ear to your brain and controls your balance and hearing.

What are the types of ENG tests?

The ENG is, in reality, a battery of tests that may include one or more of the following measurements: Calibration test. This is performed by tracking with your eyes a light about 6 to 10 feet away from you. This test helps to determine facial ocular fatigue and more importantly measures ocular dysmetria.

• Look away nystagmus test: Observe a stationary light placed either on the centre or any side as you sit or lie down. This test measures the ability to fix your gaze at an object without the involuntary movement of your eyes.
• Gaze fixation test in nystagmus: The patient is asked to fixate upon a central or lateral light while in a sitting or supine position. This tests the subject's ability to maintain a static position visually without any compensatory eye movements.
• Optokinetic test: This test assesses the capability of keeping pace with a target as it swiftly crosses the visual field in a lateral motion and returns while the person's head remains stationary.
• Positional test: Most tests of positional vertigo involve dynamic head movement about the body. For example, the head may be abruptly rotated towards one shoulder, or the participant may be instructed to stand up with haste from a prone position. The extent of eye movement produced by this activity is measured.
• Water caloric test: It introduces warm or cool water into the ear canal with a syringe so that it touches the tympanic membrane. If nothing is wrong, your eyes will involuntarily move at this stimulus. Air may be used instead of water as the stimulus for this test, especially if the individual has a damaged tympanic membrane.

Who does an ENG?

The audiologist typically performs an ENG. These are medical doctors specializing in the science of hearing and balance disorders.

How do I prepare for an electronystagmography?

Your doctor will instruct you on preparing for an electronystagmography. Generally, you need to do nothing special.

Inform your doctor about all the medications or supplements you are taking. They may advise you to stop certain medications, such as sedatives or anti-vertigo drugs, for 24 to 48 hours before this test.

How is an ENG test done?

An ENG test uses small metal discs called electrodes. Your doctor attaches the electrodes above, below and near the outer corner of each eye. You also have one electrode on your forehead. The electrodes may be attached to a headband that you wear. Or they may be separate sticky patches.

You sit in a dark exam room during an ENG. The patches record your eye movements in the following scenarios, among others:

• Putting cold and warm water or air into each ear to stimulate your vestibular nerve.
• Keeping your head still while following a light with your eyes to stimulate your oculomotor and trochlear nerves.
• Turning your head or sitting up quickly stimulates your oculomotor, trochlear and vestibular nerves.
• ENG tests are generally 90 minutes long.

What to expect after an ENG?

On the test day, you can usually go home and resume normal activities. However, you might feel dizzy or nauseous for a few hours during the test. These symptoms usually resolve the same day.

What are the risks of an ENG?

ENGs are low-risk tests. You may feel pain in your back or neck from the rapid movements of an ENG. Most people do not have any serious side effects of the test.

It is extremely rare to suffer injury to your eardrum due to high water pressure in your ear canal. Your doctor may prefer to avoid filling water in your ear if you have recently had a perforation in your eardrum.

What do ENG results indicate?

In the event an ENG finds eye movement to be abnormal, this may indicate a lesion of the cranial nerve. Damage to the cranial nerves can be caused by various factors such as Diseases related to blood vessels.

• Cholesteatoma
• Drugs like certain antimalarials, diuretics, or antibiotics.
• Disorders of posture or goal-directed movement.
• Neurological effects of infection by the rubella virus.
• Head traumas.

If your tests for ENG reveal uncharacteristic eye movements, your doctor will ask for further diagnostic tests. Treatment and follow-up will depend on the cause of the uncharacteristic eye movements or nerve damage.

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