Electronystagmography (ENG)

The eyes are closely linked to the inner ear; these organs depend on each other for good balance and clear vision. Head movement or other stimulation of the inner ear sends signals to the muscles of the eyes via the nervous system; this is called the vestibulo-ocular reflex, or VOR.

The VOR normally generates eye movements that maintain clear vision with head movement. Electronystagmography (ENG) is a battery (group) of eye-movement tests that look for signs of vestibular dysfunction or neurological problems by measuring nystagmus (a type of involuntary eye movements). ENG tests are the most common ones administered to people with dizziness, vertigo, and/or balance disorders, although the test battery and some testing methods vary widely.

During ENG, eye movements are recorded and analyzed via small electrodes placed on the skin around the eyes. The electrodes attach to the skin with an adhesive, much like a small bandage. Alternatively, eye movements may be recorded by videonystagmography (VNG) using an infrared video camera mounted inside goggles that the patient wears instead of sticky-patch electrodes.

One ENG test evaluates the movement of the eyes as they follow a moving target. Another observes eye movements as the head is positioned in different directions. During the caloric test warm or cold water or air is circulated in the ear canal. The temperature change stimulates the inner ear in order to test the nystagmus response.