Electronystagmography (ENG) is a test that shows the movement of your eyes in order to determine how well two cranial nerves within your brain are functioning. The two nerves are the acoustic (or vestibulocochlear) nerve and the oculomotor nerve. The acoustic nerve connects the brain and the inner ear and controls hearing and balance. The oculomotor nerve connects the brain to the muscles of your eyes.
The ENG detects disorders in the parts of your inner ear that are responsible for orientation, position sense, and balance, as well as in the nerves that connect your brain to your eyes and ears.
There are a number of different types of ENG tests. Your doctor may administer one or several. The standard test typically consists of three parts.
For the caloric test, electrode patches are placed above, below, and on each side of each of your eyes. Another electrode is attached to your forehead. While your head is held in position, your doctor will stimulate your balance system using warm and cool air. Sometimes water is used as well. The electrodes will record all the movements of your eyes as your inner ear and the nerves nearby react to temperature changes.
For the oculomotor test, your doctor will ask you to keep your head still while allowing your eyes to follow a light as it moves quickly across and beyond your field of vision, and then back again. This allows your doctor to understand how your eyes track and move when following a target.