Vestibular Function Test

The ear has two main functions: to aid in hearing and to maintain balance. The latter function is supported by various organs in the inner ear, including the semicircular canals, which sense rotation or angular accelerations, and the utricle and saccule, which sense linear acceleration, including gravity.

If you present with certain symptoms, such as dizziness and poor balance, and general practitioners can not identify the problem, a vestibular function test for these organs can be recommended to determine if they are functioning as required.

What is a Vestibular Function Test?

Vestibular testing is a series of tests that check the functioning of the vestibular or balance section of the inner ear.

The vestibular system works together with the eyes to maintain balance and clear vision when the head is moving. This function is known as the vestibular ocular reflex or VOR. If you present with symptoms such as regular dizziness, vestibular testing may be required.

The vestibular function test isn't one test but a series of tests that check various organs and systems in the inner ear. During your test, you will undergo various tests such as:

Video Head Impulse Test (VHIT)

This test checks the connections between the balance organs in the ear and the extraocular muscles that move the eye.

The VHIT tests your ability to match rapid head movements with equal and opposite eye movements. During this test, you will be asked to sit upright and wear a pair of lightweight video glasses. You will focus on a fixed target. The audiologist will deliver 20 head turns in the direction of each semicircular canal. The speed of eye movement is measured and expressed as a fraction of the speed of head movement. This test screens for semicircular canal function.

Vestibular Evoked Myogenic Potentials (VEMP)

The ear contains gravity sensors that are activated by sound and vibration. The purpose of the VEMP test is to exploit this sensitivity to assess the integrity of these sensors.

During this test, surface electrodes will be applied to the skin directly underlying your lower eyelids and over your neck muscles. You may be asked to look upwards or to elevate your head 45 degrees above horizontal.

You will also be asked to listen to clicking noises using headphones. Three vibration pulses per second will be delivered over your forehead. Recordings taken from your neck or eye muscles give us useful information about your gravity sensors.

The Bithermal Caloric Test

For this test, you will lie semi-recumbent on a bed. Dark goggles will be placed on your eyes, and a small infrared camera will record your eye movements. The test involves irrigating the external ear canal with warm and cool water for 40 seconds.

You will experience a sensation of tilting or turning as your balance organs are stimulated by the water. You may also notice your eyes flicking in response to the stimulus. The velocity of these eye movements is recorded and compared for left and right ear stimulation.

During the test, you will be required to keep your eyes open and remain alert. The nurses who perform the test are highly skilled and will ensure you feel safe and comfortable. You may also be engaged in a conversation to ensure you stay awake.

Several preparations are necessary for the thermal caloric test. These include having your ears examined prior to ensure they have no wax, and you must not eat or drink for at least four hours before the test.

The thermal caloric test is part of the Electronystagmography (ENG) test. The two tests check for the same balance parameters and are carried out in the same way.

Electrocochleography (ECOG)

The ECOG test measures the nervous system's response to sound. It involves listening to sounds from an earphone while an electrode measures the response.

If the tests conclude that the vestibular system is functioning okay, other tests will be carried out to determine the cause of the patient's dizziness. These can include blood pressure, psychological evaluation or MRIs.