Vestibular Function Tests - A Test to Check Imbalance

Introduction:

Maintaining a sense of balance and spatial orientation heavily relies on the crucial role played by the vestibular system. It includes the inner ear and the pathways that connect it to the brain. Vestibular system disorders result in a range of symptoms such as dizziness, vertigo, and imbalance. Vestibular function tests are a group of diagnostic tests that assess the function of the vestibular system. These tests can help diagnose vestibular disorders and guide appropriate treatment. There are several types of vestibular function tests, each with its own strengths and limitations.

What Are Vestibular Function Tests?

A vestibular function test is a group of tests that assess the function of the vestibular system, which is responsible for our sense of balance and spatial orientation. These tests are used to diagnose and evaluate a range of vestibular disorders, including benign paroxysmal positional vertigo (BPPV), Meniere's disease, and vestibular neuritis.

What Are the Vestibular Function Tests Available?

There are several types of vestibular function tests. These tests include:

Videonystagmography: Videonystagmography (VNG) is a type of vestibular function test that uses video technology to monitor eye movements and assess the function of the vestibular system. The test is typically performed by an audiologist or vestibular therapist and is used to diagnose and evaluate a range of vestibular disorders, including benign paroxysmal positional vertigo (BPPV), Meniere's disease, and vestibular neuritis.

During a VNG test, the patient wears a set of video goggles that record eye movements while the patient performs a series of specific tasks or experiences certain stimuli. These tasks may include following a moving target with their eyes, tilting their head or body, or experiencing changes in temperature or pressure within the ear canal. The eye movements are recorded by a video camera in the goggles and analyzed by a computer program.

The VNG test measures several different types of eye movements, including:

• Spontaneous Nystagmus: This measures the presence and direction of nystagmus, which is an involuntary rapid movement of the eyes that can be a sign of vestibular dysfunction.

• Gaze-Evoked Nystagmus: This measures the presence and direction of nystagmus that occurs when the patient looks to the side, up, or down.

• Smooth Pursuit: This aids in evaluating the patient's capability to track a moving object smoothly using their eyes.

• Saccades: This measures the patient's ability to make rapid eye movements to switch their gaze from one object to another.

• Positional Nystagmus: This measures the presence and direction of nystagmus that occurs when the patient changes position, such as from lying down to sitting up.

Caloric Testing: This test involves the irrigation of each ear with warm or cold water or air to stimulate the vestibular system and measure the resulting eye movements. During the test, the patient is seated in a reclined position, and water or air is delivered to the ear canal through a small tube. The patient's eye movements are then recorded using video goggles or other monitoring equipment. The test results help identify the affected ear and the extent of vestibular dysfunction.

Vestibular Evoked Myogenic Potentials (VEMPs): This test measures the response of the muscles in the neck or abdomen to sound, which can help assess the function of the vestibular system. During the test, the patient is typically lying down or sitting, and a small electrode is attached to the skin over the muscle being tested. The patient is then exposed to a series of sounds through headphones, and the muscle response is recorded using monitoring equipment.

Video Head Impulse Testing (vHIT): This test involves the rapid rotation of the patient's head while recording eye movements, to assess the function of the vestibulo-ocular reflex (VOR). During the test, the patient is typically seated or standing, and the head is moved quickly in one or more directions while the patient focuses on a visual target. The eye movements are recorded using video goggles or other monitoring equipment.

Computerized Dynamic Posturography (CDP): This test measures a patient's ability to maintain balance in various situations, such as standing on a platform that tilts or moves. During the test, the patient is typically standing or walking on a platform that moves in response to changes in body position. The patient's movements are monitored using video or other equipment.

What Are the Indications of Vestibular Function Tests?

The indications for vestibular function tests may include:

• Dizziness or vertigo.

• Imbalance or difficulty walking.

• Unsteadiness or feeling of being "off-balance".

• Nausea or vomiting associated with motion or movement.

• Hearing loss or tinnitus (ringing in the ears).

• Recent head injury or concussion.

• History of ear infections or ear surgery.

• Neurological symptoms such as headache, double vision, or numbness/weakness in the extremities.

How to Perform a Vestibular Function Test?

Here are some general steps involved in a typical vestibular function test:

• Consultation: The patient will first have a consultation with an audiologist or other healthcare provider to discuss symptoms and medical history. To identify potential underlying conditions causing the current symptoms, a physical examination may be conducted.

• Preparation: Before the test, patients may be asked to avoid certain medications, foods, or activities that could interfere with the results. They are asked to wear comfortable clothing and avoid wearing makeup, as some tests involve placing electrodes or other sensors on the skin.

• Assessment of Eye Movements: One common type of vestibular function test is the videonystagmography (VNG) test, which involves placing goggles with cameras inside them over the eyes. The cameras track eye movements while patients watch a series of visual stimuli or perform certain head movements. This test can help assess the function of one's vestibular system and ability to maintain visual focus during head movements.

• Caloric Testing: Another type of test is caloric testing, which involves irrigation of the ear canal with warm or cool water to stimulate the vestibular system. This can help assess the function of each ear and may be useful in diagnosing conditions such as vestibular neuritis or Meniere's disease.

• Balance Testing: Additionally, balance testing can be conducted to evaluate the capacity to sustain balance and posture in various positions or activities. This may involve standing on a platform that moves or walking on a treadmill while wearing a safety harness.

• Interpretation of Results: After the tests are complete, the results will be analyzed by the healthcare provider to determine the function of the vestibular system and identify any underlying conditions or abnormalities.

Conclusion:

Vestibular function tests are essential diagnostic tools for evaluating and diagnosing vestibular disorders. These tests can help identify the type and severity of vestibular dysfunction and guide appropriate treatment strategies. Caloric testing, rotational testing, and vestibular evoked myogenic potential (VEMP) testing are among the commonly performed vestibular function tests. Interpretation of test results requires careful consideration of a patient's history, symptoms, and other clinical findings.