What does vHIT test for?

The video head impulse test is an ear-specific test that detects disorders of the vestibulo-ocular reflex and identifies which ear is affected in cases of peripheral vestibular loss.

What is vHIT gain?

The video head impulse test (vHIT) is an objective test of the vestibulo-ocular reflex (VOR). The vHIT outcome parameter receiving most attention to-date has been vHIT gain, the ratio of eye movement to head movement. In normal controls, age has little impact on vHIT gain up to the 8th or 9th decades (1-3).

What does a positive head impulse test mean?

The presence of a compensatory, re-fixating saccade back to the examiner’s nose when the head stops moving is a positive clinical sign indicative of peripheral vestibular weakness (vestibular hypofunction) on side to which the head was rotated.

What is a covert Saccade?

“Overt” saccades are defined as corrective eye movements made after the head comes (substantially) to rest. “Covert” saccades are made earlier than head velocity returning to 0, usually during the high velocity part of the head movement.

What is vHIT?

The Video Head Impulse Test (vHIT) measures the vestibulo-ocular reflex (VOR), and is anatomically correlated to semicircular canal function in the peripheral vestibular system, motor nuclei in the brainstem, and extra-ocular muscles.

How is VHIT done?

The VHIT is an instrumented bedside technique used to diagnose reduction in vestibular function in one ear vs. the other. An examiner abruptly accelerates and then decellerates the head, moving the head in rapidly at high speed and then stopping it.

What is VHIT?

How can you tell the difference between peripheral and central vertigo?

[3] The most important differentiating facts are peripheral vertigo presents with predominant vestibulocochlear signs and symptoms of vertigo, tinnitus and/or hearing impairment whereas central vertigo is often associated with other brainstem signs and symptoms.

What causes Saccades catchup?

The eye crossing time, which depends on both position error and velocity error, is the criterion used to switch between smooth and saccadic pursuit, i.e., to trigger catch-up saccades. Conversely, when T(XE) becomes smaller than 40 ms or larger than 180 ms, a saccade is triggered after a short latency (around 125 ms).

What is an ENG test?

Electronystagmography (ENG or electrooculography) is used to evaluate people with vertigo (a false sense of spinning or motion that can cause dizziness) and certain other disorders that affect hearing and vision. Electrodes are placed at locations above and below the eye to record electrical activity.

What do you need to know about the VHIT?

Most vHIT systems are comprised of ultra-lightweight goggles imbedded with a camera capable of high frame rates (for capturing eye movement) and an accelerometer/gyroscope (for capturing head movement). During data collection, several head impulses are collected.

Is the caloric test the same as the VHIT?

Despite some parallels between the two tests, the short answer is a big NO. Unlike vHIT, the caloric test assesses the lateral canals and superior vestibular nerve only and cannot be used to assess the vertical canals or the inferior branch of the vestibular nerve.

What are reduced gain values on vHIT test?

The reduced gain values quantify the degree to which this patient is unable to maintain fixation in the presence of head movement. Figure 5: Abnormal left lateral vHIT The vHIT software analyzes each condition as well as the test as a whole. Results are provided in a comprehensive report that includes normative data.

Why was the video head impulse test ( VHIT ) introduced?

The introduction of the video head impulse test (vHIT) to our clinic was a turning point for me. Finally, I had something I could learn from the very beginning instead of feeling like I was perpetually playing catch up!