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What is head function test?

Published in Vestibular Function Test 2 mins read

The head impulse test (HIT) is a clinical examination used to assess the function of the vestibular system.

Understanding the Head Impulse Test

The head impulse test, also known as the Halmagyi-Curthoys test, is a crucial part of diagnosing balance disorders. It specifically examines the vestibulo-ocular reflex (VOR), which is vital for maintaining clear vision during head movements.

What Does the Head Impulse Test Measure?

The test evaluates how well your eyes move in response to quick, small head movements. The VOR works to keep your eyes steady while your head moves, so a healthy VOR will allow you to maintain focus on a target.

  • High Acceleration: The head movement is rapid and sudden.
  • High Velocity: The head is moved quickly.
  • Low Amplitude: The head movement is small and not a large rotation.

How is the Head Impulse Test Performed?

  1. The patient focuses on a stationary target, usually a point on the wall or an object.
  2. The examiner quickly and unpredictably moves the patient's head a small amount to one side and then the other.
  3. The examiner observes the patient's eye movements.

Interpreting the Results

A healthy response involves the eyes remaining fixed on the target despite the rapid head movement. When the VOR is impaired, the eyes will move off of the target during the head impulse, then make a quick corrective eye movement (saccade) to re-acquire the target. This saccade is an indication of a weakened vestibular system.

Test Result Interpretation
Eyes remain on target Normal VOR, the peripheral vestibular system is likely functioning correctly.
Eyes move off, then back Abnormal VOR, indicating dysfunction in the peripheral vestibular system on the side of the head turn.

Why is the Head Impulse Test Important?

The HIT is a quick and effective test that helps identify:

  • Peripheral Vestibular Dysfunction: Problems in the inner ear balance organs or vestibular nerve.
  • Differentiating Causes of Vertigo: Distinguishing between peripheral and central (brain-related) causes of vertigo.
  • Guiding Treatment Plans: Allowing healthcare professionals to create appropriate treatment plans based on the test findings.

In Summary

The head impulse test (HIT) is a valuable tool for assessing the function of the peripheral vestibular system. It is a clinical test that measures the vestibulo-ocular reflex’s response to quick head movements. By observing eye movement responses, clinicians can identify potential balance system problems and determine the appropriate treatment course.