The functional Head Impulse Test (fHIT) measures functional gaze stability during rapid passive head impulses. It is not the same test as bedside Head Impulse Testing (HIT) or video Head Impulse Testing (vHIT).
Important safety limit
fHIT does not independently rule out stroke and should not be used as a home test. New continuous vertigo with weakness, facial droop, slurred speech, double vision, inability to walk, fainting, a severe new headache, chest pain, or sudden hearing loss needs urgent assessment.
How fHIT is performed
During the test, the head is moved with small, rapid, passive impulses in selected canal planes. A visual optotype is displayed very briefly during the movement. The patient identifies the optotype, and the result is expressed as the percentage of optotypes recognised correctly at the tested head-acceleration levels and canal planes.
This functional task asks whether vision remains useful during rapid head movement. The protocol and equipment differ from simply watching whether the eyes make a refixation movement.
fHIT, bedside HIT, and vHIT are different
- Bedside HIT: a trained clinician observes the eyes during rapid, passive head impulses and looks for refixation saccades.
- vHIT: a video-based system measures eye and head movement and estimates vestibulo-ocular reflex gain, with recorded saccades.
- fHIT: tests the patient’s ability to recognise briefly displayed visual optotypes during passive impulses and reports functional performance.
The tests may complement one another, but their names and interpretations should not be used interchangeably.
When fHIT may add useful information
- Gaze instability or blurred vision during head movement.
- Suspected unilateral or bilateral vestibular hypofunction after clinical assessment.
- Functional assessment during vestibular rehabilitation follow-up.
- Cases where symptoms, examination, and another vestibular test need to be interpreted together.
An fHIT result is interpreted with the symptom history, eye-movement and neurological examination, hearing symptoms, fall risk, and other investigations when indicated. An abnormal result does not name the cause by itself; a normal result does not exclude every vestibular or neurological condition.
Before the test
Tell the clinician about significant neck or back disease, recent injury or surgery, severe pain, vascular problems, visual difficulty, or movement restrictions. Do not stop prescribed medicines unless the clinician who arranged the test gives individual instructions.
Book a non-emergency vestibular assessment
Prime ENT Center provides fHIT as part of selected vestibular evaluations in Hardoi. Availability and whether the test is appropriate should be confirmed during booking. Call +91 73930 62200 or contact the clinic on WhatsApp.
References
- Functional Head Impulse Test methodology and interpretation
- NIDCD: balance disorders
- GRACE-3: correct context for acute dizziness pathways
Medical disclaimer: This page explains a clinical test; it is not a diagnosis or emergency screening tool.