Functional Head Impulse Test in Professional Athletes: Sport-Specific Normative Values and Implication for Sport-Related Concussion

Abstract

Dizziness, slow visual tracking, or blurred vision following active head (or body) movements are among the most common symptoms reported following sport-related concussion, often related to concurrent dysfunctions of the vestibular system. In some cases, symptoms persist even if bedside and auxiliary standard vestibular tests are unremarkable. New functional tests have been developed in recent years to objectify neurological alterations that are not captured by standard tests. The functional head impulse test (fHIT) requires the patient to recognize an optotype that is briefly flashed during head rotations with various angular accelerations (2,001–6,000 deg/s 2 ) and assesses the proportion if correct answers ( pca ). 268 active professional athletes (23.70 ± 5.32y) from six different sports were tested using fHIT. Pca were analyzed both pooling head acceleration in the range of 2,001–6,000 deg/s 2 and computing a single pca value for each 1,000 deg/s 2 bin in the range 2,001–8,000 deg/s 2 . No significant difference ( p = 0.159) was found between responses to head impulses in the plane of horizontal ( pca : 0.977) and vertical semicircular canals ( pca : 0.97). The sport practiced had a major effect on the outcome of the fHIT. Handball players achieved a better performance ( p < 0.001) than the whole athlete group, irrespective of the direction of head impulses. The pca achieved by athletes practicing snowboard, bob and skeleton were instead significantly below those of the whole athlete group ( p < 0.001) but only when vertical head impulses were tested. Overall, pca declined with increasing head acceleration. The decline was particularly evident in the range not included in the standard fHIT exam, i.e., 6,001–8,000 deg/s 2 for horizontal and 5,001–8,000 deg/s 2 for vertical head impulses. When vertical head impulses were tested, athletes practicing snowboard, bob and skeleton (non-ball sports) showed, beside the lower overall pca , also a steeper decline as a function of vertical head acceleration. The findings suggest that: (1) functional VOR testing can help understanding sport-specific VOR requirements; (2) the fHIT is able to detect and objectify subtle, sport-specific changes of functional VOR performance; (3) if sport-specific normative values are used, the fHIT test procedure needs to be optimized, starting from the highest acceleration to minimize the number of head impulses.

A comparison of the video head impulse test and the functional head impulse test in chronic unilateral vestibular loss

“…In the study by Romano et al ., which determined the functional head impulse test normative values specific to different types of sport in the horizontal and vertical semicircular canal planes, the results for professional athletes and healthy non-athletes were compared. 9 There was no significant difference between the two groups in terms of the total percentage of correct answers, which was above 90 per cent for both groups. Accordingly, this study reported that a typical healthy individual is expected to give nearly 100 per cent of correct answers in the functional head impulse test.…”

“…A graphical user interface reports the number of impulses performed per acceleration step and the corresponding percentage of correct answers, thus helping the clinician to decide the head impulse acceleration rate. 1 , 9

Figure 1. Functional head impulse test results of the right and left lateral semicircular canals of a healthy participant.

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“…A graphical user interface reports the number of impulses performed per acceleration step and the corresponding percentage of correct answers, thus helping the clinician to decide the head impulse acceleration rate. 1,9 The mean percentage of correct answers in lateral semicircular canals in the head acceleration range of 4000-6000°/s 2 , the mean percentage of correct answers in the head acceleration range of 3000-6000°/s 2 in vertical (anterior and posterior) semicircular canals, and the mean percentage of correct answers for head acceleration steps of 3000, 4000, 5000 and 6000°/s 2 separately for all semicircular canals, were recorded and analysed (Figure 2). Thus, the correlation between head acceleration rate and the percentage of correct answers was also examined.…”

Vestibular Functioning in Children with Neurodevelopmental Disorders Using the Functional Head Impulse Test

“…This test, commercialized by BeOnSolutions society ( ), is based on the ability of a subject to read an optotype briefly presented during impulsive head rotations at varying angular accelerations [ 26 ]. Several studies have been conducted already using this test in adults from the general population [ 15 , 27 ] or with vestibular neuritis [ 16 , 28 ]. Briefly, the testing procedure was as follows: the child was seated on a chair placed at 150 cm distance from a computer screen connected to the fHIT device ( Figure 1 ).…”

Risk of falls, vestibular multimodal processing, and multisensory integration decline in the elderly–Predictive role of the functional head impulse test

“…Recently, the functional head impulse test (fHIT) was introduced among other laboratory vestibular tests (7)(8)(9)(10). Since fHIT is a subjective functional test and does not require analysis of eye movements as does vHIT, it also investigates the performance of the vestibular ocular reflex at a higher level in the brain (vestibular/associative cortex).…”