By Associate Professor James McLoughlin
Over the past decade, vestibular education has strongly emphasized the role of the Head Impulse Test (HIT) and its video-based cousin (vHIT), particularly in acute settings. This focus stems from their pivotal role in the Head Impulse, Nystagmus, Test of Skew (HINTS) protocol, which—when applied accurately and in the right context—can help differentiate central causes (e.g., stroke) from peripheral vestibulopathies (e.g., vestibular neuritis). Rightly so: it’s a powerful, bedside decision tool in emergency neurology.
However, I have noticed over the past 5 years, this stroke-centric application of HIT/vHIT taught in many vestibular courses has disproportionately shaped the broader clinical conversation—especially in rehabilitation and sports medicine. Too often, clinicians are left with the impression that a normal vHIT rules out significant dysfunction. In reality, this is where functional vestibular assessment should begin.
HIT and vHIT primarily assess high-frequency, high-acceleration components of the vestibulo-ocular reflex (VOR). They’re excellent at detecting large, acute deficits in semicircular canal output. But these tools do not capture:
In cases like concussion, cerebellar ataxia, migraine-associated dizziness, or motion sensitivity, the vHIT may be entirely normal while patients still report disabling dizziness, fogginess, or blurred vision during head movement.
Patients don’t live in a vHIT lab. They live in dynamic environments—navigating busy streets, scanning playing fields, or walking through supermarkets. These real-world tasks require gaze stability across a variety of head speeds, directions, and cognitive loads.
We must assess gaze stability across a range of speeds and tasks to:
Even simple tools like Dynamic Visual Acuity (DVA) and the VOMS battery can reveal critical deficits missed by vHIT.
In concussion, vestibular symptoms often reflect central processing issues, not peripheral loss. Patients may pass vHIT yet experience visual blurring, dizziness, or cognitive fatigue.
Cerebellar disorders affect the coordination of eye-head movement and often require dynamic, functionally relevant testing to identify deficits.
vHIT is a starting point. To support recovery, clinicians could incorporate:
If symptoms persist, dig deeper than just HIT and vHIT. Gaze stability is not binary. Like all brain functions, it must be assessed across varied speeds, loads, and contexts to understand and treat it most effectively.
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