1 research outputs found
The gain-time constant product quantifies total vestibular output in bilateral vestibular loss
Patients with inner ear damage associated with bilateral vestibular impairment often ask
“how much damage do I have.” Although there are presently three clinical methods
of measuring semicircular canal vestibular function; electronystagmography (ENG or
VENG), rotatory chair and video head-impulse (VHIT) testing; none of these methods
provides a method of measuring total vestibular output. Theory suggests that the slow
cumulative eye position can be derived from the rotatory chair test by multiplying the
high frequency gain by the time constant, or the “GainTc product.” In this retrospective
study, we compared the GainTc in three groups, 30 normal subjects, 25 patients with
surgically induced unilateral vestibular loss, and 24 patients with absent or nearly absent
vestibular responses due to gentamicin exposure. We found that the GainTc product
correlated better with remaining vestibular function than either the gain or the time
constant alone. The fraction of remaining vestibular function was predicted by the
equation R = (GainTc/11.3) – 0.6. We suggest that the GainTc product answers the
question “how much damage do I have,” and is a better measure than other clinical
tests of vestibular function