Refining the video head-impulse test diagnostic accuracy - a
retrospective case-control study.
Abstract
Abstract Objective: To appraise the added benefit of refixation saccades
(RS) towards the improvement of the video head-impulse test (vHIT)
diagnostic accuracy in cases of suspected left horizontal semicircular
canal dysfunction. Study Design: Case-control. Setting: Tertiary
referral center. Participants: Twenty patients with a final diagnosis of
left horizontal semicircular canal dysfunction and 20 patients for whom
vestibular dysfunction was ruled out. Intervention: vHIT recordings of
40 patients with left horizontal semicircular canal (LHSCC)
vestibulo-ocular reflex (VOR) gain <0.8. Main outcome
measures: LHSCC VOR gain; Presence of RS and their frequency, latency,
and velocity characteristics. Results: Gain values > 0.72
were found in all patients with no vestibular disease and in 4 (20%)
patients having vestibulopathy. Significantly higher average left-sided
RS velocity and frequency were found among the vestibular patients. VOR
gain < 0.72 was found to be highly specific for the diagnosis
of vestibular dysfunction. However, for gain values in the range of
0.72-0.79 the presence of RS with frequency > 80% largely
improved vHIT diagnostic accuracy. CONCLUSIONS: Although VOR
gain<0.8 is considered to reflect dysfunction a significant
false positive rate for left-sided horizontal vHIT was found for gains
in the range of 0.72-0.79. The presence of RS with frequency
>80% could improve vHIT diagnostic ability in these
patients. Key words: video head impulse test, re-fixation saccades,
peripheral vestibular pathology, gain asymmetry in vHIT, lateral
semicircular canal hypofunction, saccadic frequency, corrective saccade
velocity