Comparison of video head impulse test (VHIT) and functional head impulse test (FHIT) results in unilateral peripheral vestibular failure

In this study, It was aimed (1) to evaluate functional impairment in VOR with functional head impulse test (fHIT) in different head accelerations and the integrity of VOR path with video head impulse test (vHIT) in all SCCs, (2) to determine the correlation between canal paresis level in caloric test, the mean Percentage of correct Answers (PCA) in fHIT and VOR gains in vHIT, (3) to compare fHIT and vHIT test results with the results of healthy controls, and (4) to examine the correlation of subjective dizziness disability perception level obtained in the Dizziness Handicap Inventory (DHI) together with PCA and VOR gains of patients with unilateral chronic peripheral vestibular failure. This study has been conducted by the participation of 48 patients (experimental group) who have been diagnosed with 'unilateral chronic peripheral vestibular failure' and whose mean age are 48.42 ± 13.05 years and 35 healthy individuals (control group) who do not have any health problems and whose mean age are 46.06 ± 12.57. The experimental group has been also divided into three subgroups as mild, moderate and severe canal paresis. vHIT and fHIT have been applied to the experimental and control groups, respectively. DHI has also applied to the experimental group. As a result of the study, a significant difference has been obtained between the total PCA of the affected and healthy side of the experimental group in horizontal SCC plane considering the Standard fHIT Result (ratio of total correct answers in the 3000-6000 °/s2 head acceleration range) (p <0.05). There was no significant difference among the two ears in the vertical (anterior and posterior) SCC plane (p> 0.05). While the head acceleration of the experimental group has been increasing from 3000 to 6000 °/s2 in each SCC, PCA has started to decrease. It has been found that there is a significant correlation between the level of canal paresis and PCA in the lateral canal plane at a negative low level (r = -0.289), and a significant correlation in the vertical canal plane at negative and moderate level (r = -0.370 and r = -0.490). There was positive correlation at moderate level in the lateral and posterior SCCs and there was a positive relation at low level in the anterior SCC among the fHIT and vHIT results of the affected side of the experimental group (p <0.05). It has been found that there is no statistically significant correlation between DHI total score and vHIT and fHIT results (p> 0.05). The standard fHIT and vHIT results of the control group have been obtained significantly higher than the affected side of the experimental group in all SCCs (p <0.05). These results show that deterioration of fHIT appears in VOR functionality when head accelerations and the canal paresis level increases in the patients with unilateral chronic peripheral vestibular failure. It will be beneficial to conduct both vHIT and fHIT as complementary tests because vHIT evaluates the integrity of the VOR and fHIT evaluates the VOR functionality. We believe that examining the psychological factors that increase this perception can provide a more comprehensive evaluation since both tests are not related to subjective dizziness handicap perception. Keywords: Functional head impulse test (fHIT); Video head impulse test (vHIT); Caloric test; Dizziness handicap inventory (DHI)