Is regression gain or instantaneous gain the most reliable and reproducible gain value when performing video head impulse testing of the lateral semicircular canals?

Abstract

Background: Several different video Head Impulse Test (vHIT) systems exist. The function of each individual semicircular canal (SCC) may be determined by performing this test. All vHIT systems provide information about the function of the vestibular ocular reflex by means of two modalities: SACCADES and GAIN. However, different gain calculation methods exist.

Objective: Primary endpoint:•Is instantaneous gain or regression gain the most reproducible and reliable gain value when performing vHIT with testing of the lateral SCCs?Secondary endpoints:•Comparison of each of the instantaneous gain values at 40, 60, and 80ms with the regression gain.•Examination of any intra- and inter examiner variability.•Mean instantaneous gain values, and at different velocities, compared with regression gain values of the lateral SCCs.

Methods: 60 subjects between 18-65 years were included. All patients filled out the Dizziness Handicap Inventory (DHI) questionnaire and underwent four separate vHIT tests, two by an experienced neurotologist and two by an inexperienced examiner.

Results/conclusions: 240 datasets were obtained, displaying both regression and instantaneous gain values. Regression gain was more reproducible than instantaneous gain. The experienced examiner provided the most reproducible results.When comparing instantaneous gain, we found the gain at 40 ms to be the least reproducible. There was no significant difference between 60 ms and 80 ms.For both examiners no significant intra examiner variability was found.

Keywords: Instantaneous gain; gain; regression gain; vHIT; vestibular ocular reflex; video head impulse test. EyeSeeCam.