Figure 2.

Flowchart to scan for restrictive mistakes. Restrictive mistakes are artifacts preventing a confident overall video head impulse test (vHIT) interpretation of one participant (restrictive artifacts) or an insufficient head velocity stimulus in all vHIT traces of one participant. First, sufficient peak head velocity was checked (>100°/s). In a second step, data were scanned for artifacts possibly restricting overall interpretability [in analogy to (10)]: (1) Slippage: phase shift of the head with respect to eye motion, probably due to a loose goggle strap, the examiner touching the goggle strap while applying the head impulse or stretching the patient's skin. (2) Calibration problems: mostly due to participants not following the calibration instructions. Signs pointing to an insufficient calibration may be inappropriately high (>1.3) or low (< 0.79) vestibulo-ocular reflex (VOR) gain values without consecutive re-fixation saccades. (3) Blinks: oscillations crossing the baseline (no saccades, ≥75% of peak eye velocity). (4) Multiple VOR peaks: two or more eye velocity peaks during head movement (no saccades, ≥25% of peak eye velocity), probably due to the examiner touching the goggles, mini-blinks or impaired pupil detection. (5) Trace oscillations: oscillations (no saccades, < 25% of peak eye velocity during head movement and < 75% of peak eye velocity after head movement), probably due to impaired pupil detection. (6) Wrong VOR direction: no eye movement or eye movement in the same direction as the head movement, probably due to patient inattention. (7) Unclassifiable artifact: any other artifact, which restricts interpretation, but does not match the criteria above.