Figure 13.

Results for tests of every semicircular canal of a patient with left unilateral vestibular loss. The patient's eye was measured simultaneously with scleral search coils and vHIT. For every rotation direction activating the canals on the healthy right side, the eye velocity response is close to normal. However, for every rotation in a direction to activate canals on the affected left side, there is a reduced VOR response. In particular, for the vertical canals on the affected side, there is clearly reduced function. To compensate for the deficit on the affected left side, overt saccades appear after head rotation (red traces). These corrective saccades are important confirmation that the reduced VOR gain is not due to poor gaze direction. The late inverted overt saccades for right lateral stimulation are likely due to the fact that there was such a big overshoot in head velocity that the overshoot became an impulse to the affected left side, which the affected ear could not generate sufficient SPV to compensate, so the “reverse” overt saccades appeared. There is very close similarity between coils and vHIT traces, further validating vHIT [Reproduced with permission from MacDougall et al. (9)].