Abstract
Purpose :
Antihistamines make up the first line of treatment for nausea, vertigo and dizziness. The antiemetic mechanism is thought to be due to an inhibitory effect on the vestibular apparatus. A decrease in gain for the vestibulo-ocular reflex (VOR) has been recorded after antihistamine administration during sinusoidal oscillation and rough-sea voyaging. Vestibular activation is reflected in ocular counter-rolling (OCR) and a physiological skew deviation during head tilt. This balance-specific combination of eye movements (EM) can also be triggered by visual stimulation alone. As vertigo is considered to be the result of a mismatch between sensory inputs, we have constructed a set of visual- and vestibular balance provoking stimuli, aiming to discern the effect of antihistamines on respective system.
Methods :
12 healthy subjects were randomly assigned to either placebo treatment (sugar pills) or antihistamine (Meclozine, 50mg) in this double-blinded study. Subjects were exposed to three balance provoking trials in a randomized order, i) visual (VIS), ii) vestibular (VES), and iii) visuo-vestibular (VIS-VES). EM were recorded using a Chronos Eye Tracker. VIS were presented and rotated on two meters distance. VES were carried out through whole-body tilting using a mechanical sled in complete darkness. VIS-VES involved being tilted while viewing a static visual scene. All tilts and rotations were carried out in a randomized order at two magnitudes (14°- and 28°s-2) with duration of 1 sec in order to simulate low- and high movement intensities. Trials were carried out both before and after treatment intervention in order to ascertain group uniformity. EM velocities were calculated in order to assess any treatment effect.
Results :
No significant differences could be found between groups before treatment intervention. After treatment, the Meclozine group showed a significantly lower torsional velocities during VIS and VIS-VES stimulations of 14°s-2. There was no significant change in isolated vestibular provocations.
Conclusions :
While the positive effects of Meclozine on motion sickness and vertigo have been assigned to an inhibitory effect on the vestibular apparatus, this study suggests that the effect rather lies in a reduced visional sensitivity to balance provocations. Additionally, the effect is only significant during low-intensity motion.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.