Deviation of the Subjective Vertical in Long-standing Unilateral Vestibular Loss

Abstract

We evaluated changes in the subjectively perceived gravitational vertical as an index of imbalance in the function of the right and left otolith organs. In addition to normal subjects (n = 25), we measured patients with a longstanding (mean 4.5 year +/- 3.2 SD; range 0.5-11.5 years) unilateral vestibular loss after surgery for acoustic neuroma (n = 32), patients with partial unilateral vestibular loss (n = 7) and patients with bilateral vestibular hyporeflexia (n = 8). Normal subjects could accurately align a vertical luminous bar to the gravitational vertical in an otherwise completely dark room (mean setting -0.14 degree +/- 1.11 SD). Patients with left-sided (complete; n = 13) or right-sided (complete; n = 19 and partial; n = 7) unilateral vestibular loss made mean angular settings at 2.55 degrees +/- 1.57 (SD) leftward and 2.22 degrees (+/-1.96 SD) rightward, respectively. These means differed highly significantly from the normal mean (p < 0.00001). In the time interval investigated (0.5-11.5 years) the magnitude of the tilt angle showed no correlation with the time elapsed since the operation. The mean setting by patients with clinically bilateral vestibular loss (-1.17 degrees +/- 1.96 SD; n = 8) did not significantly differ from the control group. The systematic tilts of the subjective vertical in patients with a unilateral vestibular impairment were correlated with their imbalance in canal-ocular reflexes, as reflected by drift during head-oscillation at 2 Hz (r2 = 0.44) and asymmetries in VOR-gain for head-steps (r2 = 0.48-0.67). These correlations were largely determined, by the signs of the asymmetries; correlation between the absolute values of the VOR gain asymmetries and subjective vertical angles proved to be virtually absent. We conclude that the setting of the subjective vertical is a very sensitive tool in detecting a left-right imbalance in otolith function, and that small but significant deviations towards the defective side may persist for many years (probably permanently) after unilateral lesions of the labyrinth or the vestibular nerve.

Effect of Semicircular Canal Stimulation on the Perception of the Visual Vertical

“…The topic has not only physiological but also clinical implications because the clinical literature tends to view abnormal tilts of the SVV as a selective indication of otolith (graviceptive) system disease (Böhmer and Mast 1999;Brandt and Dieterich 1994;Gresty et al 1992;Halmagyi and Curthoys 1999;Tabak et al 1997;Vibert et al 1999). First we will discuss the effect of rotation on the SVV and then the relation between the SVV and eye movements.…”

“…In the upright position, stationary normal subjects are able to set a luminescent bar with great accuracy to within a mean deviation of Ϯ2°of the true gravitational vertical (Friedman 1970). As a result, clinical studies emphasize that greater than average tilts of the subjective visual vertical (SVV) are a sensitive tool for detecting an imbalance in otolith function (Böhmer and Mast 1999;Gresty et al 1992;Halmagyi and Curthoys 1999;Tabak et al 1997;Vibert et al 1999).…”

Otolith Function Assessed with the Subjective Postural Horizontal and Standardised Stance and Gait Tasks

“…It has previously been reported that approximately 6 months after unilateral vestibular deafferentation offsets with otolith function tests reach a stable, partially compensated, state for example as measured by roll tilt perception with linear acceleration [Curthoys et al, 1991b], by the subjective vertical [Tabak et al, 1997] or 'head heaves' [Nuti et al, 2005]. By choosing patients with such a stable state, that is, those operated at least 6 months (mean 34 8 20.9 months) prior to testing, we assumed that any central compensation of unilateral otolith dysfunction was complete.…”

Subjective visual vertical test in patients with chronic dizziness without abnormal findings in routine vestibular function tests

“…However, the above-mentioned tests are limited in that they mostly evaluate the function of the semicircular canal and, therefore, the possibility that such patients have disturbance in the otolithic organs and the graviceptive system cannot be excluded. The subjective visual vertical (SVV) is a highly reliable test for examining function of the otolithic organs and the graviceptive pathways [1,2]. SVV tends to indicate abnormal tilts to the affected side at the acute stages in peripheral disorders [3,4], and various abnormal tilts of SVV are observed in central disorders such as Wallenberg's syndrome [5].…”