Spatial orientation in patients with chronic unilateral vestibular hypofunction is ipsilesionally distorted

•Visual vertical (VV) was measured in 13 patients with chronic unilateral vestibular hypofunction.•VV shifts in the patients were significant only when rolled ipsilesionally.•Thus VV testing in roll-tilted positions is recommended to identify more subtle vestibular deficits.

ObjectiveAcute unilateral peripheral-vestibular hypofunction (UVH) shifts the subjective visual vertical (SVV) ipsilesionally, triggering central compensation that usually eliminates shifts when upright. We hypothesized that compensation is worse when roll-tilted.MethodsWe quantified SVV errors and variability in different roll-tilted positions (0°, ±45°, ±90°) in patients with chronic UVH affecting the superior branch (SVN; n = 4) or the entire (CVN; n = 9) vestibular nerve.ResultsErrors in SVN and CVN were not different. When roll-tilted ipsilesionally 45° (9.6 ± 5.4° vs. −0.2 ± 6.4°, patients vs. controls, p < 0.001) and 90° (23.5 ± 5.7° vs. 16.8 ± 8.8°, p = 0.003), the patient's SVV was shifted significantly towards the lesioned ear. When upright, only a trend was noted (3.6 ± 2.2° vs. 0.0 ± 1.2°, p = 0.099); for contralesional roll-tilts shifts were not different from controls. Variability was larger for CVN than SVN (p = 0.046). With increasing disease-duration, adjustment errors decayed for ipsilesional roll-tilt and upright (p ⩽ 0.025).ConclusionsThe reason verticality perception was distorted for ipsilesional roll-tilts, may be the insufficient integration of contralesional otolith-input. Similar errors in SVN and CVN suggest a dominant utricular role in verticality perception, albeit the sacculus may improve precision of SVV estimates.SignificanceWith deficiencies in central compensation being roll-angle dependent, extending SVV-testing to roll-tilted positions may improve identifying patients with chronic UVH.