Two conditions to fully recover dynamic canal function in unilateral peripheral vestibular hypofunction patients

Abstract

BACKGROUND: The crucial role of early vestibular rehabilitation (VR) to recover a dynamic semicircular canal function was recently highlighted in patients with unilateral vestibular hypofunction (UVH). However, wide inter-individual differences were observed, suggesting that parameters other than early rehabilitation are involved. OBJECTIVE: The aim of the study was to determine to what extent the degree of vestibular loss assessed by the angular vestibulo-ocular reflex (aVOR) gain could be an additional parameter interfering with rehabilitation in the recovery process. And to examine whether different VR protocols have the same effectiveness with regard to the aVOR recovery. METHODS: The aVOR gain and the percentage of compensatory saccades were recorded in 81 UVH patients with the passive head impulse test before and after early VR (first two weeks after vertigo onset: N = 43) or late VR (third to sixth week after onset: N = 38) performed twice a week for four weeks. VR was performed either with the unidirectional rotation paradigm or gaze stability exercises. Supplementary outcomes were the dizziness handicap inventory (DHI) score, and the static and dynamic subjective visual vertical. RESULTS: The cluster analysis differentiated two distinct populations of UVH patients with pre-rehab aVOR gain values on the hypofunction side below 0.20 (N = 42) or above 0.20 (N = 39). The mean gain values were respectively 0.07±0.05 and 0.34±0.12 for the lateral canal (p < 0.0001), 0.09±0.06 and 0.44±0.19 for the anterior canal (p < 0.0001). Patients with aVOR gains above 0.20 and early rehab fully recovered dynamic horizontal canal function (0.84±0.14) and showed very few compensatory saccades (18.7% ±20.1%) while those with gains below 0.20 and late rehab did not improve their aVOR gain value (0.16±0.09) and showed compensatory saccades only (82.9% ±23.7%). Similar results were found for the anterior canal function. Recovery of the dynamic function of the lateral canal was found with both VR protocols while it was observed with the gaze stability exercises only for the anterior canal. All the patients reduced their DHI score, normalized their static SVV, and exhibited uncompensated dynamic SVV. CONCLUSIONS: Early rehab is a necessary but not sufficient condition to fully recover dynamic canal function. The degree of vestibular loss plays a crucial role too, and to be effective rehabilitation protocols must be carried out in the plane of the semicircular canals.

Posture Deficits and Recovery After Unilateral Vestibular Loss: Early Rehabilitation and Degree of Hypofunction Matter

“…Taken together, this retrospective clinical study in patients with UVH extends to balance recovery the findings we recently highlighted for gaze stabilization recovery (Lacour et al, 2021). Balance function recovery also depends on the two conditions required to fully recover dynamic canal function, that is, early rehabilitation and degree of pre-rehabilitation vestibular hypofunction.…”

“…found for aVOR gain recovery (Lacour et al, 2019(Lacour et al, , 2020b(Lacour et al, , 2021. It can be explained by the multisensory integration process necessary to achieve posture control in quiet standing conditions.…”

“…As reported for dynamic canal function recovery, early rehabilitation is a necessary but not sufficient condition. Degree of vestibular hypofunction matters too (Lacour et al, 2021).…”

“…Data recorded in patients with unilateral peripheral vestibular hypofunction (UVH) rehabilitated with gaze stability exercises (Lacour et al, 2019) or the unidirectional rotation paradigm (Lacour et al, 2020b) reported better angular horizontal vestibulo-ocular reflex (aVOR) gain recovery with early rehabilitation (the first 2 weeks) compared with later rehabilitation. The degree of vestibular loss was a second crucial parameter influencing aVOR recovery: patients with pre-rehabilitation aVOR gain above 0.20 fully recovered dynamic canal function compared with patients with lower gain who used covert saccades to stabilize gaze (Lacour et al, 2021). Do early rehabilitation and degree of vestibular loss also matter for balance recovery in patients with UVH?…”

“…In other words, is there a critical period for rehabilitation of posture and balance, and is the degree of vestibular hypofunction on the weaker side another important parameter to recover balance function? On the basis of our recent findings on dynamic canal function recovery (Lacour et al, 2021), we tested the hypothesis that patients with early rehabilitation and higher pre-rehabilitation aVOR gain would recover dynamic equilibrium better than those with late rehabilitation and lower aVOR gain.…”