The protective stepping response in patients with bilateral vestibular hypofunction

Abstract

Objective: Protective stepping following postural instability is a defence mechanism that prevents falls. Vestibular patients have increased risk of falling but little is known about their stepping response. Here, we investigate whether the protective stepping response is preserved in patients with bilateral vestibular hypofunction (BVH). Methods: This cross-sectional study, conducted in a balance-research facility, measured body sway and protective stepping responses during a dynamic postural task (platform oscillations at different velocities). Patients diagnosed with BVH were recruited from neuro-otology clinics. As stepping may be dictated by instability perception, objective sway and subjective instability were also analysed for each participant. Results: 12 patients (4 males, age:65.1, SD:14.2 years) and 12 healthy age and gender matched controls (age:64.8, SD:5.3) were recruited. Patients swayed more than controls (t:-2.153,p=0.03,d=-0.39) and showed marginally steeper objective-subjective instability curves than controls (t:-2.082,p=0.053,d=-0.85), meaning they felt slightly more unstable than controls for the same amount of sway. However, stepping velocity thresholds (t:-1.013,p=0.324,d=0.45) and latencies (t:0.062,p=0.951,d=-0.02) were not different between patients and controls. Discussion: These results indicate that the protective stepping response is preserved in BVH patients, hence not critically dependent on vestibular input. Only chronic patients were included, which limits the generalisation of the results to acute phases of the vestibular loss