Background: Vestibular dysfunction is common in people with multiple sclerosis (PwMS), but responses to optokinetic stimulation (OKS) across different vestibular conditions remain unclear. This study examined the immediate effects of VR-based OKS on balance and motion sickness in PwMS.
Methods: Forty-one PwMS and 23 matched healthy controls were included. Participants were classified by videonystagmography into MS with central vestibular involvement (n = 20, Group 1), MS without vestibular involvement (n = 21, Group 2) and healthy controls (n = 23, Group 3). Postural control was assessed with the FreeMED forceplate and VR sickness with the VR Sickness Questionnaire. Individually tailored OKS was delivered using Oculus Quest 2, with assessments immediately before and after stimulation.
Results: Significant group × time interactions were found for sway length (open eyes [OE] monopodal left p = 0.024, closed eyes [CE] monopodal left p = 0.012, CE monopodal right p = 0.009), average speed (OE bipodal p = 0.004, OE monopodal left p = 0.017, CE monopodal right p = 0.026), mediolateral sway (CE bipodal p = 0.014, OE monopodal right p = 0.038) and anteroposterior sway (OE monopodal left p = 0.013). Post hoc analyses showed reduced sway length in G2 (p = 0.047), reduced average speed in G1 (p = 0.002), increased mediolateral sway in G1, G3 and G2 (p = 0.031, p = 0.026, p = 0.010) and opposite anteroposterior responses, decreasing in G1/G2 but increasing in G3, with differences between G1-G2 and G2-G3 (p = 0.007, p = 0.004). VR sickness scores did not differ between groups (p > 0.05).
Conclusion: VR-based OKS induced immediate, well-tolerated balance changes in PwMS, with group-specific responses across conditions. Greater destabilization was seen in those with central vestibular involvement. Individualized OKS may promote vestibular adaptation and improve postural control in MS rehabilitation.
Keywords: multiple sclerosis; optokinetic stimulation; vestibular dysfunction; virtual reality.