Enhanced smooth pursuit eye movements in patients with bilateral vestibular deficits

Patients with bilateral vestibular deficits experience unsteady gait and oscillopsia that can reduce the quality of life, though many patients adapt remarkably well and lead mostly normal lives. One source of adaptation could be the ability of sensory-motor systems to compensate for the vestibular loss by adaptive enhancement of their performance. We studied smooth-pursuit eye movements in five patients and six healthy control subjects using a step-ramp paradigm. Eye movements were measured with scleral search coils. Patients showed open- and closed-loop pursuit gains that were about 9% higher than controls. We suggest that the challenge of living with a deficient vestibular system caused an enhancement in the pursuit system, which contributes to the patient's overall compensation.