Determination of the time course of caloric nystagmus in patients with spinocerebellar degeneration using caloric step stimulus procedure.

CONCLUSIONS: The step stimulus procedure can provide information on the time course of the vestibulo-ocular reflex. Spinocerebellar degeneration and aging seem to shorten the time constant of the onset of the vestibulo-ocular reflex, causing a rapid rise up. Failure of the central processing of velocity storage might contribute to this rapid rise up.

OBJECTIVES: The aim of this study is to evaluate the time course characteristics of the vestibulo-ocular reflex in patients with spinocerebellar degeneration.

METHODS: Ten patients (20 ears) and 22 healthy subjects (30 ears) underwent caloric test using the step stimulus procedure. We evaluated the time course of caloric VOR and calculated the parameters of the time constant of an activation and adaptation response. We compared between the control and SCD groups to elucidate the time course characteristics of caloric VOR in patients with SCD.

RESULTS: Spinocerebellar degeneration seems to shorten the time constant of the activation response by caloric irrigation with 20 °C, 7l/min air. However, aging also possibly contributes to this shortening. No change was observed in the time constant of the adaptation response.