Controlling the caloric labyrinthine stimulus: restoring surface temperature.

Abstract

The duration of the conventional caloric stimulus is too long and the termination of the stimulus is uncontrolled. This study explores the use of a brief terminal "washout" irrigation pulse at 37 degrees C which is intended to 1. shorten the duration of action of the caloric stimulus and 2. eliminate uncertainty over the magnitude and duration of the terminal portion of the thermal labyrinthine stimulus. Twelve normal subjects were tested with 1. conventional 30-second irrigations, 2. 30-second irrigations plus a "washout" pulse, and 3. temperature-switching caloric (TSC) irrigations plus a "washout" pulse. Clinical test scores were comparable with all three irrigation methods. The "washout" pulse produced only a slight shortening of the conventional 30-second irrigation responses.