Stimulation of the vestibular receptor by means of step temperature changes during continuous aural irrigation

A technique for rapid, balanced hot/cold stimulation of the vestibular receptor is presented. During continuous aural irrigation the temperature of the irrigation fluid is switched between hot and cold values at times computed according to a mathematical model of heat conduction in the labyrinth area. As a result, the induced temperature difference across the lateral semicircular canal describes an approximately sinusoidal time course, reaching peak values of equal magnitude but opposite sign. Application of the test to 32 clinical subjects demonstrated that the heat conduction model and the analysis used in timing the sequence of thermal pulses was accurate. We expect that, with further refinements, the new technique will prove superior to conventional caloric test methods in the detection and measurement of subtle as well as gross abnormalities of the vestibular system.