Temperature Order Effects in the Caloric Reaction.

Does it matter in what order the four irrigations are conducted in the caloric test? It has been suggested that warm water (44 degrees C) elicits stronger reactions than does cold water (30 degrees C), which might be explained simply by slight differences in water temperatures. However, if it can be shown that starting with cold water diminishes the difference between the warm and cold irrigations, it might be worthwhile to apply the cold irrigations first. Binaural, bithermal caloric irrigation was conducted in darkness using electrooculography. Maximum slow-phase velocity was measured. One hundred and eighteen consecutive patients from our laboratory were tested with warm water first and then with cold irrigations. In a second run, 108 subjects were irrigated with cold water before the warm. Employing cold irrigations first produces a smaller difference between the warm and the cold irrigations than does the opposite order. However, the lateral and directional preponderances, according to the formulas of Jongkees, are not affected by this change of irrigation order. The fact that initial warm-water irrigations cause the temperature effect differences to be larger than do initial cold-water irrigations is a phenomenon having only marginal clinical implications.