Prediction of Bithermal Caloric Response from Monothermal Stimulation

Abstract

The use of either cold or warm caloric stimulation alone as a screening tool for unilateral weakness has been suggested as a means of both shortening testing time and reducing patient discomfort. The validity of the monothermal caloric test must be well established before it can be routinely used in clinical situations. The purpose of this investigation was to re-evaluate the monothermal caloric test by examining the correlations between unilateral weakness derived from bithermal caloric stimulation compared to monothermal caloric results using either warm or cool stimulation alone. A retrospective analysis of 200 patients indicated significant correlations between bithermal and monothermal unilateral weakness for patients with unilateral weakness of <15% and >30% for both warm and cool water stimulation. For patients with 15% to 30% unilateral weakness, the bithermal and monothermal calorics were significantly correlated for only the cool condition. When predicting normal or >20% unilateral weakness, either of the monothermal calorics have >85% efficiency, with specificity >94% and sensitivity >64%. However, the false-negative rate is 29% for warm and 36% for cool calorics. The high rate of false-negative findings indicates that screening tests have no place in a diagnostic battery, especially in view of the implications for missing significant pathology.