RESUMO
BACKGROUND AND OBJECTIVES: The simultaneous binaural bithermal caloric test is performed by stimulating both ear canals with the water of same temperature at the same time. There are some reports that the simultaneous binaural bithermal caloric test appears to be more sensitive than the alternative bithermal caloric test in detecting caloric vestibular abnormalities. However, it is not well known yet what effect simultaneous binaural bithermal caloric test has on the vestibulo-ocular reflex. We attempted to verify the clinical usefulness of the simultaneous binaural bithermal caloric test. MATERIALS AND METHODS: Otoneurologically normal subjects (n=20) and patients who have complaints of dizziness (n=141) were tested. The regular bithermal caloric test was performed, using Life-Tech water irrigator and the water of temperatures 30degreesC and 44degreesC. The simultaneous binaural bithermal test was performed using Brooker-Grams closed loop irrigator with 27degreesC and 44degreesC water. The irrigation time was 40 seconds and nystagmus was detected for more than 120 seconds by electronystagmography. We divided the test response into six types with the reference value of canal paresis (CP) of the regular bithermal caloric test. RESULTS: The distribution of nystagmus type did not show regular pattern in the normal controls. The distribution of type I and II was 77.4% when CP was more than 25% in patients, 50.6% when CP was less than 25% in patients, and 42.5% in the normal group. The maximal velocity of slow component increased in the unilateral canal paresis patients (CP>25%), compared with the normal controls and no unilateral canal paresis patients (Cp<0.05). CONCLUSION: We observed that the simultaneous binaural bithermal caloric test has advantages of being less time-consuming and more comfortable. When the maximal velocity of slow component is more than 22.6 deg/sec with type I or II response, we could predict canal paresis; however, further studies should be made for abnormal response of simultaneous caloric response on the central nervous ststem.