[Study of effect of caloric test in different perfusion directions on caloric test results]

Objective: To investigate whether the direction of air stimulation in caloric test affects the results, and to provide evidence for standardizing the procedure and quality control. Methods: The study subjects were 160 patients with vestibular peripheral vertigo who were treated in Tianjin First Central Hospital from June 2023 to May 2024, including 53 males and 107 females, aged from 12 to 84 years, with an average age of 51.9 years.Video nystagmography (VNG) and a thermal air stimulator were used to perform caloric tests on 160 patients with vertigo, who were randomly assigned to two groups by computer random number table method. In Group 1 (n=80), both ears were first stimulated in the posteroinferior direction, followed by anterosuperior stimulation of the left ear in 40 cases and the right ear in 40 cases. In Group 2 (n=80), the order was reversed: the left and right ears received anterosuperior stimulation first, followed by posteroinferior stimulation in both ears. The maximum slow phase velocity (SPV) of induced- nystagmus, unilateral weakness (UW), and directional preponderance (DP) were recorded and compared between different stimulation directions. Statistical analyses were performed using SPSS 26.0 software. Results: In Group 1, the slow-phase velocity (SPV) of nystagmus elicited by posterior-inferior air stimulation was consistently higher than that induced by anterior-superior stimulation. This difference was statistically significant, as determined by the Wilcoxon signed-rank test (P<0.05). Among the 31 participants who exhibited normal unilateral weakness (UW) following posterior-inferior stimulation, 24 (77.4%, 24/31) developed abnormal UW after subsequent anterior-superior stimulation. Conversely, among the 32 participants with initially abnormal UW after posterior-inferior stimulation, 14 (43.8%, 14/32) showed normalization of UW following anterior-superior stimulation. With respect to directional preponderance (DP), 65 participants had normal DP and 15 had abnormal DP after posterior-inferior stimulation. Following anterior-superior stimulation, 4 individuals with initially normal DP values became abnormal, whereas 3 individuals with initially abnormal DP values reverted to normal. In Group 2, the SPV of nystagmus induced by anterior-superior stimulation was significantly lower than that elicited by posterior-inferior stimulation, with a statistically significant difference (P<0.05) confirmed by the Wilcoxon signed-rank test. Among the 29 participants with normal UW after anterior-superior stimulation, 11 (37.9%, 11/29) exhibited abnormal UW upon subsequent posterior-inferior stimulation. Of the 39 participants with abnormal UW after anterior-superior stimulation, 21 (53.8%, 21/39) demonstrated normalized UW following posterior-inferior stimulation. Regarding DP, 70 participants had normal and 10 had abnormal baseline values after anterior-superior stimulation; after posterior-inferior stimulation, 2 participants with initially normal DP values developed abnormalities, while, 3 with initially abnormal values returned to normal. Conclusions: The direction of thermal stimulation in caloric testing significantly influences test outcomes. Posterior-inferior air stimulation appears to provide a more robust vestibular response. Standardization of airflow direction is therefore essential for ensuring reliability and accuracy in caloric testing, and should be considered a critical component of quality control in clinical vestibular assessment.