[Optimization of low frequency function of vertical semicircular canal in rotating test and analysis of three-dimensional parameters of induced nystagmus].

Objective: To study the feasibility of detecting vertical semicircular canal function and to analyze the three-dimensional(3D)characteristics and normal reference value in healthy young people. Methods: This was a cross-sectional study conducted from January to June 2024. A three-axis rotating chair was used to perform vertical sinusoidal rotation on 52 healthy young adults (26 males and 26 females, aged 18-40 years) in the left anterior-right posterior (LARP) and right anterior-left posterior (RALP) semicircular canal planes. For each plane, nystagmus was induced with six combinations of different angles and velocity front and back rotation angles of ±30°,±60°,±90°, and velocities of 40°/s and 80°/s, the slow phase velocity (SPV) and their symmetry of 3D nystagmus were analyzed. SPSS 20.0 was used to compare the statistical differences in these two parameters across different stimulation protocols. Results: There were no spontaneous nystagmus in the 52 subjects, and all tests were finished. Except the combinations of (±30°-40°/s), three components of nystagmus were induced stably in the rest of the stimulations. The SPVs of vertical components were no statistically insignificant (P>0.05), and some horizontal or torsion components were statistically significant (P<0.05). The 95% reference range of the symmetry was≤25% in the vertical and≤30% in the torsional component of the nystagmus except for (±30°-80°/s), the symmetry was 32.2% and 49.2% respectively. The trend changes of the three components were consistent, among which the vertical and torsional components induced by (±60°-80°/s) and (±90°-80°/s) were the best, the SPV value of the vertical components was higher in the latter group than the former apart from the front RALP, while no significant difference was found in the torsional components (P>0.05). Conclusion: The (±90°-80°/s) combination is the optimal method to detect the function of vertical semicircular canal in 3D chair test. When observing torsional component, the combining scheme of (±60°-80°/s) and (±90°-80°/s) is better. Considering tolerance, the (±60°-80°/s) combination is recommended.