Clinical roles of fixation suppression failure in dizzy patients in the ENT clinic

Abstract

Conclusion: Any test for visual fixation suppression by itself is insufficient for screening central pathology and should be interpreted in conjunction with other neurotologic findings. Objectives: We evaluated the correlation of visual fixation suppression (VFS) under three different test conditions (spontaneous nystagmus, caloric stimulation, and slow harmonic acceleration, SHA), as well as the diagnostic accuracy of each test for predicting central pathology, in dizzy patients. Methods: We retrospectively reviewed cases in a tertiary referral center; 504 consecutive dizzy patients who visited the ENT clinic were enrolled. The fixation index (FI, slow component velocity during fixation/slow component velocity before fixation × 100%) for the caloric test and spontaneous nystagmus was calculated and failure was indicated when the FI was greater than 60%. VFS during the SHA test at a frequency of 0.04 Hz was also performed and gain more than 0.2 was considered as failure of VFS. Results: The incidence of VFS failure was 5.4% in the caloric test, 3.4% in spontaneous nystagmus, and 2.3% in the SHA test, respectively. Significant correlation was found only between the caloric test and the SHA test (r = 0.341, p < 0.001). The sensitivity of VFS in different tests did not exceed 35%. The specificity of VFS was highest (96.4%) in the 0.04 Hz SHA test, and exceeded 80% in the other tests.