Normal Gain with Corrective Saccades in the Video Head Impulse Test: Clinical Implications and Diagnostic Considerations.

Background: The video head impulse test (vHIT) is a standard tool for assessing semicircular canal function through vestibulo-ocular reflex (VOR) gain and corrective saccades (CS). Although reduced gain accompanied by CS typically indicates vestibular hypofunction, a paradoxical pattern-normal gain with CS-is occasionally observed, and its clinical significance remains unclear. Methods: We retrospectively analyzed 1573 patients who underwent both vHIT and bithermal caloric testing between September 2022 and September 2025. Among them, 1174 subjects with normal bilateral horizontal VOR gains (0.8-1.2) were evaluated for CS. CS were defined as at least three consistent refixation saccades on one side, verified visually. Subjects were categorized into Right-, Left-, and Bilateral-CS groups. Comparisons were made between CS(+) and CS(-) sides, as well as among groups, using paired and one-way ANOVA tests. Results: CS were identified in 46.3% (544 in 1174) of subjects with normal VOR gains, most frequently on the right side. The side showing CS exhibited significantly lower caloric responses than the contralateral side (p < 0.001). Bilateral CS were more common in older patients. Canal paresis values indicated that the CS side corresponded to the weaker caloric side, suggesting subtle unilateral hypofunction. Conclusions: Even with normal gain, the presence of CS may reflect mild vestibular asymmetry rather than a benign artifact. In addition, bilateral CS were associated with older age, suggesting a possible contribution of age-related vestibular or compensatory mechanisms. Careful control of methodological biases and integration with other vestibular tests are essential for interpretation.