To characterize semicircular canal involvement and nystagmus phenotypes in acute unilateral vestibulopathy (AUVP) under the 2022 Bárány criteria, focusing on the anterior-to-posterior canal (ASC/PSC) gain ratio and its link to horizontal-only (hN) versus horizontal-upbeat (huN) patterns. Cross-sectional study of 121 patients AUVP ( n = 121), comparing AUVP-acute (spontaneous nystagmus positive, SN+, n = 102) versus AUVP-convalescent (SN−, n = 19); within SN+, patients were stratified as hN or huN. Caloric indices, six-canal video head impulse test (vHIT) gains, number of affected semicircular canals, the ASC/PSC ratio, and exploratory multivariable logistic regression results for huN. Compared with SN−, SN+ showed earlier testing, higher canal paresis/directional preponderance (CP/DP), lower HSC/ASC gains, more affected semicircular canals, and higher gain-defined vHIT positivity. Within SN+, huN exhibited greater horizontal slow-phase velocity, higher CP/DP, more affected semicircular canals, and lower HSC/ASC gains than hN. The ASC/PSC ratio differentiated phenotypes: hN clustered near unity (median ≈ 0.97), whereas huN showed a reduced ratio (median ≈ 0.76). In the exploratory multivariable model, onset time (OR 0.843, 95% CI 0.753–0.944) and the ASC/PSC ratio (OR 0.079, 95% CI 0.011–0.543) were independently associated with huN, whereas HSC gain lost independent predictive value; the combined model achieved an apparent AUC of 0.79. Caloric testing and six-canal vHIT are frequency-complementary across stages: The ASC/PSC ratio anchors nystagmus vector interpretation: values near 1.0 align with hN, whereas lower ratios indicate huN with relatively greater ASC involvement. The combined model serves as a hypothesis-generating tool for exploratory early phenotyping, rather than a definitive clinical classifier. • SN+ AUVP showed higher CP/DP and lower HSC/ASC gains than SN−. • Within SN+, huN showed stronger nystagmus and more affected canals. • The ASC/PSC ratio was lower in huN, indicating greater ASC involvement. • Shorter onset time and lower ASC/PSC ratio independently favored huN. • The combined exploratory model achieved an apparent AUC of 0.79.
Shangguan et al. (Fri,) studied this question.