Sex differences in caloric nystagmus intensity: Should reference values be updated?

Bithermal caloric irrigation of the horizontal semicircular canals is a key method of neurotological diagnostics, allowing the detection of peripheral vestibular hypofunction in the low-frequency range. Current diagnostic criteria for unilateral vestibulopathy (UVP), bilateral vestibulopathy (BVP), and presbyvestibulopathy (PVP) rely on gender-neutral absolute or relative metrics. Here, we analyzed all bithermal water caloric examinations performed in the German Center for Vertigo and Balance Disorders (DSGZ) between 07/2018 and 01/2024 and calculated the total caloric reactivity (TR). Patient age and sex were collected as covariates. For UVP, BVP, and PVP diagnoses, international diagnostic criteria were applied. In total, 11,332 patients (6219 females, mean age 55.97±17.52 years) were included. Females displayed a higher TR (mean difference: 6.41°/s, p<0.001). The frequency of UVP, BVP, and PVP diagnoses based on absolute cut-off values showed a significant male predominance (UVP: n = 1144, 548 females, odd ratio [OR] -0.32, p<0.001; BVP: n = 305, 138 females, OR -0.40, p<0.001; PVP: n = 813, 378 females, OR -0.37, p<0.001). However, the rate of UVP based on relative asymmetries showed no sex differences (n = 2971, 1595 females, OR -0.08, p = 0.06). Diagnostic criteria for UVP, BVP, or PVP, which utilize absolute caloric excitability cut-offs, might need to be updated to address sex-specific differences of caloric excitability.