Temporal bone anatomy and caloric asymmetry (Carpenter et al., 2018)

Purpose: This study assesses interaural differences in temporal bone anatomy in subjects with normal caloric findings.

Method: Eligible patients included those referred to the Duke University Medical Center otology clinic complaining of dizziness, with a head computed tomography scan and caloric stimulation results within normal ranges (inter-ear difference ≤ 10% or < 25% unilateral weakness). Three-dimensional reconstructions of computed tomography scans in 11 patients were used to calculate the surface area and volume of lateral semicircular canals (LSCCs), mastoid airspaces, mastoid bones, and internal auditory canal diameter and circumference. Percent differences in interaural temporal bone anatomy (i.e., left-to-right asymmetry) were analyzed and correlated with warm caloric inter-ear difference (WCD) and clinically indicated caloric predictor asymmetry.

Results: A multivariate model predicting WCD from 9 interaural anatomic variables demonstrated a Pearson’s coefficient of 0.999. A similarly constructed model of the clinically indicated caloric predictor demonstrated a Pearson’s coefficient of 0.999. The univariate correlation was strongest for WCD versus Proctor internal auditory canal diameter (r = 0.476; p = .139) and WCD versus lateral semicircular canal surface-area-to-volume ratio (r = −0.474; p = .141).

Conclusions: This pilot study provides multivariate models that predict caloric asymmetry in subjects without vestibular pathologic findings per caloric testing, based on interaural differences across variables of the temporal bone anatomy.

Supplemental Materials S1 and S2. Univariate analysis using the conventional caloric output formula.

Carpenter, D., Kaylie, D., Piker, E., & Frank-Ito, D. (2018). A pilot study to investigate the relationship between interaural differences in temporal bone anatomy and normal variations in caloric asymmetry. American Journal of Audiology, 27, 110–120. Advance online publication. https://doi.org/10.1044/2017_AJA-16-0048