Computed tomography supports histopathologic evidence of vestibulocochlear sexual dimorphism

Objective: To investigate whether the effects of sex (male/female) that have been demonstrated in the pathology literature using 0.1 mm histopathologic slices are measurable and statistically significant using high-resolution (0.625 mm slice) computed tomography (CT).

Methods: IRB-approved retrospective analysis of high-resolution "normal" CT temporal bone images in pediatric subjects (0-18 years) using comparative anatomic measurements between males and females obtained from the semicircular canals, cochlea and vestibule as follows: (1) lateral semicircular canal (LSCC) bony island width, (2) superior semicircular canal (SSCC) bony island width, (3) central lucency of the LSCC bony island, (4) coronal cochlear height, (5) axial cochlear height, (6) cochlear length, (7) cochlea basal turn lumen width, (8) cochlear aperture width, (9) cochlear aperture height, (10) vestibular length, (11) vestibular width, and (12) coronal vestibule oblique diameter.

Results: Eighteen females (36 ears) and twenty males (36 ears) were included in the study. Independent-samples t-tests revealed statistically significant differences in measurements for females and males as follows (differences reported as a percentage and as an absolute difference (AD) in mm): (1) vestibular width was 4.2% (0.13 mm AD) smaller in females (mean ± SD; 3.0 ± 0.27) compared to males (mean ± SD; 3.2 ± 0.25) [t(70) = 2.083, p = 0.041]; (2) cochlear length was 3.9% (.23 mm AD) smaller in females (mean ± SD; 5.8 ± 0.32) compared to males (mean ± SD; 6.0 ± 0.40) [t(70)=2.660, p = 0.010]; (3) cochlear aperture height was 11.6% (0.13 mm AD) smaller in females (mean ± SD; 1.0 ± 0.18) compared to males (mean ± SD; 1.2 ± 0.22) [t(70)=2.549, p = 0.013]; and (4) coronal cochlear height was 11.4% (0.55 mm AD) smaller in females (mean ± SD; 4.8 ± 0.58) compared to males (mean ± SD; 5.4 ± 0.48) [t(68) = 4.270, p < 0.005].

Conclusion: Sexual dimorphism of inner ear structures may contribute to variability in reported normative and pathologic measurements of inner ear structures. This variability must be taken into consideration when designing future research studies to investigate inner ear structures and for drawing accurate conclusions about possible inner ear morphologic abnormalities associated with SNHL compared to controls.