Detection of hypoplasia of bony cochlear nerve canal by virtual endoscopy: a pilot study

Abstract

Background Dimensions of the bony cochlear nerve canal (BCNC) have been proposed as a potential diagnostic standard for hypoplasia of BCNC, but the standard remains inconsistent. We have previously found that a helix-like shape appears in normal BCNCs at VE images, whereas, the sign does not appear in some hypoplastic BCNCs. Purpose To retrospectively examine the feasibility of computed tomographic (CT) virtual endoscopy (VE) in the evaluation of hypoplasia of BCNC on the basis of absence of a helix-like shape. Material and Methods Twenty ears in 14 consecutive patients (mean age 5.5 years, range 1–15 years, 6 boys, 8 girls) diagnosed with hypoplasia of BCNC were included in this work. One hundred ears in 50 gender- and age-matched individuals (mean age 6.6 years, range 1–15 years, 29 boys, 21 girls) without inner ear disease and internal auditory canal (IAC) malformations served as controls. The presence or absence of a helix-like shape was evaluated by two independent reviewers. The value of VE for the diagnosis of hypoplasia of BCNC was assessed with clinical results and routine radiologic evaluation as the reference standard. Inter-observer agreement was calculated. Sensitivity, specificity, and accuracy were selected to test the diagnostic ability of the VE. Results Absence of a helix-like shape was found in the cochlear area of 17 of 20 ears in patients with hypoplasia of BCNC but in none of the control subjects. Inter-observer agreement was substantial (к = 0.773). The diagnostic rates of absence of a helix-like shape for hypoplasia of BCNC in terms of sensitivity, specificity, and accuracy were 85%, 100%, and 98%, respectively. There were significant differences between the two groups with respect to VE findings for absence of a helix-like shape ( P < 0.001). Conclusion The absence of a helix-like shape at VE images may be used as a potentially useful sign in the diagnosis of hypoplasia of BCNC.