Anatomic Variants on Congenital Computed Tomography in Congential Aural Atresia

Abstract

Objective: Report incidence of anatomic variants in temporal bone CT scans with congenital aural atresia (CAA) or external auditory canal stenosis (EACS). Anatomic variants include: inferiorly displaced tegmen, malleus/incus complex (MIC) directly lateral to stapes, facial nerve obstruction at oval window (OW) and middle ear, middle ear area, incudostapedial (IS) joint angle.

Method: Prospective anatomic study of 134 CT scans (102 children, 32 bilateral) of CAA/EACS, graded by a blinded neuroradiologist. Both Jahrsdoerfer and absence or presence of new/refined anatomic considerations were graded. There were 32 atresiaplasty and 70 nonsurgical patients. Surgical and audiological data were reviewed retrospectively for anatomic correlations related to outcomes.

Results: Prevalence of anatomical variants: inferiorly displaced tegmen X (X%), MIC directly lateral to stapes Y (Y%), facial nerve obstructed access to oval window Z (Z%), and middle ear B (B%). Large MIC obstructing stapes access (5/7 patients) with increased intra-operative difficulty. Mean middle ear area DD (range, 0.07 to 0.86mm²) and mean IS joint angle FF (range, 50°-147°). Trend toward improved outcomes with: normal tegmen, facial nerve favorable to OW, or non-obstructing MIC. No statistically significant clinical correlations for anatomic factors including Jahrsdoerfer grading.

Conclusion: Large obstructing MIC increases the difficulty of atresiaplasty. There is a trend showing improved outcomes with normal tegmen, facial nerve favorable to oval window, or nonobstructing MIC. A larger atresiaplasty cohort is needed since the number of cases was insufficient to demonstrate statistical significance. Nonetheless, the frequency of these new/refined anatomic variants has been more clearly delineated. The presence of these anatomic variants may possibly influence the decision for or against atresiaplasty.