Anatomic variants on computed tomography in congenital aural atresia.

Objective: To report the prevalence of anatomic variants on computed tomography (CT) in congenital aural atresia (CAA) and external auditory canal stenosis (EACS). Anatomic variants included inferiorly displaced/obstructing tegmen mastoideum, malleus-incus complex (MIC) directly lateral to stapes, facial nerve obstruction of oval window (OW) or middle ear, and incudostapedial joint (ISJ) angle.

Study Design: Cross-sectional study.

Setting: Tertiary care children's hospital.

Subjects And Methods: An anatomic analysis of 130 CT scans (98 children, 32 bilateral) of CAA/EACS, performed by a blinded neuroradiologist. Both Jahrsdoerfer's and new/modified anatomic considerations were graded in 32 atresiaplasty and 66 nonsurgical patients. Surgical data were analyzed for anatomic correlations related to surgical findings.

Results: Prevalence of anatomic variants was as follows: 13% of the ears had mild inferior displacement of tegmen, 4% had a significantly obstructing tegmen, and 24% had MIC directly lateral to stapes. The facial nerve obstructed access to OW in 41% and middle ear in 21%. Six atresiaplasty patients were reported to have a large MIC obstructing stapes access with increased intraoperative difficulty in viewing and assessing the integrity and mobility of the ISJ and stapes. Five of these 6 (83%) were noted on CT scan. The mean ISJ angle was 101° (range, 51°-155°).

Conclusion: A large obstructing MIC increases difficulty of atresiaplasty. Awareness of the presence of these anatomic variants is an aid in teaching temporal bone anatomy and may possibly influence the decision regarding atresiaplasty.