Morphological characteristics of external auditory canal in congenital aural stenosis patients

Objective To investigate characteristics of congenital aural stenosis (CAS) patients' external auditory canal (EAC) (position, length, orientation, etc.) and compare them with normal EAC.

CT images of normal people and CAS patient were utilized. We obtained coordinates of EAC landmarks. Then the Matlab program could calculate some anatomic parameters about EAC, including distances from central point of tympanic annulus (CA), central point of osseous EAC opening (CO), central point of cartilaginous EAC inside opening (CCi), central point of cartilaginous EAC outside opening (CCo) to the Frankfurt horizontal plane (Pfrkt), the median sagittal plane (Psag), the coronal plane (Pcor); orientations of EAC bendings; straight and arc lengths of EAC.

Distances from CA, CO, CCi and CCo to Pfrkt were all shorter in CAS group than control group (p<0.05). The straight and arc lengths of cartilaginous EAC in CAS group were shorter than control group (p<0.05). Straight and arc lengths of EAC in CAS group were shorter than those in control group (p<0.05). The proportion of one bending in cartilaginous EAC in control group was significantly lower than CAS group (p<0.05). Orientations of EAC bendings in CAS group differed from those in control group (p<0.05).

In addition to smaller diameters, compared with normal EAC, the position of CAS patients' osseous EAC was higher compared with the normal. The majority of CAS patients have a bending and downward slanting cartilaginous EAC. Orientations of EAC bending in CAS patients were different from normal. Besides, the length of CAS patients' cartilaginous EAC was shorter. However, there were no significant differences between CAS patients and normal people in length of osseous EAC. These differences in anatomic parameters could provide the basis for optimizing the meatoplasty.