Congenital ossicular anomalies without malformations of the external ear.

Abstract

Eighteen ears of congenital ossicular malformation without deformities of the external ear were presented. They were classified into three groups; eight incudostapedial joint separations, three malleus and/or incus fixations, and seven stapes fixations. The surgical correction for the first group was to connect the malleus handle to the stapes using a silicon tube specially designed or a gelfoam wire in the uncustomary way. This group showed the best surgical results with 35.4 dB of the average hearing gain in speech frequencies. In the second group, removal of the fixed part of the ossicles yielded satisfactory results, but mobilization failed to improve the hearing. For the group of stapes fixation, stapedectomy and the gelfoam wire prosthesis were performed. The result was not satisfactory in some cases with the undeveloped oval window. The embryological consideration leads us to the following conjecture; the incudostapedial joint separation results from the failure in build-up of "the secondary continuity", the malleus and/or incus fixation is the result of disturbances in separation process by the undifferentiated mesenchyme, and the stapes fixation is due to maldevelopment of the stapedial lamina. This classification for the congenital ossicular malformation is practically valid as it would suggest the maldeveloped point in ossicular genesis and results of surgical correction.