Classification of the Ossicula in Cases with Congenital Conduction Deafness

Abstract

We classified functional anomalies of the ossicles of 14 ears in patients with congenital conduction deafness with stenosis of the external auditory canal or abnormal tympanic membrane based on embryological considerations. Each area of the ossicles is embryologically derived from one of the following 4 tissues of origin: Meckel's cartilage; Reichert's cartilage; process of Folius (derived from the mesenchyme); and the annular ligament, including the foot plate of the stapes (derived from the mesenchyme of the stapes and otic capsule). The functional anomaly of the ossicles was located in Reichert's region alone in 5 ears (in the malleus handle in 3 and in the long process of the incus in 2); in 4 ears in both the process of Folius and the malleus handle (derived from Reichert's cartilage); in one ear in a region derived from both Meckel's and Reichert's cartilages ; and in one ear in the process of Folius only. In the remaining 3 ears the ossicles showed no marked abnormality. Anomaly of the annular ligament (fixation of the stapes foot plate) was not noted in any of the ears. The tympanic membrane showed some anomaly in all ears, and, in the 3 ears with normal ossicles, this anomaly and stenosis of the external aural canal were factors in the conduction deafness. The auricle appeared normal in 4 ears and slightly abnormal in 10; no relationship was found between anomaly of the ossicles and that of the auricles.