Malformation of one ossicle in an ear which otherwise appears to have developed normally is extremely rare. Most of the reported cases with deformed ossicles are those of congenital atresia of the ear, where the ossicular abnormality is accompanied by atresia of the canal and other deformities of the middle and inner ear. In this type of case fusion of malleus and incus is frequently observed. Shambaugh (1952) records that in 22 surgically treated ears with anomalies of the sound-conduction apparatus, 15 had atresia of the external canal. In 10 the malleus and incus were malformed, and in 5 there was an abnormality of the stapes.
Altmann (1951), in a comprehensive review of malformations of the hearing organ (with 250 references), stresses the great rarity of isolated ossicular deformities and maintains that the stapes is the ossicle most frequently affected. He also draws attention to the rarity of malformations of
KELLY HDB. Congenital Malformation of Incus. AMA Arch Otolaryngol. 1958;67(5):553–555. doi:10.1001/archotol.1958.00730010567009
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