Congenital absence of the long process of the incus.

OBJECTIVE/HYPOTHESIS: To review the case reports of three generations of one family, suffering from bilateral conductive hearing loss due to congenital absence of the long process of the incus.

STUDY DESIGN

Review of the literature regarding hereditary congenital absence of the long process of the incus to determine its mode of inheritance such as autosomal dominant or X-linked. Also document the types and results of surgical repairs performed by previous investigators of this defect and compare them with the present study.

METHODS

Three female patients of direct lineage. Mother, daughter, and granddaughter, who were personally seen, operated on, and followed up over a period of 26 years.

RESULTS

All three female patients presented with similar symptoms and findings of hearing impairment since birth, with no history of ear infections, and with normal appearing tympanic membranes. However, they had severe conductive hearing loss with normal bone conduction and discrimination. Operative findings were identical in all three patients, with the incus ending in a blind stub, and with absence of the capitulum of the stapes. The type of ossicular reconstruction varied with the changing of times and advances in otologic surgery, as well as the prosthetic materials used. All three patients received improvement in their hearing, and this improvement has been maintained over the 26-year span of the study.

CONCLUSIONS

Hearing loss due to congenital absence of the incus is uncommon but not rare. Interestingly, no other instance of inherited cases were reported in the literature. In this family the defect appears to be an inherited trait either due to an autosomal dominant mutation or an X-linked dominant inheritance. This abnormality is amendable to surgery, and any well-executed technique usually gives good hearing results.