Bilateral Congenital Absence of Stapes Superstructure, Rare Ossicular Anomaly Managed Endoscopically
30 September 2019 (online)
Introduction The congenital anomalies of ossicular chain of the middle ear are an uncommon event that can present in a variety of ways. Among these malformations, the congenital absence of stapes (CAS) is a very rare condition that is seldom described in the English scientific literature. It was first reported by Mcaskile and Sullivan in 1955 in two patients with conductive hearing loss.
Case Presentation A 19-year-old male patient presented with complaints of bilateral hard of hearing since childhood, nonprogressive type. Family history was negative for any otologic or genetic problem. The audiogram showed bilateral conductive hearing loss with an average air–bone gap of 60 dB on both sides. CT temporal bone revealed the absence of stapes superstructure bilaterally, and an abnormal facial nerve location. Endoscopic exploratory tympanotomy and ossicular reconstruction were done on right side first, in the year 2017, and on left side in the year 2018 (June).
Discussion The CAS is obviously a rare entity with only 12 cases reported in the literature. In all cases, CAS present as a conductive hearing loss with normal external auditory canal and intact tympanic membrane. The exact etiology is still not known and it has been suggested that malformation or agenesis of the stapes and oval window is related to the abnormal development of the facial nerve. Various managements have been described through time. This includes a broad range of options from exploratory surgery and reconstruction prosthesis to amplification.
Conclusion Among all possible middle ear anomalies, stapes agenesis is rarely a part of the differential diagnosis for conductive hearing loss. Only 12 cases have been published in the English scientific literature (1955–2017). No cases have been published in India, till date. More than half of the patients with CAS have an abnormal facial nerve, which may complicate surgery. This patient has an anteroinferior displacement of facial nerve canal but we have done bilateral endoscopic reconstruction surgery successfully without any injury to facial nerve.