Abstract
Understanding of the embryologic origin of the stapes remains controversial. Theories diverge upon whether the entirety of the stapes arises from a single source versus the footplate and suprastructure arising from distinct sources.
A 12-year-old boy with left-sided conductive hearing loss had computed tomography of the temporal bone, revealing an inferiorly displaced left stapes, and a nonspecific density in the left Prussak’s space. Exploratory tympanotomy revealed the crura of the stapes to be attached to the promontory. The stapes footplate was located in the oval window and was mobile.
1
Introduction
At birth, the stapes has its adult form, with all development occurring during the prenatal period. Due to this fact, study of the embryology of the stapes is only possible through examination of human embryos or through inferences made from case reports of congenital anomalies. Theories regarding embryologic originations of the stapes have been proposed and can generally be divided into two major categories. The first category of theorization postulates that portions of the stapes arise from dual sources. The second category postulates that the entirety of the stapes arises from a single source .
We are presenting the case of a stapes anomaly that may have implications regarding stapes development.
A review by the Institutional Review Board at Boston Children’s Hospital was obtained.
2
Case report
A 12 year-old boy presented with left-sided hearing loss. He had two bouts of acute otitis media in his lifetime and no history of otologic trauma. There was a family history of hearing loss. He had no craniofacial dysmorphisms, normal external auditory canals bilaterally and a normal right tympanic membrane.
The left tympanic membrane was examined with the otomicroscope. A retraction pocket or perforation in the posterior superior portion was seen. An audiogram was completed, revealing a mild-to-moderate conductive hearing loss for the left ear. Tympanometry completed for the left ear revealed normal ear canal volume and tympanic membrane compliance with significant negative middle-ear pressure. The possibility of cholesteatoma was considered. A temporal bone computed tomography (CT) scan was performed.
The CT scan revealed a poorly pneumatized left mastoid with areas of sclerosis and a poorly seen, inferiorly displaced left stapes, as seen in Figs. 1 and 2 . A nonspecific density was seen in the left Prussak’s space, thought to represent a retraction pocket and cholesteatoma. A left postauricular exploratory tympanotomy, atticotomy, and lysis of adhesions were performed. A postero-superior retraction pocket was found that extended into the sinus tympani and medial to the long process of the incus and onto the tympanic potion of the facial nerve canal. This was reduced and the ossicles were examined. The incus and malleus were intact and mobile. The stapes crura were inferiorly located, separate from the footplate, and attached to the promontory. The footplate was mobile and in the oval window. Figs. 3 and 4 show the intra-operative findings. Pathological findings revealed debris removed from the retraction pocket was cholesteatoma.
A post-operative audiogram was completed and revealed a mild conductive hearing loss. Revision surgery was scheduled, at which time the patient underwent a partial ossicular chain reconstruction using a Goldenberg Incus Stapes Prosthesis. A final post-operative audiogram was completed revealing normal hearing, with air conduction levels ranging from 0 to 15 dB HL.
2
Case report
A 12 year-old boy presented with left-sided hearing loss. He had two bouts of acute otitis media in his lifetime and no history of otologic trauma. There was a family history of hearing loss. He had no craniofacial dysmorphisms, normal external auditory canals bilaterally and a normal right tympanic membrane.
The left tympanic membrane was examined with the otomicroscope. A retraction pocket or perforation in the posterior superior portion was seen. An audiogram was completed, revealing a mild-to-moderate conductive hearing loss for the left ear. Tympanometry completed for the left ear revealed normal ear canal volume and tympanic membrane compliance with significant negative middle-ear pressure. The possibility of cholesteatoma was considered. A temporal bone computed tomography (CT) scan was performed.
The CT scan revealed a poorly pneumatized left mastoid with areas of sclerosis and a poorly seen, inferiorly displaced left stapes, as seen in Figs. 1 and 2 . A nonspecific density was seen in the left Prussak’s space, thought to represent a retraction pocket and cholesteatoma. A left postauricular exploratory tympanotomy, atticotomy, and lysis of adhesions were performed. A postero-superior retraction pocket was found that extended into the sinus tympani and medial to the long process of the incus and onto the tympanic potion of the facial nerve canal. This was reduced and the ossicles were examined. The incus and malleus were intact and mobile. The stapes crura were inferiorly located, separate from the footplate, and attached to the promontory. The footplate was mobile and in the oval window. Figs. 3 and 4 show the intra-operative findings. Pathological findings revealed debris removed from the retraction pocket was cholesteatoma.
