Development of the Otic Capsule: Iv. The Fossula Post Fenestram

Abstract

In 1881 Ibsen 1 published the first description of the evagination of the periotic tissue into the otic capsule back of the stapes which Siebenmann 2 in 1890 called the "fossula post fenestram." Ibsen saw this in 23 of 60 new-born children whose ears he studied. He said that there is a funnel-shaped evagination from the vestibule back of the stapes. In his figure 6 he showed projecting into it a diverticulum of the utriculus which he called the "canalis membranaceus caecus." In a few cases he could insert a human hair into the opening from the vestibule to the middle ear. Ibsen credited Cassebohm 3 with the first description of this structure. From a careful review of Cassebohm's works, such credit does not seem to be due him. While his figure 13 showed the region posterior to the stapes, he did not picture the fossula. In his text he mentioned the entrance of a blood vessel into the capsule posterior to the stapes. Ibsen, therefore, was the first to give a specific statement regarding the fossula. The diverticulum of the utriculus which Ibsen 1 showed in his figure 31g to project into this evagination has not been observed since.Siebenmann 2 wrote :Between the posterior ampulla and the posterior end of the oval window there is in about half of my corrosions\p=m-\inthe new-born much oftener than in the adult\p=m-\ a small pyramid-like structure which projects into the bony capsule.He compared it with the funnel-like structure described by Ibsen.I made the next reference to this structure 4 in 1930. Since then I have had occasion to study serial sections of nearly 100 ears of various ages, and a more accurate account of the structure can be given.

Role of Radiologic Imaging in Otosclerosis

“…The fossula post fenestram develops similarly to the fissula ante fenestram and approaches the posterior aspect of the stapedial area. Cartilaginous changes are less common in the fossula post fenestram compared to the fissula ante fenestram, present in only 5% of temporal bone specimen [15].…”

Development of the Otic Capsule: V. Residual Cartilages and Defective Ossification and Their Relation to Otosclerotic Foci

“…A few of these types are shown in figures 3, 4, 5 and 8. They usually lie lateral to the subarcuate fossa and may be single large car¬ tilages as shown in figure 3 or multiple as in figure 5. The oldest child in whom such a cartilage was noted was 5 years old ( fig.…”