Surgical anatomy of the hypotympanum

Abstract

Anatomical characteristics of the hypotympanum were tested on 50 temporal bones. The hypotympanum has the shape of an irregular bony groove which is surrounded by five walls. The outer wall is formed by the tympanic part of the temporal bone. In 65 per cent of the cases the inner wall is formed by part of the petrous bone which extends under the promontory; in 25 per cent it is formed only by the lower part of the promontory; and in 10 per cent it corresponds to the juncture of the promontory and the petrous bone. The lower wall is clearly defined in 48.2 per cent of cases and corresponds to the juncture of its inner and outer walls. In 65 per cent of cases a recess of the inferior hypotympanic sinus is found on the floor of the hypotympanum. In 25.3 per cent of cases the jugular bulb protrudes into the tympanic cavity. In 73.4 per cent of cases the front wall is formed by part of the petrous bone which extends from its floor towards the tympanic opening of the protympanum, and in 26 per cent of the cases it is formed by the wall of the internal carotid artery. On the front wall, in 22.4 per cent of cases, a recess of the anterior hypotympanic sinus is found. The back wall is formed by elements of the styloid complex and in five per cent of the cases a recess or posterior hypotympanic sinus is found on it.

High Computed Tomographic Correlations between Carotid Canal Dehiscence and High Jugular Bulb in the Middle Ear

“…An aberrant high jugular bulb (HJB) is characterized by a high-positioned jugular fossa either medial or lateral to the cochlea. It has been estimated that the incidence of HJB protruding into the tympanic cavity is 25% in temporal bone histopathologic studies [Savic and Djeric, 1987], and was 20% in a series of computed tomographic evaluations [Atilla et al, 1995]. In our previous clinical observations, the presentation incidence of HJB varied and may have been significantly lower than the histopathological or tomographical evaluation estimations [Huang et al, 2006].…”

Inferior retrotympanum revisited: An endoscopic anatomic study

“…We called this space the sinus subtympanicus. This structure was probably already identified by Savic and Djeric in 1987 studying the surgical anatomy of the hypotympanum, and who defined the sinus lying between the hypotympanum and the posterior tympanic wall as the sinus hypotympanicus 5. We also chose in this case to rename this sinus, because owing to the retrotympanic spaces, the term sinus hypotympanicus used by Savic and Djeric could have been quite misleading.…”

“…Although in the past, some authors3–6 have already studied the anatomy of the inferior retrotympanum, a region that has been quite neglected in the literature, which is probably due to the low accessibility of that space during conventional microscopic procedures. In fact, in his studies, Proctor3, 4 had already identified almost all of the structures in that region based on several temporal bone dissections.…”

“…In the recent literature, the present authors have already studied the anatomy of the retrotympanum, describing the variation in shape of the sinus tympani, ponticulus, and pyramidal eminence 1, 2. However, until now few studies have focused on anatomic description of the retrotympanic region lying inferiorly to the subiculum 3–6. We will define that space as the inferior retrotympanum, representing the border between the retrotympanum itself and the hypotympanum.…”

“…In 1987, Savic and Djeric, studying the surgical anatomy of the hypotympanum, defined the sinus lying between the hypotympanum and posterior tympanic wall as the sinus hypotympanicus 5. It is very difficult to understand from the pictures and drawings in that study whether by that term the authors meant Proctor's area concamerata or if they were referring to a separate structure.…”