A new method of studying the anatomy of the posterior tympanum

Ear, Nose & Throat Journal, April, 2004 by James J. Holt

Documentation. The direct access to the posterior tympanum described here enabled the author to make video and photographic records of the structures as they are in the normal anatomic state, including those in the deepest recesses of the posterior tympanum. By removing the anterior bony canal wall, an endoscope was positioned directly toward the structures in the posterior tympanum so that photographs could be taken through the scope (figure 4). This method also allowed the line of vision from the video camera to project directly into the posterior tympanum. In this manner, photographic and video documentation was possible. Such permanent documentation of anatomic findings can be used for study, education, and/or scientific presentations.

[FIGURE 4 OMITTED]

Discussion

Anatomy. Other investigators have studied the anatomy of the posterior tympanum. In early studies, tracings made from horizontal serial sections (2) or photographs (4) were used to make measurements of various anatomic structures. More recently, investigators have used more modern methods to obtain computer-driven measurements generated from video images (3) and measurements obtained from CT sequences of the temporal bone. (1) Although these investigators provided useful information about the anatomy of the posterior tympanum, they used segmental reproductions of tissue. By using the methods that the author describes in this article, otologists can gain a new perspective of the actual structures in the posterior tympanum while preserving the integrity of the tissue.

The focus of other investigations of the posterior tympanum has been to provide a general description of its structures and anatomy; however, detailed descriptions are sparse, and many questions remain unanswered. For example, Proctor described the ponticulus, which extends from the pyramidal eminence to the promontory. (5) However, the size and thickness of the ponticulus, its proximity to neighboring structures, and the likelihood of disease becoming trapped under it have not been defined. Proctor also described the four sinuses of the posterior tympanum, (6) but specific information regarding their configuration and the accessibility of their deepest recesses is still unavailable. The method described in this article allows for more detailed investigation into the anatomy of the posterior tympanum, and thereby makes possible a better understanding of the concealed areas in the posterior tympanum where disease can be hidden from the surgeon. This knowledge can be applied toward refining or developing better surgical techniques in this obscure area.

Surgical techniques. Otologic surgeons must approach the operating room prepared to manage disease in any location in the ear. The challenge of operating in the posterior tympanum has long been recognized.

Various approaches to the structures in the posterior tympanum have been utilized. Surgical approaches include the anterior transcanal approach recommended by Farrior, (7) the antcroposterior approach suggested by Goodhill, (8) and the approach through the external auditory canal used by Lau and Tos. (9) Leonetti et al (10) described a technique to marsupialize a retraction pocket in the posterior tympanum, whereas Pulec (11) recommended transcanal exposure of the posterior tympanum by removal of the posterior canal wall bone to the facial nerve when possible, with a transmastoid approach as a second option if necessary.