The recesses of the retro-tympanum.

OBJECTIVE

To study the anatomy of the posterior tympanic wall and to describe the four recesses (Sinus Tympani-ST, Lateral Tympanic Sinus-LTS, Posterior Tympanic Sinus-PTS, Facial Recess-FR) with their variations in shape, dimension, internal configuration.

MATERIAL AND METHODS

Thirty-seven cadaver temporal bones were examined through the anterior dissection approach. The opening was enlarged by drilling to allow a good microscopic or rigid endoscopic view to the retro-tympanum. Measurements of the recesses were made with gradually millimeter wire, dial micrometric indicator (comparator clock), various right angled picks and sometimes by means of cast-impression--used in stomatology for dental impression (interior configuration).

RESULTS

Out of 37 specimens, we have found PTS in 64.86% (24 cases), ST in 94.59% (35 cases), and LTS in 59.45% (22 cases). For FR, we have found four types. The most constant cell, located in the inferior external part of FR and in the same time, the biggest one was suprapyramidal Sappey's fossa, which we have found in 75.67% (28 cases) of all specimens. Sinus entrance of each recess was very variable, but in the most cases, we have found that the long diameter of ST and LTS was usually directed vertically and of PTS usually horizontally. The deeper recess was ST-2.74 mm (range 0.5 to 6.2 mm). Pyramidal eminence was visualized in 100% of cases, the pyramidal ridge in 89.18%, the chordal ridge in 78.37%, the suprapyramidal ridge in 35.13%, ponticulus in 83.78% and subiculum in 75.67%. In many cases, the inner configuration of each sinus was irregular, presenting either small recesses (0.2 to 1 mm) under the bone borders at the entrance in the sinuses or communication between the two sinuses.

CONCLUSIONS

Presence of the all four recess is not a rule. Marked variation in the size and shape and especially in the internal configuration of all recesses is a rule. All recesses of the retro-tympanum can be recognized more easily, if we identify at first all elements of positive projection (pyramidal eminence, chordal ridge, styloid eminence, styloid ridge, pyramidal ridge, suprapyramidal ridge, ponticulus, subiculum).