The suprapyramidal fossa: a 3-dimensional reconstructive and surgical study.

Objective To clarify the position, occurrence rate, and configuration of the suprapyramidal fossa (SF) through surgical observation and 3-dimensional reconstruction. Methods SF of 300 ears with chronic otitis media were observed during surgery. The air cell and its abutting structures, including the facial nerve (FN), were reconstructed using high-resolution computed tomography (HRCT) data. Results In 68.3% (n = 205) of patients, the SF was observed in surgery. It is situated at the posterior wall of the facial recess of the retrotympanum. This air cell, usually the only one present on the surface of the pyramidal segment of the FN canal (FNC), is usually the largest if small air cells are found nearby. Its delineated location is as follows: pyramidal eminence and the pyramidal segment of the FNC medially, the deeper external acoustic meatus laterally, the aditus ad antrum superiorly, the posterior part of the tympanic annulus, and the chordal ridge anterior-inferiorly. Its configuration varies between rounded (11.7%, n = 35), curved-rod (52.7%, n = 158), and irregular (4%, n = 12). Additionally, the sensitivity and specificity of HRCT in detecting the SF were 79.0% and 88.4%, respectively. Conclusion Occurrence and configuration of the SF is not a rule; however, the positive positional relationship between the SF and the second genu of the FNC is a rule, if the SF is detected. Considering this, the SF may be an important anatomic landmark to identify the FN during otosurgery. However, HRCT has a limited diagnostic value when the SF is atypical.