Supracochlear approach to the petrous apex: case report and anatomic study.

OBJECTIVE: The case of an 11-month old infant with petrous apex abscess drained through the supracochlear air cells prompted an anatomic study of the dimensions of this approach. Of the various approaches to the petrous apex, the supracochlear dissection has been the least described. STUDY DESIGN: Twenty temporal bones were dissected to completely expose the epitympanum. This required mastoidectomy, exenteration of zygomatic root and epitympanic air cells, and removal of the incus. Measurements were taken from three sides of a triangle described by the tegmen tympani (TT), tympanic facial nerve (TFN), and superior semicircular canal (SSCC). Similar measurements were obtained from standard coronal computerized tomographic (CT) scans from a random series of 20 patients. RESULTS: Mean lengths of the sides of the triangle were 7.0 mm (TT), 5.3 mm (TFN), and 4.8 mm (SSCC). The superior petrous apex air cells or marrow space was accessible through the supracochlear exposure in all specimens. Mean lengths from the coronal CT images were 4.2 mm (TT), 3.2 mm (TFN), and 8.45 mm (SSCC). CONCLUSIONS: The authors conclude that the supracochlear approach may provide adequate access to the superior petrous apex for drainage and biopsy in selected cases.