Objective: The case of an 11-month old infant with petrous apex abscess dra
ined 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 a
nd epitympanic air cells, and removal of the incus. Measurements were taken
from three sides of a triangle described by the tegmen tympani (TT), tympa
nic facial nerve (TFN), and superior semicircular canal (SSCC). Similar mea
surements were obtained from standard coronal computerized tomographic (CT)
scans hom 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 sp
ace was accessible through the supracochlear exposure in all specimens. Mea
n 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 provi
de adequate access to the superior petrous apex for drainage and biopsy in
selected cases.