OBJECTIVETo provide a valuable imaging anatomic method for operation of the posterior transpetrosal approach and accurate positioning among relative structures in order to reduce the incidence of surgical complications.

METHODSThe clinical information of 119 adult cases (238 sides) was analyzed. All the cases underwent 16 layer helix CT scanning and three-dimensional image reconstruction of skull base without a skull base disease. Axial and coronal images were reconstructed using multiplanar reconstruction technique of ADW 4.2 workstation, and the anatomic objective structure were displayed by rotating imaging slices. The data were analyzed in statistically and compared with the published cadaver data.

RESULTSQuantitative measurement of anatomic structure was shown as below: The distance of width of sigmoid sinus was (11.14 + or - 2.13) mm, the distance of depth of sigmoid sinus was (6.04 + or - 1.67) mm; the distance from the lateral wall of sigmoid sinus to the surface of mastoid process was (9.74 + or - 2.95) mm; the distance from the anterior wall of sigmoid sinus to the posterior wall of external auditory meatus was (12.98 + or - 2.71) mm; the distance from the most posterior portion of the posterior semicircular canal to the anterior wall of sigmoid sinus was (9.87 + or - 2.60) mm; the distance from the most posterior portion of the posterior semicircular canal to the posterior pyramidal wall was (3.18 + or - 1.30) mm; the distance from the posterior extremity of long axis of the lateral semicircular canal to the anterior wall of sigmoid sinus was (13.17 + or - 2.59) mm; the distance from the posterior extremity of long axis of the lateral semicircular canal to the posterior pyramidal wall was (5.46 + or - 1.38) mm; the vertical distance from the lateral semicircular canal to the jugular bulb was (6.69 + or - 3.08) mm; and the distance from the vertical portion of facial nerve to the jugular bulb was (5.32 + or - 2.13) mm. Statistically, there were no significant differences between imaging quantitative measurement and published cadaver data. However, the measurement result, included the distance from the lateral wall of sigmoid sinus to the surface of mastoid process and the distance from the lateral semicircular canal to the jugular bulb as well as the distance from the vertical portion of facial nerve to the jugular bulb, were found a positively correlated to the distance from the anterior wall of sigmoid sinus to the posterior wall of external auditory meatus (r value was 0.284, 0.145, 0.208, respectively, all P < 0.05).

CONCLUSIONSThe result of three-dimensional quantitative measurement by using multiplanar reconstruction technique of 16 layer spiral CT could represent a real distance of anatomic structures. The reconstruction of spiral CT images could display a anatomic feature of temporal bone accurately, and it may provide a valuable method for surgical approach and accurate positioning of relative structure in operation. As the location of sigmoid sinus moving forward, the lateral shift of it may occur more easily and the jugular bulb become closer to the vertical portion of facial nerve, while the extension of anterior location in sigmoid sinus should be a positively correlated to the height of jugular bulb.