Image-guided localization of the internal auditory canal via the middle cranial fossa approach.
OBJECTIVE
We sought to determine the accuracy of an electromagnetic image guidance surgical navigation system in localizing the midpoint of the internal auditory canal (IAC) and other structures of the temporal bone through the middle cranial fossa approach.


METHODS
Seven fresh cadaveric whole heads were dissected via a middle cranial fossa approach. High-resolution CT scans were used with an InstaTrak 3500 Plus electromagnetic image guidance system (General Electric, Fairfield, CT). We evaluated the accuracy of identifying several middle cranial fossa landmarks including the midpoint of the IAC; the labyrinthine segment of the facial nerve; and the arcuate eminence, the carotid artery, and foramen spinosum.


RESULTS
We were able to identify the middle of the IAC within 2.31 mm (range 0.65-7.52 mm, SD 2.39 mm). The arcuate eminence could be identified within 1.86 mm (range 1.49-2.37 mm, SD 0.36 mm). We noted some interference when the handpiece was within 6 to 8 cm of the microscope.


CONCLUSIONS
Although computer-aided navigational tools are no substitute for thorough knowledge of temporal bone anatomy, we found the InstaTrak system reliable in identifying the midpoint of the IAC to within 2.4 mm through a middle fossa approach.
Miller
Robert Sean
RS
Department of Otolaryngology-Head and Neck Surgery, University of Virginia, Charlottesville, VA 22908-0713, USA.
Hashisaki
George T
GT
Kesser
Bradley W
BW
D002102:Cadaver; D035301:Cranial Fossa, Middle; D006801:Humans; D066298:In Vitro Techniques; D015203:Reproducibility of Results; D012665:Semicircular Canals / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*