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Petrous carotid canal dehiscence: an anatomic and radiographic study
Matthew J Hearst1, Aleem Kadar, Jeffrey T Keller
1Departments of Otolaryngology-Head and Neck Surgery, University of Cincinnati, Cincinnati, Ohio, USA.
Hypothesis:
Development of the osseous petrous carotid canal is frequently incomplete.
Background:
Although dehiscence of the carotid canal has been observed in previous studies, the frequency and extent of bony dehiscence have not been quantified. Inadvertent internal carotid artery injury occurs in 3 to 5% of skull base procedures, with an additional 1.9% of patients having carotid artery vasospasm. Documentation of the incidence of petrous apex carotid canal dehiscence is therefore warranted.
Methods:
Ninety-nine cadaveric skulls were evaluated physically and by computed tomographic scan.
Results:
Incidence of dorsal (endocranial) dehiscence of the petrous carotid canal was identified in 82.83% of the left side and 88.89% of the right side. Average dimensions for left dorsal dehiscence measured 10.81 mm longitudinally by 4.10 mm transversely. Dimensions for the right averaged 11.59 mm longitudinally by 4.29 mm transversely. Incidence of ventral (exocranial) dehiscence was less frequent: 37.37% on the left and 34.34% on the right. Ventral dehiscence was classified into major (absence of bone) and minor (fissure) types. Major dehiscence was observed in 8.08% and 6.06% of specimens for left and right sides, respectively; minor ventral dehiscence was present in 29.29% and 28.28% for left and right sides, respectively.
Conclusion:
Dorsal petrous carotid canal dehiscence is more common than previously recognized. Dehiscence of the dorsal carotid canal is a frequent finding with significant implications in advanced skull base approaches to the petrous apex, clivus, and lateral sellar compartment. Ventral dehiscence is a frequent finding that will become increasingly relevant as the scope of endoscopic skull base procedures.