Commentary

The authors analyzed 300 computed tomographic scans and 65 dry human skulls to investigate whether cranial morphology determines the shortest distance to the petrous apex. The cranial index was defined as width divided by length multiplied by 100 and was used to determine the best approach.

In patients with brachiocephalic skulls and high cranial indices, the distance to the petrous apex was long and depended on the approach. Regardless of the cranial index to the petrous apex, the distance was longest with the retrosigmoid approach. The pterional approach represented the shortest approach. In all approaches, the distance to the petrous apex was shortest in dolichocephalic skulls.

It is unclear, however, where the pterional and subtemporal approaches begin and end. For example, a pterional approach can be extended laterally, with or without removal of the zygoma, to approach a lesion through a combined approach. The limits would be influenced by the size and extent of a tumor and by its location above and below the tentorium.

Overall, these measurements provide useful data for skull base surgeons contemplating various skull base approaches to remove lesions of the petrous apex.