Lateral approaches to the median skull base through the petrous bone: the system of the modified transcochlear approach.

Twenty-three patients with intradural lesions of the petroclival region and prepontine cistern were managed in our centres by the modified transcochlear approach. Total tumour removal was accomplished in 17 patients, while a second stage was planned for the remaining six patients. Two cases died in the immediate post-operative period. All the remaining cases showed a good outcome and returned to work. The basic approach type A is further classified according to its anterior, superior and inferior extension into types B, C and D respectively. The surgical procedure, classification, illustrative case reports and patients' summaries are presented.