The Microsurgical Anatomy of the Modified Presigmoid Trans-Partial Bony Labyrinth Approach

To investigate the surgical techniques of the modified presigmoid trans-partial bony labyrinth approach and the advantages in the exposure of the petroclival region and in the treatment of lesions in this area.

Between April and October of 2012, a study on modification of the surgical approach was performed on 15 cadaveric heads. On the basis of the traditional presigmoid approach, semicircular canals, and the petrous apex were partially resected. The detailed conditions of the exposure of important structures of the petroclival region were recorded.

This approach provided a large operational space from the petroclival region to the posterior cavernous sinus. The range of presigmoid exposure (horizontal direction) was (19.41 ± 1.58)  mm, the exposure range of the inferior temporal (vertical direction) was (14.18 ± 1.88)  mm, the maximum exposure angle of the slope center depression was (60.54° ± 6.93°), and the depth of operation was (55.87 ± 4.34)  mm. The vertebral-basilar artery, anterior inferior cerebellar artery, superior cerebellar artery, ipsilateral III-X cranial nerves, contralateral VI cranial nerve, Meckel cave, and posterior cavernous sinus were well exposed.

The modified presigmoid trans-partial bony labyrinth approach was able to achieve excellent exposure of deep surfaces of the petroclival region and the posterior part of the cavernous sinus and showed advantages including a large range of exposure, multiple axes of visualization, preservation of hearing and facial nerve function, and early devascularization of tumors.