Surgical-Anatomical Pillars of Posterior Petrosectomy: A Tridimensional View

Introduction: Tumors, localized in the petroclival region and jugular foramen, are commonly accessed via a posterior petrosectomy. Due to complex nature of posterior fossa anatomy, surgery can be difficult, requiring enhanced technical ability. Tumors in the posterior fossa often distort the normal anatomy; this is of critical importance, especially when locating the vessels and cranial nerves. As such, enhanced and organized anatomical knowledge of the petrosectomy, which if often required for access, may be helpful in surgery.

Objectives:

1. To describe relevant anatomical landmarks for performing the posterior petrosectomy.

2. To create a coordinate-projection system in localizing the structures deep to the mastoid.

3. To represent these landmarks in clinical cases.

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Method: 10 formalin-fixed cadaver heads, injected with blue and red silicon, were used. Cadavers were also CT-scanned and images were co-registered to allow for real-time navigation of the osseous structures. We projected the superficial soft tissues (muscle) and relevant bony landmarks to important deep structures in the mastoid. Three clinical cases were described to apply this projection system to surgical practice.

Result: We described three anatomical lines as follows: (1) superior: the insertion of the nuchal muscles in the superior occipital line projects with the asterion and supramastoid crest. These landmarks are important in delineating the mastoidectomy. These landmarks project to the temporal dura, the superior part of the mastoid antrum and the sinodural angle; (2) middle: the insertion of the preauricular muscle, the spine of Henle and the suprameatal triangle projects to the horizontal semicircular canal, and tympanic segment of the facial; and (3) inferior: the mastoid tip and insertion of the posterior belly of the digastric muscle projects to the jugular bulb. The main anatomical landmarks of the superior line allow us to understand the superior limit of the mastoidectomy; the middle line is a safe zone for drilling and to localize relevant anatomical structures (i.e., facial nerve canal), and the inferior line corresponds to the mastoid tip that corresponds to contents of the jugular foramen.

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Conclusion: The proposed posterior petrosectomy projection system using three anatomic lines, from superficial to deep, permitted reliable and reproducible localization of the inner anatomical structures, especially with a more confident ability to locate the facial canal intraoperatively.

No conflict of interest has been declared by the author(s).