Temporal Bone: Posterior Petrosectomy

Abstract

The transpetrosal approach was initially used for better access to cerebellopontine angle tumors, around the petroclival and posterior cavernous sinus regions, anterior brainstem, or for basilar artery lesions. Petroclival lesions are the most challenging and include meningiomas, neurinomas, chordomas, chondrosarcomas, epidermoids, cavernomas, arteriovenous malformations, and basilar trunk aneurysms. Various approaches were developed for this region but it is the retrosigmoid approach and the combined transpetrosal approach the ones that are indicated for the majority of cases, the latter even allowing a more extensive and direct exposure of large petroclival lesions with supra and infratentorial extension, most frequently petroclival meningiomas, it allowed a more extensive and direct exposure of large petroclival lesions with supra and infratentorial extension, most frequently petroclival meningiomas.

Petroclival meningiomas will be those arising from the petroclival junction medial to the trigeminal nerve, anteromedial to the internal auditory canal, and cephalad to the jugular tubercle. Clival meningiomas are also cephalad to the jugular tubercles but originate between the petroclival junctions. The petroclival region is classified in three zones, and is exposed via the posterior petrosal approach specially the zone II that goes from the upper border of the internal auditory canal to the upper border of the jugular tubercle.

Transpetrosal approaches provide access to these areas where the main goal is brainstem decompression to restore clinical function. Complete removal of the tumor and involved dura is rare and considering the natural history of the residual; such attempts only increase the morbidity. Clival and petroclival meningiomas can be considered as one entity for operative decision-making; for most lesions the lateral portion is reached via a posterior petrosal approach with the retrolabyrinthine variation but for the central clival depression and paramedian portion, it cannot be reached via this corridor as the remaining temporal bone remains an obstacle.

There are four variations of the transpetrosal approach: retrolabyrinthine, transcrusal, transotic, transcochlear; they differ in the amount of temporal bone resected to achieve a greater exposure, while also increasing the risk of VIIth and VIIIth cranial nerves. The varied list of combinations and nomenclature can be simplified; as such we suggest in this chapter a step-by-step approach to choose the best combination.

"The difficulties are admittedly great, sometimes insurmountable, and though disappointments still are many, another generation of neurological surgeons will unquestionably see them largely overcome"

Harvey Cushing, Cavendish Lecture 1922