Skull Base Surgery of the Posterior Fossa by William T. Couldwell

Author:William T. Couldwell
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Fig. 8.7Decompressed posterior fossa. Intraoperative photograph from Case 4, the large PPFM, demonstrating a relaxed cerebellum after CSF was released from the upper cervical subarachnoid space

Discussion

Meningiomas of the CPA are the second most common tumor in this location after vestibular schwannomas. While Cushing referred to them collectively as “tumors of the cerebellar chamber,” there are distinct clinical syndromes associated with location and size. Previously, we reported an early experience with 24 patients and now have accumulated over 50 such patients [9]. The senior author has divided these now into three distinct locations with four clinical syndromes, similar to the classification of Peyre et al. and the modified Desgeorges and Sterkers classification [6, 13]. The trends in presentation size and symptomatology by location described in this chapter were also seen by Schaller et al. [16] Rather than dividing into three regions, they simply categorized the CPA meningiomas as pre- or retromeatal and found that smaller tumors were symptomatic anteriorly, while retromeatal tumors tended to grow much larger before causing symptoms. The importance of the tumor origin and dural attachment were emphasized in Robertson’s series, where they demonstrated that tumor origin determined the direction of the seventh to eighth nerve displacement [18]. They used transpetrosal or translabyrinthine approaches to reach the tumors anterior to the 7–8 nerve complex, but we have been able to resect these using the retrosigmoid approach complemented by intradural drilling of the petrosal bone, which facilitates hearing preservation.

Over recent years, the surgical approach of choice has shifted from a transpetrosal or translabyrinthine approach to the retrosigmoid approach. This has been driven by improved outcomes and hearing preservation with the retrosigmoid approach. When Thomas and King reported a series of CPA tumors and separated out the petrous face meningiomas from the petroclival tumors, they also observed the clinical syndromes described above [17]. They used a retrosigmoid approach for the posterior petrous tumors but required the more invasive translabyrinthine or transcochlear approach to the midpetrosal tumors. They used a middle fossa transtentorial approach to the anterior petrous/Meckel’s cave tumors. We are able to use the retrosigmoid approach with additional petrous drilling to reach all these tumors. Overall, they had excellent results with most patients returning to full function and achieved gross total resection in all 13 cases.

Functional preservation is one of the keys to resection, with facial and hearing outcomes being the most important for petrous face tumors. The greatest experience reported in the literature belongs to Majid Samii, who presented his experience with more than 400 CPA meningiomas in two papers [12, 15]. He used a sitting suboccipital/retrosigmoid approach in 95% of cases and achieved Simpson Grade 1 or 2 resection in 86% of patients. The facial nerve was preserved in 89% of cases, and hearing was preserved in 91% of cases where the patient had functional hearing preoperatively. In tumors that invaded the IAC and required drilling of the petrosal bone around the internal auditory canal, facial nerve function was preserved in 80% of cases and hearing in 75% of cases.

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