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Subtemporal transpetrosal apex approach: study on its use in large and giant petroclival meningiomas.

BACKGROUND
The subtemporal transtentoral approach has been reported for nearly two decades; however it was not well used due to some limitations in dealing with large and giant petroclival meningiomas. The clinical outcome and merit of the modified subtemporal transpetrosal apex approach in large and giant petroclival meningiomas, as well as the choices, the improvements and the therapy strategies of the microsurgical approach in such patients were evaluated in this study.


METHODS
Totally 25 cases of large and giant petroclival meningiomas undergone the modified subtemporal transpetrosal apex approach between April 2004 and January 2010 were enrolled in this study. The choice and improvement of the approach, the basis of anatomy and related research, the effect of accessory equipment, the exposure of tumor and the changes of neurofunction pre- and post-operation were all reviewed retrospectively. The operation outcomes and complications in this approach were also compared with those in the transpetrous presigmoid approach done in 14 cases in the same period.


RESULTS
All 25 cases underwent the modified subtemporal transpetrosal apex approach under electrophysiologic monitoring of cranial nerves and brain stem function. Trochlear nerve was partly wrapped in 14 cases, totally wrapped but can be explored in the initial segment of the cerebellum tentorium in 8 cases, totally wrapped and could not be seen until tumor was partly removed in 3 cases. The cerebellum tentorium was cut along the temporal bone from the anterior part of the apex to the mastoid part of superior petrous sinus in 6 cases, from the posterior part of the apex to the mastoid part of superior petrous sinus in 19 cases. Gross tumor resection was accomplished in 17 (68%) patients, subtotal resection in 7 (28%) patients, and partial resection in 1 (4%) patient. The most common postoperative complication was new neurological deficits or aggravations of preexisting deficit (64%). Follow-up ranged from 3 to 69 months. Compared with the transpetrous presigmoid approach done in 14 cases in the same period, the modified subtemporal transpetrosal apex approach showed obvious advantages such as simplicity in manipulating, microinvasiveness, less time-consuming, less complication, higher rate of tumor resection though the rates of gross tumor resection might be of no significant difference.


CONCLUSIONS
Modified subtemporal transpetrosal apex approach has obvious advantages compared with the transpetrous presigmoid approach. Some complications need to be solved by practice and modification of the approach as well as the accumulation of the experiences.