Retrosigmoid intradural suprameatal approach to Meckel's cave and the middle fossa: surgical technique and outcome

Object. The goal of this study was to determine whether some petroclival tu mors can be safely and efficiently treated using a modified retrosigmoid pe trosal approach that is called the retrosigmoid intradural suprameatal appr oach (RISA). Methods. The RISA was introduced in 1983, and since that time 12 patients h arboring petroclival meningiomas have been treated using this technique. Th e RISA includes a retrosigmoid craniotomy and drilling of the supra meal-us petrous bone, which is located above and anterior to the internal auditory meatus, thus providing access to Meckel's cave and the middle fos:a. Radical tumor resection (Simpson Grade I or II) was achieved in nine (75%) of the 12 patients. Two patients under went subtotal resection (Simpson Gra de LII), and one patient underwent complete resection of tumor at the poste rior fossa with subtotal resection at the middle fossa. There were no death s or severe complications in this series; all patients did well postoperati vely, being independent at the time of their last follow-up examinations (m ean 5.6 years). Neurological deficits included facial paresis in one patien t and worsening of hearing in two patients. Conclusions. The approach described here is a useful modification of the re trosigmoid approach, which allows resection of large petroclival tumors wit hout the need for supratentorial craniotomies. Although technically meticul ous, this approach is not time-consuming; it is safe and can produce good r esults. This is the first report on the use of this approach for petrocliva l meningiomas.