The extended retrosigmoid approach for neoplastic lesions in the posterior fossa: technique modification.

Approaches to the cerebellar-pontine angle and petroclival region can be challenging due to intervening eloquent neurovascular structures and cerebellar retraction required to view this anatomic compartment with the standard retrosigmoid technique. As previously described [11], the extended retrosigmoid provides additional access to space ventral to the brainstem through mobilization of the sigmoid sinus. We report our further experience and modifications of this approach for neoplastic pathology. The standard craniotomy is utilized, and the burr holes are placed slightly beyond the transverse sinus as well as the transverse-sigmoid junction and down towards the foramen magnum, as low as possible. Another burr hole is placed over the cerebral hemisphere to facilitate the dural dissection below the bone flap and over the transverse and sigmoid sinuses. We then perform a standard retrosigmoid craniotomy with a craniotome and the transverse and sigmoid sinuses are skeletonized. Consequently, the sigmoid sinus can then mobilized anteriorly to provide an unobstructed view in line with the petrous bone, while exposure of the transverse sinus provides access to the tentorium. Fifteen patients (March 2006-July 2008) underwent this approach to manage neoplastic lesions, including five meningiomas, three schwannomas, one epidermoid, and four intra-axial metastatic lesions. The nine extra-axial lesions were predominantly in the cerebellar-pontine angle with extension medial to the seventh/eighth nerve complex to the petroclival region. Gross total resection was obtained in all patients. The primary complication due to the exposure was a clinically asymptomatic sigmoid sinus thrombosis in one patient. Requiring a fundamental change in the management of the venous sinuses, the extended retrosigmoid craniotomy permits mobilization of the sigmoid and transverse sinuses. In this process, the entire cerebellar-pontine angle extending from the tentorium to the foramen magnum can be visualized with minimal cerebellar retraction. This technical modification over the standard retrosigmoid approach may provide a useful advantage to neurosurgeons dealing with these complex lesions.