Transcerebellar biopsy of posterior fossa lesions using the Leksell gamma model stereotactic frame

We describe a technical modification of the Leksell gamma stereotactic system that enables a direct transcerebellar biopsy of posterior fossa lesions. By using an additional pair of long (14 cm) posts placed in the posterior positions of the frame, the frame can be positioned low enough to allow for direct approaches to the posterior fossa. With the patient in the semisitting position, a biopsy can be performed under local anesthesia. We have found this technique provides a simple, comfortable, and effective biopsy of posterior fossa lesions.