Stereotactic Frame-Based Targeting of the Posterior Fossa: A Systematic Workflow for the Leksell G Frame.

Introduction: Cerebellar deep brain stimulation (DBS) is gaining traction as a potential treatment for movement disorders and stroke, and there is renewed interest in the cerebellum as a target for neuromodulation. Despite the safety and accuracy of frame-based approaches to the posterior fossa, unconventional stereotactic frame placement may be necessary to allow for low posterior fossa trajectories. Current literature lacks a comprehensive protocol detailing inverted frame placement and targeting.

Methods: Preoperative imaging was acquired prone. An inverted Leksell G frame was applied along with an open-topped CT fiducial box, followed by a prone CT with the scanner set to the "legs first, nose up" configuration. Target coordinates were extracted from navigation software after image fusion. Intraoperatively, the patient was positioned prone, and the stereotactic arc was mounted in the lateral-right orientation, with inverted arc supports. Confirmatory stereotaxy to a scalp staple was performed, and the DBS leads were then inserted.

Conclusion: Our standardized protocol provides a flexible platform for posterior fossa DBS, allowing for low trajectories and multiple electrodes. Unlike conventional upright frame placement, an inverted frame permits an unobstructed view of suboccipital entry sites and incision placement. A conventional frame and regular planning software are sufficient, with no additional mathematical calculations required.