A Model of Success: Incorporating 3D-Printed Models of Skull Base Pathology for Surgical Approach Planning

Introduction: Skull base pathologies are uniquely demanding with respect to surgical approach planning, given the competing demands of optimizing exposure and potential for treatment success, while minimizing brain retraction and reducing risk to adjacent neurovascular structures. Conventional 2D modalities including a variety of imaging studies are critical to preoperative assessment; however, they require significant skill and experience to integrate and synthesize mentally during approach planning. 3D modeling technology—which includes 3D printing, and virtual/augmented/mixed reality spaces—provides a powerful tool for enhancing preoperative approach planning, with potential advantages for optimizing patient safety and surgical outcomes alike.

Methods: We prospectively created 3D models of diverse, patient-specific skull base pathologies, to generate an extensive print and digital space models. Prototypical example cases were then selected for explicit study, including three cases of extra-axial, intracranial skull base neoplasms (vestibular schwannoma, trigeminal schwannoma, foramen magnum meningioma), three intracranial cerebrovascular lesions (anterior circulation aneurysm, hypoglossal dural arteriovenous fistula, brainstem cavernoma), and three pediatric complex cranial cases (MCA aneurysm, Vein-of-Galen malformation, immature teratoma of the parasellar and orbital regions). Multicolor additive printing was then used to generate physical models, which were printed within both skulls that had prespecified standard skull base craniotomy exposures completed, and complete skulls. Study subjects from both neurosurgery and ENT then participated in two-phase model assessment. In Phase 1, the first cohort of subjects were provided skulls with planned craniotomies removed which were used to determine an optimal approach, after which subjects were surveyed regarding their subjective impression of the models’ utility in approach planning. In Phase 2, subjects were asked to preselect an approached using standard 2D imaging modalities alone, after which they were provided identical pathologic lesions contained within complete skulls, on which they performed the selected approach. Following the procedure, they were provided models, and surveyed regarding whether they felt that their decision making would have been altered had the models been available prior to approach selection. Surveys were administered via a 5-point Likert agreement scale.

Results: Phase 1 subjects universally endorsed “Agreement” or “Strong agreement” that their decision making was assisted by the 3D-printed model. Phase 2 subjects reported a more diverse range of responses, with “Agreement” and “Neutral” predominating. When stratified by level-of-training, trainees and more junior staff were more likely to agree that 3D models significantly enhanced their ability to select and plan a surgical approach. These findings were preserved across pathologic categories (e.g., tumor, cerebrovascular, pediatrics), and lesion location (e.g., posterior/lateral, anterior).

Conclusion: Surgical approach planning via traditional 2D imaging modalities for complex skull base pathology depends on surgeon’s skill and, perhaps most importantly, experience. The expansion of approach planning technologies to incorporate 3D modeling for patient-specific pathologies appears to provide a significant degree of benefit, particularly among less experienced skull base surgeons. Future applications may include not just surgical planning, but simulation systems for trainees, patient education modules, and applications within neuropathology sphere.