Carotid artery visualization during anterior skull base surgery: a novel protocol for neuronavigation

Detailed knowledge of the vascular anatomy of the anterior skull base is critical to successful surgery in this area. Whereas conventional neuronavigational approaches combine MRI (+/- contrast) for tumor visualization and CT (+/- C) for bony and vascular anatomy, we describe the Canadian and Austrian experiences using a novel protocol integrating MR angiography (MRA) into surgical neuronavigation to provide superior visualization of the carotid arteries. The pre-operative imaging protocol employs a T1-weighted, 3D fast spoiled gradient echo MRI (+/- C) for soft tissue anatomy, a plain CT for bony anatomy, and a 3D time-of-flight MR angiography for carotid anatomy. The series are imported into the Medtronic StealthStation((R)) TREON((R)) Treatment Guidance System; during intra-operative neuronavigation, each series (MRI, CT, MRA) can be viewed individually, or layered and viewed as a composite image. Our protocol has important advantages. First, it provides detailed tissue, tumor, vascular and bony anatomy. Second, a contrast CT is not necessary; this is important, as numerous reports have highlighted the nephrotoxic nature of radiographic contrast material. Third, visualization of the carotid system is superior than can be obtained from CT angiography. We use this unique imaging protocol routinely for our endoscopic transsphenoidal surgeries to provide superior visualization of the carotid arteries during anterior skull base surgery.