Endoscopic cranial base surgery: Classification of operative approaches

Objective: Endoscopic cranial base surgery is a minimal access, maximally aggressive alternative to traditional transfacial, transcranial, or combined open cranial base approaches. Previous descriptions of endoscopic approaches have used varying terminology, which can be confusing to the new practitioner. Indications for surgery are not well defined. Our objective was to create a comprehensive classification system of the various approaches and describe their indications with case examples. METHODS: We prospectively compiled a comprehensive database of our endonasal endoscopic operations, detailing the nasal sinus transgressed, the cranial base approach, and the intracranial target for the first 150 consecutive cases performed at our institution. All cases were performed collaboratively by a neurosurgeon and an otolaryngologist. RESULTS: We categorized the endonasal endoscopic cranial base operations into four nasal corridors, nine cranial base approaches, and 13 intracranial targets. Each of the various approaches is described in detail and illustrated with case examples. Pathology encountered included pituitary tumor (50%), meningocele/encephalocele (14%), craniopharyngioma and Rathke cleft cyst (10%), meningioma (8%), chordoma (5%), esthesioneuroblastoma (2%), and other (11%). CONCLUSION: Endonasal endoscopic cranial base surgery is a minimal access, maximally invasive alternative to open transcranial cranial base approaches for specific indications. A clear understanding of the possible approaches is facilitated by an awareness of the nasal corridors and intracranial targets.