The radioanatomy of endonasal flap coverage of skull base defects: A tool for preoperative planning.

OBJECTIVES/HYPOTHESIS: To develop a tool for the calculation of surgical skull base defects and endonasal flap dimensions on preoperative computed tomography (CT) to aid surgical planning.

STUDY DESIGN: Case series.

METHODS: A literature search was conducted to identify all endonasal flaps. There were five basic models identified. These are the nasoseptal flap, anterior lateral nasal wall flap, bipedicled anterior septal flap, posterior pedicled inferior turbinate flap, and middle turbinate flap. Publications on the radioanatomy of endonasal flaps and surgical skull base defects were also identified. Using these descriptions as a reference, 38 radioanatomic variables were measured on CT scans obtained from 60 preoperative endonasal skull base surgery patients. These were then used to model endonasal flap coverage of six defects: transfrontal, transcribriform, transplanar, transsellar, transsphenoidal, and transclival.

RESULTS: The nasoseptal provides adequate coverage for most defects. The posteriorly pedicled inferior turbinate flap is a good alternative, and provides better coverage of posterior skull base defects. The anterior lateral nasal wall flap is the best choice for transfrontal defects. The middle turbinate flap and bipedicled anterior septal flaps provide secondary options when larger flaps are not available.

CONCLUSIONS: We have developed a simple tool for the calculation of endonasal flap coverage of surgical skull base defects on preoperative CT scans.

LEVEL OF EVIDENCE: 4. Laryngoscope, 128:1287-1293, 2018.