Improving the design of the pedicled nasoseptal flap for skull base reconstruction: a radioanatomic study

BACKGROUND: Reconstruction of the skull base after an expanded endonasal approach (EEA) is critical to achieve a good outcome. A novel technique based on the use of a pedicled nasoseptal flap has proven to be a reliable and versatile reconstructive option for extensive defects of the skull base. Data regarding the potential dimensions of a nasoseptal flap are lacking in the literature. This pilot study was developed to help optimize the design of the nasoseptal flap and to ensure that when harvesting the flap, its width and length are adequate to reconstruct the defects that are created by various EEAs. METHODS: We analyzed the computed tomographic (CT) scans of four patients who underwent EEAs for skull base lesions. Sagittal and coronal CT reconstructions were generated from axial images. The measurements were divided into skull base measurements, flap dimensions required to cover skull base defects resulting from various EEAs, and potential maximal dimensions of the nasoseptal flap. Measurements were studied for three different EEAs: sellar/transplanar, transclival, and transcribiform/anterior skull base. We measured the potential defects for each of these EEAs and the nasoseptal flap dimensions that would be required to reconstruct them. We estimated all dimensions based on the most extensive defect that could result with each EEA. We then compared these with various modifications of the nasoseptal flap. RESULTS: Two male and two female patients were studied. Twenty-seven measurements were taken to compare the different skull base defects and nasoseptal flaps. CONCLUSIONS: The length of the nasal septum comprises sufficient mucoperichondrium and mucoperiosteum to allow the harvesting of a nasoseptal flap that could cover any defect resulting from an anterior skull base, a transsellar/transplanar, or a transclival EEA. Similarly, the height of the nasal septum has the potential to yield a nasoseptal flap with a width that is adequate to cover the laterolateral aspect of any defect of the anterior skull base and clivus. Skull base defects resulting from combined EEAs, such as those that would create a defect that comprises the skull base from sella turcica to frontal sinus, are beyond the potential dimensions of a single nasoseptal flap. This and other defects resulting from a combination of EEAs require other strategies, such as the use of bilateral nasoseptal flaps, or the use of other reconstructive options.