Relaxing Sphenoidal Slit Incision: A Simple Technique to Extend the Anterior and Posterior Reach of Pedicled Nasoseptal Flaps during Endoscopic Skull Base Reconstruction of Transcribriform Defects

Objective: Endoscopic endonasal skull base surgery via the transcribriform corridor has become an accepted approach for lesions of the cribriform plate such as olfactory groove meningiomas and esthesioneuroblastomas. Nevertheless, reconstruction of the large anterior skull base (ASB) defects after endoscopic endonasal transcribriform approaches remain a technical challenge despite the advent of the vascularized pedicled nasoseptal flap (PNSF). These defects often extend from orbit to orbit in the coronal plane and from the posterior table of the frontal sinus to the planum sphenoidale in the sagittal plane. In some cases, the PNSF may be under tension and not have enough anterior reach to cover the posterior table of the frontal sinus. In addition, tension across the sphenoidal portion of the PNSF prevents the flap from covering the posterior extent of transcribriform defects. We describe a relaxing slit incision that is made in the sphenoidal portion of the PNSF that extends the anterior reach as well as the posterior reach of the PNSF to maximize tensionless flap coverage of transcribriform ASB defects. We also present illustrative cases demonstrating the operative technique and nuances.

Methods: A retrospective chart review was conducted in all cases (n = 11) of endoscopic skull base reconstruction of transcribriform ASB defects that utilized a relaxing slit incision across the sphenoidal portion of the PNSF. At the time of endoscopic skull base reconstruction, the PNSF is rotated into position so that the anterior margin of the flap is situated at the posterior table of the frontal sinus. Careful assessment is made to inspect for adequate ASB defect coverage and tension on the flap. A relaxing slit incision is made across the sphenoidal segment of the PNSF, which is the segment of flap that bridges the sphenoid sinus once the flap is rotated into position. The anterior reach of the flap is increased to cover the posterior table of the frontal sinus and the redundant sphenoidal flap is rotated to cover the planum sphenoidale. Our institutional postoperative nasal packing protocol is applied and prophylactic lumbar drainage is not used.

Results: No patients developed postoperative CSF leaks (0%). The ASB repair was monitored via postoperative outpatient nasal endoscopy at various time points which demonstrated excellent mucosalization of the ASB. Mean postoperative follow-up was 18.9 months (range, 1.2–43.1 months).

Conclusion: Our simple relaxing slit incision in the sphenoidal portion of the PNSF allows for maximal anterior reach of the flap to cover the posterior table of the frontal sinus. Posterior rotation of the sphenoidal portion of the PNSF allows for increased posterior reach of the flap to cover the planum sphenoidale. Tensionless coverage of extensive transcribriform ASB defects can be accomplished to facilitate successful endoscopic skull base reconstruction. Postoperative lumbar drainage and dural tissue sealants may not be necessary.