A Review of Corridors and Approaches for Free Flap Reconstruction after Endoscopic Endonasal Skull Base Surgery

Introduction: As endoscopic endonasal skull base surgery has gained momentum, the need for vascularized options for reconstruction of the anterior and middle skull base has become apparent. While the workhouse of reconstruction options for the anterior skull base, the nasoseptal flap, is a popular and straightforward option, multiple other pedicled and vascularized options may be more appropriate in certain situations, such as when a NSF has failed, in the setting of septal trauma, or when a larger reconstruction is needed. There are rare situations in which vascularized tissue larger than those from pedicled options is needed, such as in cases of recurrent CSF leaks, large defects following cancer resections or bone damage from clival osteomyelitis or osteoradionecrosis. In addition, in settings where local options are exhausted or have been exposed to radiation, nonradiated tissue may need to be recruited to achieve a safe skull base reconstruction. Microvascular free flaps may offer appropriate coverage in these complex situations. Since no vessel for microvascular anastomosis is in the direct vicinity, the surgeon will need to consider the appropriate route for a protected, viable pedicle. Additionally, with the acceptance of endoscopic endonasal surgery, minimizing external scars is preferred in these cases. The purpose of this review is to discuss published options for corridors for free flap transposition as well as vessel choices for microvascular reanastomosis.

Methods: A literature search was performed using search terms “free flap,” and “skull base.” This search was intended to be a review of the literature and not a systematic review. Articles were reviewed and selected for inclusion in this review based on relevance. We were interested in reporting possible routes for free flap accessibility to the anterior and middle skull base as well as microvascular vessel options, as this choice may affect the geometry of accessibility to the defect.

Results: A total of 150 article titles and 31 abstracts were reviewed, and 7 articles were found to be relevant to this review. Published options for vessel anastomosis and corridors to the anterior and middle skull base are reviewed including Caldwell-luc, buccal space, prevertebral space, transpterygoid corridor and transmaxillary approaches.

Conclusion: The field of endoscopic surgery has continued to advance and provide options for advanced tumors of the skull base. This has led to a need for creative routes to the skull base for free flap reconstruction. In this review, we describe several options for corridors for reconstruction of the anterior and middle skull base.