Technique for reconstruction of large clival defects through an endoscopic-assisted tunneled retropharyngeal approach.

Abstract

Reconstruction of the clivus and posterior cranial base defects following endoscopic skull-base surgery can be particularly challenging. Commonly, defects in this region are repaired with pedicled mucoperichondrial flaps from the sinonasal cavity. Complex and large defects often require regional or free flaps, particularly when intranasal flaps have been exhausted. While there are no primary barriers to routing flaps into the clivus or nasopharynx in large open approaches, secondary surgical corridors are necessary during endoscopic cases for routing of free flaps. Routing of free-flap pedicles for endoscopic cranial base reconstruction has been described through secondary surgical corridors created through the maxillary sinus and infratemporal fossa. Here we describe the technique of a more direct pedicle route to the clivus through the retropharyngeal space. A patient with frank cerebrospinal fluid (CSF) rhinorrhea and extensive osteoradionecrosis of the clivus and craniocervical junction presented for treatment. Due to the size and location of the defect and previous exhaustion of candidate mucoperichondrial flaps, free-flap reconstruction was performed. A radial forearm free flap was tunneled through the prevertebral space into the nasopharynx and clivus and inserted with endoscopic-assisted techniques. The flap pedicle coursed through the retropharyngeal space to the neck vessels where arterial and venous anastomosis was established. The CSF leak and clival defect were successfully repaired with this technique. Postoperative imaging demonstrated appropriate positioning of the flap as well as the location of the free-flap pedicle and anastomosis. Endoscopic evaluation at 6 months showed complete resurfacing of the previously exposed cranial base. In cadaveric dissection in 3 adult specimens, the pedicle length necessary to reach the inferior clivus and craniocervical junction from the closest recipient pedicle through a retropharyngeal route was an average of 6.5 cm vs an average of 16 cm through the transmaxillary approach. The retropharyngeal space offers a direct route for tunneling free flaps for the repair of large clival defects during endoscopic skull-base surgery. Several advantages include a less circuitous pedicle route, mucosalization of the fascial flap, avoidance of midfacial degloving, and avoidance of potential disruption of the maxillary sinus.