While the transnasal endoscopic approach to the pituitary fossa has become a widely utilized technique for surgical resection [20, 21], robotic surgery in this anatomic location may provide unique advantages over the four-handed technique. The feasibility of a robotic approach to the pituitary fossa has been described by the authors and remains investigational [22].

Similar to the approach to the anterior cranial fossa, access involves creating bilateral maxillary antrostomies and docking the robotic arms and camera, as described above. An anterior sphenoidotomy is then performed and the sellar floor removed to expose the dura of the pituitary fossa (Fig. 14.4a, b). The dura is opened sharply with the robotic scissors to allow for exploration of the pituitary gland (Fig. 14.5a). Blunt and sharp dissection may be then performed to excise the pituitary gland after the optic chiasm and hypothalamus are exposed (Fig. 14.5b). Dissection of the lateral wall of the sphenoid sinus may also be performed with high-speed drills and fine rongeurs to access the cavernous sinus. Using this technique access to the central skull base, including the planum sphenoidale, the pituitary gland, cavernous carotid, mammillary bodies, and optic chiasm, can be achieved (Fig. 14.5c).

A transcervical approach to the skull base in canine and cadaver models has been previously described. Access to the sphenoid, clivus, sella, and suprasellar anterior fossa can be obtained by placing a 30 degree robotic endoscope transorally and placing the right and left robotic arms through the lateral pharyngeal walls via a transcervical technique, posterior to the submandibular gland [23].

Robotic surgery of the nasopharynx is perhaps the only anatomic site of the skull base that is most amenable to surgical dissection with current iterations of surgical robotics. The feasibility of robotic resection of nasopharyngeal lesions in a cadaver was first described in 2008 [24], and subsequent case reports of surgical management of nasopharyngeal cancers have been published in the literature [25].

A Dingman retractor is utilized to expose the oral cavity, and the soft palate is divided under direct visualization—lateral retraction of the divided palate is achieved with Vicryl suture (Fig. 14.6a). The da Vinci robot is then docked at the head of the bed, and the robotic arms are positioned into the oral cavity. Typically, a 30 degree endoscope providing a superiorly oriented view of the oropharynx and nasopharynx is utilized. Using the Maryland forceps and the spatula cautery, the nasopharynx soft tissue may then be progressively degloved (Fig. 14.6b) between the carotid arteries and Eustachian tubes (Fig. 14.6c) laterally and the skull base and prevertebral musculature posteriorly. Once the tumor is resected, the palate is closed in three layers with absorbable suture. The advantage of this technique is that it allows for en bloc excision of nasopharyngeal lesions and may offer the advantage of decreased morbidity compared to either re-irradiation or open surgical approaches for recurrent nasopharyngeal carcinoma. Further study is necessary to delineate the optimal surgical indications.

Both preclinical studies and case reports addressing the infratemporal fossa and parapharyngeal space via robotic approaches have been described [26, 27]. Dissection is performed through the lateral pharyngeal wall to access the parapharyngeal space. Using the 30 degree endoscope directed superiorly, the parapharyngeal space can be carefully explored to identify the neurovascular contents—jugular vein, internal carotid, and CN IX, X, XI, and XII. To gain exposure superiorly and laterally (to the infratemporal fossa), the styloid musculature can be resected and pterygoid muscles partially released. This approach may be best suited for well-circumscribed benign lesions.

Perhaps the most significant limitation of current transnasal endoscopic techniques is the inability to reconstruct dural defects with a sutured watertight dural closure. Options for repair of the skull base include free mucosal grafts, fascia lata grafts, pedicled mucosal grafts, and biological materials [15, 16, 28–30]. While each has advantages and disadvantages, only the pedicled mucoperiosteal grafts are vascularized [31], a necessary component of any reconstruction in patients undergoing postoperative irradiation or in previously irradiated patients. One of the major drawbacks of the endoscopic approach is the inability to perform a suture-based reconstruction of the dura using currently available technology, an approach that is easily undertaken with a pericranial flap through the transcranial approach. We previously reported the feasibility of an endonasal robotic surgical dural reconstruction to address this problem in skull base surgery.

Repair of the skull base defect can be performed robotically with two distinct techniques. First, repair of the dura may be primarily reconstructed with both continuous and interrupted suture technique (Fig. 14.7a). Additionally, harvested sinonasal mucoperiosteal graft can be sutured into dural defects with both running and interrupted suture techniques (Fig. 14.7b). While these techniques have been demonstrated in cadaver models, their application in human use has yet to be realized.

A balanced analysis of where robotic surgery may lie on the spectrum of surgical modalities suggests that robotic-assisted skull base surgery offers unique advantages that are lacking in either microscopic or transnasal endoscopic techniques. These can be divided in four major areas: optical, ergonomic, dissection, and reconstructive. The following is a discussion of how endoscopic robotic surgery can overcome some of the limitations of these other techniques and where robotic surgery has limitations.