26.3.1 Preoperative Assessment

All patients should undergo a thorough preoperative assessment and, whenever possible, should be presented at a multidisciplinary tumor board. Work-up should include a confirmatory biopsy and imaging (contrast-enhanced computed tomography angiography [CTA] scan, magnetic resonance imaging [MRI] scan, and positron emission tomography scan fused to a CT scan [PET/CT scan]). Imaging should be performed according to appropriate surgical navigation protocols. Consideration for a carotid artery balloon occlusion test should be given to any patient who has tumor abutting or involving the ICA, and possible sacrifice or stenting of the ICA should be discussed with the patient. Preoperative circulating cell-free Epstein–Barr virus (EBV) DNA may predict the chance of resection with negative margins in patients with NPC and, therefore, may help to identify patients who will benefit from adjuvant treatment.20 Plasma EBV DNA can also provide early detection of local and distant recurrences postoperatively.21

26.3.2 Preparation and Set-up

We recommend intraoperative electrophysiologic monitoring for any patient with a tumor that is in the proximity of, or in contact with, cranial nerves or major neurovascular structures. Somatosensory evoked potentials monitor early signs of cerebral compromise due to ischemia, edema, hemorrhage, or contusion. Electromyography is recommended for any resection that may involve the posterior orbit, superior orbital fissure, cavernous sinus (CN III–VI), hypoglossal canal (CN XII), jugular foramen, or parapharyngeal space (CN IX–XI). We prefer a two-surgeon, four-handed technique and the use of image guidance/navigation system throughout the procedure (e.g., Stryker Navigation). A 0-degree rod-lens endoscope is used predominantly; however, we also use the 30-, 45-, and, occasionally, 70-degree rod-lens endoscopes also. To clean the lens of the endoscope throughout the procedure, lens irrigation systems are available; however, we prefer manual irrigation with warm saline.

26.3.3 Approach and Resection

The extent and location of the tumor, its relationship to critical structures, and available tissues and techniques for reconstruction dictate the exposure. Other factors to consider are the patient′s age, comorbidities, and the skills and experience of the surgical team. Margin status is an important prognostic factor for local control and overall survival after surgical salvage for recurrent NPC.22–24 The ability to achieve negative margins is dependent on many factors: adequate exposure, tumor involvement of critical structures, and T-stage.

Approaching the tumor via the natural air spaces of the nasal cavity (i.e., transnasal corridor) is suitable for a small lesion localized to the central nasopharynx. This may include lateralization of the inferior turbinates.

A more extensive exposure will provide access to the posterior and superior nasopharynx including the floor of the sphenoid sinus. This approach involves resection of the posterior inferior turbinates and a limited posteroinferior septectomy to facilitate binarial access. This approach can also be extended anterosuperiorly to involve resection of the front face of the sphenoid sinus and a complete sphenoidectomy. The approach can also be extended inferiorly to remove the lower third of the clivus and anterior arch of C1.

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  The patient is positioned supine in the reverse Trendelenburg position with the head tilted to the left and rotated to the right and neck slightly flexed.

  
  
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  Perioperatively, all patients receive a fourth-generation cephalosporin plus vancomycin, if they are methicillin-resistant Staphylococcus aureus positive.

  
  
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  The nasal mucosa is prepared with topical 1:10,000 epinephrine-soaked pledgets which are left in place during the positioning and draping of the patient.

  
  
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  The pledgets are removed and the nasal mucosa is injected with 1% lidocaine with 1:100,000 epinephrine, including septum, axilla of the ipsilateral (to the tumor) middle turbinate, and the region of the sphenopalatine arteries (SPAs) bilaterally.

  
  
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  If the torus tubarius is involved, then resection of the medial cartilaginous eustachian tube (ET) is required. For this resection, a mucoperiosteal incision on the posterolateral nasal cavity wall is made vertically just posterior to the inferior turbinate, over the ascending process of the palatine bone and medial pterygoid plate. This incision may be made more anteriorly as dictated by the tumor extent. The dissection then continues posteriorly in a submucoperiosteal plane exposing the medial pterygoid plate. The torus is sharply transected and soft tissue dissection continues until the tumor is removed and histopathologic examinations (i.e., frozen sections) are negative.

  
  
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  We prefer a transpterygoid approach for any tumor that extends lateral into the fossa of Rosenmüller. This includes a medial maxillectomy and transposition of the soft tissue contents of the medial pterygopalatine fossa. This exposes the entire height of the pterygoid process and permits excision of the medial pterygoid plate and its base to the level of the foramen rotundum.

  
  
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  The contralateral inferior turbinate is out-fractured using a Freer dissector.

  
  
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  The ipsilateral middle turbinate is resected using straight endoscopic scissors and straight through-biting Blakesley forceps. It is imperative to keep the skull base in view when removing the middle turbinate to avoid violating the skull base and creating a cerebrospinal fluid leak ( Fig. 26.2 ). The mucosa from the turbinate is then harvested and stored in saline.

  
  
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  The uncinate process is removed using back-biting forceps, a ball-tipped seeker probe, and the microdebrider.

  
  
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  The natural ostium of the maxillary sinus in then identified and extended posteriorly using the straight through-cutting forceps and microdebrider.

  
  
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  An ipsilateral complete anterior and posterior ethmoidectomy is then undertaken using through-cutting forceps (straight and 45 degree) and the microdebrider.

  
  
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  The inferior third of the superior turbinate is resected with straight through-biting/through-cutting Blakesley forceps and the sphenoid ostium is identified bilaterally.

  
  
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  As long as the roof of the nasopharynx, posterior septum, pterygopalatine fossa, sphenoid rostrum, and posterior choana are free of tumor, a nasoseptal flap25 is elevated. Another consideration is radiation necrosis, which could also compromise the blood supply to the flap. If there is any uncertainty, a Doppler probe may be used intraoperatively to assess the viability of the pedicle. The flap is elevated on the contralateral side as the internal maxillary artery is sacrificed on the ipsilateral side during the approach.

  
  
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  The nasoseptal flap may be stored in the maxillary sinus or may be placed along the lateral nasal wall, which avoids significant congestion of the flap. To do this, a suture is placed in the anterior aspect of the flap, which is then attached to a hemostat. The hemostat hangs from the nasal cavity and uses gravity to hold the flap in place. The shaft of the endoscope will hold the flap out of the way and prevent injury during the surgery. If the flap is on the contralateral side, then instruments must be inserted into the nasal cavity under direct vision to avoid injury.

  
  
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  If a nasoseptal flap is not available, then a temporoparietal fascia flap may be used for reconstruction. This flap is introduced to the nasal cavity via a transpterygoid tunnel.26

  
  
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  After the posterior bony septectomy, a reverse septal flap is then created to further protect the remnant septum and to minimize crusting postoperatively.27 The inferior incision of the reverse flap is made approximately 5 mm above the remnant septum ( Fig. 26.3 ). This mucosa is then rotated to the contralateral side and used as an inferiorly based flap covering the exposed bone of the maxillary crest.

  
  
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  This creates a complete posterior septectomy, thus providing a panoramic view of the nasopharynx, allowing a more lateral access for instrumentation, and allowing a two-surgeon, four-hand technique. Intraoperative image guidance may be used to ensure the septectomy does not include the structural support of the nasal septum (that portion inferior to the nasal bones and resting over the premaxilla); thus avoiding a saddle nose deformity.

  
  
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  Silicone splints are cut to size and sutured to the septum to protect the reverse flap from inadvertent injury due to the passage of instruments throughout the remainder of the procedure and to prevent synechiae. This wound heals within 1 to 2 weeks.27

  
  
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  Bilateral wide sphenoidotomies are then created using the Kerrison rongeurs and a drill. We prefer a high-speed drill and a 3 to 4 mm coarse or hybrid diamond burr (e.g., Midas Rex Stylus Legend, Medtronic, or Stryker Total Performance System). Removal of the sphenoid floor will reduce the likelihood of posterior choanal stenosis as many of these patients will have failed radiotherapy and will be at increased risk.

  
  
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  The sphenoid floor is then drilled down until it is flush with the clivus.

  
  
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  A medial maxillectomy is then undertaken extending from the roof of the antrum/inferior orbital wall to the nasal floor and from the nasolacrimal duct to the posterior wall of the antrum.

  
  
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  Using back-biter forceps, straight through-cutting forceps, and the microdebrider, the maxillary ostium is opened maximally. Posteriorly, the dissection extends to the level of the posterior wall of the maxillary sinus. Care must be taken when removing portions of the perpendicular plate of the palatine bone during this procedure as 38% of posterolateral nasal arteries (branch of the SPA) run anterior to the posterior wall of the maxillary sinus and brisk bleeding may be encountered.28 Anteriorly, the dissection ends just posterior to the nasolacrimal duct.

  
  
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  The middle third of the ipsilateral inferior turbinate is removed. First, the inferior turbinate is medialized; then, an incision is placed posterior to the level of the nasolacrimal duct opening using angled scissors. The remainder of the turbinectomy is completed using turbinectomy scissors or through-biting Blakesley forceps and the microdebrider.

  
  
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  The medial wall of the maxillary sinus is then removed to the level of the floor of the nose using the microdebrider, through-cutting Blakesley forceps, and the drill. Prior to this, a small flap of medially based mucosa is elevated off the medial wall of the maxilla and floor of the nose to be rotated over the exposed bone once the medial wall is drilled flush with the floor of the nasal cavity ( Fig. 26.4 ).

  
  
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  The SPA may be identified immediately posterior to the crista ethmoidalis, clipped, cauterized, divided, and mobilized laterally.

  
  
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  Following a medial maxillectomy, access to a tumor that extends laterally (e.g., into the infratemporal fossa) may be limited by the anchored nasolacrimal duct. If the tumor dictates that further lateral resection is required, maneuvering instruments from the contralateral side via the posterior septectomy will increase lateral access. If still further access is required laterally, then an endoscopic Denker′s approach (i.e., Sturman–Canfield approach) will permit instrumentation to reach the infratemporal fossa. Removal of the anteromedial aspect of the maxilla/bone of the piriform aperture also permits more lateral maneuverability for instrumentation ( Fig. 26.5 ).

  
  
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  An endoscopic Denker′s approach begins with removal of the remainder of the inferior turbinate. Next, a vertical incision is made over the anterior border of the piriform aperture, which is just anterior to the head of the inferior turbinate ( Fig. 26.6 ). This edge can be palpated with a blunt instrument. The incision is extended down through the periosteum to expose the anterior aspect of the maxilla. The mucosa is then elevated in a subperiosteal plane using a Cottle elevator or Freer dissector. Elevation continues laterally until the infraorbital nerve is identified and elevated and thus preserved ( Fig. 26.7 ).

  
  
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  The anteromedial maxillary wall is removed using the high-speed drill ( Fig. 26.8 ). The bone surrounding the nasolacrimal duct is drilled and the duct is divided sharply. A sharp transection obviates the need for stenting. If it is possible to preserve the nasolacrimal duct, then the dissection continues inferior to it using back-biting rongeurs and the high-speed drill. However, a full Denker′s approach involves the removal of the anteromedial aspect of the ascending process of the maxilla and transection of the nasolacrimal duct.

  
  
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  Removal of the piriform aperture and anterior maxillary wall results in a single cavity comprising the maxillary, ethmoid, and sphenoid sinuses and the nasal cavity and nasopharynx. This will provide a straight line-of-sight extending to the lateral limits of the infratemporal fossa.

  
  
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  The mucosa of the posterior wall of the maxillary sinus is elevated laterally off the bony wall and may be preserved for later use during reconstruction if it is not involved with tumor.

  
  
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  The posterior wall of the maxillary sinus is then removed using 1- to 2-mm Kerrison rongeurs, Hajek-Koeffler punch, or 45-degree through-biting Blakesley forceps. Dissection continues to a point just lateral to the inferior orbital fissure.

  
  
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  The internal maxillary artery and its branches can be identified anterior to the nerves in the pterygopalatine fossa and can be ligated to further improve access.

  
  
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  To permit further lateralization of the contents of the pterygopalatine fossa, the greater palatine nerve and artery may be sacrificed or mobilized to permit complete removal of the pterygoid process ( Fig. 26.9 ).

  
  
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  The vidian nerve is then identified exiting its foramen. The vidian foramen is then exposed and the neurovascular bundle is cauterized with bipolar cautery and then sharply divided ( Fig. 26.10 ). This allows even further lateralization of contents of the pterygopalatine fossa.

  
  
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  Dissection may then continue laterally in a subperiosteal plane in the pterygopalatine fossa leaving the soft-tissue contents contained in a sac between the periosteum of the posterior wall of the maxilla and the anterior aspect of the pterygoid process. Dissection in a subperiosteal plane avoids bleeding from the pterygoid arterial and venous plexus. The entire height of the pterygoid process, foramen rotundum, and maxillary division of the trigeminal nerve are then exposed.

  
  
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  The vidian canal is then drilled circumferentially in an anterior-to-posterior fashion toward the petrous ICA. The vidian nerve crosses lateral to the ICA at the foramen lacerum, and progressive and careful drilling will avoid inadvertent injury to the ICA.

  
  
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  Drilling the bone between the vidian nerve and V2 will lead toward the paraclival ICA, and following the foramen rotundum will lead toward the trigeminal ganglion. Drilling the inferior wall of the vidian canal, the pterygoid process, and the medial pterygoid plate will expose the superior aspect of the ET. The vidian nerve and ET converge at the lower/fibrocartilaginous portion of the foramen lacerum and the petroclival transition of the ICA occupies the upper portion.

  
  
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  The mandibular branch of the trigeminal nerve (V3) is located inferior to V2 and anterior to the petrous ICA.

  
  
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  Once the section of ICA at the foramen lacerum is identified, bone over the inferior and lateral aspect of the horizontal petrous ICA may be removed. It is best to use a hybrid burr when drilling near the ICA (coarse diamond) as it is less likely to cause injury than a cutting burr and generates less heat than a diamond burr, reducing the likelihood of thermal injury to the ICA and surrounding critical structures. When drilling the carotid canal, the bone is drilled until it is almost the thickness of an eggshell and then removed using instruments such as a 1-mm Kerrison rongeur or fractured off carefully using a Cottle dissector.

  
  
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  To obtain distal control of the ICA, the bone overlying the paraclival (vertical) ICA may be drilled thin and removed. Dissection then carefully proceeds along the ICA using surgical navigation and Doppler sonography to confirm anatomic landmarks throughout.

  
  
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  If tumor involves any segment of the ICA, then a transcervical approach could be used in combination with the expanded endonasal approach (EEA) to gain proximal control of the common, external, and internal carotid arteries. Furthermore, the ICA can be dissected distally toward the skull base and parapharyngeal ICA to mobilize away from tumor or to insert a barrier to identify it and protect it during the EEA.

  
  
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  Removal of the medial pterygoid plate will then expose the medial third of the ET ( Fig. 26.11 ). This section of eustachian tube is removed to expose the entire fossa of Rosenmüller and any tumor within and beyond. Removal of the ET will include removal of the levator veli palatini and tensor veli palatini muscles.2,17,29

  
  
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  The anterior wall of the fossa of Rosenmüller is quite adherent to the perichondrium of the torus tubarius and will be removed with the cartilaginous ET.

  
  
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  Wherever possible, the lateral pterygoid plate is preserved as a landmark for the position of V3 (immediately posterolateral to its base/root) and to protect the parapharyngeal ICA (posterolateral to V3) ( Fig. 26.12 ).

  
  
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  To expose the bony ET, the temporalis, medial pterygoid, and lateral pterygoid muscles may be displaced or removed if involved with tumor.

  
  
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  The posterior and superior aspects of the nasopharynx are invested in dense fascial tissues and the attachments of the longus capitis muscles. To separate these soft tissues from the underlying bone, a very sharp dissector and electrocautery are best.

  
  
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  The tumor is removed en bloc, in layers or sections depending on its size and relationship to critical structures.

  
  
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  Intraoperative histologic specimens are sent from the margins (frozen sections) to confirm the adequacy of resection prior to commencing reconstruction.