While radiotherapy with or without chemotherapy has been the mainstay of treatment for primary nasopharyngeal carcinoma (NPC), surgical resection of the recurrent cancer with the adjacent mucosal wall (nasopharyngectomy) has been established as an efficacious salvage treatment. Various open surgical approaches for nasopharyngectomy have been described in Chapter 43 , Chapter 44 . With advancement in technology and endoscopic endonasal surgical techniques, it is now feasible to perform endoscopic resection in selected cases of patients who have recurrent NPC using an endoscopic endonasal approach. The endoscopic approach remains a challenging operation since the limited space in the nasal cavities and nasopharynx does not provide adequate exposure, which hampers instrumentation and reduces the dexterity of the surgeon. Alternatively, a transoral robotic-assisted approach allows a minimally invasive resection of a small NPC without resorting to major incisions and osteotomies. The surgical robot is a machine designed to assist the surgeon to perform complex surgical maneuvers in confined spaces of the body cavity. It has been successfully applied to the head and neck area for minimally invasive surgery for early cancers of the oropharynx, larynx, and hypopharynx.
The application of the surgical robot has several distinct advantages when applied to minimally invasive nasopharyngectomy. The 3D magnified view and stable endoscopic camera platform allow the surgeon to visualize the anatomy and pathology with unprecedented detail and clarity. The wristed instruments with multiple degrees of freedom allow for complex surgical maneuvers to be performed with dexterity in a narrow space such as the nasopharynx.
Unfortunately the current generation of surgical robots is not designed primarily for use in the head and neck area, and there are certain restrictions and limitations when applied to nasopharyngectomy, which we will discuss in this chapter. Note that the surgical robot discussed in this chapter is restricted to the da Vinci S or da Vinci Si model by Intuitive Surgical Inc. (Sunnyvale, California).
Key Operative Learning Points
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The major benefit of the surgical robot is from the wrist of the robotic arms that increases the surgical dexterity previously lost in endoscopic instruments. The use of the surgical robot allows traction and counter-traction of tissue during dissection.
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The major disadvantage of the surgical robot is the loss of tactile sensation, and this sense needs to be substituted by vision. An example is observing denting of tissue by surgical instruments to determine if it is hard or soft.
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The anatomy of the internal carotid artery in the parapharyngeal space (PPS) is highly variable. Trace the artery on the cross-sectional images carefully. Patients with a retropharyngeal internal carotid artery or the artery too close to the tumor are not suitable for robotic nasopharyngectomy.
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Recurrent NPC frequently arising from the fossa of Rosenmüller involved the Eustachian tube cartilage. Enbloc resection of the involved fossa of Rosenmüller and ipsilateral Eustachian tube cartilage is necessary for complete resection of the disease.
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Coverage of the raw bone of the clivus, preferably with vascularized tissue, is mandatory to minimize the risk of postoperative osteoradionecrosis.
Preoperative Period
History
- 1.
History of present illness
- a.
History of previous NPC
- b.
History of treatment of NPC with radiation or chemoradiation
- c.
Diagnosis of local recurrence in the nasopharynx
- d.
Diagnosis of other malignant lesion in the nasopharynx
- e.
Benign lesions in the nasopharynx requiring resection
- f.
Presence of a mass in the neck
- a.
- 2.
Past medical history
- a.
Details of prior treatment of NPC
- b.
Prior endoscopic nasal surgeries
- c.
Comorbid medical conditions that increase anesthetic risks
- d.
Presence of velopharyngeal incompetence/hypernasality—transpalatal surgery may exacerbate the velopharyngeal incompetence
- e.
Presence of trismus and mastication problems—a common problem following radiation to the nasopharynx precluding a transoral approach
- f.
Presence of loose teeth or teeth with radiation caries—teeth may be damaged during a transoral procedure
- a.
- 3.
Medication history
- a.
Concurrent use of antiplatelet drugs—carotid stenosis is common in NPC patients after radiation
- b.
Use of herbal medicine—increase bleeding tendency
- c.
Allergies, especially to antibiotics
- a.
- 4.
Mental and social status
- a.
Ability to give informed consent
- b.
Preference for surgical salvage over salvage radiotherapy
- a.
Physical Examination
- 1.
Examination of the nasal cavities and nasopharynx
- a.
Identify the site and extent of the recurrent cancer with an endoscope.
- b.
The fossa of Rosenmüller should be inspected with a 30-degree endoscope.
- c.
Presence of intranasal adhesions
- d.
Presence of radionecrosis of the skull base
- a.
- 2.
Examination of the oral cavity
- a.
Presence of trismsus—dental gap should be more than 3.5 cm for transoral robotic surgery (TORS)
- b.
Condition of the teeth, any loose teeth, or teeth with radiation caries
- c.
Velopharyngeal closure
- a.
- 3.
Examination of the neck
- a.
Presence of metastasis to the neck
- b.
Adequate flexion and extension of neck
- a.
- 4.
Histological diagnosis
Imaging Studies
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Cross-sectional imaging with contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) should be also performed before the operation.
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The location, extent, and relationship of the cancer to the internal carotid artery (ICA) are better appreciated with MRI while CT can better demonstrate the bony anatomy and any invasion of bone.
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The course of the internal carotid artery in the PPS should be identified. Retropharyngeal ICA is a contraindication to robotic resection.
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Positron emission tomography (PET)-CT scan is also useful in recurrent cancer as some posttreatment changes may mimic active tumor infiltration.
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PET-CT can also help to rule out distant metastasis that made cure impossible.
Indications
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Small central NPC recurrent after radiotherapy/chemoradiation
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Other cancers of the nasopharynx
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Small benign lesions in the nasopharynx
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Minimal extension to the PPS
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Minimal erosion of the cortex of the clivus
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Cancer invading the prevertebral muscles or the floor of the sphenoid sinus
Contraindications
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Cancer with lateral extension beyond the lateral pterygoid plate
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Cancers invading the posterior or lateral wall of the sphenoid sinus
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Large rT3 tumors with gross invasion of the clivus
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rT4 tumors with intracranial extension
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Cancers abutting or close to ICA (<1 cm)
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Cancers with anterior extension to the nasal cavity or pterygopalatine fossa. Most cancers with nasal extension will require endonasal endoscopic approach.
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Ectatic ICA located close to the lateral or posterior wall of the nasopharynx
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Presence of metastatic retropharyngeal lymph nodes adherent to the ICA
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Patient with trismus (for transoral approach)
The indications for selecting the robotic approach for nasopharyngectomy are similar to selecting an endoscopic approach. The operation is usually performed for small local recurrence of NPC after radiotherapy, though it can also be used to resect other benign and malignant tumors in the nasopharynx. The tumor should preferably be centrally located and small. The most lateral aspect of the cancer should be medial to the lateral pterygoid plate as the current generation of surgical robot prohibits lateral access without extensive removal of the pterygoid process and pterygoid plates. As the current generation of robots lacks tactile sensation, intraoperative identification of the ICA may be difficult, and inadvertent injury is possible. Cancer with close proximity (<1 cm distance) to the ICA should not be operated on with a surgical robot.
Occasionally the local recurrence may be associated with recurrence in the superior retropharyngeal lymph nodes, or the patient may present with metastasis to an isolated retropharyngeal lymph node. Unlike in radiation-naïve patients, these retropharyngeal lymph nodes are usually adherent to or even partially encase the ICA. Removal of these lymph nodes will require sharp dissection of the lymph nodes from the ICA. Since the surgical robot lacks tactile feedback, this type of dissection should not be performed with a surgical robot.
Preoperative Preparation
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Otitis media with effusion frequently occurs after nasopharyngectomy. A preoperative pure tone audiogram as a baseline is useful for future reference.
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Plasma Epstein-Barr virus (EBV) DNA titer has prognostic implications in NPC and is useful for monitoring the response to treatment. A preoperative titer should be obtained for future reference.
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Dental consultation—loose or carious teeth should be removed prior to the operation
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The diagnosis of recurrent cancer should be confirmed with a biopsy prior to the definitive operation.
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The implications of operating without a positive histological diagnosis should be discussed with the patient.
Operative Period
Anesthesia
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The procedure is usually performed under general anesthesia. The patient should be intubated orally with a Ring-Adair-Elwyn (RAE) tube. The tube should be taped to the midline of the lower lip.
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Alternatively, tracheostomy can be performed first if prolonged edema in the upper aero-digestive tract is expected or if severe trismus prevents adequate opening of the mouth.
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Blood products should be readily available during the operation.
Positioning
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Patient is placed supine with neck slightly extended. The patient cart of the surgical robot will be docked at the head end of the patient. The bedside surgeon can be positioned on either side of the patient.
Perioperative Antibiotics Prophylaxis
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Standard antibiotics prophylaxis regime for intraoral surgery should be employed.
Monitoring
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Invasive and noninvasive monitoring for blood pressure, urine output, and central venous pressure should be employed during the operation.
Instruments to Have Available
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A Dingman retractor or Crowe-Davis retractor for opening the mouth
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Endoscopic holder or similar device to hold the mouth retractor in position
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Five-millimeter Maryland and 5-mm monopolar cautery spatula robotic instruments. Occasionally an 8-mm bipolar cautery scissor can be used in lieu of the 5-mm monopolar cautery for dissection.
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Zero-degree and 30-degree robotic telescopes
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Yankauer suction or similar metal suction device for the bedside surgeon to evacuate smoke and blood from the operative field
Key Anatomic Landmarks
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The nasopharynx is situated posterior to the nasal cavities, about 9 to 10 cm behind the nostril. It is a box-shaped cavity surrounded by bony walls on all sides except the inferior aspect where it opens to the oropharynx. Fig. 42.1 is a line drawing showing the cross-section anatomy of the nasopharynx and adjacent structures.
Fig. 42.1
Cross-section anatomy of the nasopharynx and the adjacent structures. A, Pharyngobasilar fascia; B, Superior constrictor muscle; C, Prevertebral fascia; D, Prevertebral muscles; S, Carotid sheath; 1, Lateral pterygoid muscle; 2, Medial pterygoid muscle; 3, Tensor veli palatini muscle; 4, Levator palatini muscle; 5, Parapharyngeal space; 6, Fossa of Rosenmüller; 7, Styloid process; 8, Retropharyngeal lymph node.
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The floor of the sphenoid sinus forms the roof and slants downward posteriorly as the clivus to form the posterior wall.
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The inferior aspect of the posterior wall is formed by the vertebral bodies of C1 and C2, with prevertebral muscles covering it. The roof and superior aspect of the nasopharynx are covered by mucosa and periosteum with no muscular layer.
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Posterior edge of the vomer denotes the midline and the anterior extent of resection
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The cartilaginous Eustachian tube penetrates the lateral nasopharynx wall to open into the nasopharynx. A recess, the fossa of Rosenmüller, is formed by the posterior crus of the Eustachian tube cartilage and the posterior nasopharyngeal mucosa. NPC frequently arises from this fossa.
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Fossa of Rosenmüller—recurrent cancers are often found deep in the fossa. The entire ipsilateral fossa and the ipsilateral Eustachian tube cartilage should be resected enbloc to ensure completeness.
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Medial pterygoid plate—the buccopharyngeal fascia should be detached from the medial pterygoid plate to remove the entire lateral nasopharyngeal wall.
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Prevertebral fascia—Resection should always include the prevertebral fascia as the deep margin. If imaging shows that the cancer has invaded the prevertebral muscles, then part of the muscles would need to be resected enbloc with the tumor.
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Lateral to the lateral nasopharyngeal wall is the PPS. NPC frequently extends to this area.
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The lymph nodes in the retropharyngeal space are the first echelon of lymphatic spread.
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The anatomy of the ICA in the PPS is highly variable. The ICA can abut on the fossa of Rosenmüller and travel in a medial course just deep to the mucosa of the lateral nasopharynx. It is imperative to trace the course of the ICA on imaging studies and ascertain that the ICA is not in close proximity with the intended resection area to avoid inadvertent injury.
Prerequisite Skills
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Basic transoral robotic surgical skills—certification for console surgeon in TORS. Experience with TORS will facilitate docking of the robot and manipulation of the robotic arms.
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Endoscopic endonasal surgery skills—It is not uncommon to perform the superior resection with endoscopic endonasal approach. A nasoseptal flap (NS) is frequently required for coverage of the raw area after resection. Proficiency in endoscopic endonasal surgery is required to perform both procedures.
Surgical Technique
The surgical robot can be deployed by either the transoral, transnasal, or a combined transnasal and transoral route. For the transoral route, the soft palate will be an obstacle for the robotic arms in approaching the nasopharynx. In the transnasal approach, bones of the medial wall of the maxilla and nasal septum need to be removed to increase the space for deployment of the robotic instruments. There is more experience with the transoral route in the literature so that the discussion in this chapter will focus on the transoral route.
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A Dingman or Crowe-Davis retractor is placed to open the mouth and retract the tongue inferiorly. A plastic lip retractor is placed around the upper and lower lips to prevent injury to the lips by the robotic instruments.
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There are generally three techniques to manage the soft palate in deploying the surgical robot via a transoral approach: (1) midline palatal split, (2) palatal suspension, and (3) lateral palatal flap technique. The approach used most commonly includes the midline palatal split technique.
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Midline palatal split approach
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An incision is made extending from the incisor foramen to the uvula. The mucosa of the hard palate is incised down to the bony hard palate, and the soft palate is divided.
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The soft palate is detached from the hard palate, and sutures are placed in the mucosa of the hard palate and through the entire soft palate. Using these sutures, the palate can be retracted laterally, thereby exposing the nasopharynx.
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The approach is ideal for centrally located cancers, but the lateral reach of the instruments can be blocked by the retracted soft palate. Figs. 42.2 and 42.3 demonstrate the midline palate split incision and the view of the nasopharynx from the telescope of the da Vinci robot.
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