Introduction
The management of patients with tumors of the parapharyngeal space (PPS) is a challenge for head and neck surgeons. The diverse anatomic structures in the PPS give rise to many different tumors, and the relationship of such lesions to critical neurovascular contents provides a technical challenge during surgery. Various operative techniques have been described to safely approach this deep neck space. However, while considering that 80% of PPS tumors are benign, the correct approach to minimize surgical morbidity while successfully treating the patient should be chosen. Of the many approaches to the PPS, the transoral approach has been an ideal technique for carefully selected tumors and minimizes complications experienced with other surgical alternatives.
Key Operative Learning Points
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The transoral approach to the PPS should be reserved for benign prestyloid tumors.
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Fine-needle aspiration should be performed preoperatively to rule out malignancy.
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Cross-sectional imaging should identify that the carotid artery is displaced posterolaterally.
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The transoral robotic approach can provide improvement in optics of the surgical procedure and allow for a surgical assistant at the bedside to facilitate dissection.
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Blunt dissection, meticulous hemostasis, and careful attention to closure of the pharyngeal incision are critical in avoiding complications.
Preoperative Period
History
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Most patients are asymptomatic, with tumors incidentally found during unrelated imaging.
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When symptomatic, patients commonly present with awareness of an intraoral mass or a mass in the neck.
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Facial pain or cranial neuropathies are usually associated with malignant lesions, which are not amenable to transoral removal.
Physical Examination
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Oral cavity/oropharyngeal exam ination: The most common finding is a mass displacing the tonsil/soft palate or both, medially. In addition, the mouth opening should be adequate for transoral surgical exposure.
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Examination of the neck may demonstrate a palpable mass. However, only 28% of patients present with both an intraoral and external neck mass.
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Additional findings may include paralysis of the vocal cord and/or palate, middle ear fluid on the side of the lesion, Horner’s syndrome, and pulsations over the mass in the neck.
Imaging
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Cross-sectional imaging with contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI) is used to determine the relationship of neoplasms to vasculature structures. In addition, imaging provides information on the location of the tumor in the prestyloid versus poststyloid space.
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Imaging can provide information on the vascularity of the mass.
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Transoral fine-needle aspiration (FNA) of palpable and visible lesions is usually well tolerated by patients in the office setting. However, inadequate stabilization of PPS masses as well as limits of intraoral angles may require a CT-guided FNA through the skin, rather than making a “blind” pass toward a mass with large caliber vasculature structures adjacent to the lesion.
Indications
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Benign cysts/neoplasms isolated to the prestyloid PPS
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Salivary gland neoplasms; most commonly pleomorphic adenomas
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Trigeminal nerve branch schwannomas
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Lipomas
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Contraindications
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Malignant tumors
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Poststyloid PPS masses
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Patients with significant trismus
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Vascular tumors such as paragangliomas due to proximity to the carotid artery
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Tumors involving the skull base
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Tumors with significant extension to the deep lobe of the parotid or the stylomandibular tunnel
Operative Period
Anesthesia
General endotracheal intubation with the tube in the side of the nose opposite the mass
Positioning
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Supine
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Robotic-assisted cases should have the bed positioned flat and with the operating table as low as possible to maximize the access of mechanical arms in the operative field. A constant communication is important with the anesthesia team to ensure that the bed position is not moved during surgery without adjusting the position of the robotic arms, since the robot with its arms docked in the oral cavity is fixed in position relative to the bed and the patient.
Perioperative Antibiotic Prophylaxis
Preoperative antibiotics may be given within 60 minutes of the mucosal incision to provide coverage for oral flora.
Monitoring
Monitoring by the Anesthesia Team
The patient should be paralyzed to improve mouth opening.
Instrument and Equipment to Have Available
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Modified (for transoral robotic surgery [TORS]) Crowe-Davis mouth gag ( Fig. 70.1 )
Fig. 70.1
Crowe-Davis mouth gag provides exposure of the surgical field. The tongue is lateralized to improve surgical access.
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A da Vinci surgical system robot is not required but improves surgical optics and allows for “4 handed” surgery, rather than a single bedside surgeon.
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0-degree endoscope placed at center robotic arm. Thirty-degree endoscope is useful in select cases to visualize the superior aspect of the PPS.
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Monopolar cautery with spatula tip placed in robotic arm ipsilateral to PPS lesion
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5-mm endowrist Maryland dissector can be used in a contralateral robotic arm
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Two Yankauer suctions are used bedside by the assistant to provide retraction and evacuate blood and smoke.
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Bipolar cautery should be available for precise cautery while dissecting in close proximity to neurovascular structures.
Key Anatomic Landmarks
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Surgical view should have exposure of anterior tonsillar pillar and have oral tongue displaced to the contralateral side of the lesion.
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Pterygomandibular raphe should be identified and be the lateral border of surgical dissection.
Prerequisite Skills
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Prior extensive experience with da Vinci surgical system
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Comprehension of anatomic boundaries and contents of PPS
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Experience with open, transcervical approaches to the PPS
Operative Risks
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Injury to lip, gums/teeth during placement of the mouth gag
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Injury to the lingual nerve
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Major hemorrhage
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Dehiscence of mucosal incision
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Infection of surgical site
Surgical Technique
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Approach
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Exposure of the surgical field is attained with a Crowe-Davis mouth gag, with attention to displacing the oral tongue away from side of the planned surgical incision.
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The mucosal incision is made in a curvilinear fashion over the soft palate, making sure to stay superficial and not violate the tumor capsule. Care is taken to avoid injury to the lingual nerve and to preserve adequate mucosa for closure.
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Blunt dissection to approach the pterygomandibular raphe and lateralizing the fascia while maintaining the pharyngeal constrictor musculature medially
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The exposure of the tumor is aimed toward allowing circumferential access to the border of the lesion. Superior medial pterygoid muscule fibers are dissected and transected as needed to gain exposure superiorly and laterally ( Fig. 70.2 ).
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