Introduction

Currently, transoral robotic surgery with the daVinci robot is mainly used for the surgical treatment of tumors of the oropharynx and the supraglottic larynx. The safety, efficacy, and functional outcomes regarding this approach have previously been described [1, 2]. In addition to transoral resection of squamous cell carcinoma, we have applied this technique to remove tumors of the parapharyngeal space. We present three patients with parapharyngeal tumors (two benign parapharyngeal masses and an adenoid cystic carcinoma) that underwent successful transoral resection using the daVinci robot.

The aim of this study was to demonstrate the safety and efficacy of transoral robotic surgery on selected benign and malignant tumors of the parapharyngeal space as well as to describe the surgical technique and limitations of robotic surgery in this setting.

Patients and methods

A total of 186 TORS procedures were performed between January 2008 and May 2012 at the Ohio State University James Cancer Hospital. Three patients with benign or malignant tumors of parapharyngeal space who underwent successful transoral resection using the daVinci robot were included in the study. Institutional review board approval was obtained prior to patient recruitment for an ongoing prospective TORS clinical trial.

Case 1

The patient was a 68-year old man referred to our institution for evaluation of a parapharyngeal space lesion. The mass was discovered incidentally during the workup for spasmodic dysphonia. He presented with MRI findings of a 6.6 × 4.2 × 1.9 cm left parapharyngeal mass with distinct borders (Fig. 1). On flexible nasopharyngoscopy, left parapharyngeal fullness was noted but otherwise the examination was unremarkable. The decision was made to perform a transoral robotic resection.

Fig. 1
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Coronal MRI showing benign appearing mass in the left parapharyngeal space

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After complete tumor resection was achieved en bloc, the patient was admitted overnight. The next day he was able to tolerate a regular diet and was discharged. Final pathology revealed that the mass was a lipoma. At his 6-month follow up, there was no sign of recurrence and no complaints of dysphagia.

Case 2

The patient was a 58-year-old man referred for a mass on the soft palate. He stated that it had been slowly growing for the past 2 years. He denied pain, breathing difficulty, or dysphagia. There was a remote tobacco use history. On exam, there was a 3 cm submucosal mass protruding into the right side of the soft palate. There was no cervical lymphadenopathy. CT of the neck revealed a 3.1 × 2.5 × 2.8 cm well circumscribed mass deep to the soft palate on the right, extending to the parapharyngeal space (Fig. 2). The patient agreed to transoral robotic resection of this mass.

Fig. 2
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Axial CT image of the second case (pleomorphic adenoma), arrows show the tumor boundaries

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Complete tumor excision was accomplished en bloc without any complications and the patient was discharged home the same day. Final pathology revealed a benign pleomorphic adenoma originating from minor salivary glands. Upon 1-month follow-up, he had no complaints of discomfort or dysphagia.

Case 3

This patient was a 46-year-old male referred for an incidentally discovered right soft palate mass during routine examination. Biopsy of the lesion showed fragments of adenoid cystic carcinoma. The patient denied any pain, growth of lesion, dysphagia or any neck mass. He had a 25-year tobacco use history. On physical examination, there was a 1.5 × 2 cm right soft palate, submucosal mass with central ulceration. There was no cervical lymphadenopathy. CT of the neck revealed a 2.0 × 2.3 × 2.6 cm mildly enhancing soft tissue mass in the right soft palate, extending into the parapharyngeal space (Fig. 3). There was no radiological evidence of perineural invasion. Re-evaluation of the previous pathology specimen revealed low grade adenocarcinoma. The decision was made to perform transoral robotic surgery.

Fig. 3
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Axial CT image of the third case (adenoid cystic carcinoma), arrows show the tumor boundaries

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Transoral robotic wide excision of the malignant lesion was performed. The patient did well postoperatively and was discharged the next day. Final pathology report reflected a completely excised adenoid cystic carcinoma with negative surgical margins. No adjuvant treatment was recommended. The patient was found to be clinically and radiologically disease free at 6 months after the surgery.

Surgical technique and procedure

After endotracheal intubation with fiberoptic guidance, the patient (case 3) was placed in the supine position and a Crowe–Davis mouth gag was inserted. The daVinci S HD Surgical System (Intuitive Surgical, Inc., Sunnyvale, CA) was placed to the right of the patient’s bed (Fig. 4). A 0° 8 mm camera was inserted into the mouth for visualization throughout the surgery. The left robotic arm was mounted with a 5 mm monopolar cautery with spatula tip and the right arm was mounted with a 5 mm Maryland dissector. The assistant sat at the head of the bed with a pediatric Yankauer suction in hand. Using the robotic arms, the lesion was demarcated and manipulated to determine the borders. An incision was made at the medial aspect with the unipolar cautery. Medial retraction of the tumor with Maryland dissector allowed deep dissection throughout superior constrictor muscle. Blunt dissection continued towards the parapharyngeal space, through the superior constrictor and medial to the medial pterygoid muscle. Multiple minor arterial branches were encountered and cauterized with the 5 mm monopolar cautery. The dissection was extended to the parapharyngeal fat pad and the tumor was then freed from the prestyloid parapharyngeal space, using a capsular dissection. Special attention was paid to the location of the carotid artery by visually monitoring the carotid pulsation. The resection planes were maintained anterior and medial to the stylohyoid and styloglossus muscles. The tumor capsule was kept intact and separated from parapharyngeal structures carefully. The camera afforded a 3D, detailed view and allowed a circumferential dissection of the tumor (Fig. 5). Sutures were then placed using the robotic arms (Fig. 6).

Fig. 4
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Position of the robot, assisting surgeon and anesthesia in a typical TORS case

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Fig. 5
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Intraoperative view of patient 1, showing good visualization of the parapharyngeal mass and clean plane of dissection

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Fig. 6
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Immediate post operative view of patient 1

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Mean TORS operative time and intraoperative blood loss for the three cases was 16.3 min and 4.7 mL respectively (Table 1).

Table 1 TORS Technical Details
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Discussion

To date, most of the literature regarding transoral robotic resection of head and neck tumors has involved malignant tumors, usually squamous cell carcinoma of the oropharynx. More recently, studies have emerged showing expanded use in the head and neck region such as for tumors of the skull base, larynx, hypopharynx and nasopharynx [3–5]. Only one other study, by O’Malley et al.[6] has been published specifically focusing on the feasibility of resecting benign parapharyngeal tumors via transoral robotic surgery; nine of ten patients were able to undergo the robotic resection. Of these, seven had no local recurrence.

One of the advantages of the robotic system is the ability to use a stereo-optic 0° or 30°camera. It allows visualization around the tongue blade of the Crowe–Davis mouth gag. In addition, neck incisions or mandibulotomies that require post-operative drain placement and a longer hospital admission can be avoided. While one of the disadvantages is lack of tactile feedback, one can partially overcome this by replacing it with visual feedback while manipulating the tumor with the robotic instruments. In addition, the use of an assistant at the head of the bed for additional retraction and suctioning is essential in facilitating the surgery.

Contraindications to this approach include inadequate oral exposure, involvement of the carotid artery, and limited cervical spine mobility. One should also determine if the size of the tumor would allow en bloc resection through the mouth. This is largely a clinical assessment that must be made by the surgeon, as there are currently no pre-determined size criteria.

Conclusion

In this case series, a transoral robotic approach was found to be safe and feasible in selected parapharyngeal space tumors. Magnified 3D visualization allows the surgeon en bloc resection of the tumor, close to vital structures. Significant experience with trans-oral robotic surgery and detailed anatomic knowledge of the parapharyngeal space is essential for success with this approach.