Transoral Robotic Approach to Parapharyngeal Space Tumors: Changes in Paradigm of Surgery

Abstract

PPS space tumors are extremely rare, accounting for 0.5% of head and neck neoplasms. Trans-oral, Trans-cervical, Trans-parotid, Trans-cervical-trans-mandibular, and infratemporal are various surgical approaches that have been described for PPS tumors. Of late, with the advent of robotic surgery, Trans Oral Robotic Surgery (TORS) for PPS tumors is being increasingly advocated with promising results. To establish both efficacy and safety of Trans Oral Robotic Surgery, Five cases of pleomorphic adenoma of parapharyngeal space with sizes varying between 2.5 cm to 7.5 cm were evaluated and removed using Trans oral robotic approach using the Da Vinci system. Three were removed in toto and two in piecemeal fashion. There was capsule breach in 2 cases, no major complication was reported in any of the cases. Transoral Robotic Approach for PPS tumors can provide the much-required bridge between Transcervical and Trans mandibular Oral Approach. It provides a better direct approach. Carefully selected patients with well encapsulated tumors are more amenable to this approach.

Introduction

The parapharyngeal space (PPS) is a complex anatomical entity that is described as an inverted pyramid. It is located at the apex of the hyoid bone, the Base of the Skull, the Superior Constrictor, and the Ramus of the Mandible [1]. PPS is divided into prestyloid and poststyloid compartments by the aponeurosis of Testut and Zuckerkandl. Various structures like fat, lymph nodes, lower cranial nerves, the deep lobe of the parotid, great vessels, and the sympathetic chain are present in PPS and can give rise to tumors of their respective origins [1].

Overall, PPS space tumors are extremely rare, accounting for 0.5% of head and neck neoplasms, 80% of which are benign. Prestyloid compartment tumors are usually of the salivary gland in origin, and post-styloid tumors are neurogenic or vascular in origin. [2] Salivary gland tumors account for 40–50% of PPS lesions, with pleomorphic adenomas accounting for over 80% of diagnoses. The patient usually presents with a smooth submucosal bulge in the oropharynx [2].

Trans-oral, Trans-cervical, Trans-parotid, Trans-cervical-trans-mandibular, and infratemporal are various surgical approaches that have been described for PPS tumors. Of late, with the advent of robotic surgery, Trans Oral Robotic Surgery (TORS) for PPS tumors is being increasingly advocated with promising results. Because most PPS tumors are benign, the approach chosen should be less morbid and have better functional and cosmetic outcomes. This has led to a paradigm shift in the surgical approach over the last decade.

In this series, we report five cases of PPS tumors that underwent resection via TORS.

Case Series

Case 1

A 31-year-old female presented with progressive swelling in the left tonsillar fossa, accompanied by a gradual change in voice for 7 months. On examination, there was a bulge in the left tonsillar fossa, anterior tonsillar pillar, and soft palate, pushing the uvula to the right side. CECT showed a 47 × 27 × 40-mm heterogeneously enhancing mass in the left oropharyngeal wall, reaching the pre-vertebral space, abutting the left submandibular gland, compressing the pharyngeal airway, and extending to the pterygoid plates. Fine Needle Aspirate showed Pleomorphic Adenoma on cytology.

Case 2

A 47-year-old male presented with a history of snoring. He had a history of transoral excision of the left parapharyngeal space tumor 13 years ago, in which the histopathology came out to be a pleomorphic adenoma. He was asymptomatic for 13 years post-surgery. On evaluation, there was a bulge on the soft palate reaching to the midline and pushing the uvula to the right side. CEMRI revealed a well-defined lobulated heterogeneously enhancing T2 heterogeneously hyperintense and T1 heterogeneously hypointense lesion in the left parapharyngeal space, posterolaterally abutting the deep lobe of the parotid and posteriorly abutting the cervical ICA, measuring 44 × 19 × 50 mm. FNAC done from intraoral lesion was Pleomorphic Adenoma.

Case 3

A 64-year-old male presented with a progressive change in voice for one year. On examination, there was a right oropharyngeal bulge involving the tonsillar fossa, both tonsillar pillars, and the adjoining soft palate, causing a shift of the uvula to the right. CEMRI showed a well-defined,75 × 53 × 35 mm lesion in the right PPS which was T1/T2 isointense with internal T2 hyperintense areas. It was adjacent to the deep lobe tumor, but with a preserved fat plane. It was FNAC was done from the oral mass, which showed Pleomorphic Adenoma.

Case 4

A 35-year-old female presented with left intraoral swelling for 12 years. Upon examination, there was globular soft to firm swelling in the soft palate and oropharynx on the left side, pushing the uvula to the right. CEMRI showed a well-defined lobulated mass in the left parapharyngeal space measuring 48 × 40 × 34 mm, causing a mass effect in the oral cavity with luminal compromise (Fig. 1). It was displacing the carotid artery posterolaterally and indenting the lateral pterygoid muscle. Fine needle aspiration showed a polymorphous population of lymphocytes. Post Op histopathology showed pleomorphic adenoma.

Fig. 1.

CEMRI showing a well encapsulated heterogeneous mass in Left parapharyngeal Space

Case 5

A 34-year-old male presented with snoring for 2 years. On examination, there was a firm globular swelling in the right soft palate and oropharynx. CEMRI showed a 28 × 34 × 53 mm altered signal intensity mass in parapharyngeal space, causing lateral displacement of ICA and CCA and focally compressing IJV Fine Needle aspiration showed monolayer sheets of benign ductal epithelial cells. Postoperatively Histopathology showed pleomorphic adenoma.

There was no involvement of the internal carotid, external carotid, or internal jugular vessels in all five cases.

Surgical Technique (Fig. 2)

Fig. 2.

Steps of Robotic surgery.A Incision using cautery over pterygomandibular raphe. B Exposure of parapharyngeal space. C Finger dissection for superomedial aspect of tumor. D Removal of specimen in toto. E Final specimen after delivery

All patients were operated on under general anesthesia via nasotracheal intubation. The Da Vinci system with three arms was used (one endoscopic arm with integrated cameras for the 3-dimensional view and two instrument arms, a 5 mm Maryland forceps, and a 5 mm monopolar spatula cautery). A bedside assistant was tasked with suctioning fumes and blood, performing retraction, and helping in the control of intraoperative bleeding. Transoral exposure was obtained with a Feyh-Kastenbauer retractor (Gyrus ACMI, Southborough, Massachusetts). Transoral robotic dissection of the tumor was supplemented with finger dissection to dissect the posterior and superior extents. We were able to remove the tumor in toto in the first, fourth, and fifth patients, while in the second and third cases, the tumor was removed in a piecemeal fashion. While attempting dissection, especially in the superior and lateral extents, tumor breach of the capsule occurred in all cases, resulting in tumor spillage. In the second case, tumor extension superiorly to the greater wing of the sphenoid and superomedially to the nasopharynx was dissected bluntly with a finger and periosteum elevator. Dissection at this region inadvertently caused a mucosal breach into the nasopharynx. However, no major complication was encountered, and the wound healed spontaneously. In the post-op follow-up, there was wound dehiscence in the same patient on postoperative day 7, which was treated conservatively, and wound closure by secondary healing was satisfactory and complete by postoperative day 15. On a six-month follow-up, all patients were asymptomatic without recurrence (Fig. 3), (Fig. 4).

Fig. 3.

CEMRI showing fibrotic changes in the left parapharyngeal space with complete removal of tumor

Fig. 4.

Post operative well healed operated site in patient

Discussion

The management of PPS tumors is primarily surgical, with guiding principles like tumor location, proximity to critical neurovascular structures, potential histologic behavior, and cell of origin determining not only the question of resectability but the surgical approach to be used [3]. The most commonly used approaches include the transcervical and transparotid routes or a combination of both. Khafif et al. [3] and Hughes et al. [4] were able to use these two approaches to resect 87% (n = 47) and 94% (n = 172) of the PPS masses in their series, respectively. However, these approaches were not able to give adequate exposure to many of these tumors with extensive lateral and superior spread. Combining the transmandibular and orbitozygomatic maneuvers with adjunctive approaches may increase the likelihood of resectability. But these approaches are associated with increased morbidity and poor cosmetic outcomes [5].

The direct transoral approach has been used since the early 1950s. Although it is a direct pathway to the PPS, this approach has been used sparingly due to several disadvantages, including limited visibility and maneuverability, which lead to the possibility of increased tumor spillage, recurrence, and the risk of neurovascular injury [6].

The advent of robotic surgery, the TORS approach, and instrumentation provided several advantages, including improved visualization (especially out of direct line-of-sight) with a highly illuminated three-dimensional (3D) high-definition camera, tremor-reduction technology, and wristed instruments with seven degrees of freedom [7, 8].

The modern era of the robotic approach to PPS tumors was heralded by O’Malley et al., who reported the successful excision of a benign salivary cyst and 10 benign salivary neoplasms of the PPS, excised with TORS. They reported one case where an open approach was used to preserve the ICA and three cases where tumor fragmentation and capsule disruption occurred. Though size was not mentioned as a risk factor for complications or conversion, the largest tumor size operated on, at 7 cm, showed a conversion to the conventional approach[9].

In another case series, Ducic et al. reported successful transoral approaches on eight patients with tumors isolated to the superomedial PPS. The neoplasms averaged 3.3 cm in size, and the largest tumor that was removed was 7 cm in maximal dimension. No patient had evidence of recurrence in this series over an average follow-up period of 28.2 months, but there were no patients with PAs and no distinction between clinical and radiographic follow-up. Interestingly, Ducic et al. also reported adequate exposure and control of the ICA, which is in contrast to previous concerns regarding this approach[10].

We reported five cases of PPS tumors that were resected via TORS. The first patient had a tumor with a maximum dimension of 4.7 cm and limited extension. The exposure was excellent with the 3D camera, with the posterior and superior borders of the tumor comfortably accessible, and the tumor was excised in toto with an intact capsule. In contrast, the third case was a large pleomorphic adenoma with a maximum dimension of 7.5 cm, with extension superiorly to the infratemporal fossa with proximity to the skull base, and superiomedially abutting the nasopharyngeal mucosa. The limited exposure caused the surgeon to change his plan and attempt finger dissection to release the superior and superomedial borders of the tumor. There was an inadvertent rupture of the capsule with a mucosal breach of the nasopharynx. However, there were no major intraoperative or postoperative sequelae, and the patient was managed conservatively with nasogastric tube feeding for one week. Intraoperatively, copious saline irrigation was done to prevent tumor seeding.

Boyce et al. reported in their case series of 17 patients with PPS tumors that those tumors approaching the skull base are difficult to dissect with TORS alone and might require a transcervical assist for removal[11].

Although in our patients, a combined approach of TORS and transcervical surgery with or without a mandibular swing could have been planned, a single approach would always result in less morbidity and better chances of faster rehabilitation for the patient and would always be favorable for benign tumors. If a TORS approach is planned, as desired by the patient or for the other advantages discussed earlier, a detailed preoperative workup including high-resolution radiological imaging will guide the surgeon about the expected complexities of the procedure. The pros and cons of the approaches also need to be discussed in detail with the patient, before a definitive decision is made.

Conclusion

In conclusion, Transoral Robotic Approach for PPS tumors can provide the much-required bridge between Transcervical and Trans mandibular Oral Approach. It provides a better direct approach. However, this approach requires a special skill set and equipment. Also the incidence of capsular breach too is higher. Carefully selected patients with well encapsulated tumors are more amenable to this approach.

Funding

The authors have no relevant financial or non-financial interests to disclose. All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript.The authors have no financial or proprietary interests in any material discussed in this article.

Declarations

Ethics Approval

Ethical approval was waived by the local Ethics Committee of PGIMER in view of the procedures being performed were part of the routine care in the tertiary care institute .

Consent for Publication

No identification of any patients done in the paper. appropriate sections covered to hide identity.consent from patient taken.

Competing Interests

The authors have no competing interests to declare that are relevant to the content of this article.