The Use of Water Sac Dilation in Resecting Parapharyngeal Space Benign Tumor via Transoral Approach

INTRODUCTION

Parapharyngeal space tumors are relatively infrequent, comprising around 0.5% of all head and neck tumors. Among them, approximately 80% are benign, and the primary treatment approach involves surgical resection. Due to the unique location of parapharyngeal space tumors and the intricate neighboring anatomical structures, however, surgical resection presents significant challenges. Traditional surgical methods for such tumors include the cervical lateral approach, cervical–parotid approach, cervical–mandibulotomy approach, and infratemporal fossa approach. In recent years, with advancements in endoscopic technology, the endoscopic-assisted transoral approach and nasal approach have gained popularity in clinical practice. These approaches offer the advantage of avoiding visible scars in the head and neck area for eligible patients, leading to their increasing adoption by surgeons. The endoscopic surgical approach presents challenges due to the deep cavity involved, however, making tumor resection a complex task.

The safe and effective resection of parapharyngeal space benign tumor (PSBT) holds significant clinical importance. This study aims to evaluate the utility of the water sac dilation (WSD) method in the endoscopy-assisted transoral approach for the resection of these tumors.

MATERIALS AND METHODS

Subjects

Between February 2017 and January 2022, data from a total of 32 patients with PSBT who underwent endoscopy-assisted transoral approach in Zhengzhou Central Hospital (Zhengzhou, China) were prospectively analyzed. Apart from physical examination, patients underwent color Doppler ultrasound, magnetic resonance imaging (MRI), and computed tomography. The inclusion criteria for the study were as follows: (1) age at least 18 years; (2) no history of surgery and radiotherapy in the surgical area; (3) pre-operative comprehensive evaluation, indicating benign tumors; (4) normal mouth opening; (5) confirmation through three-dimensional (3D) reconstruction that the tumor was located anterior to the internal carotid artery; (6) patient consent to the transoral approach, including the possibility of switching to an open approach if the transoral approach was infeasible. A patient’s data would not be included in further analysis if any of the following occurred: (1) pathological malignancy; (2) post-operative complications unrelated to surgical techniques, such as surgical wound dehiscence, infection, or bleeding due to patients’ inability to follow dietary requirements. This study received approval from the Ethics Committee of Zhengzhou Central Hospital [Approval No. 201716], and all participants provided informed consent after being acquainted with the research protocol before enrollment.

Grouping

Before surgical treatment, patients were randomly divided into two groups, including WSD group and control group, using the random number table method. Transoral surgery was performed on all patients by the same surgical team. In the WSD group, tumors were dissected and resected with the assistance of WSD, whereas in the control group, tumors were dissected and resected using traditional surgical methods. Other surgical procedures were conducted in an identical manner for both groups. Following surgery, all patients received routine anti-infection and other symptomatic and supportive treatments. Negative pressure drainage in the surgical area was monitored daily, and the drainage tube was removed once the drainage volume was reduced to less than 10 mL per day. After discharge, all patients were scheduled for six-month follow-up, in which MRI was performed. The main variables collected for analysis included operation time, intra-operative blood loss, drainage volume in the surgical area on the first post-operative day, total duration with drainage, total drainage volume in the surgical area, surgical complications, recurrence rate, and other prognostic data.

Surgical Procedures

The main surgical equipment included KARL STORZ 70° endoscope (diameter of 4 mm, length of 18 mm, Germany), Stryker multiscreen imaging system (USA), low-temperature plasma surgical system, retractable electric knife, long bipolar suction hook, disposable catheter, and traditional surgical instruments.

Endoscopic-assisted transoral PSBT resection: After routine anesthesia, drape was spread with disinfection, and the mouth was opened with a mouth gag to fully expose the lesion area (Fig. 1a). After soaking the surgical area with diluted povidone iodine solution, the surgical area was re-rinsed with normal saline. On the inner side of the pterygomandibular suture, at the most raised part of the tumor, the mucosa was incised in parallel to the pterygomandibular suture, and the incision was slightly longer than the upper and lower diameters of the tumor. Using a high-definition 70° endoscope, a low-temperature plasma surgical system was utilized to deeply dissect the incision until it reached the surface of the tumor (Fig. 1b). During this period, blood vessels were encountered, which were cut off after bipolar coagulation of bleeding area. After reaching the surface of the tumor, the low-temperature plasma surgical system was used to dissect it from the tumor capsule at both sides. A disposable catheter was inserted close to the tumor capsule into the space between the tumor and the tissue (Fig. 1c), and water was injected into the disposable catheter and was kept for one to two minutes, after which the tumor was bluntly dissected from the surrounding tissue (Fig. 1d). During the maintenance of the water sac, the surrounding tissue of the tumor was dissected using a plasma knife head or a long bipolar suction hook in close proximity to the water sac for further separation (Fig. 1e). After the water sac was withdrawn, under endoscopic visualization, the tissue around the tumor at the site of water sac expansion was further dissected (Fig. 1f). Similarly, the tumor itself was further dissected and removed. Following tumor extraction, the surgical cavity was thoroughly rinsed with diluted povidone iodine solution and sterilized water. Subsequently, a careful examination was conducted to ensure there were no residual tumors or active bleeding. The surgical cavity was appropriately filled with hemostatic materials, and negative pressure drainage was placed. The drainage tube was then secured on the buccal mucosa of the affected side (Fig. 1h). A gastric tube was left in place for one week post-surgery, and antibiotics were administered to prevent infection. The drainage tube was removed when the drainage volume reduced to less than 10 mL within 24 h after the surgery. The follow-up MRI was conducted at five to seven days post-surgery to evaluate the surgical site. Patients were discharged from the hospital once there was no significant swelling of the surgical cavity and hematoma formation.

Endoscopic-assisted transoral PSBT resection (traditional method): Fingers and cotton sheets were intra-operatively used to bluntly dissect the tumor, and the subsequent surgical steps were carried out following the same approach as in the WSD method.

Statistical Analysis

The statistical analysis was carried out by SPSS 20.0 software (IBM, Armonk, NY, USA). Continuous variables were expressed as mean ± standard deviation, and continuous variables were compared by independent sample t-test. Categorical variables were compared by 2 test; p < 0.05 was considered statistically significant.

RESULTS

Post-operative pathology of all 32 studied patients confirmed the absence of malignant lesions. Among the patients, 17 (53.1%) were in the WSD group, whereas 15 (46.9%) were in the control group. All these patients successfully underwent tumor resection via transoral approach. The baseline data were compared between the two groups, and no significant differences were noted in gender, age, tumor size, and pathological type (all p > 0.05).

The operation time, intra-operative blood loss, drainage volume in the surgical area on the first day after surgery, duration of drainage, and the total amount of drainage in the surgical area in the WSD group were significantly lower than those in the control group (all p < 0.05). In the two groups, no surgery-related complications occurred during the recovery period, no residual tumor or recurrence could be found in MRI at six months after surgery, and no local surgery-related dysfunction occurred during the follow-up. The typical pre-operative and post-operative MRI findings of one patient in the WSD group are shown in Figure 2.

CONCLUSION

In conclusion, the findings of the present study demonstrated that the implementation of the WSD method in endoscopy-assisted transoral resection of PSBT effectively minimized intra-operative injury, enhanced surgical efficiency, and expedited post-operative recovery. The development of specialized WSD instruments tailored for such procedures holds significant clinical value and has the potential to further optimize surgical outcomes.