Parapharyngeal space tumors, a rare occurrence accounting for approximately 0.5% of all head and neck malignancies, present a significant surgical challenge. While the vast majority, around 80%, are benign and primarily treated through surgical resection, their deep-seated location and proximity to critical neurovascular structures necessitate meticulous operative techniques. Historically, surgeons have relied on more invasive external approaches such as the cervical lateral, cervical-parotid, cervical-mandibulotomy, and infratemporal fossa techniques. However, recent advancements in endoscopic technology have paved the way for less invasive transoral and nasal routes, offering the distinct advantage of avoiding visible scarring for eligible patients. Despite these advancements, the endoscopic transoral approach, while cosmetically superior, contends with the inherent difficulty of operating within a deep and confined surgical cavity, making complete tumor resection a complex undertaking.
A recent study conducted at Zhengzhou Central Hospital in China has explored an innovative technique, Water Sac Dilation (WSD), as an adjunct to the endoscopy-assisted transoral approach for the resection of benign tumors in the parapharyngeal space (PSBT). This method aims to enhance surgical precision and efficiency, potentially reducing patient morbidity and improving recovery times. The research, published in the journal Laryngoscope, meticulously details the methodology and outcomes of a prospective study involving 32 patients.
Background: The Parapharyngeal Space and Surgical Challenges
The parapharyngeal space, a fascial compartment located lateral to the pharynx and medial to the masticator space, is a complex anatomical region. It houses critical structures including the internal and external carotid arteries, internal jugular vein, cranial nerves IX-XII, and the sympathetic trunk. Tumors arising in this space, though often benign, can grow to significant sizes before becoming symptomatic, often presenting with dysphagia, odynophagia, or even airway compromise. The benign nature of most PSBTs underscores the importance of achieving complete resection while minimizing damage to surrounding vital structures.
Traditional open surgical approaches, while effective, carry inherent risks such as facial nerve injury, salivary fistula, and significant scarring. The evolution towards minimally invasive techniques reflects a broader trend in surgery to reduce patient trauma and accelerate recovery. The transoral approach, utilizing endoscopes to visualize and operate through the mouth, offers a direct pathway to the parapharyngeal space, circumventing external incisions. However, the limited working space and the need for precise dissection in the presence of delicate nerves and blood vessels have remained significant hurdles.
Study Design and Methodology: Evaluating the Water Sac Dilation Technique
The prospective study, conducted between February 2017 and January 2022, enrolled 32 patients diagnosed with PSBT at Zhengzhou Central Hospital. All patients underwent a comprehensive pre-operative workup including physical examination, color Doppler ultrasound, magnetic resonance imaging (MRI), and computed tomography (CT). Strict inclusion criteria were established to ensure patient suitability for the transoral approach and to minimize confounding factors. These included an age of 18 years or older, no prior history of surgery or radiotherapy in the head and neck region, pre-operative confirmation of benign tumor status, adequate mouth opening, and importantly, three-dimensional (3D) reconstruction confirming the tumor’s location anterior to the internal carotid artery. Patients also provided informed consent for the transoral approach, acknowledging the possibility of conversion to an open procedure if necessary. Exclusion criteria focused on pathological malignancy, and post-operative complications unrelated to surgical technique, such as wound dehiscence, infection, or bleeding due to non-adherence to post-operative dietary instructions. The study received approval from the Ethics Committee of Zhengzhou Central Hospital (Approval No. 201716), and all participants provided informed consent.
Patients were randomly assigned to one of two groups: the Water Sac Dilation (WSD) group or the control group. Both groups underwent transoral surgery performed by the same experienced surgical team. In the WSD group, the tumor was resected with the assistance of the WSD technique, while the control group received tumor resection using conventional transoral endoscopic methods. All other surgical procedures, including anesthesia, post-operative care, and supportive treatments, were standardized across both groups. Routine anti-infection therapy and symptomatic management were administered post-operatively. Negative pressure drainage was employed in the surgical site, with the drain removed once daily output dropped below 10 mL. A rigorous six-month follow-up protocol, including MRI, was implemented for all patients.
Key variables collected for comparative analysis included operative time, intra-operative blood loss, post-operative drainage volume on day one, total duration of drainage, total drainage volume, incidence of surgical complications, and recurrence rates.
Surgical Procedures: A Detailed Look at the WSD Technique
The surgical armamentarium for this study was state-of-the-art, featuring a KARL STORZ 70° endoscope (4mm diameter, 18mm length), a Stryker multiscreen imaging system, a low-temperature plasma surgical system, a retractable electric knife, a long bipolar suction hook, a disposable catheter, and traditional surgical instruments.
For the endoscopy-assisted transoral PSBT resection utilizing the WSD method, the procedure commenced with routine anesthesia and meticulous preparation of the surgical field. After opening the mouth with a gag to ensure full visualization, the surgical area was disinfected with diluted povidone-iodine solution and then rinsed with normal saline. An incision was made in the mucosa, parallel to the pterygomandibular suture, positioned over the most prominent part of the tumor. This incision was designed to be slightly longer than the tumor’s maximal diameter. A high-definition 70° endoscope was then employed, alongside the low-temperature plasma surgical system, to dissect deeply towards the tumor surface. Any encountered bleeding vessels were managed with bipolar coagulation.
Upon reaching the tumor capsule, the low-temperature plasma system was used to dissect the tumor from its surrounding capsule. At this critical juncture, a disposable catheter was carefully inserted into the space between the tumor capsule and the surrounding tissue. Water was then injected into the catheter, creating a water sac that remained inflated for one to two minutes. This gentle distension facilitated blunt dissection of the tumor from adjacent structures. While the water sac was maintained, the surrounding tissues were further dissected using the plasma knife head or a long bipolar suction hook, working in close proximity to the expanding water sac to achieve optimal separation. After the water sac was withdrawn, endoscopic visualization guided further dissection of the tumor and any remaining connective tissues in the area previously occupied by the water sac. Following complete tumor extraction, the surgical cavity was thoroughly irrigated with diluted povidone-iodine and sterile water. A meticulous examination was performed to ensure no residual tumor or active bleeding points remained. Hemostatic materials were applied, and a negative pressure drainage tube was inserted and secured to the buccal mucosa of the affected side. A gastric tube was retained for one week, and prophylactic antibiotics were administered. The drainage tube was removed when the daily drainage volume consistently fell below 10 mL. Follow-up MRI was performed five to seven days post-surgery to assess the surgical site. Patients were discharged once significant post-operative swelling and hematoma formation were absent.
In contrast, the traditional endoscopic-assisted transoral PSBT resection in the control group relied on intra-operative manual dissection using fingers and cotton swabs for blunt dissection of the tumor. Subsequent steps mirrored those of the WSD group.
Statistical Analysis
Statistical analysis was performed using SPSS 20.0 software. Continuous variables were presented as mean ± standard deviation and compared using independent sample t-tests. Categorical variables were analyzed using the chi-square test. A p-value of less than 0.05 was considered statistically significant.
Results: Demonstrating the Efficacy of WSD
The study’s findings revealed that post-operative pathology confirmed the absence of malignancy in all 32 patients. The WSD group comprised 17 patients (53.1%), while the control group consisted of 15 patients (46.9%). Crucially, all patients successfully underwent tumor resection via the transoral approach. A thorough comparison of baseline demographic and clinical data, including gender, age, tumor size, and pathological type, showed no statistically significant differences between the two groups (all p > 0.05), ensuring that any observed differences in outcomes could be attributed to the surgical technique employed.
The comparative analysis of surgical outcomes yielded compelling results. Patients in the WSD group experienced significantly shorter operation times, reduced intra-operative blood loss, and lower drainage volumes on the first post-operative day compared to the control group. Furthermore, the total duration of drainage and the overall volume of drainage were also significantly reduced in the WSD cohort. These findings suggest that the WSD technique enhances surgical efficiency and minimizes tissue trauma.
Importantly, no surgery-related complications were reported in either group during the recovery period. Follow-up MRI at six months post-surgery confirmed the absence of residual tumors or recurrence in all patients. Furthermore, no local surgery-related dysfunctions were noted during the follow-up period. The study included representative pre-operative and post-operative MRI findings of a patient from the WSD group, visually illustrating the successful tumor removal and the integrity of the surgical site.
Conclusion: A Promising Advance in Parapharyngeal Space Tumor Resection
The findings of this study strongly indicate that the Water Sac Dilation (WSD) method, when integrated with the endoscopy-assisted transoral approach for parapharyngeal space benign tumor resection, offers substantial clinical benefits. The WSD technique demonstrably minimizes intra-operative injury, thereby enhancing surgical efficiency and expediting post-operative recovery. The ability to create a controlled, distensible space around the tumor allows for more precise and gentler dissection, reducing the risk of damage to adjacent vital structures.
The implications of this research are significant for patients and surgeons alike. For patients, it promises a less invasive surgical experience with faster healing and potentially fewer complications. For the surgical community, it highlights a valuable refinement to an already minimally invasive technique. The study authors suggest that the development of specialized WSD instruments tailored specifically for these procedures could further optimize surgical outcomes, making this approach even more robust and adaptable. This innovation represents a promising stride towards improving the management of parapharyngeal space benign tumors, aligning with the growing demand for oncological procedures that prioritize both efficacy and patient well-being. The study’s success in achieving complete resection without complications and with minimal post-operative sequelae underscores the potential for WSD to become a standard adjunct in the armamentarium of endoscopic head and neck surgeons.
