How To: Full Endoscopic Procedures of Total Parotidectomy

INTRODUCTION

Parotid tumors (PTs) account for approximately 64% to 80% of salivary gland tumors, with the majority being benign and located in the superficial lobe. Generally, conservative surgical resection is the primary treatment for benign PTs, while total parotidectomy is recommended for malignant parotid lesions to obtain safe histological margins. Following the total parotidectomy, the sternocleidomastoid muscle flap (SCMF) can be used to prevent Frey’s syndrome and partially restore facial contour defects.

Conventional total parotidectomy is typically conducted through a Blair incision, which can leave a visible facial scar, impacting the cosmetic satisfaction and quality of life of some patients. Recently, endoscopic surgery has been increasingly applied to head and neck surgery to achieve minimally invasive effects and improved aesthetic outcomes. There are few reports on the full endoscopic technique of total parotidectomy followed by SCMF transplantation to our knowledge, however.

We aim to describe the surgical procedures of full endoscopic total parotidectomy (FETP) and assess patient outcomes to evaluate the feasibility and efficacy of this novel approach.

MATERIALS AND METHODS

A case of parotid malignancy managed with FETP and SCMF transplantation at our department was retrospectively reviewed. Pre-operative contrast-enhanced CT revealed a 2×2 cm-sized mass with heterogeneous enhancement in the left superficial parotid gland (Fig. 1A). Preparation of hair removal involved a 2-3 cm area in the temporal region above the hairline and the postauricular region behind the hairline.

The operation was conducted according to the Declaration of Helsinki (as revised in 2013) and was approved by the Ethics Committee of West China Hospital of Stomatology, Sichuan University (Approval No. WCHSIRB-D-2020-311-R1). The patient was fully informed about the benefits and drawbacks of this procedure, as well as risks of conversion to conventional open surgery.

Surgical Technique

Following general endotracheal anesthesia and routine disinfection, the terminals of the neuromonitor were placed into the subcutaneous tissue of the manubriosternal region, orbicularis oculi, and orbicularis oris, respectively, for intra-operative facial nerve monitoring (Fig. 2A). To improve the post-operative aesthetic results, an approximately 5-cm incision was designed along the postauricular hairline region, with the reflection of neoplasm marked (Fig. 2B). Noticeably, a 1-cm temporal incision and cavity were designed to accommodate the suction device or other endoscopic instruments, facilitating cavity separation, blood suction, and tissue lifting. We referred to these designs as the “plus” incision and cavity in FETP surgery. The electrocautery, sterile cotton swab, and skin retractor were used when incising the skin and subcutaneous tissue (Fig. 2C). Following the creation of the main working cavity, a surgical retractor system was used to lift the skin flap stably and maintain a wide operative cavity (Fig. 2D). Then we expanded the main working cavity using a 5-mm laparoscope with 0° viewing angles and miniature instruments. Manipulation at this step may be obstructed by the cartilage of the external auditory canal. The “plus” cavity can then be established with blunt dissection to proceed with the separation of the superficial musculoaponeurotic system and achieve a distinct anatomical layer (Fig. 2E). Incise the connected fascia under endoscopic view until two cavities are fully merged. Additionally, stitches can be used to pull the earlobe area, achieving a larger operative cavity (Fig. 2F). To reduce post-operative numbness in the auricular skin, careful protection of the great auricular nerve (GAN) is crucial during the extension of the surgical tunnel (Fig. 3A).

Surgical separation began with the posterior boundary of the parotid, defined by the anterior tissue of the sternocleidomastoid muscle. Following adequate exposure of the superficial parotid tissue, the retromandibular vein became visible in the deep region of the neoplasm. An ultrasonic scalpel and vascular clap were used to ligate and cut the distal end of the retromandibular vein. Subsequent antegrade dissection allowed clear identification of the facial nerve trunk and its branches as the superficial parotid gland was elevated by the “plus” instrument. The electromyographic signal was collected by placing the neuromonitor on the branches of the facial nerve, which may help to identify the nerve tissue and reduce the risk of facial palsy. After the proximal end of the retromandibular vein and adjacent tissues were cut, the neoplasm and superficial parotid gland were completely excised and sent for rapid frozen pathological examination.

The intra-operative pathological report indicated mucoepidermoid carcinoma, which required total parotidectomy to ensure a tumor-free margin. Consequently, we continued to excise the remaining deep lobe tissues of the parotid using an ultrasonic scalpel or surgical scissors. Due to the advantages of magnification and illumination of the endoscope, the anatomic structures in the surgical field were identified clearly after irrigation with normal saline, facilitating the effective conservation of facial nerves and branches (Fig. 3B). Following the removal of deep lobe tissues, neural integrity was reassessed by observing the waveform on the neuromonitoring device. In the final step, the local SCMF was designed and transferred as a reconstruction modality. The local flap was divided from the anterior border of the SCM, with a thickness of up to one-third or half of the muscle. Careful attention should be given when dissecting the muscle to avoid injury to the accessory nerve. The flap was then rotated forward to fill the defect and cover the surface of the facial nerve, and it was sutured to the surrounding tissues (Fig. 3C).

After transferring the SCMF, the surgical cavity was irrigated through both the postauricular and the “plus” incisions. Local bleeding spots were clearly visible under the endoscopic view, and hemostasis was achieved with long bipolar electrocoagulation. The incisions were closed in layers following the placement of a negative-pressure drainage tube. Post-operatively, a bandage was applied to the parotid area with appropriate pressure.

RESULTS

The operation was successfully completed without converting to conventional open surgery. The incisions were hidden in postauricular and temporal regions, with lengths of 5.5 and 1 cm, respectively. The total operation duration was 230 minutes, of which 195 minutes were completed under endoscopic vision. The final pathological diagnosis was well-differentiated mucoepidermoid carcinoma (pT2N0M0).

Post-operatively, the patient remained hospitalized for five days and was discharged as planned. Temporary numbness of the auricular region was identified, resolving gradually over three weeks. At a 32-month follow-up, no severe complications or recurrence were observed. The patient reported high satisfaction with post-operative facial function and aesthetic outcomes.

CONCLUSION

FETP combined with SCMF transplantation could achieve excellent aesthetic outcomes with minimal complications, and it is a safe and feasible option for patients diagnosed with low-grade malignant parotid tumors.