Extracapsular dissection and minimally invasive procedures of primary benign parotid tumours: Case series

Parotid neoplasms represent 2-3% of head and neck tumors¹, and 80% of them are associated with salivary glands, although they are mostly benign lesions (80%). The clinical signs include an asymptomatic, long-lasting, and slow increase in volume, and the majority appear with the diagnosis of pleomorphic adenoma (PA) as the most common lesion². Treatment for these injuries is surgical, and within the widely used techniques, superficial parotidectomy (SP) has prevailed in last decades as the leading management. Indeed, SP (also called suprafacial or lateral parotidectomy) consists in removing the superficial parotid lobe (where the lesion is in most cases) with excellent results in terms of decreased recurrence. Nevertheless, there are postoperative complications, such as aesthetic alterations, temporary or permanent facial paralysis, local seroma, Frey’s syndrome, and preauricular pain³.

On the other hand, extracapsular dissection (ECD), a minimally invasive approach for benign parotid lesions, shows excellent results in terms of aesthetics. Developed in 1940-1960, this technique consists in a “meticulous dissection just outside the tumour capsule where an excision plane is generally found”⁴. Furthermore, has been considered for its limited temporal paresthesia since facial nerve dissection is not necessary⁵. This surgical procedure is recommended for primary, superficial lesions with diameters not exceeding 4 cm. As they increase in size, a more extensive resection like superficial parotidectomy (as SP), is necessary. The search for a “gold standard” technique persists for benign parotid tumours⁶, especially those without prior intervention. By this, the main objective of this series case study is to analyze and classify subjects diagnosed with primary benign parotid tumour (PBPT) and treated with ECD by the maxillofacial surgery department at Libertador Bernardo O’Higgins Regional Hospital (LBORH), in Rancagua (Chile), between the years 2018 and 2020.

This study followed the Declaration of Helsinki on Medical Protocols and Ethics, and the LBORH Regional Ethical Review Board approved the study. The inclusion criteria were the availability of physical and electronic clinical records of patients admitted to the LBORH, diagnosis with superficial PBPT, and removal by ECD between January 2018 and January 2020.

Anaesthesia and surgical protocol

All procedures are under general anaesthesia with orotracheal intubation. The first option for antibiotic prophylaxis is intravenous cefazolin (1 g) or clindamycin (600 mg) in the case of penicillin allergy. In all procedures participated the surgeon with the most experiences and one of the three maxillofacial specialists from the team as an assistant surgeon. The approach used in all cases was the modified Blair incision, which consists of an incision through preauricular area extends to the mastoid process and posterior border of ramus, or the submandibular region in major lesions⁷. Posteriorly, the dissection through ECD is without the use of an intraoperative nerve-monitoring system. After ensuring hemostasis using a Valsalva manoeuvre, the parotid capsule is closed, followed by plane closure with polyglycolic acid 4-0. For the surface plane, Nylon 5-0 is the first option in a transdermal technique (figures 1-4).

Figure 1
The lesion is reached by access through a modified Blair incision.

Figure 2
Visualization of the tumour through the parotid capsule.

Figure 3
Exeresis of the lesion (area of prehension with instruments with perforation of tumour capsule).

Figure 4
Closure of the parotid capsule, with subsequent repositioning of flaps by planes.

The post-surgical pharmacological treatment consisted of cefazolin (1 g), metamizole (1 g), and ketorolac (30 mg) every 8 hours intravenously for two or three days. For lengthy procedures (2 hours or more), dexamethasone (4 mg) was added every 8 hours for the first 24 hours after the operation. Finally, the discharged of patients are in 72 hours with clinical monitoring at 3, 7, and 14 days, followed by 1, 2, and 6 months, and then every year for discharge or the planning of subsequent monitoring if necessary.

A total of 18 patients (13 women and 5 men) treated between 2018 and 2020 met the inclusion criteria. The age range was 20-72 years. The dimensions of the lesions were within the range of 11 to 50 mm. The primary lesion was PA (n: 9). The side most frequently affected was left in 12 cases. The capsules were kept unscathed in 14 cases. Complications were observed in three patients and included oedema, a sialocele, and hypoesthesia of the area accompanied by recurrence (Table 1).

Table 1
Resume of patients treated between 2018-2020

Abbreviations: M (male), F (female), mm (millimeters). Foot-notes: Not specified (Not describes in the histopathological inform).

In the last decade, ECD begins to settle as a valuable technique for PBPT as an essentially conservative approach^8-10. As an option for SP, it shows high effectiveness, especially in superficial, mobile and isolated lesions. Indeed, in a retrospective series of 377 patients (Erlangen, Germany)¹¹, only 2% of patients developed permanent facial nerve injury. This approach applies to deep lobes lesions (Osaka, Japan) even without recurrence or permanent nerve lesion in a media of 61 months of control¹². In specific tumours like solitary cystadenolymphomas, similar data is appreciable in a retrospective report of 327 patients treated with ECD. The occurrence rate of ipsilateral metachronous tumours was 3.1% from the previous study, with a mean follow-up of 108.4 months¹³. Regardless of recurrence, authors report that it is similar to SP, even with trials without reappearance like in Guy’s Hospital (London, England), with 156 treated patients and a range size lesions from 0.5 to 7.5 cm¹⁴. The main recommendation for this technique is adequate prior training. The four maxillofacial specialists in the hospital respected this consideration.

Regarding the use of intraoperative continuous facial nerve monitoring (IFNM), immediate and late nerve dysfunction incidences are similar in patients treated with or without this system in the SP technique¹⁵. On the other hand, all the ECD techniques investigations included here used IFNM^8-14, unlike this series case. Still, the complications were similar in comparison to the retrospective study with the largest population (n: 1359) and 16 years of experience, with reports of 68 temporary postoperative paralyses (5%), Frey’s syndrome (2.3%), recurrence (0.8%) and permanent facial palsy (0.3%). In this study, one patient (5%) developed a sialocele, and another (5%) oedema and temporal hypoesthesia. Both patients had total recovery in the first month. However, a third patient developed a recurrence associated with a dermoid cyst in the fourth month, highlighting that the capsule unscathed at the time of its removal. Fortunately, was programmed a new intervention with excellent results until the last follow-up. On the other hand, due to the lack of subject and a limited follow-up period (30.8 months), continuously control is necessary to establish a successful treatment considering a minimum follow-up of 10 years for patients.

In trained surgeons, ECD is a favourable indication in superficial and solitary deep PBPT for size lesions up to 50 mm accord to our results and publications available, with minimal complications of recurrence and hypoesthesia, even without IFNM. Additionally, a long-term follow-up control is necessary for patients treated.