Parotidectomy

INTRODUCTION — A parotid mass is often incidentally found in an otherwise asymptomatic patient. History and physical examination can often determine if the mass is a manifestation of a systemic disease or a true neoplasm. Additional evaluations, including imaging studies and biopsy, are offered to properly selected patients before parotidectomy. (See "Salivary gland tumors: Epidemiology, diagnosis, evaluation, and staging".)

Parotidectomy is a common procedure in head and neck surgery and is quite safe. Most patients have significant trepidation about potential complications, such as facial nerve injury. However, the risk can be minimized by adhering to principles outlined in this topic.

The indications, preoperative evaluation, techniques, and complications of parotid surgery are presented here. Treatment for other salivary gland tumors is discussed elsewhere. (See "Salivary gland tumors: Treatment of locoregional disease" and "Malignant salivary gland tumors: Treatment of recurrent and metastatic disease".)

SURGICAL INDICATIONS — The main indication for parotid surgery is to remove a parotid mass (table 1).

●Although most parotid neoplasms are benign, some benign neoplasms may enlarge and cause significant deformity or local tissue destruction, while others may degenerate into malignancy. Therefore, the majority of parotid masses should be removed.

●Parotid lesions that are malignant or indeterminant should also be removed, regardless of the tumor grade. High-grade malignancies include high-grade mucoepidermoid carcinoma, carcinoma ex-pleomorphic adenoma, solid type adenoid cystic carcinoma, squamous cell carcinoma, salivary duct carcinoma, and adenocarcinoma; low-grade mucoepidermoid carcinoma is regarded as low grade, while all remaining malignancies are in the intermediate-grade group (table 2) [1]. (See "Salivary gland tumors: Epidemiology, diagnosis, evaluation, and staging", section on 'Spectrum of salivary gland tumors'.)

In general, benign lesions are more amenable to less invasive surgical approaches, and malignant lesions require more extensive surgery. (See 'Extent of resection' below.)

PREOPERATIVE EVALUATION — While some type of parotid imaging is often performed preoperatively, it is not required in all circumstances. The imaging modalities should be selected based upon the features to be elucidated.

Whereas many clinicians perform routine anatomic imaging (computed tomography [CT] or magnetic resonance imaging [MRI]) as part of the initial assessment, others biopsy the lesion first and determine the need for parotid imaging based on the results of the biopsy and clinical assessment:

●If the biopsy is benign and the lesion is completely palpated and clinically benign, additional imaging is not mandatory.

●If the biopsy is malignant or indeterminant, or if the patient has a large mass, pain, clinical evidence of disease extension outside of the parotid gland (eg, trismus, facial weakness, skin involvement), or a history of cutaneous malignancy in the head and neck, anatomic imaging should be performed.

Biopsy — In most circumstances, a tissue diagnosis is required prior to parotidectomy. The mainstay of tissue sampling for parotid lesions is fine needle aspiration (FNA). Core needle biopsy (CNB) should be reserved for when FNA is nondiagnostic to either avoid open surgery or better define the disease for surgical planning.

Fine needle aspiration — FNA of parotid lesions can be performed with or without ultrasound guidance. CT guidance may be required to biopsy deep lobe tumors that are not well visualized on ultrasound and are not palpable. Although there has been debate in the past regarding the need for biopsy of a lesion that will be removed, in contemporary practice, FNA is employed in most situations to guide the extent of the planned parotid surgery and help frame the preoperative counselling for the patient.

Although the accuracy of FNA has been debated for several decades, most would agree that FNA is highly predictive of malignancy versus benignity, but less of the definitive histologic correlation. In various studies, FNA had a sensitivity of 75 to 82 percent, a specificity of 90 to 98 percent, a positive predictive value (PPV) of 77 to 100 percent, a negative predictive value (NPV) of 91 percent, and an overall accuracy of 83 to 95 percent [2-5]. Preoperative FNA led to change in surgical plan in 19 percent of patients [3].

The Milan system for reporting salivary cytopathology results (table 3) has become more commonplace and resembles the Bethesda system for thyroid biopsies. The focus of the Milan system is on the risk of malignancy, as opposed to a specific diagnosis, which is often more accurate than the prior practice of estimating histology. In a prospective study of 315 patients, the accuracy of this system in distinguishing benign versus malignant lesions was 95 percent [6]. In a review of 12,898 patients in the Dutch Pathology Registry, the sensitivity of FNA using the Milan system was higher in head and neck oncology centers (88 percent) than in general hospitals (75 percent), demonstrating the importance of specialized assessment [7].

Core needle biopsy — CNB is generally reserved for situations in which FNA is nondiagnostic, but there is a compelling reason to obtain a preoperative histologic assessment for:

●Pathologies that do not require excision (eg, systemic disease such as lymphoma or sarcoidosis)

●Patients who are too ill to tolerate parotid surgery

●When preoperative knowledge of the histology is required for operative planning

Although CNB of the parotid gland has traditionally been avoided due to the potential for facial nerve injury or needle tract seeding, more contemporary studies have shown CNB to be safe with a high accuracy and low complication rate. Current CNB technique that uses ultrasound guidance to ensure appropriate sampling of the mass is becoming more commonplace.

In a meta-analysis of 211 patients undergoing ultrasound-guided CNB of salivary lesions with histologic confirmation, the rates for identifying true neoplasms and malignancies, respectively, are sensitivity 98 and 93 percent, specificity 100 and 99 percent, accuracy 98 and 98 percent, PPV 100 and 98 percent, and NPV 69 and 97 percent [8].

A 2022 review of over 2050 CNB and over 15,900 FNAs found that ultrasound-guided CNB has higher sensitivity, specificity, and lower nondiagnostic rates than FNA. It also has a significantly higher sensitivity for the detection of malignancy. Significant complications post-ultrasound-guided CNB are uncommon, with only one reported case of tumor seeding and no cases of permanent facial nerve dysfunction [9].

Other studies investigated using CNB selectively or in tandem with FNA:

●When CNB is used only if malignancy is suspected based upon ultrasonographic characteristics, new facial palsy, rapid increase in size, pain, or a known head and neck malignancy, the accuracy of making the correct histopathological diagnosis was 93.5 percent [10]. Two patients in this series of 138 experienced post-biopsy facial weakness.

●Another study of 141 patients with salivary tumors performed CNB immediately after ultrasound-guided FNA if the FNA was inadequate [11]. Employing this strategy resulted in 135 patients who had FNA alone and 26 (19 percent) who underwent FNA plus CNB. When analyzed for the assessment of malignancy, the sensitivity and specificity was 100 and 92 percent, respectively.

Open biopsy — Although rare, there are times when open biopsy of a parotid mass is warranted. Open biopsy should only be performed after FNA/CNB, usually with the goal of obtaining additional tissue for lymphoma assessment, or if the lesion is felt to be systemic in nature (eg, sarcoid or another inflammatory process).

Open biopsy should not be performed on a suspected primary salivary neoplasm or a malignant process; such parotid masses are generally removed in toto for both diagnosis and treatment (ie, "grand biopsy"). Occasionally, open biopsy may also be necessary to diagnose deep lobe tumors.

Imaging — Parotid imaging has evolved from sialograms and plain films to the more discriminating multiplanar images produced by CT and MRI. In contemporary practice, ultrasonography is performed to guide FNA or CNB of parotid lesions. CT and MRI are used primarily as an adjunct to FNA/CNB in determining the extent of surgery required, as well as providing an assessment of adjacent cervical lymph nodes. Neither CT nor MRI can independently differentiate between benign and malignant lesions.

Ultrasound — The application of office ultrasound has brought about a resurgence in the use of this imaging modality in the head and neck, parotid glands included. Ultrasound is widely available and can be performed without ionizing radiation. It is also quite useful to guide FNA but is less applicable to deep lobe lesions and can be challenging due to interference from adjacent bony structures.

CT — CT can be done rapidly and is generally more accessible than MRI. CT generally gives excellent information regarding the location and characteristics of the parotid lesion and its relationship to surrounding structures and has the ability to detect changes to adjacent bone, such as enlargement of the stylomastoid foramen and erosion or invasion of the skull base and mandible. CT does not always demonstrate masses, however, and cannot be relied upon to rule out a clinically palpable parotid mass. In addition, it must be done with intravenous contrast, which is a limitation for patients with impaired renal function.

MRI — Compared with CT, MRI has superior soft tissue discrimination and therefore is favored by many to image the parotid gland. Tumors that are not demonstrated on CT can often be identified on MRI, which has the added benefit of no ionizing irradiation. A comparison of the different MRI sequences (eg, T1 weighed, T2 weighted, etc) can often provide an accurate diagnosis of the mass as well, as pleomorphic adenomas, Warthin's tumors, schwannomas, and vascular lesions often have characteristic imaging features. MRI is also superior to CT for evaluation of the facial nerve and extension of a deep lobe parotid tumor into the parapharyngeal space. Intravenous contrast enhancement is also recommended for MRI, and other potential limitations include the longer duration of the image acquisition and the claustrophobic feeling many patients have in an MRI scanner.

Both CT and MRI have significant limitations in diagnosing benign versus malignant lesions. In a study of 260 patients undergoing parotidectomy, preoperative CT or MRI had an accuracy of 85 percent, a sensitivity of 39 percent, a specificity of 96 percent, a PPV of 67 percent, and an NPV of 87 percent in determining whether a parotid lesion is benign or malignant [12]. Thus, CT and MRI should be used as an adjunct to FNA/CNB in determining the extent of surgery required, as well as providing an assessment of adjacent cervical lymph nodes instead.

PET — Positron emission tomography (PET) imaging is rarely indicated for the assessment or staging of parotid tumors. Since the majority of parotid tumors are slow growing, they will often not show significant avidity on a PET scan.

Exceptions to this include Warthin's tumors (which are often noted on PET scans done for routine surveillance of another primary malignancy, either within or outside of the head and neck) and high-grade malignancies (such as a salivary duct carcinoma, adenocarcinoma, high-grade mucoepidermoid carcinoma, or squamous cell carcinoma).

SURGICAL TECHNIQUES

Incisions — The modified Blair incision is the standard approach to exposing the parotid gland. A modified facelift incision may be used in select patients with a lesion in the tail of the parotid gland [13].

Modified Blair incision — It includes a vertical limb (either pre- or post-tragal) extending posterior at the lobule and then curving inferiorly and anteriorly in the neck as far forward as necessary (figure 1). When laid out correctly and closed meticulously, this incision is quite cosmetic.

The vertical component should extend only as superiorly as necessary to allow tumor exposure for resection. If the patient has a pretragal crease (usually in older adults), the incision should be placed within that crease. If the patient does not have such a crease, the post-tragal incision is favored for cosmesis. When closing the post-tragal incision, an absorbable suture should be placed in the deep subcutaneous soft tissue of the pretragal region to recreate the soft fold in the pretragal area, while the skin is closed post-auricularly.

The curve at the lobule can be placed slightly anterior to the junction of the parotid tissue and the lobule, or within the fold itself. Care must be taken to meticulously reapproximate this area during closure to maximize the cosmetic result. If the incision is within the fold itself, a single vertical mattress suture should be placed during skin closure to evert the skin edges.

The horizontal limb should be at least 3.5 cm inferior to the lower border of the mandible to protect the marginal mandibular branch of the facial nerve and carried anteriorly enough to adequately expose the region of the parotid gland to be removed.

Modified facelift incision — The modified facelift incision can also be used for parotidectomy in appropriately selected patients (figure 2). Since this incision extends posteriorly along the hairline, instead of anteriorly into the submandibular region, lesions in the parotid tail and posterior parotid gland are most suitable to this approach. The size of the mass to be excised and the type of parotidectomy should also be factored into the choice of this incision.

A systematic review and meta-analysis found that cosmetic satisfaction was significantly higher using this approach when compared with the modified Blair incision [14,15]. The tumors removed using the modified facelift approach were smaller, and facial palsy and salivary complication rates were comparable between the groups.

Identification of the facial nerve — The most important intraoperative step during dissection is accurate identification of the facial nerve. Nerve identification will allow mobilization of the mass off the nerve, preservation of the nerve, and minimization of the risk of nerve injury. (See 'Facial nerve sacrifice' below.)

Several anatomical structures are commonly used to identify the facial nerve during parotid surgery (figure 3):

●The tragal pointer – In adults, the main reference point for facial nerve identification is the tragal pointer, which is located at the angled medial end of the tragal cartilage. The tragal pointer is exposed during mobilization of the parotid gland along its posterior border, anterior to the tragus. The main trunk of the facial nerve can be found approximately 1 centimeter anterior, inferior, and medial to that pointer.

●The tympanomastoid suture – In children, because the tragus is less developed, the tympanomastoid suture should be followed medially and the facial nerve can be found emanating from the stylomastoid foramen at that point. A study of 26 embalmed cadavers found that the tympanomastoid suture is closer to the nerve (2.5 mm) than either the tragal pointer or the posterior belly of the digastric muscle [16]. The nerve is also closer to the tympanomastoid suture in males than in females.

●The facial canal in the mastoid – As the facial nerve exits the stylomastoid foramen, it is surrounded by dense connective tissue. In patients with disease at the stylomastoid foramen, a mastoidectomy can also be performed, if necessary, to identify the nerve in the facial canal and trace it distally.

●Peripheral identification – Another method to identify the branches of the facial nerve is to locate a branch in the fatty tissue anterior to the border of the gland and trace it proximally, toward the pes anserinus and the main trunk of the nerve. If this approach is used, the surgeon must be meticulous with the dissection and avoid transecting the nerve inadvertently at a branch point, especially if the nerve takes a tortuous course. Identifying the nerve anteriorly can be quite challenging, and a nerve stimulator can occasionally be used to facilitate that process.

●The posterior belly of the digastric muscle – The digastric muscle can be used to help identify the depth of the nerve by following the muscle from the neck toward the skull base along its inferior border. In general, the facial nerve will be cephalic and anterior to the digastric insertion, but distortion and anatomic variation can put the nerve at risk superiorly. This is generally used adjunctively and to facilitate a broad exposure.

●The retromandibular vein – The posterior facial or retromandibular vein can be followed superiorly into the parotid gland to isolate the nerve, which generally will course superficial to the vein.

Extent of resection — The present trend of parotid surgery is toward using minimally invasive techniques to reduce the volume of normal parotid tissue removed while maintaining an adequate tumor margin. The goals of this trend are to maintain a low tumor recurrence rate and reduce the incidence of major surgical complications, namely facial weakness due to facial nerve injury and Frey syndrome. (See 'Surgical complications' below.)

●Small (<4 cm), mobile, benign, and peripheral tumors without preoperative or intraoperative concerns may be safely removed using an extracapsular technique by experienced parotid surgeons (who can recognize high-risk features and convert to partial or complete parotidectomy when necessary). (See 'Extracapsular dissection/nodulectomy' below.)

●Most benign and low-grade malignant tumors can be removed by partial superficial parotidectomy. (See 'Partial superficial parotidectomy' below.)

●Very large benign or malignant tumors should be removed by complete superficial parotidectomy. (See 'Complete superficial parotidectomy' below.)

●Tumors that involve the deep lobe of the parotid gland should be removed with total parotidectomy. (See 'Total parotidectomy' below.)

Complete superficial parotidectomy — Complete superficial parotidectomy is the gold standard of parotid surgery to which other less extensive procedures are compared. This technique entails complete dissection of the lateral, superficial lobe of the parotid gland with identification and dissection of all branches of the facial nerve. This provides a comprehensive assessment of the tumor with maximal margins but also can result in significant complications and cosmetic deformities due to the loss of a substantial volume of tissue in the pretragal and mandibular ramus areas. The high complication rate has driven surgeons toward performing less extensive dissection for primary parotid tumors. The main indications for superficial parotidectomy at this time are parotid metastases from cutaneous carcinoma or extensive gland involvement from any tumor.

Partial superficial parotidectomy — Partial superficial parotidectomy is the most commonly performed procedure in parotid surgery. It involves facial nerve identification and dissection with removal of a cuff of normal tissue surrounding the excised tumor. The rationale behind limiting the resection to an appropriate cuff of normal tissue is related to the closest margin found during resection. Most tumors of significant size will abut a branch of the facial nerve. Since a functional nerve that is abutting a tumor should not be removed, the margin in this area will be minimal. Therefore, if the closest margin (near the nerve) is a millimeter or less, it would be unnecessary for the same tumor to have a multicentimeter margin in another area (eg, the cranial aspect of the superficial lobe for an inferiorly based tumor). Reducing the amount of normal tissue removed results in fewer complications and a shorter surgical duration and obviates the need for defect reconstruction required for a complete superficial parotidectomy [17]. This procedure is the standard for many parotid surgeons when removing benign parotid tumors.

Extracapsular dissection/nodulectomy — For these techniques, the facial nerve is not identified or specifically dissected prior to isolation of the parotid mass. Instead, dissection proceeds in a plane several millimeters away from the mass (extracapsular dissection [ECD]) or immediately adjacent to the mass with a narrow margin of normal parotid tissue (nodulectomy/minimal margin ECD). The rationale for both approaches is similar to that of partial superficial parotidectomy and also resides in the minimal margin obtained in a superficial parotidectomy along the facial nerve branches. In superficial parotidectomies, it is common to have a margin of several centimeters within the parotid tissue but a close or "positive" margin along the nerve itself, if it has to be peeled off the tumor. Since the recurrence rates are very low with superficial parotidectomy, and the margins along the nerve are very close, it stands to reason that a close or narrow margin adjacent to the mass may also suffice.

Tumors selected for this approach should be <4 cm, mobile, peripherally located, and have a benign fine needle aspiration (FNA; most often pleomorphic adenoma or Warthin's tumor) and should not have any worrisome intraoperative features, such as fibrotic or inflammatory involvement of the surrounding tissue, invasion of adjacent structures, or any other clinical concerns. Additionally, many feel this technique should be performed only by experienced parotid surgeons who can recognize concerning, high-risk clinical features and readily convert the procedure to a standard partial or complete superficial parotidectomy when necessary. One should always discuss with the patient preoperatively the potential for converting to a standard superficial parotidectomy in case concerning intraoperative features are encountered.

Controversy remains regarding the appropriateness of these techniques.

●One study in support of ECD is a retrospective analysis that reported temporary facial palsy in 5 percent, permanent facial palsy in 0.37 percent, Frey syndrome in 2.3 percent, and pleomorphic adenoma recurrence in 0.87 percent of 1359 patients who underwent ECD from 2000 to 2015 [18]. These outcomes compared similarly or favorably to those of historical control patients who underwent superficial or total parotidectomy.

●However, in another retrospective study of 894 patients undergoing surgery for pleomorphic adenoma or Warthin's tumor from 1960 to 2015, ECD was associated with a higher rate of positive margins (29.4 versus 10.2 percent), recurrent disease (7.2 versus 2.2 percent), and permanent facial palsy (2.2 versus 0.6 percent) [19]. Since ECD was predominantly performed from 1960 to 1990 in that study, one may question whether some of the ECDs were actually enucleations. (See 'Enucleation (no longer performed)' below.)

Total parotidectomy — In modern surgery, total parotidectomy is no longer used routinely to treat benign diseases. In a randomized trial of 101 patients undergoing parotidectomy for benign disease, only four patients required total parotidectomy, and transient facial weakness, decreased sensation in the operative area, and late salivary function were all judged more favorable in those who underwent partial parotidectomy [17].

Instead, total parotidectomy is used for removal of either a deep lobe tumor or the entire gland plus intraparotid nodal groups for complete extirpation of a high-grade parotid malignancy.

However, removal of the lateral lobe to manage a deep lobe benign tumor is not always necessary, as the superficial lobe may often be mobilized and elevated off the facial nerve through careful dissection, providing access to the deep lobe, thus allowing excision with excellent control of the facial nerve. The superficial lobe can then be replaced in its normal position, ameliorating the cosmetic defect often seen following total parotidectomy (picture 1).

Total parotidectomy may be used for larger high-grade malignancy in the absence of deep lobe involvement to ensure complete removal of the tumor and all intraparotid nodes. In a multisurgeon review of 75 patients who underwent total parotidectomy for high-grade malignancies, deep lobe parotid nodal metastasis occurred in 22.7 percent of patients and could occur without superficial parotid nodal metastasis [20]. High-grade parotid malignancies, such as high-grade mucoepidermoid carcinoma, carcinoma ex-pleomorphic adenoma, adenocarcinoma, squamous cell carcinoma, and salivary duct carcinoma, are most often managed in this fashion. Metastatic disease from a skin cancer to the parotid gland may also warrant a total parotidectomy, but the data are evolving.

Enucleation (no longer performed) — Enucleation is a procedure whereby the capsule of a tumor is incised and the tumor removed from within by blunt dissection. This technique is never indicated for a primary parotid neoplasm and is not part of contemporary parotid surgery. Recurrence rates are very high, and this technique can lead to tumor spillage and multifocal recurrence in pleomorphic adenoma.

Adjunctive procedures — The following procedures may be required at the time of a parotidectomy, depending upon the extent of tumor involvement.

Facial nerve sacrifice — During parotid surgery, the facial nerve can be preserved in almost all circumstances. Facial nerve involvement requiring sacrifice generally indicates a high-grade parotid cancer or metastatic skin cancer.

Traditionally, the nerve is resected when it is encased by malignancy. This would necessitate an intraoperative frozen section of the tumor to establish a definitive diagnosis of malignancy, rather than relying solely upon a preoperative biopsy. (See 'Frozen section' below.)

The current debate surrounds the degree of nerve involvement by malignancy that would necessitate sacrifice. Most agree that an intact nerve on the surface of the malignancy should be peeled off the tumor and left intact and in situ but that frank nerve involvement, heralded by loss of function preoperatively, circumferential involvement of the nerve, or visible disease within the nerve sheath, requires nerve sacrifice.

A retrospective review of 75 patients undergoing parotidectomy for malignancy noted that 40 percent required either partial (21.3 percent) or complete (18.7 percent) sacrifice of the facial nerve [21]. Preoperative facial nerve dysfunction (odds ratio [OR] 154.3), preoperative pain (OR 7.84), and total parotidectomy (OR 9.85) were predictive of the need for nerve sacrifice.

The potential need for facial nerve sacrifice should be discussed in detail with the patient at the time of consent, including the possibility of nerve reconstruction, as the cosmetic and oncologic impact of nerve sacrifice on the patient is significant. In one study, the need for nerve sacrifice was associated with much higher risks of recurrence (hazard ratio of 51.4) and death (hazard ratio of 4.92) despite the use of adjuvant therapy [22].

When facial nerve sacrifice is anticipated, all distal branches of the facial nerve should be identified during parotid dissection to assess nerve involvement and facilitate immediate reconstruction. A complete superficial parotidectomy, or generally, a total parotidectomy, should be performed to allow complete tumor removal and elimination of intraparotid lymph nodes. Once the diagnosis of malignancy is confirmed on frozen section, the nerve is sacrificed, and frozen section assessment of the remaining nerve stumps should be performed to ensure a negative nerve margin. This is particularly important for neurotropic tumors, such as adenoid cystic carcinoma, which can track along the nerve for significant distances, despite a normal appearance of the nerve. This may require performing a mastoidectomy to access the proximal facial nerve for both assessment and reconstruction. (See 'Facial nerve reconstruction' below.)

Facial nerve reconstruction — Facial nerve reconstruction should be performed if possible. Immediate reconstruction is preferred and optimal, but delayed reconstruction may be considered under certain circumstances. Ideally, the patient should be warned of the possibility for nerve reconstruction before surgery.

If the facial nerve is sacrificed intraoperatively, immediate reconstruction is the optimal reconstructive method. Reconstruction using a cable graft is most common, employing the greater auricular or sural nerves, dependent upon the length and branching needs of the reconstruction. The advantage of the greater auricular nerve is that it is in the same operative field, although one must be concerned about the potential for tumor involvement in the case of malignancy. The sural nerve will provide a longer graft length and has several branches, which is advantageous in certain situations. A hypoglossal nerve transfer is also an option for immediate reconstruction, although it is less favored currently as a branch of the masseter nerve can accomplish the same results with less significant donor defects.

Delayed reconstruction often results from an unexpected nerve sacrifice coupled with either the need for a nerve other than the greater auricular nerve to perform the reconstruction or the surgeon's inability to perform nerve reconstruction. In either case, when immediate reconstruction is not possible, the cut ends of the nerve should be tagged with a permanent suture and the location of the nerve carefully described in the operative note to allow easier identification at a subsequent procedure.

Some patients, especially older adults, may require adjuvant reconstructive methods, such as fascial slings, eyelid procedures, and other methods to rehabilitate the face. Adjunctive procedures to maintain eye closure, such as the placement of a gold weight, should also be considered at the primary surgery to ensure ocular health. (See 'Eye protection' below.)

Adjacent structure sacrifice — Similarly, structures adjacent to the parotid gland should only be sacrificed in the presence of direct tumor invasion. Structures that parotid tumors could potentially invade include the temporal bone, the temporomandibular joint (TMJ), the mandible, the distal external carotid artery, skin, and components of the parapharyngeal space. Temporal bone resection may be necessary for ear tumors spreading anteriorly through the external auditory canal (EAC) or for parotid malignancies that spread posteriorly to involve the mastoid or EAC. Superiorly based parotid tumors will have easy access to the TMJ. The need for sacrificing adjacent structures should be apparent on preoperative imaging. (See 'Imaging' above.)

Neck dissection — A concurrent neck dissection should be performed when there is clinical or imaging evidence of nodal metastasis. The extent of the neck dissection should cover the nodal basins at risk, including levels II, III, and Va, with extension to other levels dictated by the extent of disease and nodal burden (figure 4). Level I is potentially another primary nodal basin. Level V should be dissected when disease is clinically evident in other cervical levels, most commonly level II [23].  

There is ongoing debate about the need to perform a neck dissection in the absence of clinically evident metastatic disease. In several large studies of elective neck dissection in patients with clinically node-negative salivary gland tumors, occult nodal metastasis was more likely to occur in T3/4 tumors than in T1/2 tumors and more likely to occur in high-grade tumors than in low-/intermediate-grade tumors. As such, many feel that patients at the highest risk of harboring occult nodal disease have high-grade tumors and thus would require postoperative radiation anyway. A review of 1547 patients with high-grade but clinically node-negative parotid cancer from the National Cancer Database found no survival benefit for elective neck dissection when controlling for adjuvant therapy and cancer type [24]. (See "Salivary gland tumors: Treatment of locoregional disease", section on 'Management of the neck'.)

Frozen section — Frozen section can be used intraoperatively to definitively diagnose a malignancy and determine its grade. The result of a frozen section may have an impact on surgical decision making with regard to facial nerve sacrifice and/or neck dissection. It is our practice to perform frozen section for all parotid resections to help define the extent of surgery, particularly when performing ECD.

In a review of 1339 parotid tumors, the sensitivity and specificity of frozen section for malignant diagnosis was 98.5 and 99 percent, respectively [25]. The concordance rate between the frozen section and permanent section was 84 percent. Upon permanent analysis, the diagnosis was changed from benign to malignant or vice versa in <1 percent of the patients, and there was no change from a low-grade tumor to a high-grade tumor or vice versa. Overall, only three patients required additional surgery based on permanent section, and only one patient was overtreated.

Another study of 260 patients undergoing parotid surgery with frozen section found it to have a sensitivity, specificity, and accuracy of 75.0, 100, and 96.8 percent, respectively, and recommended its use only when the FNA is nondiagnostic, indeterminant, or positive for malignancy [12].

Reconstruction of surgical defects — Reconstruction of the parotidectomy defect has taken many forms over the years, ranging from no reconstruction to free tissue transfer. The main goal is to use the least invasive and destructive technique possible to minimize the cosmetic consequences from removing the entire superficial lobe, the entire gland, or an extended parotidectomy. The extent of reconstruction is determined by the size of the defect produced by the surgery.

The defect following partial superficial parotidectomy or ECD can often be closed primarily through reapproximation of the superficial parotid fascia or superficial musculoaponeurotic system (SMAS), or with a sternocleidomastoid (SCM) rotational flap. One retrospective study of 99 patients found the SCM reconstruction to be superior to the SMAS for cosmetic results [26].

Free fat grafting and/or free tissue transfer may be required for defects that are larger or more complex [27]. Although larger free fat grafts, such as those obtained from the abdomen or thigh, may be effective, their sizes may reduce by as much as 30 percent over the long term.

POSTOPERATIVE CARE AND FOLLOW-UP — Postoperative care is largely dictated by the procedure performed and any complications that may occur. We typically remove sutures in five to seven days after surgery and evaluate the patient again in another four to six weeks to ensure appropriate wound healing and address any concerns the patient may have about potential complications. Routine postoperative care includes the following:

●Antibiotics are not necessary for more than 24 hours following parotid surgery and are often not necessary at all.

●The incision should be kept clean, and many surgeons apply a topical antibiotic ointment to the incision twice a day while the sutures are in place and for a few days to a week following suture removal.

●Sutures should be removed in five to seven days after routine parotidectomy procedures to minimize the risk of wound scarring.

●The patient must guard against thermal injury in the early postoperative period as there will be areas of hypoesthesia in the ear and face around the incision. (See 'Sensory loss (hypoesthesia)' below.)

●In several weeks to months after the surgery, it is not uncommon for the postauricular portion of the incision to develop some hypertrophic scarring, which can be managed topically with silicone Band-Aids or gel, or with steroid injections in severe cases.

The potential need for adjuvant radiotherapy and post-treatment follow-up for patients with malignant salivary gland tumors is beyond the scope of this topic and can be found elsewhere. (See "Salivary gland tumors: Treatment of locoregional disease", section on 'Adjuvant therapy' and "Salivary gland tumors: Treatment of locoregional disease", section on 'Posttreatment surveillance'.)

SURGICAL COMPLICATIONS

Facial nerve paresis/paralysis — Postoperative facial weakness or immobility is the most feared complication of parotid surgery. Fortunately, this complication is reasonably uncommon, particularly in experienced hands. The current trend toward using less extensive surgical approaches has also decreased the incidence of facial nerve injury.

●The risk of facial dysfunction varies with the type of parotid surgery performed [19,28]. A systematic review and meta-analysis assessed 6646 patients for temporary facial weakness and 6060 patients for permanent facial paralysis [29].

●In benign parotid tumors, increased tumor size and deep lobe tumor have been shown to increase the risk of temporary facial weakness; however, 50 percent of patients recovered by 2 months and 90 percent by 12 months [30].

Eye protection — For patients with nerve paresis/paralysis, postoperative adjuvant techniques are required to protect the eye.

●It is important to keep the eye well lubricated and moist with the liberal use of artificial tears. To avoid corneal trauma and desiccation, it is imperative to tape the eye completely closed while sleeping. Lacri-Lube, or a similar moisturizer, is often placed prior to taping the lid closed.

●Ophthalmology evaluation is appropriate for patients in whom a long recovery is anticipated or the nerve had been sacrificed, or else exposure keratitis can lead to permanent visual changes. In addition to the upper lid weight placement, tarsorrhaphy or lid shortening procedures may be necessary for eye protection.

●Nimodipine, a calcium channel blocker, may improve recovery in patients who develop facial weakness after surgery. In a systematic review, nimodipine use was associated with greater facial motion recovery (odds ratio [OR] 2.78, 95% 1.2-6.4) [31]. However, since the majority of patients in the studies reviewed developed facial nerve injury as a result of vestibular schwannoma excision, the exact benefit of nimodipine to parotid surgery remains uncertain.

Intraoperative facial nerve monitoring — The significant functional and psychological consequences of facial nerve dysfunction have prompted the utilization of facial nerve monitoring in an attempt to reduce the incidence of nerve injury and dysfunction [32]. Our group does not routinely incorporate facial nerve monitoring but selectively employs it for reoperation or surgeries that are complex and high-risk as defined by the surgeon. At this time facial nerve monitoring during parotidectomy should not be considered standard of care, particularly since the long-term facial weakness results are the same with or without nerve monitoring.

●In a systematic review and meta-analysis of facial nerve monitoring during parotid surgery involving seven studies, the incidence of immediate postoperative facial weakness was significantly lower in the nerve monitoring group (22.5 versus 34.9 percent) [33]. The incidence of permanent weakness, however, was not different (3.9 versus 7.1 percent, p = 0.18). Subgroup analysis of superficial or total parotidectomy failed to demonstrate the same benefit; extracapsular dissection was not studied.

●A subsequent retrospective study of 267 patients also associated nerve monitoring with a lower incidence of transient postoperative facial nerve dysfunction after superficial parotidectomy (15 versus 47 percent) and total parotidectomy (8.3 versus 43 percent) [34].

●Intraoperative facial nerve monitoring parameters have been studied in 222 patients to determine factors predicting postoperative facial dysfunction [35]. If a post-dissection stimulation threshold of 0.25 mA was paired with 8 intraoperative mechanical stimulating events, a 77 percent incidence of postoperative weakness was found, dropping to 31 percent if those criteria were not reached.

Frey syndrome — Frey syndrome, or gustatory sweating, arises from the parasympathetic parotid neurons reinnervating the sweat glands in the overlying skin. It is commonly found if specifically tested for with an iodine-starch test but is less noticed clinically. The incidence of clinically evident Frey syndrome ranges from 1 to 44 percent and is largely dependent upon the extent of the parotid surgery [18,19,36].

The optimal management of Frey syndrome is prevention, which can be facilitated by limiting parotid dissection, the placing of graft material between the residual parotid gland and the skin, or altering subcutaneous tissue plane flap elevation. As examples:

●A systematic review and meta-analysis of five studies demonstrated a lower objective incidence (relative risk [RR] 0.15, 95% CI 0.08-0.30) and a lower subjective incidence (RR 0.32, 95% CI 0.19-0.57) of Frey syndrome with acellular dermal matrix (ADM) implant without any increase in seroma or wound infection [37]. However, the only trial showed a higher wound complication rate with ADM use [38,39].

●One small trial found a lower incidence of objective Frey syndrome with sternocleidomastoid (SCM) flap reconstruction [40], whereas another small trial did not [41]. Another larger but nonrandomized comparative study found that either an SCM or superficial musculoaponeurotic system (SMAS) flap reconstruction after parotidectomy reduced the incidence of Frey syndrome compared with no flap reconstruction, particularly when the tumor resected was greater than 3 cm [26].

●A systematic review and meta-analysis of 3830 patients was performed to assess the effect of surgical technique on the incidence of Frey syndrome [42]. A free fat graft (FFG) was best at reducing objective Frey syndrome (followed in order by temporoparietal fascia [TPFF], ADM, SCM, and SMAS), while TPFF was most effective in reducing subjective Frey syndrome (followed by ADM, FFG, SCM, and SMAS, respectively) when compared with no intervention.

Clinically evident Frey syndrome can be quite concerning to the patient and can be managed with topical antiperspirants or botulinum toxin A injections. In a study of 100 patients with Frey syndrome, patients did not seek treatment until a mean of 2.8 years after surgery, but once Botox treatment was initiated, each injection was effective for a median of 12 months, an interval that remained stable over time [43]. However, the effectiveness of these treatments has not been proven in randomized trials [44].

Sensory loss (hypoesthesia) — Sensory changes are expected in all patients following parotid surgery and have a variable recovery. This is due to transection of the cutaneous sensory branches of nerves innervating the upper neck, ear, and preauricular skin of the face. Anticipated sensory loss (hypoesthesia) in this distribution should be discussed with the patient preoperatively, noting the fact that recovery may be delayed for up to a year or more and that decreased sensation in certain areas may be permanent.

Transection of the greater auricular nerve (GAN) during parotidectomy has led to many of the long-term issues with hypoesthesia. Therefore, many surgeons attempt to preserve the posterior branch of the GAN to minimize long-term hypoesthesia. In a trial of 130 patients undergoing superficial parotidectomy, preservation, rather than transection, of the posterior branch of the GAN led to greater improvement of sensation in the lobule and antitragus areas at both 12 (59 versus 24 percent) and 24 months (71 versus 31 percent) after surgery [45].

First bite syndrome — Another rare but potentially debilitating complication is first bite syndrome (severe spasm and pain in the region of the parotid gland present upon the first bite of a meal, which diminishes with additional bites). This has been reported in 9.6 percent of patients in one series of 499 patients following deep lobe parotidectomy and is associated with sympathetic chain sacrifice (OR 4.2), parapharyngeal space dissection (OR 8.7), and resection of the deep lobe only (OR 4.2) [46].

First bite syndrome is related to damage to sympathetic innervation of the parotid gland, with which parasympathetic hyperactivation is believed to stimulate an exaggerated myoepithelial cell contraction causing pain [47]. In small case series, botulinum toxin A injection into the affected parotid gland paralyzes the parasympathetic nerves and decreases the severity of first bite syndrome [48]. Usual analgesic treatments are not effective.

Others — Other complications may occur following parotidectomy, including seroma or sialocele, hemorrhage, salivary fistula, and infection. The incidences of these rare complications are often difficult to determine as most publications focus on facial nerve dysfunction and Frey syndrome, but all should be discussed with the patient prior to surgery [28,49].

In a systematic review of 235 studies, the pooled incidences of minor complications reported were hematoma 2.9 percent (95% CI 2.4-3.5), wound infection 2.3 percent (95% CI 1.8-2.9), sialocele 4.5 percent (95% CI 3.5-5.7), salivary fistula 3.1 percent (95% CI 2.6-3.7), flap necrosis 1.7 percent (95% CI 1.1-2.5), scar issues 3.6 percent (95% CI 2.4-5.4), numbness 33.9 percent (95% CI 25.6-43.4), and deformity 11.8 percent (95% CI: 6.9-19.5) [50].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Head and neck cancer".)

SUMMARY AND RECOMMENDATIONS

●Indications – The main indication for parotid surgery is to remove a parotid mass (table 1). The majority of parotid masses, both benign and malignant, should be removed. (See 'Surgical indications' above.)

●Biopsy – A tissue diagnosis is highly recommended to facilitate operative planning and patient counselling. The mainstay of tissue sampling for parotid lesions is fine needle aspiration (FNA). Core needle biopsy (CNB) should be reserved for situations in which FNA is nondiagnostic. Open biopsy is only performed after FNA/CNB with the purpose of obtaining more tissue to diagnose systemic diseases (eg, lymphoma or sarcoidosis) and should not be performed on suspected primary salivary neoplasm or malignant process. (See 'Biopsy' above.)

●Imaging – Anatomic imaging (computed tomography [CT] or magnetic resonance imaging [MRI]) is not required routinely for benign lesions but should be performed if the biopsy is malignant or indeterminant or if the patient has a large mass, pain, clinical evidence of disease extension outside the parotid gland (eg, trismus, facial weakness, skin involvement), or a history of cutaneous malignancy in the head and neck. (See 'Imaging' above.)

●Incisions – The modified Blair incision (figure 1) is the standard approach to exposing the parotid gland. A modified facelift incision (figure 2) may be used in select patients with a lesion in the tail of the parotid gland. (See 'Incisions' above.)

●Facial nerve identification – Identification of the facial nerve is the most important intraoperative step during dissection. The facial nerve may be identified in relationship to one of the following anatomic structures: the tragal pointer, the tympanomastoid suture, the facial canal in the mastoid, the posterior belly of the digastric muscle, the retromandibular vein, and peripheral identification (figure 3). (See 'Identification of the facial nerve' above.)

●Surgical techniques – Contemporary parotid surgery is trending toward minimally invasive techniques when possible. Our approach is as follows:

•For small (<4 cm), mobile, benign, and peripheral tumors without preoperative or intraoperative concerning features, we suggest an extracapsular technique, rather than partial or complete parotidectomy, when an experienced parotid surgeon is available (Grade 2C). (See 'Extracapsular dissection/nodulectomy' above.)

•For most other benign and low-grade malignant tumors, we suggest partial superficial parotidectomy (Grade 2C). (See 'Partial superficial parotidectomy' above.)

•For very large benign or malignant tumors, we suggest complete superficial parotidectomy (Grade 2C). (See 'Complete superficial parotidectomy' above.)

•Total parotidectomy is reserved for removal of either a deep lobe tumor or the entire gland plus intraparotid nodal groups for complete extirpation of a high-grade parotid malignancy. (See 'Total parotidectomy' above.)

●Facial nerve preservation – During parotid surgery, the facial nerve can be preserved in almost all circumstances. An intact nerve on the surface of the malignancy should be peeled off the tumor and left intact and in situ, but frank nerve involvement requires nerve sacrifice. If the facial nerve is sacrificed, immediate reconstruction is preferred and optimal, but delayed reconstruction may be required under certain circumstances when nerve sacrifice is not anticipated. (See 'Facial nerve sacrifice' above and 'Facial nerve reconstruction' above.)

●Neck dissection – A concurrent neck dissection is performed when there is clinical or imaging evidence of nodal metastasis. Neck dissection in clinically node-negative patients is controversial. (See 'Neck dissection' above.)

●Complications – The most common major complications of parotid surgery are facial weakness and Frey syndrome (gustatory sweating). Less common or minor complications include sensory loss (hypoesthesia), seroma or sialocele, hemorrhage, salivary fistula, infection, and first bite syndrome (severe spasm and pain in the region of the parotid gland present upon the first bite of a meal, which diminishes with additional bites). (See 'Surgical complications' above.)