Deep Lobe Parotidectomy




Introduction


The most common indication for surgery of the parotid gland is the presence of a mass or tumor. The majority of distinct parotid masses are neoplasms with benign tumors predominating. Pleomorphic adenoma (mixed tumor) and Warthin tumor (papillary cystadenoma lymphomatosum) account for the majority of benign lesions with adenomas and oncocytomas being encountered regularly.


Malignant tumors of the parotid gland represent a heterogeneous group of different pathologies with varying clinicopathologic characteristics. Mucoepidermoid carcinoma is the most common malignancy found in the parotid gland with adenoid cystic carcinoma being encountered nearly as often. Other malignant tumors include acinic cell carcinoma, adenocarcinoma, salivary duct carcinoma, primary squamous cell carcinoma of the parotid gland, and carcinoma ex-pleomorphic adenoma. Nodal metastasis to intraparotid lymph nodes from skin cancers of the face and scalp are also seen with reasonable frequency; more rare are metastases from malignancies originating outside the head and neck with spread to the parotid.


Lymphoma can also present in the parotid gland and is more commonly seen in patients with chronic inflammatory disease of the parotid(s) such as Sjogren’s syndrome. The majority of parotid lymph nodes lie within the superficial lobe of the gland and thus are somewhat less germane to a discussion of deep lobe parotid lesions and surgery. However, in the management of a malignant tumor originating within the deep lobe, metastasis can occur that requires removal of the superficial gland as a means of lymphadenectomy.


Although it is decreasing in frequency, parotidectomy is also sometimes undertaken for chronic parotiditis. In instances of parotidectomy for chronic parotitis, the goal of the surgery is typically removal of all remaining parotid tissue, including the glandular tissue of the deep lobe. Other causes of swelling and possible masses of the parotid include congenital lesions such as first branchial cleft cysts and inflammatory conditions such as Sjogren’s syndrome and sarcoidosis.


Any condition that can affect the superficial lobe of the parotid may affect the deep lobe as well, and despite modern imaging techniques and examination characteristics, the discovery of the relationship of a mass to the facial nerve often cannot be made until the time of surgery. Parotidectomy is a procedure that has standardized steps and a variable component that must be personalized at each operation while considering the pathology, location of the lesion, and patient-specific factors.




Key Operative Learning Points





  • Deep lobe parotidectomy is a procedure with both standardized steps and variable portions that should be tailored to the patient and his or her pathology.



  • Preoperative imaging (computed tomography [CT] or magnetic resonance imaging [MRI]) is recommended for all suspected deep lobe parotid lesions, as it can provide useful information regarding the tumor and its relationship to critical structures.



  • Facial nerve dissection and mobilization are likely to be necessary unless the tumor is purely parapharyngeal.



  • Preoperative tissue sampling is recommended, as deep lobe malignancy often requires additional exposure with a mandibulotomy.



  • The surgeon should have a low threshold for removal or division of structures such as the great auricular nerve, posterior belly of digastric muscle, or stylomandibular ligament to improve access and exposure.





Patient Selection/Preoperative Period


Masses originating in the deep lobe of the parotid are typically either discovered by the presence of the mass on examination or found incidentally on cross-sectional imaging such as CT or MRI. Most benign tumors will present with minimal symptomatology related to the lesion except for the presence of the mass itself and possibly some mild discomfort. Significant or worsening pain, trismus, immobility of the lesion, skin change overlying the mass, and facial nerve weakness are all clinical signs that should raise the suspicion for malignancy. Given their anatomic location, however, benign tumors that arise in the deep lobe of the parotid may have decreased mobility on physical examination as compared to a mass in the superficial lobe or may not be readily palpable at all.


Palpable masses can be evaluated in similar fashion to a superficial parotid mass and are often first investigated with fine-needle aspiration (FNA) biopsy. Masses that are found incidentally are often not readily palpable, and FNA of the mass often needs to be done with image guidance such as ultrasound or CT. The necessity of obtaining FNA biopsy of parotid lesions prior to surgery is debatable and goes beyond the scope of this chapter focused on surgical planning and technique. We feel that the complication rate of FNA is so low and the potential information gathered from the FNA is often quite accurate in terms of differentiating between benign and malignant lesions that we favor performing this preoperatively whenever feasible. The information obtained from FNA can often allow more informed preoperative discussion with the patient and may also allow observation of likely benign lesions such as Warthin tumors in patients who are poor operative candidates.


FNA of suspected deep lobe parotid masses can be more difficult than for superficial lesions and may require image guidance. Given the anatomic location of a deep lobe parotid tumor, however, information regarding potential malignancy may be of even greater value. Complete discussion regarding possible need for mandibulotomy, nerve manipulation or even nerve resection allows for informed consent prior to removal of a deep lobe mass worrisome for malignancy. Similar to with a superficial parotid tumor, we recommend wiating for either frozen section or final pathologic confirmation of parotid malignancy prior to resecting vital structures such as the facial nerve.




Preoperative Period




  • 1.

    History of present illness



    • a.

      Presence of the mass—how discovered, how long present, growth


    • b.

      Associated symptoms—pain, trismus, facial twitching, facial paralysis, or weakness


    • c.

      Other head and neck symptoms—dysphagia, otalgia, aural fullness, decreased hearing, epistaxis, visual change, and voice change


    • d.

      Constitutional/general symptoms—weight loss, fevers, chills, night sweats, and malaise



  • 2.

    Past head and neck specific history



    • a.

      Prior salivary gland surgery or infection


    • b.

      Prior tobacco exposure (Warthin tumor)


    • c.

      Prior head and neck cancer, prior radiation treatment including radioactive iodine


    • d.

      Prior skin cancer of the head and neck region, primarily squamous cell carcinoma or melanoma



  • 3.

    General medical history



    • a.

      Comorbid conditions including autoimmune issues and sarcoidosis


    • b.

      Cardiovascular health—prior pacemarker of automated implantable cardioverter defibrillator (AICD) – able to have MRI


    • c.

      Medications/allergies—anticoagulants




Physical Examination




  • 1.

    General appearance



    • a.

      Obvious parotid/neck mass or asymmetry


    • b.

      Facial weakness


    • c.

      Voice change, that is, muffled


    • d.

      Secretion management, airway obstruction



  • 2.

    Complete examination of the head and neck with attention to areas noted below


  • 3.

    Skin



    • a.

      Worrisome or suspicious lesions of the facial skin or scalp—infiltration, ulceration, erythema, asymmetry, and melanotic lesions



  • 4.

    Otologic



    • a.

      Worrisome skin lesions of auricle or ear canal


    • b.

      Middle ear effusion, possible parapharyngeal extension



  • 5.

    Oral cavity/oropharynx



    • a.

      Trismus


    • b.

      Dentition/height of mandible if mandibulotomy possible


    • c.

      Pharyngeal asymmetry, soft palate, tonsillar fossa, and lateral pharyngeal wall



  • 6.

    Salivary glands/neck



    • a.

      Palpable mass


    • b.

      Size, mobility, and tenderness/firmness


    • c.

      Borders of mass if palpable, apparent depth of extension, and relationship to angle of mandible


    • d.

      Facial nerve function, upper and lower divisions, and weakness/twitching/paralysis


    • e.

      Cervical adenopathy




Imaging


Cross-sectional imaging is recommended for tumors with possible deep lobe location. Imaging of a parotid mass provides information regarding both the possible location (superficial or deep lobe) and nature of the pathology (benign or malignant). Imaging landmarks that offer clues to the location of the facial nerve include the styloid and mastoid processes, the posterior belly of the digastric muscle, and the retromandibular vein. The vein is typically a superior extension of the external jugular vein (or occasionally the common facial vein) and can be identified by following the vein in an inferior to superior fashion in the axial plane. In a normal anatomic situation, the facial nerve and its branches will lie just superficial to the vein within the substance of the parotid gland; thus, the relationship of a parotid mass to the vein can be used to infer the relationship between the nerve and a mass. Given this, a deep lobe tumor will often displace the retromandibular vein laterally and superficially.



  • 1.

    MRI with contrast



    • a.

      Superior assessment of tumor, soft tissues, and possible perineural invasion



  • 2.

    CT with contrast



    • a.

      Best assessment of bone anatomy, mandible, mastoid, and styloid processes



  • 3.

    Positron emission tomography (PET)/CT



    • a.

      Fluorodeoxyglucose (FDG) avidity of salivary gland tumors can be unreliable. Positron emission tomography (PET)/CT is rarely needed but can be considered in cases of possible high-grade malignancy or other known malignancy where a parotid lesion may represent a metastasis or to be aware of lung metastasis as part of preoperative evaluation.




Indications




  • 1.

    The treatment for parotid neoplasms is surgical excision.


  • 2.

    The treatment of inflammatory conditions of the parotid is first management of the underlying inflammatory condition, but surgery may eventually be indicated for refractory cases.


  • 3.

    Subtotal resection or biopsy of parotid lesions may be indicated if the likely diagnosis is a condition that is typically not treated surgically such as lymphoma or sarcoidosis.



Contraindications




  • 1.

    Medical comorbidities that place the patient at high risk for general anesthesia particularly if imaging and FNA suggests a benign tumor


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Apr 3, 2019 | Posted by in OTOLARYNGOLOGY | Comments Off on Deep Lobe Parotidectomy
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