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Parotidectomy for Parotid Tumors


MRI right parotid tumor

The parotid glands are the largest of the paired major salivary glands (the others being the submandibular and sublingual glands). There are also thousands of minor salivary glands in the submucosa throughout the mouth and throat.

Anatomy salivary glands

Tumors can arise from any of the salivary glands, though tend to be most common in the parotid glands. A rule of thumb is that 80% of parotid tumors are benign, while half of submandibular tumors are malignant, and even higher percentage of minor salivary gland tumors are cancerous.

Incidence of salivary tumors

Parotid lesions can be benign or malignant, and neoplastic or non-neoplastic. As 80% of parotid tumors are benign, the procedure is most frequently performed for benign indications. The reason for proceeding with surgery, even for benign tumors, is to establish the histologic diagnosis as definitively as possible, prevent future enlargement of the tumor, and prevent future malignant transformation of a benign tumor. The question of malignancy and the possibility of altering the extent of surgery based on surgical findings makes for complex intraoperative deci­sion making. Handling of the facial nerve is the most significant point in parotid surgery.



Prior to surgery, it is possible to attempt to diagnose the lesion with a fine needle aspiration (FNA). This is a convenient, well-tolerated biopsy procedure which can typically be done even in the office with local anesthesia. It is useful in giving some indication of the pathology, especially if it turns out to be a cancer. Unfortunately, there are limitations on establishing the diagnosis on the small amounts of tissue from a needle, and it can not be said that the cytology diagnosis is 100% accurate. Studies identify the probability of a false negative FNA diagnosis (stating it is benign, when in truth it is a cancer) in the 10-15% range. Hence, a benign parotid cytology diagnosis has between a 5-10% risk of cancer, including risk of malignant transformation in the future.

parotidectomy facial nerve identified

The parotid is described as having a superficial and deep lobe, though there is no true fascial separation of these lobes; instead, the plane of the facial nerve bran­ches running through the parotid establishes the boundary of these lobes. Tumors lateral to the facial nerve branches are described as ‘superficial’, while medial to the facial nerve are ‘deep’.




parotidectomy facial nerve dissected

The facial nerve controls movement of the various facial muscles, and arises as a large main trunk from the bone of the skull base at the stylomastoid foramen (just below and medial to the ear). The nerve immediately enters the parotid gland, as it courses anteriorly, it branches into an upper and lower division at the ‘pes’ and then these divisions continue to branch as they travel to the anterior edge of the parotid gland boundary, exiting the gland as fairly small individual nerve branches coursing towards facial muscle groups. These branches are described as temporal, zygomatic, buccal, mandibular, and cervical — though many variations exist.

blair incision for parotidectomy

Parotidectomy is the name of the operation to dissect lesions from the parotid gland. This operation is tailored to the specific pathology, and does not necessarily mean the entire parotid gland is being dissected or removed. Typically, as small as possible an amount of parotid gland is disturbed, depending on the specific situation. The operation is typically accomplished through an incision in front of the ear and extending to the neck crease below the ear and jaw. Common side effects from the surgery are numbness of the skin of the ear and face, as well as some depression of the soft tissue depending on how much parotid gland is removed.

parotidectomy


A key risk is that the facial nerve (and therefore facial muscles) could be temporarily or permanently weakened. This is avoidable in most cases — except when the pathology, such as an invasive cancer, is involving the nerve and impossible to be separated.


The surgery is well tolerated in general, requiring minimal stay in the hospital and usually a quick return to normal activities. It does not limit swallowing, breathing, or speaking following surgery, and pain is typically low.

CT parotid tumors on right

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