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Parotidectomy
Removal of the parotid gland

The parotid gland is the largest of the salivary glands that produce saliva that is important in the digestion of food. The gland lies under the angle of the jaw just beneath the ear. Surgery of the parotid gland may become necessary in the presence of infection and tumor. Of historical interest is that surgery on the parotid gland was the first operation to be performed under ether gas anesthesia in Boston in 1846.

Anatomy and Physiology

  • The parotid gland is shaped like an upside-down triangle and lies in front and below the opening to the ear canal (Figure 1). In front of the gland is the posterior (back) surface of the jawbone and the masseter muscle (the muscle felt on the side of the jaw when the teeth are clenched). The deep surface of the gland lies alongside the back of the throat, near the tonsils. Normally, the parotid gland cannot be felt
  • The facial nerve divides the gland into a superficial and deep lobe (Figures1 and 2). The facial nerve supplies all of the muscles that move the face. It arises in the skull and then exits through a small opening behind the parotid gland. It then enters the parotid, runs through it, and divides to supply the muscles of the face
  • The parotid gland helps in the secretion of saliva, which is necessary for the proper digestion of food. Saliva drains through a small duct from the front of the parotid gland and empties into the mouth near the upper second molar tooth
Figure 1 - The parotid gland lies in front and below the ear. The superficial lobe of the parotid gland lies outside the mandible (jawbone) while the deep lobe wraps around the back angle of the mandible. The most common incision is represented by the continuous line and possible extensions are indicated by the dotted lines. © C. McKee Figure 2 - The parotid lies on the masseter muscle that clenches the jaw. It lies in front of the sternomastoid muscle that turns the head to the opposite side. The facial nerve divides the parotid gland into superficial and deep lobes. The parotid duct delivers saliva from the gland into the mouth. © C. McKee

Pathology

  • The main conditions that effect the parotid gland are:
    1. Inflammation and infection of the gland
    2. Tumors of the parotid gland
  • Inflammatory and Infectious conditions:
    1. Stones in the saliva may obstruct the duct that drains the parotid gland. The stones develop minerals found in the saliva. This is usually seen in an elderly, dehydrated patient
    2. The obstructed parotid duct may lead to infection of the gland and to the formation of an abscess in the parotid gland
    3. Viral disease may also involve the parotid gland such as mumps or coxsackie virus
    • Illnesses like tuberculosis or the fungus, actinomycoses, may infect the gland
  • Tumors of the parotid
    1. Seventy to eighty percent of parotid tumors are benign
    2. The most common benign tumor is the pleomorphic adenoma. It usually is seen in patients in their forties and is seen more often in females. About 5 - 10% of patients with pleomorphic adenoma develop cancer
    3. The second most frequent benign tumor is called a Warthin's tumor. This tumor is seen more often in males and occurs in both parotid glands in about a 10% of patients
    4. Cancer of the parotid gland occurs in about 20 - 25% of parotid tumors. It must always be considered with any tumor of the parotid gland
    • The most common cancer of the parotid glad is the mucoepidermoid carcinoma. This occurs in two forms low grade in which the tumor cells are abnormal but still look similar to parotid gland cells and high grade in which the cells are very abnormal and no longer look quite like parotid gland cells
    • Adenoid cystic carcinoma is a more malignant tumor and has a tendency to metastasize (cells go to another part of the body) to the lungs. The tumor may also extend along the local nerves
  • Cancers of the parotid may have risk of spread to the lymph nodes in the neck. They may also involve the facial nerve (20% of cancers), which runs through the gland. This may result in facial pain or paralysis of the muscles of the face. They may also get fixed to muscles near the parotid gland (15% of cancers), causing difficulty in moving the jaw. A tumor of the deep lobe is rare, but may present with a swelling inside the throat, near the tonsil

History and Physical Examination

  • Infection and inflammation
    1. Infections of the parotid from blockage of the parotid duct may result in fever and pain on eating especially with sour foods, which tend to increase the flow of saliva
    2. An abscess in the parotid may give rise to a large, swollen mass over the parotid area
    3. Other inflammatory conditions of the parotid are usually painless, seen bilaterally and disappear by themselves
  • Cancer
    1. A lump in front of the ear should be assumed to be from the parotid. Even if a swelling has been present for years, it may still be cancerous, as these tumors may be slow growing
    2. Tumors of the parotid are usually painless and slow growing. Pain in this area or paralysis of the facial muscles is a poor sign, as it may be a reason to suspect a cancer involving the facial nerve
    3. Another symptom is called formication. It is described as the feeling of ants crawling over the side of the face. This may also mean involvement of the facial nerve with tumor
    4. Involvement of the facial nerve is almost never seen in benign tumors
    5. Spread to lymph nodes may present as swellings along the side of the neck

Diagnostic tests

  • Fine Needle Aspiration (FNA) - a small needle is inserted into the mass and some cells are sucked out. This helps determine if the mass is parotid tissue, a lymph node or even a collection of fat. If it is parotid tissue, unfortunately, a FNA cannot reliably tell the difference between benign and cancerous disease
  • Contrast sialography - a small tube is placed in the parotid duct and a dye is injected that shows up on X-ray and outlines the duct system. This may demonstrate a narrowing of the duct or a stone. Sometimes this is combined with a CT scan
  • CT scan or MRI scan - these studies may show the size and character of the mass and whether the mass is truly in the parotid gland. If the tumor is large, there is evidence of local spread, or if it is a deep lobe tumor this knowledge helps in planning the extent of surgery

Indications for Surgery

  • Surgery on the parotid gland may be indicated for an infection causing an abscess in the parotid. This may involve opening the duct of the parotid gland and flushing it out or draining the abscess
  • Parotidectomies are usually indicated for a suspected tumor of the parotid gland unless the patient is too sick to undergo a surgical procedure. It is not always possible to tell the difference between a benign and cancerous tumor unless the entire tumor is removed and examined

Surgical Procedure

  • The surgery is carried out under general anesthesia in which a tube is placed into the trachea (windpipe) to keep the airway open
  • The patient's head is turned away from the side of the tumor and the neck extended (arched back). The incision starts in front of the ear, curves around the bottom of the ear and then down the posterior aspect of the jawbone. The incision may be continued down into the neck along the front surface of the sternomastoid muscle (the muscles on the front of the neck that are felt as the head is turned from side to side) (Figure 1)
  • In case of smaller tumors, a facelift type of incision may be used, with the lower end of it going back along the hairline to hide the scar
  • The ear lobe is lifted up and backward and the posterior border of the parotid gland is exposed first. The facial nerve trunk (before it divides into smaller branches) is identified at this stage of the operation. (Figure 3A)
  • Once this is identified, dissection is done along the nerve freeing up the parotid tissue lying superficial to the nerve and making sure not to injure the nerve (Figure 3B)
  • The parotid tumor usually lies in the superficial lobe and this should be removed with a rim of normal parotid tissue around it (Figure 3C)
  • The skin is then closed. A drain is usually left in place
  • Tumors of the deep lobe are much less common and more difficult to remove. The usual method of removal requires removing the superficial lobe first, as described above, and then dissecting out of the deep lobe between the branches of the facial nerve. Care is taken not to injure the facial nerve branches
  • In extreme situations, when the tumor is excessively large or stuck to surrounding tissues, the tumor may need to be approached from inside the mouth. Sometimes the jaw bone has to be divided to get at the tumor
  • A careful dissection of the tissues of the neck may need to be carried out to remove all the lymph nodes if the node are involved with tumor (radical neck dissection)
Figure 3a - The posterior border of the gland is exposed first to uncover the trunk of the facial nerve © C. McKeeFigure 3b - The superficial lobe containing the tumor is dissected off of the facial nerve. © C. McKee
Figure 3C - The superficial lobe is removed. The deep lobe is seen along the posterior border of the jawbone. © C. McKee

Complications

  • Paralysis of the face as a result of injury or purposeful resection (removal) of the facial nerve. In case of injury to the facial nerve during the operation, an attempt may be made to reattach the nerve together. In case part of the facial nerve is involved with tumor, especially in with adenoid cystic carcinoma, the facial nerve may need to be resected. Sometimes a nerve graft procedure can be carried out to try to bridge the gap of resected tumor. The results usually do not fully restore facial function even when successful. Partial injuries of the facial nerve are more common, and these may resolve in a few weeks or months. Overall the incidence of such injuries is low.
  • Auriculotemporal nerve (Frey's) syndrome - this is an unusual complication where the patient may experience sweating or flushing of the skin over the parotid gland every time the patient eats. This is caused by injury to the facial nerve and the mixing up of very small nerve fibers that produce salivation and sweating. This syndrome may stop by itself, but if prolonged may require an operation to either divide the nerves causing this syndrom or injection of alcohol to kill the nerve
  • Facial defect - removal of a large tumor may cause a visible defect in the soft tissues of the face, which may not be cosmetically nice. There are plastic surgery procedures to reduce the cosmetic
  • Numbness around the earlobe
  • Infection in the operative site
  • Excessive bleeding
  • Swelling resulting in temporary difficulty in breathing and swallowing
  • Complications related to the anesthesia

Postoperative Care

  • Patients may have a drain in the operative site, which may be removed in 24 - 48 hours
  • Most patients go home the same day of surgery or after 24 hours
  • Skin sutures are taken out by the end of the week
  • There may be some weakness of the facial muscles on the side of the surgery due to swelling of the tissues around the nerve. This usually resolves in a few days
  • Radiation therapy may sometimes be necessary if the tumor was very large, involved nearby tissues or lymph nodes or in cases of deep lobe tumors; as it is sometimes difficult to assess the full extent of the dissection
  • The prognosis (outcome prediction) of tumors of the parotid varies with the pathologic type, the size of the tumor and the spread of tumor to surrounding tissues. Most, however, have good prognoses