Parotid Duct Injuries

Parotid duct injuries have been described in the literature for several hundred years, and published surgical treatments of parotid duct injuries began to appear in the 1890s.

Nicoladoni reported the first primary anastomosis of the parotid duct in 1896.[2] Morestin reported ligation of the proximal stump in 1917, and formation of an oral fistula was described in 1918.[3]

Experience in the care of parotid duct injuries greatly increased with the outbreak of World War I, which witnessed many penetrating facial injuries. Many present treatment modalities were developed during the war years.

Frequency

Approximately 0.21% of patients with penetrating trauma in the parotid region experience an injury to the parotid duct.

Males are twice as likely to experience parotid duct injury as females, a fact probably related to the more aggressive behavior of males.

The mean age of patients with parotid duct injury is approximately 30 years.

See the list below:

• Penetrating injuries in the parotid region

• Blunt trauma

• Complication of parotid duct cannulation for sialography

• Intraoperative iatrogenic injury

History

A careful detailed history is necessary to facilitate communication between various health care professionals involved in the care of the patient and to document why the plan of care was appropriate. Patients with damage to the parotid duct often have multiple injuries requiring cooperation of several medical specialists.

Important aspects of the natural history of the wound include the circumstances surrounding the injury, precipitating event or activity, exact mechanism of injury, time of occurrence, location of occurrence, and treatment initiated prior to presentation.

Important signs and symptoms related to the wound include pain, fever, edema, discharge, and/or odor.

Other important aspects of the history include tobacco, alcohol, or recreational drug use; medications or allergies to medications; tetanus immune status; ability to comprehend the magnitude of injury; and ability to cooperate with the treatment plan.

Comorbid conditions that may place the patient at a higher risk for infection or its sequelae include diabetes mellitus, prior splenectomy, liver disease, immunosuppression, and presence of a prosthetic valve or joint.

Physical examination

A thorough physical examination is necessary in order to evaluate the overall state of health, comorbidities, nutritional status, and mental status of the patient. Following the general physical examination, turn attention to the wound. Assessment of the wound can be quite difficult and is often inaccurately or inadequately performed. Adequate examination of the wound may require administration of intravenous or oral pain medication to ensure patient comfort. Children, intoxicated individuals, and individuals with mental disabilities may require general anesthesia to allow adequate wound examination.

Important aspects of wound assessment are listed below.

• Location

• Shape

• Size

• Type (eg, puncture, laceration, avulsion, crush, abrasion)

• Depth of penetration

• Drainage (ie, quality, character, odor)

• Presence of a foreign body (eg, glass, tooth fragments)

• Loss of tissue

• Tenderness

• Asymmetry

• Surrounding erythema, edema, cellulitis, or crepitation

• Facial nerve status

Photographs are a wise addition to the documentation present on the chart.

See Treatment.

The parotid glands are the largest salivary glands. The paired parotid glands are formed as epithelial invaginations into the embryologic mesoderm and first appear at approximately 6 weeks' gestation. The glands are roughly pyramidal in shape, with the main body overlying the masseter muscle. The glands extend to the zygomatic process and mastoid tip of the temporal bone and curve around the angle of the mandible to extend to the retromandibular and parapharyngeal spaces.

The gland is divided into superficial and deep lobes with regard to its relation to the facial nerve (ie, cranial nerve VII), which travels through the gland. This division is not truly anatomic but rather is used to facilitate surgical treatment of parotid masses. The facial nerve exits the cranium via the stylomastoid foramen and courses through the substance of the parotid gland. The superficial lobe of the parotid gland rests superficial to or lateral to the facial nerve, and the deep lobe rests deep to or medial to the facial nerve. The facial nerve branches within the substance of the parotid gland in a highly variable pattern.

The parotid duct is approximately 7 cm long and is composed of an inner epithelium, a smooth muscle coat, and an outer adventitial layer much like a blood vessel. The parotid duct exits the parotid gland anteriorly and crosses the superficial border of the masseter. It then turns medially and pierces the buccinator muscle. After traveling for a variable distance between the buccinator muscle and the oral mucosa, it enters the oral cavity through a papilla in the buccal mucosa opposite the second maxillary molar. The course of the parotid duct generally follows a line drawn from the tragus to the midportion of the upper lip. Any injury that crosses this line should be considered to involve the parotid duct until proven otherwise. Parotid duct injuries are often overlooked because of more severe concomitant injury or difficulty in obtaining the diagnosis.

The parotid duct travels adjacent to the buccal branch of the facial nerve and the transverse facial artery, which also are at risk in injuries causing damage to the parotid duct. In a cadaveric study, eighty-five percent of the cadavers had a single buccal branch of the facial nerve, whereas 15% had two branches. In 75% of cases, the nerve was inferior to the duct as it emerged from the parotid gland, whereas in 25% of cases the nerve crossed the duct, usually from superior to inferior. The parotid duct was found to be interrelated with the buccal fat pad in cadaveric dissections.

In addition, a 26% chance of injuring the parotid duct exists with the removal of the buccal fat pad. The transverse facial artery, if injured, need not be repaired. However, injury to this artery may cause bleeding into the tissues, which may obscure adequate delineation of structures and confuse the diagnosis. Above all, blind clamping of bleeding vessels in the wound is strongly discouraged because of the extremely high risk of further damage to the delicate structures in this area.

Anatomy of the parotid region. Line A connecting the tragus to the midportion of the upper lip estimates the general location of the parotid duct, which lies along the middle third of this line.

An injury classification system has been devised for parotid duct injuries. This system divides the parotid duct into the following 3 regions:

• Posterior to the masseter or intraglandular (site A)

• Overlying the masseter (site B)

• Anterior to the masseter (site C)

Wounds older than 24 hours should probably be managed expectantly because many heal without untoward event.

Perform appropriate preoperative laboratory studies as dictated by patient's age, sex, and overall medical condition.

Appropriate preoperative chest radiography may be indicated as dictated by the patient's age, sex, and overall medical condition.

Sialography may be performed but is usually not necessary to establish the diagnosis of parotid duct injury. If performed, a water-soluble contrast material should be used because it is more easily drained and absorbed and does not remain as an irritant to the gland. Sialography can be used to detect perforations, fistula tracts, calculi, and tumor, and it defines the ductal anatomy well. It is rarely used at present, however. If undertaken, it should be performed as sterilely as possible to prevent introduction of intraoral bacteria to the parotid duct.

The most straightforward way to diagnose a parotid duct injury in the emergency department is to cannulate the intraoral parotid duct papilla with a small (ie, 19-gauge) silastic tube and observe if the tube is visible in the wound.

This test does require patient cooperation; therefore, it may be difficult or impossible in children, intoxicated individuals, or individuals with mental disabilities.

If any question regarding the diagnosis remains, a small amount of saline may be injected through the tube and observed for flow through the wound.

Methylene blue probably should not be injected through the tube because it terribly discolors tissues and makes subsequent operation even more challenging.

Wounds in the parotid region generally heal well with a low rate of infection, but patients with wounds that involve the oral cavity or require manipulation of the parotid duct through the oral cavity should probably receive prophylactic antibiotics for a brief time after primary closure. Saliva containing as many as 100,000,000 organisms per mL and representing as many as 190 different species may be inadvertently introduced to the wound. These species are both aerobes and anaerobes, and several of the more common species produce beta-lactamase, rendering them resistant to penicillin.

Routine cultures are not necessary because they are costly, demonstrate no growth in over 80% of cases, and rarely alter first-line therapy. Moreover, wounds subsequently manifesting signs of infection often have bacteriologic profiles differing from the initial cultures.

Wound care is the cornerstone of therapy; antibiotics cannot avert or cure infections in the setting of poor wound care. In regards to antibiotic therapy, err on the side of caution because the risk of antibiotic therapy is minimal, while the potential complications of wound infections are considerable. Prophylactic antibiotics should be continued for 5-7 days.

Selection of the appropriate antibiotic involves multiple factors, including culture results if obtained and available, drug sensitivities, patient age, drug interactions, expected compliance, and renal and hepatic function.

The drug of choice is amoxicillin/clavulanate potassium (Augmentin; adult dosage 500/125 mg PO tid or 875/125 mg PO bid). It is the most effective and economical choice for outpatient therapy, unless contraindicated because of penicillin allergy. Doxycycline is an alternative choice for oral therapy in patients allergic to penicillin (adult dosage 100 mg PO bid). Rocephin 1 g administered intramuscularly or intravenously is useful in patients whose compliance with dosage schedules is questionable.

In rare cases, human saliva has been shown to contain and occasionally transmit Clostridium tetani. Assess all patients for tetanus immune status and update their immunization as appropriate. Err on the side of caution when deciding to administer tetanus toxoid or tetanus immune globulin.

Some authors choose to use anticholinergic agents to suppress glandular function during healing or in an attempt to close a fistula or resolve a sialocele spontaneously. A commonly used agent is propantheline bromide (Pro-Banthine), which inhibits the action of acetylcholine at the postganglionic nerve endings of the parasympathetic nervous system (adult dose 15 mg PO qid half an hour prior to meals).

Sialocele and salivary fistula can frequently be managed nonoperatively with antibiotics, pressure dressings, and serial aspiration. Anticholinergic medications and the injection of botulinum toxin represent additional measures before resorting to surgical therapies such as tympanic neurectomy or parotidectomy.[4]

Intraoral buccal fat pad removal (BFPR) has increasingly come into use as a means of improving facial contour and balance in cases of buccal lipodystrophy or buccal fat pad pseudoherniation. Weissler et al noted the following steps in the treatment of parotid duct injuries resulting from BFPR[5] :

• Early aspiration/decompression, with the patient closely observed and treated with oral antibiotic therapy
• Antisialagogue medication therapy
• If symptoms persist, botulinum toxin therapy to chemodenervate the parotid gland
• If resolution is absent, repair and/or stent placement

Meticulous wound care is the cornerstone of treatment for penetrating injuries in the parotid region. Copious irrigation has been shown to decrease the incidence of wound infection. Use isotonic sodium chloride solution, dilute Betadine, or dilute hydrogen peroxide to cleanse the wound thoroughly. Irrigation is best performed with a 10-mL syringe with an 18-gauge angiocatheter attached. Take care to avoid injection of the tissues and to prevent additional trauma. Careful debridement of devitalized tissue, particulate matter, and clot is necessary to reduce the infection risk and to improve the cosmetic result. Clean, surgically created wound margins allow for faster wound healing and better scarring.

Head and neck wounds, being in a cosmetically sensitive area, may be closed if they are less than 12 hours old and not obviously infected. These have been closed with a low incidence of infection. The low infection rate is probably related to the excellent regional blood supply and infrequency of edema in these areas. Perform closure in a simple interrupted fashion, avoiding layered closure with buried sutures.

A retrospective study by Hu et al indicated that even surgical treatment delayed 1-3 months for parotid gland and duct injuries can effectively reestablish tissue function and facial aesthetic. The nine patients in the study, five of whom had sialoceles and four of whom had fistulas, underwent delayed treatment with parotid duct ligation, microsurgical anastomosis, or salivary flow diversion, with no recurrences within the group. Three of four patients who experienced postsurgical facial paralysis recovered following nerve nutrition treatment.[6]

In a report on two cases, Mohan et al indicated that in traumatic parotid duct injury associated with a sialocele, internalization can effectively be accomplished via a Foley catheter. In the investigators’ cases, the catheter was inserted through an intraoral opening and, once secured, left in situ for 15 days. A normal salivary flow occurred through the intraoral opening, and no postoperative recurrence was found.[7]

Appropriate consent must be obtained, including an explanation of the possible need for duct repair, ligation, or reimplantation into the oral mucosa. Informed consent includes a discussion of the possible complications, including but not limited to infection, hematoma, hypertrophic scarring, nerve injury, parotid fistula, sialocele, and death from anesthesia. Discuss expectant care with the patient as a viable alternate course of treatment that is probably less than ideal. Repair at initial presentation is technically simpler than in the case of delayed presentation with development of complications such as a fistula or sialocele.

Administer 1 dose of intravenous broad-spectrum antibiotics within 1 hour prior to the operation.

After initiation of general anesthesia, prepare and drape the head and neck in the usual sterile fashion. Plan the initial incision based on the level of suspected injury indicated by preoperative examination of the wound, the oral papilla, and cannulation of the duct with a silastic tube. All but the most distal injuries require a standard approach to the parotid gland. Distal injuries may sometimes be appropriately approached through an intraoral buccal mucosal incision, and often the facial wound is extensive enough to allow adequate visualization of key structures and their repair.

The most important initial step is the identification of the buccal branches of the facial nerve and the parotid duct itself. If the buccal branch was transected, repair it with fine sutures (8-0 to 10-0 nylon is appropriate) under microscopic aid. Use of a nerve stimulator intraoperatively and avoidance of the use of paralytic agents by the anesthesiologist can greatly aid in identification of facial nerve branches. The distal end of the parotid duct is identified by the silastic tube, which was placed via cannulation of the intraoral papilla. The proximal parotid duct can usually be identified by the flow of saliva into the wound. If not clearly identified, gentle pressure over the gland may cause an increased flow of saliva, facilitating identification. Once all key structures are identified, a decision is made regarding which repair technique to employ.

Distal lacerations, occurring at site C, may be treated in several ways. If the papilla is uninjured, the proximal portion may be dissected free and reimplanted into the papilla. The papilla may be gently dilated if this technique is chosen. Alternatively, if the papilla is injured or if the proximal duct does not reach the papilla, the duct may be reimplanted into the oral mucosa posterior to the papilla. This should be performed with fine interrupted absorbable sutures with meticulous approximation of duct epithelium to oral mucosa. This should probably be performed under loupe magnification because of the difficulty of using the surgical microscope deep in the oral cavity. If the distal injury does not leave enough duct to be reimplanted into the oral mucosa without undue tension, then the best decision is to ligate the proximal duct.

Injuries occurring over the masseter muscle, at site B, are the most common injuries to the parotid duct and may be treated by repair or ligation. Perform primary repair if enough length remains. Trim the edges cleanly and perform anastomosis over the silastic stent. A recent article advocates using an epidural catheter to guide the anastomosis.[8] A single layer of interrupted fine sutures (8-0 to 10-0 nylon or similar suture) is used to carefully reapproximate the severed ends with the surgical microscope or under loupe magnification. If a portion of the duct is damaged beyond repair or is missing, the proximal and distal duct should be ligated. Reports of attempts to use a vein graft to replace missing or damaged segments of parotid duct have generally found such attempts unsuccessful.

Laceration of the parotid duct over the masseter. Note that a stent has been placed through the intraoral papilla and can be visualized in the wound exiting the distal end of the transected duct.

Injuries of the proximal duct near the parotid substance, at site A, are usually best treated by ligation of the duct. The amount of proximal duct remaining is usually insufficient to result in a useful repair. Laceration of the gland itself without disruption of the parotid duct may be oversewn with fine absorbable sutures (5-0 or 6-0 Vicryl).

If the surgeon is able to repair the duct over a stent, the stent is trimmed at the level of the oral papilla and sewn to the oral mucosa or around the maxillary second molar with a chromic suture. This is designed to hold the stent in place for the recommended 2-3 weeks while the injured duct heals and to help prevent stenosis at the repair site. It may also prevent postoperative edema in the region from collapsing the fragile duct. Patient tolerance of the stent is highly variable. Some patients require stent removal early or remove it themselves without untoward consequence.

Repair of the parotid duct over a silastic stent with interrupted sutures using loupe or microscopic magnification.

Sialendoscopy is established in the diagnostics and treatment of obstructive salivary gland diseases, but it has not previously been reported in patients with injuries to the Stensen duct. Sialendoscopy-assisted repair of a transected Stensen duct in zone B has been reported.[9] The duct injury itself, its location, and its severity could be visualized and precisely assessed and allowed intraductal assessment of the ductal tissue.

Most authors recommend a drain in the bed of the wound. This serves to drain any residual salivary leak and prevents early sialocele formation. Drains are removed once drainage is minimal and the skin has become adherent to the operative site.

The remaining facial and intraoral lacerations, as well as any incisions required for exposure, are then closed in the standard fashion.

Place a compression dressing over the operative field postoperatively for several days. Perform routine drain care.

Continue antibiotic prophylaxis for 5-7 days. Antibiotic prophylaxis may be administered orally to prevent retrograde infection if the duct has been repaired over a stent that protrudes into the oral cavity.

If ductal injury required ligation of the proximal duct, expect marked temporary swelling of the gland followed by rapid glandular atrophy.

If leaking of saliva occurs as in the development of a fistula or sialocele, a pressure dressing should be continued or reinstituted. Intermittent aspiration of sialoceles has led to resolution in many cases. Anticholinergics may be used to temporarily decrease salivary flow in order to effect wound healing. Others have reported dividing the tympanic branch of the glossopharyngeal nerve (ie, Jacobsen nerve) as it runs through the middle ear. This serves to interrupt the preganglionic secretomotor fibers to the parotid gland. This measure only temporarily reduces salivary flow, but it may provide enough time for spontaneous closure of the salivary leak.

In the case of a chronic parotid duct fistula, an intraoral diversion technique to reestablish salivary flow in the setting of a nonfunctional parotid duct punctum has been described. In this case report, a fistula tract and the surrounding ellipse of skin were passed in the oral cavity and sutured to the buccal mucosa with 4-0 chromic sutures.[10] This allows for correction of a chronic fistula and simultaneous revision of a traumatic scar without need for stenting.

Alternatively, chronic fistula and sialocele have been medically managed with botulinum toxin type A.[11] In this case, the authors injected only 100 IU divided among 3 injection points in the superficial part of the parotid to stop salivary secretion. After 5 days, the sialocele disappeared and subsequent problems were related to the scar. Three months later, because of the reappearance of facial tension and the initial effectiveness of this dosage, 100 IU of botulinum toxin were again injected. Maintenance injections of 100 IU were performed every 3 months.

A study by Awana et al described a case in which, following traumatic avulsion of a parotid duct and facial vein, the parotid duct was surgically lengthened using the facial vein as a free graft.[12]

No special follow-up is necessary over and above routine postoperative care.

Complications may result from inadequate initial diagnosis and treatment or following appropriate care.

A retrospective cross-sectional study by Al-Qurayshi et al using the Nationwide Readmissions Database indicated, through multivariate analysis, that in adults who undergo major head and neck surgery, the salivary glands and ducts are among the sites at particularly high risk of infection.[13]

Persistent salivary fistula may be most troubling to the patient. If fistula occurs in the oral cavity, it is of no consequence and requires no further therapy. If the fistula occurs to the overlying skin, the patient experiences saliva dripping down the cheek. Initial expectant management, with or without anticholinergic medications, has led to resolution in many cases. Other cases have required surgical excision of the fistula tract with repair of the duct as previously described. Some have even required superficial parotidectomy for resolution. Anticholinergics may be beneficial in the treatment of fistulas.

Sialocele, ie, a collection of saliva beneath the skin, may occur if the duct leaks but no fistula forms. This may also result when the glandular substance of the parotid is disrupted but the parotid duct is intact. This condition usually resolves with intermittent aspiration and compression and rarely requires drain placement. Anticholinergics may be beneficial in the treatment of sialoceles.

A case study by Lee et al reported on the creation of a controlled intraoral fistula to treat a patient who, subsequent to a facial injury, developed a parotid sialocele. Saliva drained through the fistula into the oral cavity, and the sialocele resolved.[14]

Duct ligation may lead to early edema of the gland with accompanying pain from stretching of the capsule. This usually subsides spontaneously within 1-2 weeks as atrophy of the gland occurs. Late complications of ligating the duct include chronic infections of the remaining glandular substance.

Sialadenitis may result from manipulation of the intraoral papilla or from sialography and may require drainage and antibiotics.

Facial nerve injury and sensory nerve injury are well-recognized complications of surgery conducted in the region of the parotid duct, particularly in cases where trauma and blood extravasation have discolored the tissues and disrupted tissue planes.

Some controversy exists regarding optimal treatment of isolated parotid duct injuries. Most authors agree that the treatment of choice is immediate repair over a stent whenever possible, and certainly this is indicated if other injuries, such as facial nerve injuries, are present and require surgical intervention. At least one study, however, documents successful expectant treatment of isolated parotid duct injuries.[15] Immediate repair may prevent some complications, such as fistula or sialocele formation, but it also places the patient at risk for other complications, such as iatrogenic facial nerve injury, even in experienced hands.

Exploration and repair also involves significantly increased costs because this requires surgery and inpatient care, whereas expectant care is managed on an outpatient basis. On the other hand, a missed injury requires treatment that is also costly—not just financially but also in terms of quality of life. The responsible physician must decide which treatment plan is appropriate to each unique patient-care situation. Certainly, wounds older than 24 hours should probably be managed expectantly because many will heal without untoward event.