Although a rare sequala of soft tissue injury, salivary gland trauma may result in significant morbidity. Salivary gland injury can involve the major as well as the minor glands. Because of the proximity of adjacent vital structures, a thorough history and physical examination are mandatory during patient evaluation. Trauma to the major salivary glands may involve the parenchyma, duct, or neural injury. Treatment requires adherence to primary principles of soft tissue management. Ductal and neural injury should be repaired primarily. Sialocele and fistula are potential complications of repaired and unrepaired salivary gland injury.
History and physical examination are integral in recognizing salivary gland trauma.
Parenchymal injury may be managed conservatively with standard wound care measures.
Current consensus dictates urgent repair of ductal injury.
Cranial nerve injury should be addressed during the initial management of salivary gland trauma.
Salivary gland injuries represent a small portion of soft tissue trauma but have dramatic sequelae if not diagnosed and treated. These injuries are often due to penetrating trauma but may also be iatrogenic. Salivary glands may suffer injury to either the parenchyma or the duct and range from self-limiting contusions to open lacerations. Ductal injuries may not be immediately obvious and can develop stenosis and obstruction later.
The parotid glands are relatively superficial under the skin and are therefore at risk during penetrating trauma of the face. The gland is encapsulated in fascia, which serves as an anatomic barrier that is important during repair. The facial nerve is at risk of injury, as it courses through the gland and exits anteriorly. The parotid duct also exits the gland anteriorly and pierces the buccinator muscle before entering the oral cavity in the maxillary molar region. The external carotid artery and the retromandibular vein pass along the posterior and deep aspect of the gland.
The submandibular glands rest below the inferior border of the mandible deep to the platysma muscle. The gland cups around the mylohyoid muscle anteriorly and droops over the digastric muscles inferiorly. The submandibular duct exits anteriorly and travels deep to the mylohyoid muscle before entering the oral cavity in the floor of the mouth. Nerves in close proximity to the submandibular gland include the lingual nerve, the hypoglossal nerve, and the marginal mandibular branch of the facial nerve. The facial artery enters the gland from the deep surface and exits superiorly to course over the mandible. The facial vein travels superficial to the gland.
The sublingual glands in the floor of the mouth are positioned on the lingual aspect of the mandible superior to the mylohyoid muscle. The submandibular ducts run adjacent to the sublingual glands and sometimes assist in salivary outflow from the sublingual gland. Parenchymal injury is uncommon but possible because of the superficial location under the oral mucosa.
It is critical for the oral and maxillofacial surgeon to have intimate familiarity with this anatomy, which allows prompt recognition of injury and the symptoms, aiding in the evaluation and treatment ( Fig. 1 ).
Patient evaluation overview
The authors begin their examination with A general history and physical examination. How the patient noticed the injury can be very telling, such as swelling at the area of the trauma, leaking of fluid (saliva) at the skin or from the ears, pain associated with eating, numbness of the face and lips, and a “crooked” smile or frown. Salivary gland trauma itself is less critical than the injury to the structures near them, and these signs and symptoms can aid in localizing the damage. From parotid down, these adjacent structures of interest include the facial nerve, external acoustic meatus, facial vasculature, lingual nerve, hypoglossal nerve, great vessels, and pharyngolaryngeal complex. By combining the location and the signs and symptoms elicited from the patient, a focused workup can be completed. Neurosensory testing, House-Brackman scale, duct cannulation and sialography, and more can facilitate a decision of whether an injury should be investigated further in the operating room (OR) or whether it can be repaired bedside.
For a ductal injury and parenchymal injury, dye injection study with or without radiograph may be useful. Briefly, the procedure is performed after cannulation of the duct with lacrimal probe, and the duct is injected via syringe with either an anterior chamber cannula or a small angiocatheter. Dye of choice can be methylene blue, although propofol or saline also can be used and is somewhat easier to handle because of the lack of intense staining and obscuring of the field. Observation of the dye from the wound bed can be indicative of parenchymal injury or ductal injury, and if at that location the catheter or cannula becomes exposed, ductal injury is confirmed. If difficulty arises with cannulation, injection of radiographic dye and panorex could be taken to localize the area of injury.
Although radiographs are not very useful for evaluation of trauma to the salivary glands themselves, there should be a low threshold for obtaining the studies especially in regard to deep penetrating trauma. Formal sialography with contrast and then computed tomography (CT), or fluoroscopy can be useful, but requires significant coordination with radiologist, and perhaps without much more benefit than dye injection studies bedside or in the OR. As such, radiographs are more useful for evaluating collateral damage, such as the vasculature, and CT angiogram to assess the critical vessels, such as the internal carotid, should be considered for deep penetrating injuries. A general outline of the evaluation and an algorithm for exploration are shown in Fig. 2 , and in the next section the authors discuss the principles of repair.
Surgical and nonsurgical treatment options
As emphasized in the patient evaluation section, it is important to recognize the rare salivary gland trauma and damage to adjacent structures. Ductal systems, motor and sensory nerves, as well as gland function are at risk when these organs are traumatized. It should be noted that salivary gland injury may frequently go unrecognized even with a detailed history and examination. ,
Preoperative planning is vital to addressing injury of the salivary gland and associated structures. Classifying injury to gland parenchyma, the ductal system, and associated nerves aids in formulating a treatment plan. Attention should be paid to adequate cleansing of the wound and surgical exploration in a controlled environment ( Fig. 3 ). The clinician should consider basic principles, such as layered closure, elimination of dead space, and suture choice. Nerve stimulators, ductal cannulation instruments, and ductal stenting materials should be available for identification and repair.
Current evidence advocates for urgent surgical repair of the injured salivary gland and associated structures. , Proceeding to the OR should be considered within 24 hours of injury. Every attempt should be made to explore within 72 hours when associated with a facial nerve injury. The ends of the transected nerve may still stimulate with electromyography during this time frame. Long-term muscle relaxants should be avoided during induction and anesthetic maintenance. Of course, proceeding to the OR within this time frame will need to be balanced in the setting of serious life-threatening polytrauma. Despite consensus in the literature, controversy does exist regarding conservative nonsurgical management of salivary gland injury. , , Clinical judgment is critical when managing these injuries.
Parotid Gland Injury
Parotid parenchymal injury is managed conservatively in accordance with general principles. , , Exploration, debridement, cleansing, and closing the wound in a layered fashion are mandatory. Focus should be on reapproximating the parotid capsule, superficial muscular aponeurotic system, and then overlying subcutaneous tissues and skin. The integrity of the duct can be verified with intraoral cannulation and retrograde injection of methylene blue or propofol. Again, care should be taken when injecting with methylene blue, as extravasation may discolor adjacent tissue and complicate repair. Some advocate stenting of the duct for a period of 2 weeks to ensure patency during the inflammatory phase of healing. Meticulous care should be taken when exploring the parotid region, as inadvertent damage to surrounding structures may occur.
Application of a pressure dressing for 48 hours after closure is useful in preventing unwanted sequelae, such as sialocele or fistula. , , It may be necessary to aspirate fluid accumulation during postoperative visits and reapply pressure dressing to prevent these complications. Some advocate for the administration of antisialagogues and avoidance of salivary stimulation (ie, nothing by mouth [NPO]) during recovery. , Injection of botulinum toxin A (50–100 U) into the gland can help prevent salivary stimulation and has shown to be beneficial in salivary gland injury. ,
Fortunately, isolated parenchymal injury tends to heal without significant complications. , , A prospective study suggests that isolated parenchymal injury without damage to an intraparenchymal ducts heal 2 to 3 times faster as those with damage to the ductal system. Close follow-up and exceptional wound care are required.
The presence of a ductal injury presents additional challenges to management. An anatomic classification system was created to plan for the appropriate repair of the duct ( Fig. 4 ). Type A injury occurs within the intraparenchymal ductal system. Type B injury occurs overlying the masseter muscle. Type C injury involves injury distal to the masseter muscle.