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Case report

An 18-year-old male was involved in a motor vehicle collision (MVC). He was the front seat passenger, restrained with lap and shoulder belts and with an airbag that deployed in the crash. He had no loss of consciousness and was transported to hospital by ambulance. Upon presentation to the trauma center, the patient’s sole complaint was moderate pain in the right jaw area. Tenderness and moderate swelling were noted at the site of pain, along with some ecchymosis. Trauma surveys did not reveal any airway compromise, hemodynamic instability, or distracting injuries. A computed tomography (CT) of the head, face, and neck was obtained. In addition to the routine noncontrasted trauma examination, a contrasted study was obtained to rule out vascular injury. Soon after emerging from the scanner (which was between 1 and 2 hours after the crash), the patient experienced progressive difficulty swallowing and breathing. He was promptly intubated for airway protection. Otolaryngology consultation was then sought.

Physical examination at this stage identified moderate swelling of the right submandibular area with fullness in the floor of mouth. There were no signs of skin or mucosal penetration, airway disruption, or bony injury. Vascular injury could not be ruled out clinically at this point, and cranial nerve examination was limited due to sedation and neuromuscular blockade. An endotracheal tube and cervical collar were in place.

The scans confirmed an intact facial skeleton and cervical vessels but revealed disruption of the right SMG with associated edema of the floor of mouth and neck ( Fig. 1 ). The glandular injury was not well visualized on the noncontrasted images ( Fig. 2 ).

Neck CT with intravenous contrast. (A) Axial view. (B) Coronal view.

Neck CT without intravenous contrast. (A) Axial view. (B) Coronal view.

The patient was managed with serial examinations and prophylactic antibiotics to cover salivary soilage. With this conservative approach, the swelling improved such that the patient was extubated on hospital day 2 and discharged home on day 3. One week later, the patient had residual swelling in the right submandibular area, although this was much improved since discharge from hospital. Although palpation of the gland elicited mild tenderness, it also caused saliva to flow from the submandibular duct orifice, suggesting integrity of Wharton’s duct. Cranial nerve examination was normal, specifically with regard to the motor and sensory functions of the tongue. Four months later, the patient was in his preinjury state of health, with no evidence of sequelae from his submandibular gland injury.

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Discussion

Most clinically significant salivary gland injuries involve the parotid because the submandibular gland has a relatively protected position inside the mandibular arch. Stabbings, shootings, and iatrogenic factors have all been implicated in penetrating SMG injuries . The few published cases of blunt SMG trauma involved mechanisms related to MVCs. Roebker reported an unrestrained driver whose head hit the windshield and who presented 12 hours later with trouble swallowing, neck pain, and a growing mass. Tonerini described a driver of unknown restraint status whose neck hit the steering wheel and who presented 10 hours later with trouble swallowing, neck pain, and a growing mass. Boyd told of an unrestrained driver whose neck hit the airbag and who was brought to hospital by ambulance with painful swallowing, neck pain and swelling, and difficulty opening the jaw. Our patient was a restrained passenger whose neck was in contact with an obliquely oriented shoulder strap. Likely, the SMG was compressed between the strap and the cervical vertebrae, leading to gland rupture. To our knowledge, this is the first reported case of SMG injury caused by a seat belt.

The evaluation of the patient presenting with blunt neck trauma requires an organized, prompt approach. It is important to get a history whenever possible. Important information to obtain includes mechanism and timing of injury, other associated injuries that may be present, and presence of any evolving symptoms or changes. Interestingly, all the cases of blunt SMG trauma occurred in low to moderate speed crashes, had variable delays in seeking medical attention, and had no other injuries. The common symptoms of SMG rupture include painful swelling below the angle of the mandible, dysphagia, and if severe, respiratory difficulties. These may all be delayed in onset.

The examination of the patient should include a detailed inspection of the gland and surrounding tissues, including overlying skin, oral mucosa, and teeth. Palpation of nearby bony structures, especially the mandible, may reveal collateral injuries. Testing of the tongue’s taste sensation and mobility are important because the lingual and hypoglossal nerves lie near the gland. The marginal mandibular branch of the facial nerve is also at risk and should be evaluated. It is also important to assess the integrity of Wharton’s duct. This can be done by massaging the gland and observing pooling or by probing the duct with a lacrimal probe or silastic catheter. Injury to the SMG may occur with vascular damage as well. This may be obvious in the presence of a hematoma or hemorrhage, but a more subtle pseudoaneurysm may be found by auscultation of a bruit.

The diagnosis of gland injury is usually made radiographically. There are a number of available modalities, but the urgency of evaluation and associated injuries should be considered in any imaging choice. Although magnetic resonance imaging has been regarded as the gold standard for imaging parenchymal neoplasms, its use in the acute situation may be somewhat limited. Computed tomography, with and without contrast, is the preferred modality of most authors. It can be performed more quickly than MRI that is of obvious value when an evolving airway is of concern. It also offers the advantage of visualizing the surrounding bony structures well, of which integrity should always be assessed. Computed tomography can usually provide adequate visualization of the vasculature and soft tissues, provided intravenous contrast is used. The associated CT findings include inflammation, edema, and fat stranding . In the presence of hemorrhage, the precontrast CT is especially helpful and will show increased attenuation in the region of the gland, whereas in the postcontrast images, the hemorrhage may be hard to distinguish from the glandular parenchyma . It is worth noting that in the trauma setting, the face and head are primarily imaged without contrast. Our patient received a contrasted scan because the mechanism of injury raised concern for vascular involvement. This proved key to making the diagnosis because the glandular rupture was not well visualized on the unenhanced images (Fig. 2 ). Lastly, sialography can be used to assess the ductal system, although it poses the risk of infection.

The management of SMG trauma starts with assessment and protection of the airway. As seen with our patient, progressive submandibular swelling can lead to delayed airway compromise in what seemed initially to be a nonserious injury. Although the present case had a delayed airway embarrassment on the order of 1 to 2 hours after the injury, existing reports of blunt SMG trauma describe progression of swelling up to 36 hours after the injury . We propose that the period of airway observation should encompass this time frame, especially if intubation is withheld. Beyond attending to the airway, there is no strong evidence with regard to managing blunt SMG injuries because they are so rare. There is agreement among the few available reports that a good outcome can be achieved with careful observation and perhaps a short course of antibiotics. Whereas sialoceles and salivary fistulae have occurred after penetrating SMG trauma and certainly after parotid injuries, there are no reports of long-term complication from blunt SMG insults. If a complication were to occur, the management strategies that apply to the parotid could be adapted to the SMG. These include aspiration and pressure dressing in the case of a sialocele and duct reanastomosis, ligation, or rerouting in the case of a fistula. Although parotidectomy is often reserved as a last resort, submandibular gland excision could be considered earlier given its lower risk of damage to nearby structures.

In conclusion, isolated blunt injury to the submandibular gland is rare, and MVCs are the primary cause. Unquestionably, seat belts reduce the morbidity and mortality of MVCs; however, the shoulder strap can cause SMG rupture leading to delayed airway compromise, even when the patient’s initial complaint seems minor and the facial skeleton is intact. The CT evaluation—with and without contrast—is the most useful diagnostic tool, and close airway monitoring is essential. Spontaneous resolution is expected with conservative management.