Pneumomediastinum as a Complication of Oral and Maxillofacial Injuries: Report of 3 Cases and a 50-Year Systematic Review of Case Reports

Abstract

Objectives: Pneumomediastinum (PM) secondary to oromaxillofacial trauma (OMF) is a rare but well-described com- plication/pathologic finding. The aim of this study was twofold: first, to report our experience in treatment of maxillofacial trauma patients with PM, and second, to review the literature regarding the clinical features, severity, course, and management of the aforementioned complication. Material and methods: We retrospectively reviewed the medical records and charts of patients who suffered from maxillofacial trauma and treated in our hospital between September 1, 2013 and September 31, 2017. The inclusion criteria were patients with radiologically confirmed PM. In addition, the electronic databases PubMed, Scopus, and Science Direct were queried for articles reporting PM cases secondary to OMF injuries and published in English, French, and German language. Results: Three cases of PM out of 3,514 cases of craniomaxillofacial trauma were found; there were 3 male patients who presented in our emergency department with the chief complaint of cervicofacial swelling. Literature search isolated 58 selected articles and 63 cases were assessed in total; posttraumatic repeated blowing of nose was proved as most frequent triggering factor among them. Furthermore, the outcomes of review showed that thoracic pain, respiratory distress, and swallowing difficulties were not frequently reported in patients with ME due to facial trauma. Conclusions: Both our experience and the results of systematic literature review indicated that patients with PM due to OMF injuries present mild clinical course. If properly managed, this specific pathologic condition may have no further complications or relative comorbidities. The exact etiology and mechanism of PM in the context of maxillofacial injuries always needs to be identified. Radiographic, laboratory, and endoscopic examinations should be applied to rule out the more serious and frequently diagnosed aerodigestive, thoracic, and abdominal causes of PM.

Introduction

Pneumomediastinum (PM) or mediastinal emphysema (ME) is a pathologic clinical finding that denotes abnormal collection of air or gas within the mediastinal cavity. Its occurrence may be spontaneous in otherwise healthy indi- viduals or may involve various causes of either intra- or extrathoracic origin. PM can be referred as ether sponta- neous (primary) or secondary (related injury or underlying disease), depending the variety of its causes. In 1827, Laenek made the first clinical description of PM,[1] while Hamman published a case of post-partum PM combined with subcutaneous emphysema that is currently termed as Hamman’s syndrome.[2,3]

PM in the context of oromaxillofacial (OMF) trauma is a rare but well-known complication; several case reports have been published due to the involvement of facial fractures and/or orofacial lacerations in PM formation.[4,5] However, the literature currently lacks adequate informa- tion on the prevalence of PM as result of OMF injuries, as well as on frequency and severity of its presenting signs and symptoms, accompanying comorbidities, complica- tions, clinical course, and prognosis.

The purpose of this article was twofold; first, to retro- spectively report our clinical experience in management of patients with various OMF injuries that resulted in forma- tion of PM, and second, to systematically review the liter- ature regarding the clinic-epidemiological aspects of the aforementioned complication.

Material and Methods

An electronic search of PubMed, Scopus, and ScienceDirect was carried out for identifying case reports and short case series of PM or ME secondary to craniomaxillo- facial (CMF) trauma that had been published in English, German, and French from January 1, 1970 to January 1, 2020. The search included combination of the follo- wing terms “pneumomediastinum,” “mediastinal emphysema,” “cervicofacial emphysema,” “retropharyngeal emphysema,” “massive emphysema,” “facial fracture,” “orbital fracture,” “orbital trauma,” “mandibular fracture,” “zygomatic fracture,” “maxillofacial fracture,” “maxillofacial trauma,” “facial trauma,” and “facial injury.”

The study was made in accordance with Preferred Reporting Items for Systematic Reviews and Meta- Analyses (PRISMA) statement (Figure 1). First, there was removal of the duplicates, book chapters, encyclopedia texts, editorials, conference papers, and posters abstracts. Afterwards, all the titles and abstracts of the remaining 1338 results were reviewed. Publications were only included if they reported patients with a history of an intraoral and/or CMF injury that provoked emphysema in at least one of the following anatomic sites: orbit, face, neck, thorax, and mediastinum. We excluded cases of PM that either was induced spontaneously or air leakage arose from an anatomical site other than CMF complex. More- over, non-traumatic cases of PM/ME such as those resulted from tracheostomy, tonsillectomy, dental/intraoral proce- dures, orthognathic surgery, and other iatrogenic interven- tions were also not included.

Of 98 full-text articles assessed for eligibility, 57 were chosen for review and analysis. To increase the validity of clinical information derived from patients (chief complaint, symptoms, history of injury etc.), we did not also encom- pass 2 publications that involved self-induced PM in patients with either a history of psychiatric disease or in custody. References of the selected articles were checked to consider other eligible publications and ultimately 3 arti- cles were integrated for analysis too. Finally, we isolated 58 articles.

Eligible articles were evaluated independently by 2 investigators (IP and SES). Disagreements were resolved by consensus and, as necessary, involvement of a 3rd reviewer (LG). Data extracted included author and year of publication, demographics (gender, age), injury mechan- ism and pattern, presenting signs and symptoms e.g. crepi- tus, respiratory distress, chest pain, Hamman’s sign (a crunch-like sound that is best audible over the left side of the patient’s chest or retrosternum during the systole and expiration),[2] dysphagia, voice alteration, concurrent comorbidities and complications (e.g. pneumocephalus, mediastinitis, death), and therapeutic outcomes.

In addition, a retrospective search of the comprehensive clinical database of Evaggelismos General Hospital of Athens was applied to isolate patients who treated for var- ious types of oromaxillofacial injuries in our clinic; the hard-copy records of our emergency department were scru- tinized too. Special focus was laid on those patients who were diagnosed with cervicofacial emphysema and under- went radiologic chest examinations. This study was approved by the institutional review board of Evaggelismos General Hospital of Athens (protocol number 380/20-11- 2018)

Results

Concerning to our clinic’s experience, we managed between September 1, 2013 and September 31, 2017 over- all 3,514 patients who presented with different types of OMF injuries in ED. Among them, we found 13 cases (0.37%) that had been clinically diagnosed) with cervicofacial emphysema (puffy facial/ periocular swelling, crepitation on palpation). Three males of this subgroup (0.09%) were admitted or referred to our clinic due OMS injuries, and a PM was documented after clinical and radiographic exams (Figure 2, Figure 3 and Figure 4). All the patients were conservatively treated with administration of antibio- tics, oxygen administration (with a non-rebreather mask at a rate of 10-15 lt/min), corticosteroids, and analgesics. Vision abnormalities did not found, while endoscopic evaluation of esophagus, larynx, and trachea did not reveal other sources of air leakage.

In addition, the selected publications contained 61 patients (

Table 1. List of Cases.

).[4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61] One of the selected articles com- prised one which was among the 3 aforementioned identi- fied patients of our retrospective search. The overwhelming majority of them were males (87.1%, n ¼ 56) with mean age 34.9 years (median 34.5; 2 months-82 years).

The most commonly reported sign was crepitation or SE (81%), while Hamman’s sign was recorded in 14.3% of cases (

Table 2. Signs and Symptoms.

). Respiratory distress was reported in only 12.7%% of cases, whereas dysphagia and voice alteration (rhinolalia, hoarseness) was cited in 6 and 4 cases respec- tively. Among OMF injuries, bone fractures were princi- pally diagnosed in 74.6% (n ¼ 47) of cases. Within this category, maxillary sinus fractures and orbital floor and inner wall fractures were the most frequently seen pattern (

Table 3. Injuries.

). A single case of mediastinitis was recorded by Shuker et al [49] who cited a case of deep cervical infection being extended to the upper anterior mediastinum (

Table 4. Complications and Comorbidities.

.). Besides, there was 1 death reported by Gouda et al[28] and it was attributed to both blood aspiration and PM caused by isolated facial fractures. Furthermore, nasal blowing was recognized as the most common mechanism responsible for cervicofacial emphysema and PM (

Table 5. Triggering Factor.

).

Discussion

PM formation secondary to OMF injuries implies the pres- ence of cervicofacial emphysema. The responsible mechanism involves either forceful entrance of air/gas through skin or mucosal lacerations in orofacial region or exit of air via mucoperiostal tears on the fractured bones making up the walls of paranasal sinuses. From an epide- miological perspective, among 390 patients who were diag- nosed with 458 paranasal sinus fractures, traumatic surgical emphysema was identified in 29 patients (7.43%) patients[62]; however, there was no information in this pro- spective study about the prevalence of PM in this group. SE is most commonly localized in orbital cavity, whereas an orbital emphysema more frequently occurs whenever med- ial orbital wall is fractured (isolated or combined).[63]

Various factors such as vigorous nose blowing, sneeze, or cough as well as fierce blast from a compressed air- device, Valsalva maneuver, drugs inhalation, crying, vomiting, asthma crisis, and barotrauma have been found responsible to cause this mechanism.[38,64] Depending on the intensity and/or repeatability of the triggering factor, the entrapped air accumulations within cervicofacial soft tis- sues may propagate downwards to mediastinal cavity by dissecting neck fascial spaces the route of the least resis- tance. The anatomical communications of parapharyngeal space with the carotid sheath and retropharyngeal space enable this emphysema propagation .Except for OMF inju- ries, another type of head injury, i.e. comminuted mastoid process fracture, may inflict PM with the triggering mechanism of Valsalva maneuver.[65] PM is considered an acute medical condition given that patients are almost always used to visit hospital less than 24 hours from the onset of symptoms.[66] SE of the face has been observed by Von Arx et al[67] even 7 years after an orbital fracture.

Taking into account the results of this review, crepita- tion is the predominant sign among patients with PM secondary to OMS injuries. Nevertheless, clinical manifes- tations seem to differ from those of spontaneous PM. In the event of latter, the symptom of retrosternal thoracic pain is predominately seen in various studies (60-100%),[68] and is characterized by radiation to the dorsum, neck, and shoulder.[22] It may be aggravated by swallowing, coughing, deep inspiration, and clinostatism.[30] Similarly to pain, other more commonly observed symptoms may include dyspnea (up to 75%), coughing spells (up to 80%), and neck pain (up to 44%).[68] The positivity of Hamman’s sign varies among different studies of PM other than OMF inju- ries (0%-100%)[66]; this percentage was over 50% in older studies,[44] while in more recent the sign was found positive in approximately 1 out 5 patients.[69]

Voice alteration, dysphonia, aphonia, dysphagia, odyno-phagia, and rhinolalia may also be associated with PM. In some retrospective studies the prevalence of these clinical findings exceeds 20% of cases with spontaneous PM,[66,70,71] while hoarseness was present in 8% of 410 PM cases due to blunt neck or chest trauma in a systematic review.[72] Hoover et al have postulated that closed rhinolalia due to PM may be not duly appreciated by thoracic surgeons.[73] Closed rhinola- lia in the context of cervicofacial emphysema is likely to signify pneumonasopharynx and air within the retropharyn- geal space. The latter represents a potential risk of respiratory obstruction. Closed rhinolalia or “rhinolalia clausa” is char- acterized by hyponasal voice quality, which entails reduction or absence of normal resonance of nasal the nasal “m,” “n,” “ng” to be heard as their plosives “b,” “d,” and “g,” respec- tively.[74,75] Examiners should never neglect the clinical sce- nario where a subcutaneous neck emphysema combined with dysphonia, neck asymmetry, and pain upon deglutition may be result from a laryngeal fracture.[76] Five to 6 cm³ have been enough to lead to mechanical obstruction of the larynx and emergency tracheotomy or decompression.[77]

Although a CT scan is the imaging modality of choice for PM diagnosis, simple radiographs may also provide reliable evidence for entrapped air collections. A poster- oanterior chest radiography is able to suggest the diagnosis of PM providing whether an air line is seen parallel to the left hilus.[27] Other diagnostic radiological signs for PM are the “ring-around-the-artery sign” (well- defined lucency along or surrounding the right pulmonary artery on lateral chest radiographs), “Naclerio’s V sign” (V-shaped air lucency in the left lower mediastinal area), and “continuous diaphragm sign” (lucency is above the diaphragm).[64] Noteworthy, Kaneki et al[77] demonstrated that a normal radiograph is seen in up to 30%.

Management of PM is very similar to subcutaneous emphysema and is mainly conservative; surgical decom- pression may be reserved only for those rare cases where there is compression of mediastinal structures (respiratory or vascular compromise) due to large quantities of entrapped gas.[46] Bronchodilators, steroids, cough suppres- sants, decongestants, stool softeners, oxygen, and antibio- tics are used to be administrated.[78] Patients with PM should refrain from any strenuous physical activity and bed rest is warranted too. Strong recommendations are given to them to avoid coughing, nose blowing, arrest of sneezing, or performing any other maneuver that may potentially pro- duce increased air pressure within the paranasal sinuses. Hospitalization is advised for cases presented with respira- tory distress, visual disturbances, generalized facial edema and emphysema, fever, infection development, need for fracture reconstruction, overanxiety, malaise, and discom- fort. Anterior nasal packing is also suggested as a

Administration of 100% oxygen is recommended because it can accelerate gas absorption by six fold.[68] Oxy- gen induces decrease of partial pressure of blood nitrogen and, consequently, rapid resorption of subcutaneous (nitro- gen-containing) air is facilitated by creating a nitrogen incline between the enclosed air and arterial blood.[80] On the other hand, nitrous oxide during general anesthesia and devices of high pressure oxygen strongly need to be avoided.[46,81,82] Moreover, clinicians should pay attention to not perform vigorous palpation of head and neck SCEs, since such a maneuver could move the air into a deeper location such as the mediastinum.[81]

Provided that emphysematous air collections are derived from upper aerodigestive tract, pathogenic bacteria may be transferred into mediastinal cavity. The vast majority of the authors endorsed the administration of prophylactic anti- microbials to eliminate the risk of locoregional infection. Only Alix et al[25] did not prescribe antibiotics in their patient with maxillary sinus fracture and PM and ques- tioned their prophylactic use too.

Many publications underlined that PM may potentially provoke life-threatening complications such as pneu- mothorax, pneumopericardium, and mediastinitis.[21] Though rare, when a large amount of air is entrapped within the cervical fascial planes and mediastinal cavity, airway obstruction may occur due to trachea compression. Further- more, a serious subtype of PM is defined as malignant as long as it impairs venous return to the heart resulting in cardiac tamponade and cardiopulmonary collapse.[78] Severe dyspnea, dysphagia, dysphonia, retrosternal chest pain irra- diating to the arms, neck, and back, cyanosis, distended nonpulsatile jugular veins, tachycardia, hypotension, and collapse are emergent manifestations that require emergent intervention.[22] If cardiac tamponade occurs secondary to pneumopericardium, pericardial needle aspiration must be accurately applied.[83] Relevant clinical signs and symptoms hypotension may comprise distended neck veins, Hamman crunch, and muffled heart sounds. To prevent irreversible loss of vision, Linberg first proposed decompression of orbital emphysema with a syringe.[84] Accurate penetration of an air pocket can be confirmed where a blunt-tipped Atkinson needle (or sharp 22-25 gauge) joined with a syr- inge filled with normal saline (without its plunger) is inserted and bubbles are appeared within the fluid.[85]

The entrapped air is progressively absorbed and PM typically is anticipated to resolve within over a 2-to 14 day period[11]; yet, Carmicael et al[39] cited that both swelling and crepitus in a patient lasted for several weeks.

A very special form of PM occurs as a result of self- induced facial emphysema and is related to medico-legal issues. In 1950, Reading used the term “autemphysesis” to describe self-induced facial emphysema in Second World War captives who attempted to alter their facial features and their identity.[86] Indeed, they made an incision with a safety-razor blade either in the mucosal side of the cheek or in interdental gingiva of maxillary molars and, afterwards they applied the Valsalva maneuver to provoke it. Mart’ınez-Carpio et al[87] cited the forensic term “camouflaging facial emphysema” to report six cases of intimates who had carried out punctures on their upper lips by using either a sewing needle or fishbone. To achieve facial camouflaging deformation, they repeated intensively the Valsalva maneuver many times over approximately 10–15 min. Similar cases (factitious subcutaneous emphy- sema) have been documented among psychiatric patients and some of them were diagnosed with PM during radiolo- gic evaluation; consequently, clinicians should methodi- cally investigate the presence of mucosal puncture marks whether there is a suspicious case of self-infliction.[88]

Current literature does not provide complete and extended documentation about the exact period of absti- nence from air flights in case of facial fractures. According to Boyle’s law,[89] the volume and pressure of a gas are inversely proportional considering that temperature remains stable. Therefore, a potential risk arises for patients with facial emphysema or fractured walls of paranasal sinuses due to air expansion as long as the airplane ascends and cabin’s pressure decreases. A study from UK had eval- uated the recommendations of 184 oral and maxillofacial surgeons to patients with zygomatic complex fractures regarding the required post-injury period of avoidance air travels.[90] The outcomes of study did not provide evidence- based recommendations, with a significant percentage (40%) of participants did not indicate a specific time- frame.[91] Some authors have suggested 4 weeks of avoiding air for small orbital fractures with minimal displacement.[90] Due to the fact that bone callus is typically formed approx- imately 2 to 3 weeks after fracture, it can be hypothesized that structural integrity is achieved.[89]

Taking into account that the atmospheric pressure at sea level is approximately 760 mm Hg, or 1 atm absolute (ATA), Seiff mentioned that ocular problems because of orbital emphysema probably take place if there is rapid unpressur- ized ascent to 18,000 feet where the ambient pressure decreases to 0.5 ATA.[91] Yet, commercial aircraft cabins are pressurized to between 5000 and 10,000 feet. Tan-Gore et al[92] drawn the conclusion that air transports should be not consid- ered as contraindication for patients with midfacial fractures. Their retrospective study did not report orbital complications in that category of patients (n ¼ 48) who transferred to hos- pitals via aircrafts. Remarkably, Ye et al[93] published a case of a fatal exacerbation of dermatomyositis-related PM after a flight and this complication was not attributed to rapid disease progression. Even though commercial airplane cabins are pressurized at the flight altitude of 8000 ft (2438 m) or less, the authors pointed out that entrapped air/gas maintains its ability to enlarge within lung parenchyma or mediastinal cav- ity by approximately 38%. Furthermore, they advocated that PM must be an absolute contraindication for air travel simi- larly to pneumothorax

Conclusions

PM is considered as a multi-origin disorder and may con- cern several specialties. Patients, who present OMF injuries and in addition have experienced a recent episode of intense or repeated nasal blowing or vigorous sneeze, should be examined for the development of widespread emphysema extending to the mediastinal cavity. Crepitation on palpa- tion of cervicofacial region, closed rhinolalia, or symptoms such as sudden onset facial swelling, sensation of fullness of the face may represent the first clinical sign of a widespread SE. It is imperative for examiners not only to detect PM and but to accurately determine its etiology. Taking into con- sideration the history and mechanism of injury, patients with PM should undergo thorough diagnostic evaluation and be guided with appropriate instructions to eliminate further complications. Meticulous laboratory and endo- scopic examinations contribute to accurate differential diagnosis especially in patients with multiple injuries and/ or suffered from high-energy trauma. Notwithstanding that a traumatic source of air leakage in CMF region may be easily assumed during clinical examination, the likelihood of additional latent injuries in larynx, tracheobronchial tree, oesophagus, abdomen, or chest should be not disregarded. The outcomes of our experience have limitations due to the retrospective nature of our study, while many different clinicians/authors were involved in examination methods and collection of medical data for the other included cases. Within the limits of this systematic review of case reports, PM arisen from OMF injuries has very good prognosis if properly treated. It can be hypothesized that PM secondary OMF injuries have milder clinical manifestations and lower rate of complications than spontaneous PM. When the origin of the air entrance/leakage is located in OMF region, the air collections may perhaps have to “travel a long dis- tance” to produce similar clinical findings to those of PM of different etiologies.