Pneumomediastinum and subcutaneous emphysema associated with temporomandibular joint surgery Robert Chuong, MD, DMD, Thomas J. Boland, MD, DMD, and Mark A. Piper, MD, DMD, St. Petersburg, Fla. MAXILLOFACIAL

SURGERY

INSTITUTE

OF FLORIDA

Pneumomediastinum may occur as a result of trauma or surgery of the head and neck. It has been reported in association with various dental procedures and with a variety of maxillofacial surgical procedures. However, this potentially life-threatening problem has not previously been reported in association with temporomandibular joint surgery. This report reviews two cases of pneumomediastinum and subcutaneous emphysema occurring in association with temporomandibular joint surgery and presents an overview of the dental and medical literature concerning this phenomenon occurring in association with injuries and treatment of the maxillofacial complex. (ORAL SURC ORAL MED ORAL PATHOL 1992;74:2-6)

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neumomediastinum is a potentially life-threatening processcaused by either infection or cardiorespiratory compromise. It has been reported in association with a variety of surgical and anesthetic procedures, and with injuries to the head and neck, chest, and abdomen. It may occur in isolation or in association with subcutaneous emphysema, prevertebral emphysema, pneumothorax, or pneumopericardium, depending on the location of the soft tissue violation, its size, and the presenceof an escapemechanism for the air through the same defect.’ To our knowledge pneumomediastinum and subcutaneous emphysema have not been reported in association with temporomandibular joint (TMJ) surgery. We report two cases discussing this association and emphasize the potentially life-threatening nature of this process and the importance of early recognition. CASEREPORT Case 1

S. C., an 18-year-old woman, was admitted for left TMJ arthroplasty. Two years earlier she had undergone bilateral diskectomiesafter failure of arthroscopic procedures.These procedureshad been performed elsewhere.Medical history was otherwise unremarkable. She had no history of previ7/12/35820

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ous trauma. Preoperative laboratory workup included a normal chemistry profile (SMA 18), complete blood cell count, and urinalysis. Becauseof the patient’s age and benign history, preoperative chest radiograph and electrocardiogram (ECG) were not obtained. Microscopic arthroplasty2 of the left TMJ was carried out uneventfully after an uncomplicated, routine nasotracheal intubation. In fact, a fiber-optic bronchoscope was used according to the routine of the anesthesiologist managing the case.Visualization was excellent throughout the induction. The surgical procedure consistedof debridement of the joint to remove scar and to contour the condyle. Standard rotary instrumentation was used. A high density Silastic implant was placed and was stabilized to the periosteum of the zygomatic arch. A surgical drain was passed percutaneously through a stab incision below the ear lobule and placed to bulb suction. The intraoperative surgical and anesthetic course was uneventful, aswas the first postoperative night. However, by the next morning the patient had retrosternal discomfort, which was exaggerated by inspiration. She also had tendernessaround the midportion of the sternum. Physical examination revealed a slightly anxious patient with stable blood pressureand pulse, no orthostatic changes,clear lung fields by auscultation, marked tenderness over the midsternum without crepitation, normal voice quality, normal peripheral pulses,absenceof jugular venous distention, unlabored respirations at a rate of 20 breaths/min, and normal auscultatory findings on cardiac examination. The surgical

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site was moderately edematousand was initially believed to be unremarkable. ECG findings were normal. Chest radiograph revealed a moderate pneumomediastinum without pneumothorax and a slight amount of cervical subcutaneous gas (Fig. 1). Subsequent clinical examination demonstrated slight crepitus in the subcutaneous tissues of the right and left sides of the neck and around the left parotid region, that is, in the region of the surgical site. The patient was given oral penicillin and oxygen by nasal cannula. The patient was advised to refrain from coughing and straining, although no sedation was used. Observation during the next 3 days with serial chest radiographs demonstrated resolution of the pneumomediastinum and cervical emphysema. Baseline arterial blood gas analysis revealed normal oxygenation and ventilation. The subsequent postoperative course was uneventful. Case 2

J. K., a 3%year-old man was initially seen for surgical evaluation of constant, severeright preauricular pain with associated ipsilateral temporal headache. He also had painful grinding and clicking sounds within the samejoint. Jaw opening was limited to 28 mm with pain. A lateral open-bite malocclusion was present. History was significant for midfacial fractures, apparently of the Le Fort I type, that were treated by closed reduction 4 years earlier. A malunion had developed,causing a malocclusion. During the weeksafter maxillomandibular fixation he noted increasing right TMJ pain and was subsequently treated by simultaneous Le Fort I osteotomy, maxillomandibular fixation, and right TMJ diskectomy and reconstruction with a Proplast-Teflon implant. These procedures were performed elsewhere. History, including absence of sinus disease and any other episodesof facial or cervical trauma, was otherwise unremarkable. Magnetic resonance imaging demonstrated marked condylar and fossaerosion with a soft tissue masssurrounding the implant. The implant appearedto be fractured. The patient was taken to the operating room for removal of the implant and of intraosseous maxillary fixation wires. He was under nasoendotracheal general anesthesia.Intubation and the entire intraoperative coursewere unremarkable. No difficulty had been noted during the passageof the endotracheal tube. Fixation wires were removed at the patient’s request becauseof periodic mucosal irritation. This part of the operation was achieved through small horizontal vestibular incisions without evidence of violation of the bony walls of the maxilla. The TMJ procedure consisted of implant removal and bone debridement through the old preauricular incision. The implant was indeed fractured, and an extensive foreign body reaction was noted. The operating microscope2was used to improve visualization. Debridement was achievedwith curettes and a large round bur. The fossa was not perforated. The immediate postoperative course was uneventful. However, approximately 8 hours after surgery, the patient noted swelling around the right eye after he sneezed.This swelling rapidly spread over the bridge of the nose to the contralateral periorbital tissues, as observedby the nursing

Fig. 1. Chest x-ray film demonstrating moderate pneumomediastinum without pneumothorax.

staff. Physical examination shortly thereafter revealed subcutaneous crepitus involving both right and left periorbital areas, and crepitus of the right parotid and submandibular regions. During the next 6 hours the subcutaneous emphysemaextended into the contralateral aspectof the neck and into both sides of the upper portion of the chest. Chest radiograph obtained shortly after onset of symptoms showed no pneumothorax or pneumomediastinum, but subsequent films demonstrated increasing volume of mediastinal and cervical subcutaneous air. Meanwhile, subcutaneous emphysema of the face becamemassive,completely occluding the palpebral fissures. The patient was intubated electively in the operating room and, under sedation, he was then observedin the intensive care unit. Otolaryngologic evaluation revealed no detectable source for the air leak, although accessthrough the ethmoid air cells or possibly through the intraoral incisions was presumed. No evidence of nasal or pharyngeal mucosal violation was noted by endoscopicexamination of the nasopharynx, hypopharynx, and tracheobronchial tree. The TMJ wound itself was unremarkable. Four days later, after slow resolution of the subcutaneous emphysema and pneumomediastinum, the patient extubated himself. He did well until approximately 24 hours later, when periorbital edema was noted around the right eye, contiguous to the TMJ surgical site and extending rapidly to include both orbital areas and the face and neck.

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Upper airway obstruction occurred rapidly, causing respiratory arrest. Rapid resuscitation by endotracheal intubation and intravenous fluid administration were accomplished. Chest radiograph revealed pneumomediastinum without pneumothorax. The patient remained hemodynamically stable and continued to breath spontaneously. Becauseof the persistent nature of the air leak, the patient was taken to the operating room later the sameday for tracheostomy and exploration of the maxillary wounds. Tracheostomy was routine. Gas clearly bubbled from the subcutaneous tissuesof the neck as the neck incision was made. Efforts were employed to express air from the subcutaneous tissuesof the neck and upper chest through this route. There was no palpable crepitus or evidence of gas escapefrom the intraoral incisions as they were opened. The anterior maxillary walls appeared to be intact. The incisions were then left open, and bilateral nasal antrostomies were completed. The patient received intravenous cefazolin, which had been initiated immediately preoperatively. The subsequenthospital course was marked by fluctuating levels of subcutaneousair around the face and neck, and variable amounts of pneumomediastinal air, as indicated by serial chest radiographs. His condition was stable throughout the hospital course with no evidence of wound, sinus, pulmonary, or mediastinal infection. Two weeksafter TMJ surgery the patient was discharged with the tracheostomy tube in place. Decannulation was achieved 2 months later. DISCUSSION As is clear from the surgical literature, pneumomediastinum can be a complication of a variety of oral and maxillofacial surgical procedures and at times may be life threatening.’ Pneumomediastinum may be associated with pneumothorax, pneumopericardium, and subcutaneous emphysema of the face, neck, and chest wall. However, it may occur in isolation, without superficial tissue involvement that would be helpful in diagnosis. Air enters the mediastinum by four possible mechanisms3%4: ( 1) through violations of the trachea, bronchus, or the esophagus directly into the mediastinum; (2) through mucosal violation of the paranasal sinuses, nose, oral cavity, or pharynx with dissection along the fascial planes of the neck; (3) through violation of the pulmonary interstitial tissues by alveolar rupture; and (4) through the retroperitoneal space through the diaphragmatic hiatuses. Anesthesic-related causes of pneumomediastinum may be caused by any of these mechanisms, with violation of the tracheobronchial, nasal, or pharyngeal mucosa being the most likely.3 Also possible is introduction of air into the mediastinum as a result of alveolar rupture caused by positive-pressure ventilation. Positive pressure can blow out the alveoli by direct intra-alveolar pressure but also by decreasing the perivascular and perialveolar pressure by impeding

venous return. Diminished venous return directly decreases cardiac output by decreasing preload. Air and other gases take the path of least resistance along the investing fascia of the bronchovascular tree to enter the mediastinum.3M6 This process may be potentiated by right mainstem bronchus intubation, which may cause overinflation of the right lung. The use of nitrous oxide can grossly increase the volume of gas-containing spaces in the body. Pneumomediastinal and subcutaneous gas collections are no exception.3’ ‘3 8 This phenomenon may lead to rapid intraoperative decompensation by decreasing venous return. Included in the differential diagnosis of intraoperative cardiopulmonary instability must be an enlarging pneumomediastinum or pneumothorax, which could impede venous return and therefore cardiac output, and by compromise of oxygenation caused by increasing right-to-left shunting. Even with a heightened level of awareness of this phenomenon, the clinician may still find pneumomediastinum difficult to diagnose intraoperatively, particularly when subcutaneous emphysema around the face and neck is absent or minimal. Pneumomediastinum and subcutaneous emphysema have been reported in association with endoscopic procedures of the upper and lower gastrointestinal tracts.9-‘3 In such circumstances air may enter the retroperitoneal space, which subsequently communicates with the mediastinum, with the fascial spaces of the neck, or with the pleural space. A variety of traumatic maxillofacial injuries have been reported in association with pneumomediastinum and subcutaneous emphysema, including fractures of the mandible,14-‘6 zygomal’~tS orbit,19 and maxilla,20‘24 and combined facial fractures.24, I5 This phenomenon has also been reported in association with gunshot injuries to the mandible,26 dental extractions,27-30 endodontic treatment,3’ and restorative dental procedures; 32-34the latter typically related to the handpiece used. Several cases occurring in association with orthognathic surgery35V39involved either the maxilla or the mandible. In all these cases air dissected along the fascial planes of the neck and subsequently into the mediastinum. Because continued ingress of air into the mediastinum may lead to hemodynamic instability, either directly or secondarily by the development of pneumothorax, particularly of the tension variety, a lifethreatening situation may develop rapidly. Therefore timely diagnosis is critical. In the urgent situation decompression may need to be established rapidly but the airway must first be secured by endotracheal intubation or tracheostomy. Surgical decompression of the mediastinum may be established by cervical me-

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diastinotomy, whereas decompression of the pleural space is achieved by tube thoracostomy. The airway itself may be compromised by cervical subcutaneous and by retropharyngeal air, and therefore must be secured in a controlled setting. Early recognition of pneumomediastinum is based on an understanding of the pathophysiology and the associated signs and symptoms of this process. The major symptom is sharp retrosternal chest pain, sometimesradiating to the back, neck, and shoulders. Dyspnea may occur and is typically most pronounced when the volume of gas accumulation is severe.Other symptoms may include swelling of the neck or face, neck pain, and dysphagia. Physical findings may include crepitation of the affected areas of skin, including possibly the chest and abdominal walls as well as the axillae and scrotum. Dulled heart sounds; diminished breath sounds if there is associated pneumothorax; and crunching sounds, so-called Hamman’s crunch, noted by ausculation of the precordium, particularly along the left sternal border between the third and sixth intercostal spaces,may be present.40 Distention of the neck veins and engorgement of the face and neck may be seen with so-called malignant pneumomediastinum, that is, when massive air entrapment occurs without a point of exit. Hypotension, tachycardia, and tachypnea may be manifestations. Analysis of arterial blood gases may reveal hypoxemia, hypercarbia, and acidemia. ECG changes may include low voltage and axis shifts4’ as well as sinus tachycardia or otherwise unexplained dysrhythmias. Diagnosis is confirmed by chest radiography. A gas shadow along the cardiac border is best visualized on an expiratory posterior-anterior film. A lateral view is necessary to visualize air around the aorta or retrosternally.3 Secondary infectious mediastinitis may occur through the site of mucosal or skin violation, depending on the mechanism of disruption, Therefore prophylactic antibiotics are appropriate. If the likely site of injury is the oral or nasal mucosal barriers or the upper gastrointestinal tract, penicillin, erythromycin, or clindamycin should be considered. If the skin is the portal to the fascial spacesof the neck, antibiotics effective against Staphylococcus should be employed. Antibiotics effective against the enteric bacteria should be employed if the lower gastrointestinal tract is the site of injury. Treatment consists largely of observation. Preservation of the airway is the primary concern, possibly with judicious use of sedativesto decreasegeneral activity and anxiety, stool softeners to limit the need for the Valsalva maneuver, antitussive agents to suppress coughing, or possibly nasal decongestants and anti-

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histamines to suppress nose blowing. Smoking must be prohibited. Administration of 100%oxygen may be considered40to increase the tendency for resorption of nitrogen by reducing its surrounding partial pressure. Oxygen toxicity must be considered. Cardiac monitoring and pulse oximetry are appropriate. Serial chest radiographs must be obtained to follow the progress of air reabsorption, to guide treatment. Pneumomediastinum and subcutaneous emphysema have not to our knowledge been reported in association with TMJ surgery. A direct pathway of dissection along the fascial planes of the neck and face is conceivable, with initiation through the parotidmasseteric fascia. Violation of the ear canal could conceivably provide the actual point of entry into these spaces,perhaps potentiated by positive-pressure ventilation by mask during emergencefrom anesthesia after extubation. In neither of these cases,however, was ear canal violation evident. In case 1 subcutaneous emphysema was noted around the left TMJ surgical site, but only after a chest radiograph, ordered because of complaints about chest pain, revealed cervical subcutaneous gas. In case 2 the recurrent facial emphysemastarted in each instance on the right, that is, ipsilateral to the site of TMJ surgery. In each case the point of entry of air was likely the nasal or pharyngeal mucosa with subsequentinvolvement of the parotid space, or conceivably air was somehowentering through the TMJ surgical sites and subsequently involving the neck and mediastinum. In both cases subcutaneous emphysema was noted initially ipsilateral to the surgical site. We report these casesto emphasizethe importance of early diagnosis and careful subsequentobservation of our patients, even young, healthy patients who undergo surgical procedures of the head and neck, including TMJ surgery, becauseunusual and potentially fatal complications such as malignant pneumomediastinum may occur. It is essential that the nursing staff, the anesthesiologist, and the surgeon not dismiss early complaints of chest discomfort as perhaps related to postanesthesiasequelaeof depolarizing muscle relaxants, and mild dyspnea or tachypnea as a manifestation of anxiety, which is a common responsein the TMJ surgical patient, particularly when the anesthetic and surgical procedures were uneventful. As in every clinical endeavor, a proper index of suspicion must be maintained in the interpretation of our patients’ postoperative complaints. REFERENCES 1. Gray JM, Hanson GC. Mediastinal emphysema: aetiology, diagnosis and treatment. Thorax 1966;21:325-32. 2. Piper MA. Microscopic disk preservation surgery of the tem-

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25. Heslop IH. Surgical emphysema of the face, neck, and upper thoracic wall associated with fracture of the facial skeleton. Br J Plast Surg 1955:8:243-5. 26. Shuker S, Hirmiz NH, Abd Al-Sada RS. Pneumomediastinum and cervical emphysema subsequent to mandibular injury associated with flare pistol shot. J Oral Maxillofac Surg 1989;47:741-4. 27. Aragon SB, Dolwick MF, Buckley S. Pneumomediastinum and subcutaneous emphysema during third molar extraction under general anesthesia. J Oral Maxillofac Surg 1986; 44:141-4. 28. Sandier CM, Libshitz HI, Marks G, et al. Pneumoperitoneum, pneumomediastinum, and pneumopericardium following dental extraction. Radiology 1979;115:539-40. 29. Rhymes R. Postextraction subcutaneous emphysema. ORAL SURG ORAL MED ORAL PATHOL

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30. Ikard RW. Pneumomediastinum after dental extraction. South Med J 1984;77:801-2. 3 1. Lloyd RE. Surgical emphysema as a complication in endodontics. Br Dent J 1975;138:393-4. 32. Hunt RB, Sakler OD. Mediastinal emphysema produced by air turbine dental drills. JAMA 1968;205:241-2. 33. Trummer MJ, Fosburg RG. Mediastinal emphysema foliowing the use of a high-speed air-turbine dental drill. Ann Thorat Surg 1970;9:378-8 1. 34. Breznick DA, Saporito JL. Iatrogenic retropharyngeal emphysema with impending airway obstruction. Arch Otolaryngol Head Neck Surg 1989:115:1367-72. 35. Piecuch JF, West RA. Spontaneous pneumomediastinum associated with orthognathic surgery. J Oral Surg 1979;48:506-8. 36. Edwards DB, Scheffer RB, Jackler I. Postoperative pneumomediastinum and pneumothorax following orthognathic surgery. J Oral Maxillofac Surg 1986;44: I 37-4 1. 37. Nannini V, Sachs SA. Mediastinal emphysema following Le Fort I osteotomy: report of a case. ORAL SURC ORAL MED ORAL PATH~L

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Pneumomediastinum and subcutaneous emphysema associated with temporomandibular joint surgery.

Pneumomediastinum may occur as a result of trauma or surgery of the head and neck. It has been reported in association with various dental procedures ...
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