Article, Emergency Medicine

Tracheal diverticulum masquerading as pneumomediastinum in a trauma victim

American Journal of Emergency Medicine 33 (2015) 310.e1-310.e3

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Case Report

Tracheal diverticulum masquerading as pneumomediastinum in a trauma victim

Abstract

Background: The differential diagnosis for a paratracheal air collection includes Zenker diverticulum, tracheal diverticulum, apical herniation of the lung, and pneumomediastinum. In the setting of trauma, pneumomediastinum is traditionally regarded as an alarm sign that warrants investigation for tracheal or Esophageal rupture, both highly morbid conditions.

Case report: A patient presented to the emergency department

with neck pain several hours after being involved in a low-speed, side-impact automobile collision. She was discharged with analge- sics after cervical spine radiographs showed no fracture and physical examination found no Neurological deficits. She returned 18 days later with retrosternal pain and worsening neck pain, and cervical computed tomographic scan demonstrated an abnormal paratra- cheal air collection. Follow-up chest computed tomographic scan identified a right-sided tracheal diverticulum without evidence of pneumomediastinum.

Blunt trauma to the chest is a common presenting concern in emergency patients, particularly those post Motor vehicle collisions. The diagnostic algorithm for these patients can lead to the discovery of nontraumatic abnormalities that can be misdiagnostic as traumatic in nature. Tracheal diverticula are one such finding. Tracheal diverticula are present in approximately 1% of the population. The patient we discuss demonstrated an incidental diverticulum in the setting of persistent pain following a motor vehicle collision, which was initially concerning for pneumomediastinum. The case illustrates a nonacute cause of paratracheal air and highlights the importance of using clinical judgment to guide decision making regarding advanced imaging or procedures.

A previously healthy 33-year-old woman presented to the emergency department several hours after having been a restrained driver in a low-speed, side-impact automobile collision. She com- plained only of neck pain. On examination, she was found to have mild midline and paraspinal cervical tenderness without neurological deficits. She was diagnosed with cervical strain after a radiograph showed no acute fracture or listhesis, and was discharged with analgesics and cyclobenzaprine. She subsequently received chiro- practic treatment. She returned to the emergency department 18 days later, reporting worsening pain in the left side of her neck and new retrosternal pain. A cervical spine computed tomographic (CT) scan was ordered to rule out missed fracture, and a paratracheal gas collection was visualized in the prevertebral Soft tissues anterior and to the right of T1. This focus of air appeared separate from the left- sided esophagus. Three cervical spine CT images are shown in Figs. 1 to 3, moving inferior sequentially. Note that the lung apices can be seen on Fig. 1.

This was determined to be pneumomediastinum, and a chest CT scan was then ordered for further characterization. The chest CT was read as follows: (1) “No definite evidence for pneumomediastinum” and (2) “A linear focus of air is noted along the right posterolateral aspect of the trachea … incidental tracheal diverticulum.” One image is shown in Fig. 4. Note that the paratracheal gas collection communicates with the trachea in this image.

The patient was subsequently diagnosed with tracheal diverticu- lum and then discharged with supportive care.

A tracheal diverticulum is an abnormal air- or fluid-filled paratracheal cavity that communicates with the trachea. It is an important differential diagnosis for a “paratracheal air cyst,” a somewhat vague term that refers to paratracheal air. Imaging modalities that prove connection of the cyst to the trachea are diagnostic for diverticulum [1]. Tracheal diverticula are found incidentally in about 1% of autopsies, and they can be either congenital or acquired. The acquired form is a herniation thought to arise due to high intratracheal pressure secondary to Chronic cough or lung disease. Most commonly, these form in the right side of the thoracic inlet (level T1) posterolateral to the trachea; this area lacks the external support from the esophagus and aortic arch that is present on the left [2]. Their walls contain only respiratory epithelium and lack mucous glands. Although rarely symptomatic, they can collect secretions leading to recurrent infection and chronic cough. Congen- ital diverticula are the result of altered embryonic development of the lung buds. Commonly located near the vocal cords or carina, they are generally small and narrow mouthed. Their walls contain respiratory epithelium, smooth muscle, and cartilage. Surgical treatment is possible but is rarely required for either form [3].

Pneumomediastinum occurs when gas is present in the interstitial

spaces of the mediastinum. Presenting symptoms include chest pain, dyspnea, and hoarseness [4]. Physical examination findings may include subcutaneous emphysema and Hamman sign, which is crunching sound auscultated during systole [5]. Pneumothorax is highly associated with traumatic pneumomediastinum [6], and pneumorachis can also accompany; this is probably the result of direct extension of air [7]. plain radiographs may identify pneumomediastinum, but CT imaging is much more sensitive [4,6]. Pneumomediastinum can be caused by the following: alveolar rupture with subsequent dissection of air to the mediastinum around the bronchovascular sheath (the Macklin effect); rupture or perforation of the esophagus, trachea, or bronchi; and air dissecting into the mediastinum from the neck or abdomen [8].

The Macklin effect may result from non-trauma-related events that increase intrathoracic pressure, including asthma, positive pressure ventilation, or Valsalva maneuvers [4]. In these cases, it is called spontaneous pneumomediastinum [9]. Spontaneous pneumo- mediastinum is normally a benign entity that resolves rapidly with

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310.e2 D.L. Gorgas, B. Miller / American Journal of Emergency Medicine 33 (2015) 310.e1310.e3

Fig. 1. Chest CT with paratracheal air collection (arrow).

Fig. 3. Chest CT with paratracheal air collection (arrow).

Conservative therapy consisting of oxygen, bed rest, and analgesia; mean hospital stay for spontaneous pneumomediastinum patients was 3 to 10 days in one study, and the recurrence rate was very low [10]. Pneumomediastinum has also been associated with marijuana use: Valsalva maneuvers and barotrauma secondary to Muller maneuvers (deep inspiration against resistance, encountered with use of a bong) have both been implicated [7].

In the setting of trauma, pneumomediastinum was seen in 5.2% of 1364 patients who received a thoracic CT scan: either the Macklin effect or pneumothorax with concomitant pleural tear was implicated for 89.7% of this fraction. No specific treatment was required for the pneumomediastinum in any of these cases [11]. Most cases of pneumomediastinum in the trauma patient are probably the result of abruptly increased intrathoracic pressure secondary to blunt trauma [6].

Because of its association with aerodigestive tract rupture, pneumomediastinum in the trauma patient has classically mandated investigation with esophagography and bronchoscopy [4]. This is understandable because these injuries have high mortality and usually require Surgical repair [5]. Tracheobronchial disruption can lead to acute failure of respiration or subacute atelectasis; it may

Fig. 2. Chest CT with paratracheal air collection (arrow).

result from blunt or penetrating trauma. The pathophysiology of esophageal rupture is related to bacterial and chemical mediastinitis caused by spilled contents. Esophageal rupture in the trauma patient is more commonly associated with penetrating trauma than blunt trauma. Other possible causes of esophageal perforation include traumatic instrumentation, caustic or foreign body ingestions, and forceful vomiting (Boerhaave syndrome) [12].

Due to the low sensitivity and specificity that pneumomediasti- num has for predicting aerodigestive tract rupture [4,6], several authors have proposed that esophagography and bronchoscopy need not always be performed when pneumomediastinum is found in the trauma patient [4,6,11,13]. High-resolution CT scans have very high sensitivity for detecting concerning tracheobronchial or esophageal injuries in the setting of pneumomediastinum [4]. The likelihood that traumatic pneumomediastinum is the result of life-threatening injury in children is even lower than that of adults [13]. Esophagography and bronchoscopy should be advocated though when there is High clinical suspicion for an aerodigestive cause of pneumomediastinum in trauma patients. High clinical suspicion is required for the following: mechanism of isolated blow to the neck; penetrating trauma; and presence of dyspnea, stridor, hoarseness, hemoptysis, odynophagia, or dysphagia [4,11].

It should be noted that, in the acute care setting, pneumomedias- tinum can be caused by tracheal perforation during endotracheal intubation; at least one case report describes this happening in the setting of tracheal diverticulum [14].

Fig. 4. Chest CT with paratracheal air collection (arrow).

D.L. Gorgas, B. Miller / American Journal of Emergency Medicine 33 (2015) 310.e1310.e3 310.e3

The differential diagnosis for a paratracheal air cyst imaged in the trauma patient includes pneumomediastinum and tracheal divertic- ulum. Incidental tracheal diverticulum, usually a benign finding, can be diagnosed with imaging modalities that demonstrate communi- cation with the trachea. Pneumomediastinum is also usually a benign finding; but in rare cases, it is an indicator of potentially fatal trauma. Therefore, a clinician should consider advanced diagnostics if there is specific clinical indication of an aerodigestive tract rupture in the setting of pneumomediastinum.

Diane L. Gorgas, MD?

Brian Miller, MD

Department of Emergency Medicine The Ohio State Universitys Wexner Medical Center

Columbus, Ohio

?Corresponding author.

E-mail address: [email protected] http://dx.doi.org/10.1016/j.ajem.2014.08.014

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