Volume 7, Case 10
Orn-Usa Lisa Boonprakong, Medical Student
Loren G. Yamamoto, MD, MPH
Kapiolani Medical Center For Women And Children
University of Hawaii John A. Burns School of Medicine
This is an 8 month old male who was in his usual state of health until 2 weeks ago when he developed fever (38 to 39 degrees C), intermittent cough, congestion, and increased secretions. He was treated with antibiotics by his primary care physician. One week ago, he developed hives with wheezing, stridor and tachypnea. He was treated with albuterol and prednisolone with subsequent relief. Three days ago, he then developed a dry cough, shallow respirations, and apparent stiffness of his neck with an inability to straighten his neck or bring his head to midline. He was most comfortable in the position of being upright or lying on his side. Gradually, his respirations became "noisy and gurgly". He now presents to a rural emergency department with worsening stridor. His past medical history is unremarkable.
Exam: VS T39, P120, R40, oxygen saturation 98-100% on RA. He is somewhat irritable but easily arousable and consolable, holding his neck in a solitary position. Eyes normal. Nares are clear without drainage. Tympanic membranes normal. His oral cavity is clear, with moist mucosa. The posterior pharynx is very full, with slightly enlarged tonsils bilaterally. His neck is slightly stiff with discomfort experienced on movement. There is right-sided cervical lymphadenopathy, with slight tracheal deviation to the right. Breath sounds demonstrate moderate stridor with slight coarse rhonchi. Heart regular rate and rhythm, without murmur. Abdomen is soft and flat, normal bowel sounds, no organomegaly. His extremities are warm with normal capillary refill. His skin demonstrates no rashes or lesions.
Radiographs of his chest and neck are ordered.
Can you identify the abnormalities on his radiographs.
View his chest and lateral neck radiographs.
His chest radiographs
His lateral neck radiograph
His lateral neck radiograph shows severe prevertebral soft tissue swelling with extension inferiorly. The width of the prevertebral soft tissue should normally be about half the width of a vertebral body (see Case 10 of Volume 1). In this case, it is very wide. His chest radiograph demonstrates a widened mediastinum and shift of the airway to the right.
He is intubated using rapid sequence intubation to ensure a stable airway during air transport to a children's hospital for further management. A CT scan of the chest is obtained prior to transport.
View his chest CT scan.
Scout view showing image cut levels
The CT scan demonstrates a retropharyngeal abscess that extends towards the posterior mediastinum to the level of the aortic arch. This image shows the abscess (black arrows) on cuts 8, 11, 14, 17 and 19 from his CT study. The level of these cuts are demonstrated on the scout view. At a level through his mouth, cut 8 shows the large abscess cavity which bulges anteriorly. At chin level, cut 11 shows the abscess with a typical enhancing rim. Cut 14 shows the abscess at mid-neck level. Cut 17 shows extension of the abscess into the mediastinum at the level of the lung apices. Cut 19 shows extension of the abscess into the mediastinum at the level of the upper lobes.
He was initially placed on clindamycin and cefotaxime. He underwent a surgical drainage procedure for both the retropharyngeal and mediastinal abscesses. Cultures of the pus grew Group A beta hemolytic streptococci, at which time he was changed to penicillin.
Discussion
The retropharyngeal space is a potential space in the deep neck that is bordered by the buccopharyngeal fascia anteriorly, the prevertebral fascia posteriorly, and the carotid sheath laterally. An infection developing in this space could potentially spread into the mediastinum and other deep neck compartments. In the pediatric population, this space contains lymph nodes draining the nasopharynx, paranasal sinuses, nasal cavity, and soft palate. These retropharyngeal nodes atrophy at puberty making abscess formation less likely in teens and adults.
Retropharyngeal abscesses are most commonly present in children less than 3 years of age. In the pediatric population, retropharyngeal abscesses typically result from upper respiratory infections (particularly oropharyngeal infections) with suppurative cervical lymphadenopathy, whereas in adults they normally occur secondary to trauma to the oropharynx, iatrogenic instrumentation, foreign bodies, or dental infections.
Initial antimicrobial empiric therapy is directed towards the aerobic and anaerobic flora of the nasopharynx. Common aerobes are Staphylococcus aureas, alpha hemolytic and non-hemolytic streptococci, Haemophilus species, and group A beta-hemolytic Streptococci. Common anaerobes are bacteriodes, peptostreptococci, and fusobacteria. During surgical drainage, an aspirate of the pus is obtained for specific determination of the causative microorganism(s).
Signs and symptoms include high fever, dysphagia, odynophagia, drooling, neck/cervical rigidity and swelling, anorexia, a "hot potato"/muffled voice, bulging/fluctuance of the posterior pharyngeal wall which is usually difficult to see. Dysphagia and drooling are more common indicators of actual upper airway involvement, whereas inspiratory stridor is less common.
When suspected clinically, a lateral neck radiograph is usually adequate to diagnose the presence of a retropharyngeal abscess. A true lateral neck x-ray should be taken in extension (cervical spine lordosis should be visible on the radiograph) and inspiration. The anteroposterior diameter of the prevertebral soft tissues should not exceed the width of the vertebral bodies. With a retropharyngeal abscess, a classic widened soft tissue shadow anterior to the cervical vertebrae is seen with a normal epiglottis and aryepiglottic folds.
A CT scan is diagnostically useful to distinguish between abscess (requiring surgical drainage) and a phlegmon cellulitis (which may not require surgical drainage), indicating the extent of abscess involvement, localizing the lesion prior to surgical intervention, and to differentiate which deep neck spaces are involved (see Case 1 of Volume 5).
Retropharyngeal abscess is in the differential diagnosis of a febrile infant with airway obstruction. Usually a high index of suspicion is needed to identify a child with a retropharyngeal abscess. The presentation of a stiff neck can initially be misdiagnosed as meningitis, and inspiratory stridor may mimic croup or epiglottitis.
Treatment of a retropharyngeal abscess requiers the maintainance of a stable airway, thus, endotracheal intubation may be necessary if airway compromise is present. IV antibiotics are required. Surgical drainage is usually required in a true abscess. Perioral drainage is normally adequate for uncomplicated infections that have not entered other deep neck spaces or affected the airway. External drainage, along the anterior aspect of the sternocleidomastoid, between the carotid sheath and inferior constrictor muscle, is usually required for the more severe infections that have spread to other compartments. Antibiotics should initially cover the common microbes (i.e. streptococci, staph aureus, anaerobes).
Complications include mediastinitis and mediastinal abscess secondary to spread from the retropharyngeal space (being contiguous with the mediastinum), airway obstruction, and rupture of the abscess with potential aspiration of pus and pneumonia. Mediastinitis is a rare and life-threatening complication with a mortality rate as high as 40%. Most cases of reported suppurative mediastinitis have been secondary to esophageal perforation (traumatic or nontraumatic) and after median sternotomy.
When managing a patient with a retropharyngeal abscess, physicians should consider the possibility of this complication. Chest radiographs may be necessary to rule out mediastinal or pulmonary involvement. A CT scan will also be helpful in determining the extent of the abscess. The extension of the infection of the neck to the mediastinum has been attributed to synergistic necrotizing bacterial growth, negative intrathoracic pressure, and dependent drainage from the neck to the mediastinum. The high occurrence of mixed aerobic and anaerobic flora in retropharyngeal abscess complicated by mediastinitis may account for the necrotizing nature of this type of infection. Immediate diagnosis and surgical drainage of the retropharyngeal and mediastinal abscesses are essential for treatment.
References