What diagnosis would you suspect on the basis of the radiographic findings?

The anteroposterior radiograph shows an asymmetric soft tissue swelling of the right lateral neck and mild tracheal buckling, which does not indicate mass effect. The lateral view shows widening of the retropharyngeal soft tissues; there is also prominence of the adenoids, with narrowing of the nasopharyngeal airway. Vertebral body alignment and epiglottis, aryepiglottic folds, and glottis appear normal. No foreign body is visible.

The retropharyngeal space extends from the base of the skull to the mediastinum. It is limited anteriorly by the posterior pharyngeal wall, laterally by the carotid sheath, and posteriorly by the prevertebral fascia. Infection of the retropharyngeal space most commonly occurs in children younger than 6 years as a complication of an upper respiratory tract illness. In older children, the infection usually results from penetrating pharyngeal trauma. Retropharyngeal cellulitis progresses to phlegmon to abscess and often represents a suppurative infection of the lymph nodes (the nodes of Rouvière) that occupy the space. These nodes atrophy before puberty and drain the nasopharynx, paranasal sinuses, and middle ear. Retropharyngeal abscess is predominantly caused by Streptococcus pyogenes, Staphylococcus aureus, and respiratory anaerobes.

Retropharyngeal abscesses in children can be life- threatening. The clinical presentation varies depending on the extent of disease. Cellulitis may present similarly to pharyngitis, whereas an abscess may present with signs of airway obstruction.

The initial step in the evaluation of an infant or child with a potential deep neck space infection is assessment of the airway for obstruction. When the diagnosis is unclear, plain radiographs may be necessary. In patients with a retropharyngeal abscess, the prevertebral space is wider than twice the anteroposterior measurement of the vertebral body: greater than 7 mm at C2 or greater than 14 mm at C6. The soft tissue inflammation (phlegmon or abscess) may also reverse the normal lordotic cervical spine curvature. When suspi- cion is high, a CT scan with intravenous contrast is the preferred study to assess abscess formation and extent of disease.¹

Management includes empiric antibiotics with incision and drainage when the abscess causes imminent airway obstruction, is larger than 2 cm, or fails to resolve with antibiotic treatment alone. Exclusive antibiot- ic treatment is effective in only 25% of patients. Taking into consideration the growing prevalence of community-acquired methicillin-resistant S aureus, clindamycin is often the first-line agent of choice. Reported complications (aspiration pneumonia, carotid artery sheath or internal jugular vein infection, osteomyelitis, and necrotizing fasciitis) are rare with timely institution of therapy.

In this infant, an initial CT scan of the neck showed lymphadenopathy and phlegmon. A second CT scan, performed 3 days later because of persistent fever and neck swelling despite antibiotic treatment, showed ab- scesses in the retrophar yngeal and posterior cer vical spaces. Incision and drainage under anesthesia was performed with complete resolution.