A retropharyngeal abscess can occur either anterior or posterior to the prevertebral fascia. An anterior location is much more common and usually results either from a penetrating injury to the posterior pharyngeal wall or from suppuration of retropharyngeal lymph nodes after an acute upper respiratory infection. This type of abscess lies between the prevertebral and pharyngobasilar fascia. The classic symptoms are painful swallowing, dyspnea, and nasal obstruction. The radiographic findings consist of marked widening of the retropharyngeal soft tissue which can compromise the adjacent airway. Small amounts of air are sometimes seen in the area of a foreign body that caused the initial injury. If not properly drained and treated with antibiotics, the infection may extend laterally into the parapharyngeal space. This is a dangerous complication because of the proximity of the carotid artery as well as other vital neural structures.
Abscesses located posterior to the prevertebral fascia are usually the result of a vertebral osteomyelitis. This location should be suspected if a soft-tissue mass is seen in association with erosion of the adjacent vertebral body. Such infections are rare, but when they occur, tuberculosis or a fungal infection such as coccidioidomycosis should be considered.