Pediatric Retropharyngeal Abscess 

Retropharyngeal abscesses are deep neck space infections that can pose an immediate life-threatening emergency, with potential for airway compromise and other catastrophic complications.

In order to best understand deep space infections, knowledge of the anatomy of the fascial planes of the neck is necessary. Superficial and deep fascia layers are found in the neck. Although fascia is typically adherent to adjacent structures, potential spaces can be created when an infection intercolates between the fascial layers and creates a real space, with rapid spread of inflammation and pus in the space between the fascial planes.

The retropharyngeal space is located immediately posterior to the pharynx (nasopharynx, oropharynx, hypopharynx), larynx, and trachea. The visceral (buccopharyngeal) fascia, which surrounds the pharynx, trachea, esophagus, and thyroid, forms the anterior border of the retropharyngeal space. Bounded posteriorly by the alar fascia, the retropharyngeal space is bounded laterally by the carotid sheaths and parapharyngeal spaces. It extends superiorly to the base of the skull and inferiorly to the mediastinum at the level of the tracheal bifurcation (see image below).

Two other potential spaces (the danger space and prevertebral space) are in close proximity to the retropharyngeal space. The danger space is formed anteriorly by the alar fascia and posteriorly by the prevertebral fascia. The prevertebral space is bounded anteriorly by the prevertebral fascia and posteriorly by the longus colli muscles of the spine. The danger space extends down the mediastinum to the level of the diaphragm, whereas the prevertebral space continues to the insertion of the psoas muscles. These anatomic relationships can allow an infection of the retropharyngeal space to spread to the mediastinum, leading to potentially fatal mediastinitis.

The retropharyngeal space can become infected in two ways. Infection can either spread from a contiguous area or the space can be directly inoculated from penetrating trauma. The "classic" retropharyngeal abscess observed in pediatric patients occurs when an upper respiratory infection (URI) spreads to retropharyngeal lymph nodes, forming chains in the retropharyngeal space on either side of the superior constrictor muscle.

Sources of infection can include pharyngitis, tonsillitis, adenoiditis, adenitis, otitis, sinusitis, and other infections (ie, nasal, salivary, dental). Degeneration/suppuration of these nodes leads to abscess formation. Infectious sources (eg, osteomyelitis of the spine) also can spread directly anteriorly from the prevertebral space.

Of specific interest is the group of lateral retropharyngeal nodes at the base of the skull that bear the name of French anatomist Henri Rouviere. These Rouviere nodes are typically not of great clinical interest, but as the primary lymphatic drainage of the nasopharynx, they can become significant in cases of nasopharyngeal cancer. They are also pertinent to the discussion of retropharyngeal abscess, as they can suppurate and lead to a retropharyngeal abscess.

Penetrating trauma can also be involved in retropharyngeal space infection. Accidental lacerations are not uncommon in children who run and fall down after they have placed a sharp object in their mouths. Foreign bodies (for example, fishbones) have been implicated in penetrating trauma to the retropharyngeal space. Iatrogenic causes of inoculation to this space include instrumentation with laryngoscopy, endotracheal intubation, surgery, endoscopy, feeding tube placement, and dental injections and procedures.

Complications of retropharyngeal abscesses are secondary to mass effect, rupture of the abscess, or spread of infection. The most urgent complication involves the abscess expanding against the pharynx or trachea, causing airway compression. Rupture of the abscess can cause aspiration of pus, resulting in asphyxiation or pneumonia. The infection can spread, resulting in inflammation and destruction of adjacent tissues. Spread of the infection to the mediastinum can result in mediastinitis, purulent pericarditis and tamponade, pyopneumothorax, pleuritis, empyema, or bronchial erosion.

Spread of the infection laterally can involve the carotid sheath and cause jugular vein thrombosis or carotid artery rupture. Posterior spread of infection can result in osteomyelitis and erosion of the spinal column, causing vertebral subluxation and spinal cord injury. The infection itself can evolve into necrotizing fasciitis, sepsis, and death.

Hence, accurate and prompt treatment and intervention for presumed retropharyngeal abscess is crucial to prevent significant untoward sequelae.

Frequency

United States

Lander et al analyzed a large national database of pediatric admissions in the United States.^[1] They found 1,321 cases of retropharyngeal abscess in 2003. A large retrospective review of pediatric head and neck infections at the University of Mississippi Medical Center was published in 2006.^[2] Of the 1,010 documented pediatric head and neck infections, 26 were retropharyngeal abscesses.

International

With less access to health care and less availability of antibiotics, deep space infection is a more common complication of URI in developing nations. Pathogens not typically seen in the United States are also seen in this population (including tuberculosis) and should be considered.

A tertiary hospital in Freiburg, Germany studied deep neck infections occurring over 8 years.^[3] Of the 234 documented deep neck infections, 15 (6.4%) were retropharyngeal abscesses. Although no subgroup analysis was specifically performed for retropharyngeal abscesses, one interesting finding was a higher than expected rate of Bartonella henselae infection (Catscratch Disease) and cervical tuberculosis. The treating physician should thus consider all infectious etiologies when treating and evaluating patients with a suspected infection.

A study from India also described a socioeconomic correlation with deep neck abscesses.^[4] Most patients with retropharyngeal abscesses were of low socioeconomic status, which was theorized to contribute to the incidence of abscesses due to poor oro-dental hygiene and a lack of access to health care.

Mortality/Morbidity

When assessing a patient with a potential deep neck space infection, airway compromise should immediately be identified and addressed. Evaluation by an otolaryngologist, if possible, should be obtained. Large abscesses can compress the pharynx or trachea, causing suffocation. The abscess also can rupture, causing asphyxiation or aspiration and pneumonia. Proper positioning and avoiding unnecessary manipulation is essential. Closely monitor patients with airway compromise and do not allow these patients to leave the acute care area until deemed sufficiently stable.

Sedation and paralytics should be avoided until an airway assessment is performed because they can relax airway muscles, leading to complete obstruction. Endotracheal intubation is dangerous unless performed under direct visualization. If direct visualization is not possible secondary to trismus or anatomic distortion, consider fiberoptic intubation or a surgical airway (eg, cricothyroidotomy, tracheotomy).

Spread of infection to adjacent structures in the neck can be lethal. Carotid artery rupture has a 20-40% mortality rate. Even if the artery is successfully ligated, long-term morbidity secondary to stroke is common. Jugular vein thrombosis had a mortality rate of 60% prior to the use of antibiotics. Identifying this complication is essential. Osteomyelitis and vertebral erosion can cause subluxation and subsequent spinal cord injury. Atlantooccipital separation secondary to erosion of the transverse ligament of the atlas has been reported. These complications are rare in children in the postantibiotic era. In older children and adults, the disease spreads directly into the fascial planes and is a more deadly disease that must receive immediate surgical treatment.

Spread of infection into the chest has significant complications. Mediastinitis has a 40-50% mortality rate secondary to sepsis. Acute necrotizing mediastinitis and purulent pericarditis with tamponade can also be fatal. Mediastinal abscess, bronchial erosion, pyopneumothorax, pleuritis, and empyema also have significant morbidity and mortality.

Race

No racial predilection has been described in the literature.

Sex

Although no sex predilection has been described in the literature, several studies have noted a higher incidence of deep neck infections in boys. In a large national database, 63% of patients were male.^[1]

Age

Retropharyngeal abscess is almost exclusively a pediatric diagnosis. Most incidents occur in children aged 6 months to 6 years, with a mean age of 3-5 years.^{[1, 2, 5, 5]} Other deep neck abscesses (eg, parapharyngeal, peritonsillar) are observed more frequently in adults and older children.

In children, a retropharyngeal abscess is usually caused by an infection that spreads to the retropharyngeal lymph nodes, with subsequent cellulitis and abscess formation. Fibrosis and atrophy start in these nodes at age 4 years, and, by the time the child is aged 6 years, the retropharyngeal nodes have typically regressed.

In older patients, infection of the retropharyngeal space usually occurs from penetrating trauma or direct spread from an adjacent space.