The retropharyngeal space is bounded posterolaterally by the deep layer of the deep cervical fascia and anteriorly by the buccopharyngeal fascia (also referred to as the middle layer of the deep cervical fascia). This compartment contains lymph nodes that drain surrounding structures, specifically the nasopharynx, tonsils, adenoids, sinuses, and middle ear. Early infections are often contained by this series of fascial planes, but with progression of infection, these compartments can become overwhelmed by increasing pressure from abscess and pus formation, allowing the infection to spread across planes into nearby structures.

RPAs in children usually develop due contiguous or hematogenous spread from bacterial infections of the nasopharynx, middle ear, or (rarely) dentition. These infections are most often polymicrobial, with Staphylococcus aureus and Group A Streptococcus the most commonly isolated bacteria.^4,5 Anaerobic species are less frequently encountered but have also been cultured, particularly in cases arising from an odontogenic source.

Most Ludwig angina cases arise from an odontogenic source, particularly the first or second molar teeth (teeth numbers 19 and 30 are the most frequently reported source). Poor dentition, history of recent dental extraction, other infections of the pharynx, alcoholism, malnutrition, history of immunocompromise, poorly controlled diabetes mellitus (DM), and recent oral or maxillofacial trauma are risk factors for the development of this infection.

Ludwig angina spreads rapidly and contiguously to surrounding compartments via fascial planes. Infection most often originates in the submylohyoid space, which is divided from the sublingual space by the mylohyoid muscle. Together, these compartments form the submandibular space. When bacteria inoculates the submylohyoid region, it can spread superiorly and posteriorly into the sublingual space, causing elevation of the tongue and potential airway compromise.

Cultures from fluid aspirates usually demonstrate mixed oral flora but can vary depending on underlying risk factors, disease processes, and concomitant infections (Table 14.1). Klebsiella species are frequently present in patients with a history of alcoholism, and dental anaerobes are often cultured when the patient has a concurrent dental abscess or history of recent extraction.

Lemierre syndrome is most commonly associated with a recent history of acute pharyngitis or tonsillitis, although case reports have demonstrated other sources of infection, including otitis media, mastoiditis, sinusitis, or dental infection.³ The most common initial clinical presentation is that of a throat infection, followed by unilateral neck tenderness and swelling 4 to 12 days afterward.

F. necrophorum is the most common offending organism, with other Fusobacterium species, anaerobic Streptococci, Bacteroides species, and Klebsiella pneumoniae all being reported as causative agents. Although F. necrophorum occurs naturally in the human oropharynx, the current consensus is that Fusobacterium should always be treated as a pathogen. It is thought that infection of the oropharynx renders the mucosa more vulnerable to penetration by the bacteria, which can then exert its effects through endotoxins. There is an association between Lemierre syndrome and recent Epstein-Barr viral infection, which may represent an alteration of T cell-mediated immunity.

Regardless of how Fusobacterium and other anaerobes become invasive, once they penetrate the mucosal lining, the bacteria can migrate through lymphatics or hematogenously. F. necrophorum produces hemagglutinin, which has been shown to aggregate human platelets in vitro, resulting in intravascular coagulation and thrombocytopenia.³ Venous thrombosis first occurs in the peritonsillar veins, then extends proximally into the larger veins, and ultimately into the internal jugular vein. The release of septic emboli from the internal jugular vein can result in widespread dissemination of bacteria through septic metastases, most commonly into the pulmonary capillaries, which can present as cavitary nodules or empyema. Septic emboli can affect the joints, resulting in septic arthritis; muscles, liver and spleen, resulting in abscesses; and even the central nervous system in the form of abscesses or meningitis.