Deep neck infections are a serious but treatable group of infections affecting the deep cervical space and characterized by their rapid progression and life-threatening complications. The treatment and diagnosis of deep neck space infections have always been challenging due to their deep location, complex anatomy of this region, and unfamiliarity of physicians given its declining incidence in the post-antibiotic era. Nevertheless, these infections remain an important health problem with significant morbidity and mortality These infections can arise from a distant focus via hematogenous spread or as a consequence of local extension from tonsils, parotid glands, cervical lymph nodes, middle ear, or sinuses
Deep neck infections classically present with high fever, systemic toxicity, and local pressure effects on the respiratory, nervous, or gastrointestinal (GI) tract.
Deep neck space infections are usually polymicrobial, representing their origin from the normal flora of the oral cavity and upper respiratory tract. Most infections among adults originate from dental infections and the tonsillopharyngeal area in children. Streptococcus viridans is the most commonly identified organism causing deep neck infections. Other organisms identified include Staphylococcus aureus, gram-negative rods, anaerobes, Mycobacterium, and fungi. The presence of risk factors such as immunocompromised state, diabetes mellitus, intravenous (IV) drug use, as well as the site of origin of infection, influences the type of causative organism.
Deep neck infections account for approximately 3400 hospitalizations annually in the United States. A study using the Kids' Inpatient Database (KID) to determine the incidence of deep neck infections found that the incidence of retropharyngeal abscess increased significantly from 0.1/10,000 in 2000 to 0.22/10,000 in 2009. The incidence of peritonsillar abscess in 2009 was 0.94 cases/10,000, and that of parapharyngeal abscess was 0.14 cases/10,000.
To understand the pathophysiology of deep neck infections, clinicians should have a good understanding of the cervical compartments and interfascial spaces. The cervical fascia can be divided into the superficial and deep fascia. The superficial fascia is the subcutaneous tissue of the neck, which completely covers the head and neck. The deep fascia on the neck is divided into superficial, middle, and deep layers. The superficial layer of the deep fascia covers the submaxillary and parotid glands, the trapezius, sternocleidomastoid, and strap muscles. The middle layer encloses the vital parts of the neck including the pharynx, larynx, trachea, upper esophagus, thyroid, and parathyroid glands. The deep layer, which is also called prevertebral fascia, covers the vertebral column and muscles of the spine.
Moreover, there are 3 major fascial spaces scattered among the planes of the deep cervical fascia, each of which possesses vast clinical importance. These are submandibular, parapharyngeal, and retropharyngeal spaces. Other spaces that have the potential to host deep neck infections are the so-called “danger” space, the prevertebral space, the pre-tracheal space, the peritonsillar space, and the parotid space. There is an abundance of lymphatic tissue and several groups of lymph nodes that are located in the neck. As the deep cervical spaces are interconnected, the spread of infection from the primary source of origin and spread through lymphatic tissues can occur to deeper spaces. Host factors such as immunocompromised state, the presence of comorbid conditions such as diabetes, trauma, or instrumentation in the area can further influence the spread of infection to deeper layers.
Clinical presentation of these infections is variable based on the primary site of infection, fascial plane involved, the extent of inflammation, and presence of local pressure effects and systemic complications. Most patients present with fever and neck pain. Associated symptoms such as dental pain, dysphagia, stridor, respiratory distress can provide clues regarding the affected facial plane. Predisposing factors such as immunocompromised state, recent oral/dental procedures, recent neck or oral trauma, recent neck surgery or radiation, or presence of comorbid conditions such as diabetes should be sought.
Patients are usually febrile and may appear ill and toxic. Inspection of the neck may reveal asymmetry, redness, swelling and regional lymphadenitis. Torticollis may be present. Abscesses in this area are harder to detect due to frequent absence of fluctuance due to the taut fascia, overlying muscles, and the deep location.
Proximal deep neck infections (peritonsillar, parapharyngeal, parotid and submandibular) infections and abscesses tend to present with a sore throat and sometimes with trismus. Trismus occurs due to the local pressure on the muscles of mastication or the trigeminal nerve. A physical exam may reveal neck or lower facial swelling, local erythema, tenderness, and regional lymphadenitis. Lateral displacement of the uvula suggests peritonsillar abscess, whereas medial displacement of the pharyngeal wall is strongly suggestive of parapharyngeal space infection. Local pressure may result in dysphagia or odynophagia and may have associated inflammation in the cricoarytenoid joints. If the vagus nerve is affected, dysphonia and hoarseness can occur. Infections in the submandibular space may occur after spreading from dental abscesses, sublingual or submaxillary salivary glands or oral infections following trauma. Cellulitis in this space is also known as Ludwig’s angina that can lead to airway obstruction. Ludwig’s angina presents with drooling, inability to swallow, trismus, and induration of the floor of the mouth.
Retropharyngeal space infections are more common in children and usually are preceded by an upper respiratory infection. They often present with dysphagia, drooling and stridor and can lead to airway compromise or spread into the chest to cause mediastinitis. Infections in the danger space (located posterior to the retropharyngeal space and anterior to prevertebral space) that has loose areolar tissue facilitates the rapid spread of infection to surrounding regions and often presents with complications such as mediastinitis, empyema, and sepsis.
A complete blood count (CBC) usually shows leukocytosis, and chemistry may reveal evidence of dehydration if patient’s intake is poor. A blood culture should be obtained if the patient is septic, and cultures should be obtained of any purulent discharge in the affected region.
Plain radiography of the neck in children may suggest retropharyngeal abscess when the prevertebral soft tissue shadow is greater than 7 mm at the C2 level or greater than 14 mm at C6 level. Among adults, the soft tissue shadow is greater than 22 mm at C6 level. Additionally, plain x-rays may reveal foreign body or subcutaneous air when present. A chest x-ray is indicated if there is suspicion for mediastinitis, pneumomediastinum, or empyema.
Ultrasound is useful for relatively superficial infections to differentiate between phlegmon and abscesses but is not adequate for deep infections.
The gold standard imaging modality to diagnose the source and extent of the deep neck infection is computed tomography (CT) or magnetic resonance imaging (MRI) of the neck with intravenous contrast.
Directed antimicrobial coverage, surgical drainage for discrete abscesses and aggressive supportive care are the main management options. Empiric regimens which are based on the expected microbiology and local resistance data should be initiated and adjusted appropriately once the organism and its sensitivities become available. The choice of antimicrobial regimens for the treatment of deep neck space infections has not yet been studied in clinical trials. Intravenous nafcillin or vancomycin plus gentamycin or tobramycin combination, ampicillin/sulbactam, or clindamycin are generally accepted initial choices. For methicillin-resistant Staphylococcus aureus (MRSA) infections, vancomycin or linezolid plus cefepime (alternates are metronidazole, imipenem, meropenem, piperacillin-tazobactam) can be used. MRSA coverage must be included as part of the initial treatment regimen for patients that are at risk for MRSA carriage or infection, such as those with comorbid disease (for example, diabetes mellitus), history of intravenous drug use, and in communities or hospitals where there is a substantial incidence of MRSA. For the majority of deep neck infections especially parapharyngeal, retropharyngeal, or prevertebral space infections, antibiotic treatment should generally be continued for 2 to 3 weeks, and longer courses may be required when complications are present. Antibiotics can be switched to the oral route once there is significant clinical improvement and patient able to tolerate oral intake. Consultation with head and neck surgeons is recommended as surgical drainage may become necessary if there is no improvement after 48 hours of antibiotic therapy.
Nonetheless, in the acute setting, airway always comes first so patients with potential airway compromise from a deep neck space infection should have their airways adequately secured first and foremost. The use of glucocorticoids for symptomatic relief in patients with acute airway obstruction remains controversial and lacks supporting evidence.
Differential diagnosis of deep neck infections is variable based on presenting symptoms. Neck pain with fever can be caused by meningitis, apical pneumonia or subarachnoid hemorrhage. Acute neck pain, especially with asymmetry, can be a result of trauma causing cervical fractures/dislocations, neck muscle hematomas or neck muscle strains. Among, patients presenting with stridor, acute epiglottitis, bacterial tracheitis and croup should be considered, and for those with significant odynophagia or dysphagia, foreign body ingestion and acute esophagitis need to be considered.
Prognosis is variable depending on the immunological status of the host and severity and location of the infection. Mortality rate rates range between 1% to 25%.
Lateral pharyngeal space infections can spread tot he carotid sheath and cause septic thrombophlebitis (Lemierre syndrome) and erosion. Retropharyngeal or danger space infections can spread to the mediastinum and cause acute Mediastinitis that may further spread and cause empyema and pericarditis. Respiratory failure can occur from an obstructed airway and spread into the systemic circulation can result in sepsis and intracranial infections.
Consultation with head and neck surgeons is recommended as a good proportion of patients need surgical intervention. Specialists such as intensivists and anesthesia can also be consulted to provide airway and life support if needed.
Oral hygiene and early treatment for dental caries and dental infections can help prevent deep neck infections.