Introduction
Background
Mediastinitis is an infection involving the mediastinum. It is a surgical emergency with a high mortality rate. Mediastinitis may begin primarily from structures in the mediastinum, or it may be the result of an infection extending downward from the oropharynx, in which case it is called descending necrotizing mediastinitis.
The criteria for the diagnosis of descending necrotizing mediastinitis include the following:
- Clinical evidence of severe oropharyngeal infection
- Characteristic radiographic features of mediastinitis
- Documentation of necrotizing mediastinal infection at operation or at postmortem
- Establishment of the relationship between the descending necrotizing mediastinitis and the oropharyngeal infection
Pathophysiology
Infection of the mediastinum is typically polymicrobial in nature resulting from a disruption of normal mucosal and tissue barriers. Infection may result from a rupture of the esophagus or trachea or from surgical intervention. When infection extends from the head and neck downward into the mediastinum, the condition is described as descending necrotizing mediastinitis because the infection uses the fascial planes in the neck to gain access to the mediastinum. It is necrotizing, as the infection is often polymicrobial in etiology with gas-producing organisms. The potential spaces that can allow infections from the head or neck to enter the mediastinum include the following:
Carotid space
The carotid sheath is a thick, matted, fibrous investment over the main longitudinal vessels of the neck. Lymph nodes are contained within the sheath, and infection in these nodes potentially could spread downward into the mediastinum. The carotid sheath extends from the arch of the aorta to the base of the skull.
Prevertebral space
This space is bounded anteriorly by the prevertebral fascia, which overlies the prevertebral muscles in the neck. The prevertebral fascia extends from the base of the skull to the lower limit of the longus colli muscle, which is approximately at the level of T3 vertebra.
Danger space
This potential space lies between the alar and prevertebral fasciae. It is patent from the skull base to the diaphragm. Its upper part is the retropharyngeal space, which lies between the prevertebral fascia and the buccopharyngeal fascia on the outer surface of the pharynx. Lymph nodes are present in this space.
Pathological walling-off of infection usually occurs in the retropharyngeal space, but no anatomical barrier exists to the spread of infection downward into the mediastinum. The lower part of this potential space extends behind the esophagus, through the superior mediastinum, and into the posterior mediastinum.
More than 90% of cases of acute mediastinitis are caused by esophageal rupture. This may be due to trauma (eg, MVA, chicken bone), neoplasm, surgery, or endoscopy. See Esophageal Perforation, Rupture and Tears for more detail on this subject.
Comorbid conditions (eg, diabetes) may make certain patients highly susceptible to spreading cellulitis. Mediastinitis may also result from direct extension from an adjacent source of infection including osteomyelitis of the sternoclavicular junction. Pulmonary infections may also extend into the mediastinal space. Mediastinitis may also result from extension of granulomatous disease from mediastinal lymph nodes.
Pathogens
This is often a mixed infection, with facultative and strict aerobes acting together. Obligate anaerobes usually outnumber facultative organisms by 10:1. Streptococcus species are the most common facultative organisms, while Bacteroides species are the most common strict aerobes. Other organisms implicated include Pseudomonas aeruginosa and species of Fusobacterium, Peptostreptococcus, and Staphylococcus. Case reports have identified Eikenella corrodens and species of Prevotella, Haemophilus, and Salmonella as responsible pathogens. Histoplasmosis and tuberculosis have also been implicated in mediastinitis. As the incidence of iatrogenic mediastinitis rises compared with infections acquired outside the hospital, methicillin-resistant Staphylococcus aureus infections become a cause for great concern.
Candidal species and even aspergillus have been implicated in cases of meningitis.
Frequency
United States
Esophageal rupture is the most common cause of mediastinitis currently. Descending necrotizing infection is relatively rare in the era of antibiotic use.
International
In developing countries, mediastinitis still is a common devastating potential complication of head and neck infections.
Mortality/Morbidity
- Data suggest an overall mortality rate of 19-47%.
- In the presence of comorbid conditions, the mortality rate for patients presenting with established infections may be as high as 67%.
- Patients often require prolonged intensive care stay and long period of recovery.
Sex
Prevalence is higher among males than females, with a male-to-female ratio of 6:1.
Age
- Mediastinitis appears to be a disease of young men with a mean age in the mid fourth decade of life.
- Most persons with mediastinitis are in their third to fifth decades of life; however, case reports have documented mediastinitis in patients as young as 2 months and as old as the eighth decade.
Clinical
History
Patients usually have experienced symptoms for a few days before presentation to the ED. Occasionally, patients present with a fulminant course and symptoms that have lasted only a few hours.
- Common symptoms and signs of patients with mediastinitis include the following:
- History of an upper respiratory tract infection or a recent dental infection (common), or thoracic surgery/instrumentation
- Fever, chills
- Pleuritic, retrosternal chest pain radiating to the neck or interscapular pain
- Shortness of breath
- Confusion
- Sore throat
- Swelling in the neck
- History may be significant for recent endoscopy, bronchoscopy, intubation, or surgery.
- Some patients are at an increased risk for mediastinitis. Obtaining the patient's medical history, which should include explicit questions about diabetes, possible immunocompromise (eg, malignancy/chemotherapy, HIV, autoimmune disease), and drug abuse, is very important.
Physical
A complete examination of the head and neck, including the oral cavity, is essential. Such an examination may yield findings such as the following:
- Ill appearance
- Fever
- Edema of the neck and face
- Crepitus of chest or neck
Causes
- Pharyngitis
- Tonsillitis
- Sinusitis
- Otitis media
- Dental infections
- Sialadenitis
- Suppurative thyroiditis
- Endotracheal intubation
- Perforation of the hypopharynx or esophagus during intubation may cause mediastinitis.
- This is particularly likely to occur if the intubation was difficult and required the use of a rigid stylet.
- Patients usually develop symptoms and signs in the immediate postintubation period, although delayed presentations are reported. Consider this complication if a patient's condition deteriorates in the postintubation period and if signs of sepsis or cardiovascular compromise are observed.
- Fibrosing mediastinitis
- This very rare entity is an excessive fibrotic reaction in the mediastinum. It is usually observed as a result of histoplasmosis or other granulomatous disease.
- Patients usually present with symptoms of compression or occlusion of mediastinal structures.
- Presenting symptoms include cough, superior vena caval obstruction, shortness of breath, chest pain, or hemoptysis.
- The onset is usually insidious.
- Other causes
- Tuberculous mediastinitis may occur after the rupture of a tuberculous lymph node into the mediastinum. The diagnosis may be difficult to make because some patients initially may have few symptoms or signs. Radiographic findings may indicate a mediastinal mass, and the diagnosis may not be made until further investigations, including an MRI, are completed.
- Mediastinitis may present as a delayed nosocomial infection following coronary artery bypass surgery.
- Fungal infection, usually caused by Candida species, is observed after cardiothoracic surgery in 0.3% of cases.
- Iatrogenic mishap following endoscopy or endoscopic ultrasonographic-guided transesophageal biopsy may be a cause.
- Ingestion of a sharp object and esophageal perforation may be a cause.
- Recently, mediastinitis has been described as a complication of laparoscopic cholecystectomy.
More on Mediastinitis |
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| Differential Diagnoses & Workup: Mediastinitis |
| Treatment & Medication: Mediastinitis |
| Follow-up: Mediastinitis |
| Multimedia: Mediastinitis |
| References |
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Further Reading
Keywords
descending necrotizing mediastinitis, oropharynx, oropharyngeal infection, mediastinum, mediastinitis, infection of the mediastinum, head and neck infection, head infection, neck infection
