Mediastinitis is

inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...

of the tissues in the mid-chest, or

mediastinum The mediastinum (from ) is the central compartment of the thoracic cavity. Surrounded by loose connective tissue, it is an undelineated region that contains a group of structures within the thorax, namely the heart and its vessels, the esophagu ...

. It can be either

acute Acute may refer to: Science and technology * Acute angle ** Acute triangle ** Acute, a leaf shape in the glossary of leaf morphology * Acute (medicine), a disease that it is of short duration and of recent onset. ** Acute toxicity, the adverse eff ...

or chronic. It is thought to be due to four different etiologies: * direct contamination *

hematogenous Bloodstream infections (BSIs), which include bacteremias when the infections are bacterial and fungemias when the infections are fungal, are infections present in the blood. Blood is normally a sterile environment, so the detection of micro ...

lymphatic Lymph (from Latin, , meaning "water") is the fluid that flows through the lymphatic system, a system composed of lymph vessels (channels) and intervening lymph nodes whose function, like the venous system, is to return fluid from the tissues to ...

spread * extension of infection from the neck or

retroperitoneum The retroperitoneal space (retroperitoneum) is the anatomical space (sometimes a potential space) behind (''retro'') the peritoneum. It has no specific delineating anatomical structures. Organs are retroperitoneal if they have peritoneum on their ...

* extension from the lung or pleura Acute mediastinitis is usually caused by bacteria and is most often due to perforation of the esophagus. As the infection can progress rapidly, this is considered a serious condition. Chronic

sclerosing Sclerotherapy (the word reflects the Greek ''skleros'', meaning ''hard'') is a procedure used to treat blood vessel malformations ( vascular malformations) and also malformations of the lymphatic system. A medicine is injected into the vessels, ...

(or fibrosing) mediastinitis, while potentially serious, is caused by a long-standing inflammation of the mediastinum, leading to growth of acellular collagen and fibrous tissue within the chest and around the central vessels and airways. It has a different cause, treatment, and prognosis than acute infectious mediastinitis. Space infections: Pretracheal space – lies anterior to trachea. Pretracheal space infection leads to mediastinitis. Here, the fascia fuses with the pericardium and the parietal pleura, which explains the occurrence of

empyema An empyema () is a collection or gathering of pus within a naturally existing anatomical cavity. For example, pleural empyema is empyema of the pleural cavity. It must be differentiated from an abscess, which is a collection of pus in a newly fo ...

and

pericardial effusion A pericardial effusion is an abnormal accumulation of fluid in the pericardial cavity. The pericardium is a two-part membrane surrounding the heart: the outer fibrous connective membrane and an inner two-layered serous membrane. The two layers of t ...

in mediastinitis. However, infectious of other spaces can also lead to mediastinitis.

Symptoms

Acute

Acute mediastinitis is an

infectious An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...

process and can cause fever, chills,

tachycardia Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults. Heart rates above the resting rate may be normal (su ...

. Pain can occur with mediastinitis but the location of the pain depends on which part of the mediastinum is involved. When the upper mediastinum is involved, the pain is typically retro-sternal pain. When the lower mediastinum is involved, pain can be located between in the

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eithe ...

e and radiate around to the chest.

Chronic

Symptoms depend on what organs of the mediastinum the disease is affecting. They might be caused by a constricted airway, constricted esophagus, or constricted blood vessels. Symptoms also depend on how mush fibrosis has occurred. There may be cough, shortness of breath, coughing up blood, pain in the chest, and difficulty in swallowing.

Causes

Acute

CT scan of a patient with Descending Necrotizing Mediastinitis

Esophageal perforation, a form of direct contamination, accounts for 90% of acute mediastinal infections. Esophageal perforation can arise from vomiting, incidental trauma from a procedure or operation, external trauma, ingestion of corrosive substances, malignancy, or other esophageal disease. Other causes of acute mediastinitis include infection secondary to cervical disease which arises from dental procedures, skin infections of the neck, neck trauma, or neck procedures. Descending necrotizing mediastinitis (DNM) was first described by Herman E. Pearse Jr., M.D. in 1938 and he stated, "the term 'mediastinitis' means little unless qualified by a description of its type and kind." Although Descending Necrotizing Mediastinitis is an acute mediastinitis, it is distinct because it does not originate from structures within the mediastinum. Therefore, the term Descending Necrotizing Mediastinitis implies that the infection of the mediastinum originated from a primary site in the head or neck and descended through fascial spaces into the mediastinum. Though rare in developed countries, acute mediastinitis can be caused by inhalation of bacterial spores such as

Anthrax Anthrax is an infection caused by the bacterium ''Bacillus anthracis''. It can occur in four forms: skin, lungs, intestinal, and injection. Symptom onset occurs between one day and more than two months after the infection is contracted. The sk ...

. Historically, this infection was referred to as ''Wool-sorter's Disease''. In the lungs, spores can spread via lymphatics to mediastinal lymph nodes, where the mature rods can release exotoxins promoting edema and tissue necrosis. Clinically, persons infected with anthrax can develop a hemorrhagic mediastinitis, which manifests as acute pulmonary hemorrhage and meningitis. Hallmark finding of disease is a widened mediastinum visualized on chest x-ray. Once clinical symptoms of anthrax induced mediastinitis appear, disease is nearly 100% fatal. Individuals with known exposure to spores may be treated prophylactically with antibiotics (fluoroquinolones or tetracycline) to prevent disease progression.

Chronic

There are two types of fibrosing mediastinitis: granulomatous and non-granulomatous.

Granuloma A granuloma is an aggregation of macrophages that forms in response to chronic inflammation. This occurs when the immune system attempts to isolate foreign substances that it is otherwise unable to eliminate. Such substances include infectious ...

tous mediastinitis is due to a granulomatous process of the mediastinal lymph nodes leading to fibrosis and chronic abscesses in the mediastinum. The most common causes are

histoplasmosis Histoplasmosis is a fungal infection caused by ''Histoplasma capsulatum''. Symptoms of this infection vary greatly, but the disease affects primarily the lungs. Occasionally, other organs are affected; called disseminated histoplasmosis, it can ...

and

tuberculosis Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in ...

infections. Non-granulomatous fibrosing mediastinitis is caused by an idiopathic reaction to drugs and

radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...

therapy. Autoimmune disease and Behcet's disease are also causes.

Etiology

An observational retrospective study of 17 patients diagnosed with DNM found that the infections most often originated from neck infections including tonsillar abscess,

pharyngitis Pharyngitis is inflammation of the back of the throat, known as the pharynx. It typically results in a sore throat and fever. Other symptoms may include a Rhinorrhea, runny nose, cough, headache, difficulty swallowing, swollen lymph nodes, and a ...

, and

epiglottitis Epiglottitis is the inflammation of the epiglottis—the flap at the base of the tongue that prevents food entering the trachea (windpipe). Symptoms are usually rapid in onset and include trouble swallowing which can result in drooling, changes t ...

. The study also found that most infections are poly-microbial. Often the culprits are usually

Gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bacte ...

bacteria and

anaerobes An anaerobic organism or anaerobe is any organism that does not require molecular oxygen for growth. It may react negatively or even die if free oxygen is present. In contrast, an aerobic organism (aerobe) is an organism that requires an oxygenate ...

, though rarely,

Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall ...

bacteria are also present. This severe form represents 20% of acute mediastinitis cases.

Diagnosis

Acute

Acute mediastinitis can be confirmed by contrast

x-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

s since most cases of acute mediastinitis are due to esophageal perforation. Other studies that can be used include endoscopic visualization, Chest CT scan with oral and intravenous contrast. With regards to CT Imaging, the extent of involvement of the mediastinum can be evaluated. Therefore, acute mediastinitis can be classified into three categories: # diffuse mediastinitis # isolated mediastinal abscess # mediastinitis or mediastinal abscess complicated by empyema or subphrenic abscess.

Chronic

Most cases of granulomatous mediastinitis (75%) are incidentally found on chest x-rays which show a mediastinal mass, or widening of the mediastinum.

Treatment

Treatment for acute mediastinitis usually involves aggressive intravenous antibiotic therapy and hydration. If discrete fluid collections or grossly infected tissue have formed (such as abscesses), they may have to be surgically drained or debrided. Treatment for DNM usually requires an operation to remove and drain infected necrotic tissue. Broad spectrum intravenous antibiotics are also given to treat the infection. Patients are typically managed in the intensive care unit due to the severity of the disease. Treatment for chronic fibrosing mediastinitis is somewhat controversial, and may include steroids or surgical decompression of affected vessels.

Prognosis

Fibrosing mediastinitis can lead to entrapment of mediastinal structures. The mortality of DNM ranges from 10 to 40% due to

sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...

and multi-organ failure if not recognized and intervened upon early.

References

External links

* {{Respiratory pathology Respiratory diseases Thorax (human anatomy) IgG4-related disease