Widened mediastinum

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Widened mediastinum
Widened mediastinum

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Varun Kumar, M.B.B.S.

Overview

A widened mediastinum is a mediastinum which measures greater than 8 cm in width on PA chest x-ray. A widened mediastinum can be indicative of life threatening conditions such as aortic dissection and esophageal rupture.

Anatomy

Causes

Common Causes

  • Anterior mediastinal mass

Causes by Organ System

Cardiovascular
Chemical / poisoning No underlying causes
Dermatologic Dermoid cyst
Drug Side Effect No underlying causes
Ear Nose Throat
Endocrine
  • Goitre, when more than 50% of the mass is located below the thoracic inlet, is termed intrathoracic goitre[1] which appear as mediastinal mass.
  • Thyroid cancer
Environmental Intrathoracic goitre
Gastroenterologic
Genetic No underlying causes
Hematologic
Iatrogenic Mediastinitis
Infectious Disease
Musculoskeletal / Ortho No underlying causes
Neurologic Mediastinal neurilemmoma may originate from right phrenic nerve[9], intrathoracic vagal nerve[10]
Nutritional / Metabolic Intrathoracic goitre
Obstetric/Gynecologic No underlying causes
Oncologic
Opthalmologic No underlying causes
Overdose / Toxicity Inhaled recreational drugs such as cocaine which induced bronschospasm, increased alveolar pressure followed by alveolar rupture leading to interstitial emphysema and pneumomediastinum[11].
Psychiatric No underlying causes
Pulmonary
Renal / Electrolyte No underlying causes
Rheum / Immune / Allergy
Sexual No underlying causes
Trauma
Urologic No underlying causes
Miscellaneous
  • Dermoid cyst is thick-walled and contains various tissue materials of skin, hair, occasionally teeth, and caseous (cheesy) substance. They are usually found in the front of the chest, but rarely are located within the pericardium. If not removed, it may get infected and rupture.
  • Supine AP chest x ray can yield a false positive "widened mediastinum".

Causes in Alphabetical Order

Diagnosis

History and Symptoms

The age of the patient can also help in narrowing down the differential in the diagnosis of a mediastinal mass in the setting of a widened mediastinum. In infants and children, it is likely that the mass will be a neurogenic tumor or an enterogenous cyst. In adults, neurogenic tumors, thymomas and thymic cysts are the most common causes. Between the ages of 20 and 40, a malignant mass should be high on the differential, as this is the age range at which Hodgkin's and non-Hodgkins lymphoma presents.

Laboratory Findings

Laboratory testing for infectious, rheumatologic, hematologic, and endocrine abnormalities, based on a thorough history and physical examination and imaging can lead to diagnosis in the remaining causes of a widened mediastinum.

Chest X Ray

To narrow the differential of a mediastinal mass in the setting of a widened mediastinum, it is useful to know in what part of the mediastinal cavity the mass is located. A mediastinal mass is first detected and evaluated on a chest radiograph. Due to an extensive differential diagnosis list for a widened mediastinum, life-threatening situations such as aortic dissection and esophageal rupture should be ruled out first.

Diagnosis in the Acute Setting

Widening of the mediastinum on the chest x ray may represent a medical emergency and the following diagnoses should be excluded immediately:

  1. Aortic dissection
  2. Esophageal rupture (Boerhaave's syndrome)

To confirm a widened mediastinum, a measurement of more than or equal to 8cm at the level of the aortic knob on a good quality plain film should be obtained.In ruling out the presence of traumatic aortic injury in a patient, a widened mediastinum is reported as having a 53% sensitivity, 59% specificity and 83% negative predictive value.

Aortic Dissection

In the evaluation of aortic dissection or aortic injury, other less sensitive signs on the chest x ray include the following:

  1. Depression of the left main-stem bronchus
  2. Deviation of the trachea or the esophagus to the right
  3. Apical pleural hematoma (also known as a pleural cap)
  4. Disruption of the calcium ring in the aortic knob (broken-halo)
  5. First and second rib fracture
  6. Obliterated aorto-pulmonary window
Esophageal Rupture

Esophageal rupture usually occurs after esophageal surgery due to injury with a surgical instrument, but can also occur due to trauma or repeated vomiting, and can be spontaneous. Initial evaluation is with a chest radiograph which will show a widened mediastinum with free air in the peritoneum. This should be followed up with contrast studies of the esophagus, and a CT scan.


Shown below is the development of a new widened mediastinum in a patient with aortic dissection


CT

If a mass is visualized on a plain radiograph, its specific location should be determined and further visualization using CT with contrast can aid in the specific diagnosis.

Multi-detector spiral CT scan has widely replaced the use of angiography for the initial evaluation of a widened mediastinum in the setting of trauma. Chest CT should be obtained even if there is a negative chest radiograph in the setting of trauma, due to the false negative appearance of a normal mediastinum despite aortic injury being present. If no periarotic mediastinal blood can be visualized on CT, then aortic injury can be ruled out. Trans-esophageal echocardiography is also a good method of imaging which has a sensitivity and specificity approaching 100%.

In the setting of a blunt deceleration trauma, disruption of the thoracic aorta can occur. This injury usually occurs at the ductus arteriosum just distal to the take-off of the left subclavian artery. Occasionally, the aorta may rupture in the ascending portion and at the take-off of the major vessels. If aortic dissection is suspected, asses for symptomatic blood pressure differences (of more that 10mmHg), pseudocoarctation syndrome or infrascapular murmur.

MRI

MRI rarely adds any additional imaging information for most mediastinal masses, however it is indicated for the evaluation of neurogenic tumors, and may also provide additional information in the evaluation of cystic lesions and vascular invasion. MRI is also useful to image a mediastinal mass in a patient with a contrast allergy or renal failure.

Ultrasound

Ultrasonographic evaluation can be useful to assess for cystic versus solid masses, in particular those that are close to the heart.

References

  1. Netterville JL, Coleman SC, Smith JC, Smith MM, Day TA, Burkey BB (1998). "Management of substernal goiter". Laryngoscope. 108 (11 Pt 1): 1611–7. PMID 9818814.
  2. MKSAP 11: Medical knowledge self-assessment program. Philadelphia: American College of Physicians, 1998:966-7.
  3. Corsten MJ, Shamji FM, Odell PF, Frederico JA, Laframboise GG, Reid KR, et al. Optimal treatment of descending necrotising mediastinitis. Thorax 1997;52:702-8.
  4. Wheatley MJ, Stirling MC, Kirsch MM, Gago O, Orringer MB. Descending necrotizing mediastinitis: transcervical drainage is not enough. Ann Thorac Surg 1990;49:780-4.
  5. Estrera AS, Landay MJ, Grisham JM, Sinn DP, Platt MR. Descending necrotizing mediastinitis. Surg Gynecol Obstet 1983;157:545-52.
  6. Alsoub H, Chacko KC. Descending necrotising mediastinitis. Postgrad Med J 1995;71:98-101.
  7. Sakamoto H, Aoki T, Kise Y, Watanabe D, Sasaki J (2000). "Descending necrotizing mediastinitis due to odontogenic infections". Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 89 (4): 412–9. PMID 10760723.
  8. 8.0 8.1 Jernigan JA, Stephens DS, Ashford DA; et al. (2001). "Bioterrorism-related inhalational anthrax: the first 10 cases reported in the United States". Emerging Infect. Dis. 7 (6): 933–44. PMID 11747719.
  9. Hirose H, Ohmori K, Nakaoka Y, Kitamura K, Muramatsu T, Namiki Y; et al. (1998). "[Mediastinal neurilemmoma originating in the right phrenic nerve: a case report]". Nihon Kokyuki Gakkai Zasshi. 36 (12): 1027–31. PMID 10064956.
  10. Ito I, Komota K, Nakajima T, Ishibashi K, Kawazoe K (1994). "[A case of mediastinal neurilemmoma originating from the intrathoracic vagal nerve]". Kyobu Geka. 47 (4): 325–7. PMID 8152184.
  11. Panacek EA, Singer AJ, Sherman BW, Prescott A, Rutherford WF (1992). "Spontaneous pneumomediastinum: clinical and natural history". Ann Emerg Med. 21 (10): 1222–7. PMID 1416301.
  12. MKSAP 11: Medical knowledge self-assessment program. Philadelphia: American College of Physicians, 1998:966-7.
  13. Corsten MJ, Shamji FM, Odell PF, Frederico JA, Laframboise GG, Reid KR, et al. Optimal treatment of descending necrotising mediastinitis. Thorax 1997;52:702-8.
  14. Wheatley MJ, Stirling MC, Kirsch MM, Gago O, Orringer MB. Descending necrotizing mediastinitis: transcervical drainage is not enough. Ann Thorac Surg 1990;49:780-4.
  15. Estrera AS, Landay MJ, Grisham JM, Sinn DP, Platt MR. Descending necrotizing mediastinitis. Surg Gynecol Obstet 1983;157:545-52.
  16. Alsoub H, Chacko KC. Descending necrotising mediastinitis. Postgrad Med J 1995;71:98-101.


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