Mediastinum
Updates to Article Attributes
The mediastinum is a space in the thorax that contains a group of organs, vessels, nerves, lymphatics and their surrounding connective tissue. It lies in the midline of the chest between the pleura of each lung and extends from the sternum to the vertebral column.
Gross anatomy
The mediastinum contains all the thoracic viscera except the lungs: heart and great vessels, internal mammary vessels, proximal aspect of azygos venous system, oesophagus, trachea, phrenic nerve, cardiac nerve, supra-aortic and para-aortic bodies, thoracic duct, thymus, and mediastinal lymph nodes.
Anatomical division
Division of the mediastinum is generally conceptualized as comprising 3three or 4four compartments, depending on the schema. For example, the mediastinum can be divided into parts based on their relationship to the fibrous pericardium:
- superior mediastinum: above the upper level of the pericardium and plane of Ludwig
-
inferior mediastinum: below the plane of Ludwig
- anterior mediastinum: anterior to the pericardium
- middle mediastinum: within the pericardium
- posterior mediastinum: posterior to the pericardium 8
Historically, there have been discrepant definitions of the mediastinal compartments between medical disciplines. For example, radiologists originally used arbitrary radiologic landmarks on lateral radiographs, while surgeons considered the mediastinum according to anatomic limits encountered intraoperatively (e.g. Shields classification). In response, there have been efforts to reconcile mediastinal classification systems for consistency.2.
The more modern ITMIG classification system, developed in by a multidisciplinary group including radiologists and thoracic surgeons, relies on CT-based anatomic divisions3.3 It divides dethe mediastinum ininto three compartments with the following boundaries:
-
Pré-vascularprevascular mediastinum:-
Superior limitsuperior:thethoracic inlet -
Inferior limitinferior:thediaphragm -
Lateral limitslateral: parietal mediastinal pleura -
Posterior limitposterior: anterioraspectoaspect of the pericardium.
-
-
Visceralvisceral mediastinum:-
Superior limitsuperior: thoracic inlet -
Inferior limitinferior:thediaphragm -
Anterior limitanterior:theposterior boundaries of the prevascular compartment.
-
-
Paravertebralparavertebral mediastinum:-
Superior limitsuperior: thoracic inlet -
Inferior limitinferior:thediaphragm -
Anterior limitanterior: posterior boundaries of the visceral compartment -
Posterior limitposterior: a vertical line along the posterior margin of the chest wall at the lateral aspect of the transverse processes.
-
Pathology
Broadly, pathology that affects the mediastinum can be divided into those that result in a focal mass, or those that result in diffuse disease involving the mediastinum.
The differential diagnosis of a mediastinal mass is highly dependent on its location within the mediastinum, as this may reveal the structure of origin. Thus, there is a specific differential diagnosis for each compartment:
- thoracic inlet masses
- anterior mediastinal masses
- middle mediastinal masses
- posterior mediastinal masses
In cases where localisation is difficult due involvement of multiple compartments, the ITMIG recommends a "centre method" technique by which the central point on the axial slice where the lesion appears largest is used for localisation.3. Alternatively, a "structure displacement" technique whereby displacement of organs from adjacent compartments may be used to localise the lesion.4.
Diffuse mediastinal disease can can be separated into groups depending on whether the mediastinal disease is smooth or lobulated:
- smooth
- lobulated
Finally, air tracking into the potential mediastinal spaces (pneumomediastinum) may occur when there is rupture of an air-containing structure, penetrating injury, or may be iatrogenic.
-<p>The <strong>mediastinum</strong> is a space in the thorax that contains a group of organs, vessels, nerves, lymphatics and their surrounding <a href="/articles/connective-tissue">connective tissue</a>. It lies in the midline of the <a href="/articles/chest">chest</a> between the <a href="/articles/pleura">pleura</a> of each <a href="/articles/lung">lung</a> and extends from the <a href="/articles/sternum">sternum</a> to the <a href="/articles/vertebral-column">vertebral column</a>. </p><h4>Gross anatomy</h4><p>The mediastinum contains all the thoracic viscera except the lungs: <a href="/articles/heart_and_great_vessels">heart and great vessels</a>, <a href="/articles/internal-thoracic-artery">internal mammary vessels</a>, proximal aspect of<a href="/articles/azygos-venous-system"> azygos venous system</a>, <a href="/articles/oesophagus">oesophagus</a>, <a href="/articles/trachea">trachea</a>, <a href="/articles/phrenic-nerve">phrenic nerve</a>, <a href="/articles/cardiac-nerve">cardiac nerve</a>, supra-aortic and <a href="/articles/organ-of-zuckerkandl">para-aortic bodies</a>, <a href="/articles/thoracic-duct">thoracic duct</a>, <a href="/articles/thymus">thymus</a>, and <a href="/articles/mediastinal-lymph-nodes">mediastinal lymph nodes</a>.</p><h5>Anatomical division</h5><p>Division of the mediastinum is generally conceptualized as comprising 3 or 4 compartments, depending on the schema. For example, the mediastinum can be divided into parts based on their relationship to the fibrous <a href="/articles/pericardium">pericardium</a>:</p><ul>- +<p>The <strong>mediastinum</strong> is a space in the thorax that contains a group of organs, vessels, nerves, lymphatics and their surrounding connective tissue. It lies in the midline of the <a href="/articles/chest">chest</a> between the <a href="/articles/pleura">pleura</a> of each <a href="/articles/lung">lung</a> and extends from the <a href="/articles/sternum">sternum</a> to the <a title="Vertebral column anatomy" href="/articles/spinal-anatomy-1">vertebral column</a>. </p><h4>Gross anatomy</h4><p>The mediastinum contains all the thoracic viscera except the lungs: <a title="Heart anatomy" href="/articles/heart">heart</a> and <a title="Great vessels" href="/articles/great-vessels">great vessels</a>, <a href="/articles/internal-thoracic-artery">internal mammary vessels</a>, proximal aspect of<a href="/articles/azygos-venous-system"> azygos venous system</a>, <a href="/articles/oesophagus">oesophagus</a>, <a href="/articles/trachea">trachea</a>, <a href="/articles/phrenic-nerve">phrenic nerve</a>, <a href="/articles/cardiac-nerve">cardiac nerve</a>, supra-aortic and para-aortic bodies, <a href="/articles/thoracic-duct">thoracic duct</a>, <a href="/articles/thymus">thymus</a>, and <a title="Thoracic lymph node stations" href="/articles/thoracic-lymph-node-stations">mediastinal lymph nodes</a>.</p><h5>Anatomical division</h5><p>Division of the mediastinum is generally conceptualized as comprising three or four compartments, depending on the schema. For example, the mediastinum can be divided into parts based on their relationship to the fibrous <a href="/articles/pericardium">pericardium</a>:</p><ul>
-<a href="/articles/posterior-mediastinum">posterior mediastinum</a>: posterior to the pericardium <sup><span style="font-size:10.8333px">8</span></sup>- +<a href="/articles/posterior-mediastinum">posterior mediastinum</a>: posterior to the pericardium <sup>8</sup>
-</ul><p>Historically, there have been discrepant definitions of the mediastinal compartments between medical disciplines. For example, radiologists originally used arbitrary radiologic landmarks on lateral radiographs, while surgeons considered the mediastinum according to anatomic limits encountered intraoperatively (e.g. Shields classification). In response, there have been efforts to reconcile mediastinal classification systems for consistency.<sup>2</sup> </p><p>The more modern <a href="/articles/mediastinum-itmig-classification">ITMIG classification</a> system, developed in by a multidisciplinary group including radiologists and thoracic surgeons, relies on CT-based anatomic divisions.<sup>3 </sup>It divides de mediastinum in three compartments:</p><ul>-<li>Pré-vascular mediastinum: <ul>-<li>Superior limit: the thoracic inlet</li>-<li>Inferior limit: the diaphragm</li>-<li>Lateral limits: parietal mediastinal pleura</li>-<li>Posterior limit: anterior aspecto of the pericardium.</li>- +</ul><p>Historically, there have been discrepant definitions of the mediastinal compartments between medical disciplines. For example, radiologists originally used arbitrary radiologic landmarks on lateral radiographs, while surgeons considered the mediastinum according to anatomic limits encountered intraoperatively (e.g. Shields classification). In response, there have been efforts to reconcile mediastinal classification systems for consistency <sup>2</sup>. </p><p>The more modern <a href="/articles/mediastinum-itmig-classification">ITMIG classification</a> system, developed in by a multidisciplinary group including radiologists and thoracic surgeons, relies on CT-based anatomic divisions <sup>3</sup>.<sup> </sup>It divides the mediastinum into three compartments with the following boundaries:</p><ul>
- +<li>prevascular mediastinum: <ul>
- +<li>superior: <a title="Thoracic inlet" href="/articles/superior-thoracic-aperture">thoracic inlet</a>
- +</li>
- +<li>inferior: <a title="Diaphragm" href="/articles/diaphragm">diaphragm</a>
- +</li>
- +<li>lateral: parietal mediastinal <a title="Pleura" href="/articles/pleura">pleura</a>
- +</li>
- +<li>posterior: anterior aspect of the <a title="Pericardium" href="/articles/pericardium">pericardium</a>
- +</li>
-<li>Visceral mediastinum:<ul>-<li>Superior limit: thoracic inlet</li>-<li>Inferior limit: the diaphragm</li>-<li>Anterior limit: the posterior boundaries of the prevascular compartment.</li>- +<li>visceral mediastinum:<ul>
- +<li>superior: <a title="Thoracic inlet" href="/articles/superior-thoracic-aperture">thoracic inlet</a>
- +</li>
- +<li>inferior: <a title="Diaphragm" href="/articles/diaphragm">diaphragm</a>
- +</li>
- +<li>anterior: posterior boundaries of the prevascular compartment</li>
-<li>Paravertebral mediastinum: <ul>-<li>Superior limit: thoracic inlet</li>-<li>Inferior limit: the diaphragm </li>-<li>Anterior limit: posterior boundaries of the visceral compartment</li>-<li>Posterior limit: a vertical line along the posterior margin of the chest wall at the lateral aspect of the transverse processes. </li>- +<li>paravertebral mediastinum: <ul>
- +<li>superior: <a title="Thoracic inlet" href="/articles/superior-thoracic-aperture">thoracic inlet</a>
- +</li>
- +<li>inferior: <a title="Diaphragm" href="/articles/diaphragm">diaphragm</a>
- +</li>
- +<li>anterior: posterior boundaries of the visceral compartment</li>
- +<li>posterior: a vertical line along the posterior margin of the chest wall at the lateral aspect of the transverse processes</li>
-<li><a href="/articles/middle-mediastinal-masses">middle mediastinal masses</a></li>- +<li><a title="Middle mediastinal mass" href="/articles/middle-mediastinal-mass">middle mediastinal masses</a></li>
-</ul><p>In cases where localisation is difficult due involvement of multiple compartments, the ITMIG recommends a "centre method" technique by which the central point on the axial slice where the lesion appears largest is used for localisation.<sup>3</sup> Alternatively, a "structure displacement" technique whereby displacement of organs from adjacent compartments may be used to localise the lesion.<sup>4 </sup></p><p><a href="/articles/diffuse-mediastinal-disease">Diffuse mediastinal disease</a> can be separated into groups depending on whether the mediastinal disease is smooth or lobulated:</p><ul>- +</ul><p>In cases where localisation is difficult due involvement of multiple compartments, the ITMIG recommends a "centre method" technique by which the central point on the axial slice where the lesion appears largest is used for localisation <sup>3</sup>. Alternatively, a "structure displacement" technique whereby displacement of organs from adjacent compartments may be used to localise the lesion <sup>4</sup>.</p><p>Diffuse mediastinal disease can be separated into groups depending on whether the mediastinal disease is smooth or lobulated:</p><ul>
-<li><a href="/articles/thymic-mass">thymic mass</a></li>-<li><a href="/articles/germ-cell-neoplasm">germ cell neoplasm</a></li>-<li><a href="/articles/mediastinal-vascular-abnormality">mediastinal vascular abnormality</a></li>-<li><a href="/articles/mediastinal-neurofibromatosis">mediastinal neurofibromatosis</a></li>- +<li><a title="Thymic epithelial tumours" href="/articles/thymic-epithelial-tumours">thymic mass</a></li>
- +<li><a title="Anterior mediastinal germ cell tumor" href="/articles/anterior-mediastinal-germ-cell-tumours">germ cell neoplasm</a></li>
- +<li><a title="Congenital vascular abnormality" href="/articles/congenital-vascular-anomalies">mediastinal vascular abnormality</a></li>
- +<li>mediastinal <a title="Neurofibromatosis" href="/articles/neurofibromatosis">neurofibromatosis</a>
- +</li>