Orris

Superior mediastinum and applied aspects

Reading File
Finding Sources
Finding Sources
Searching PubMed

mediastinum anatomy

Searching the Web

superior mediastinum anatomy contents clinical applied anatomy

Searching Images

superior mediastinum anatomical diagram contents

The composite image illustrates an open surgical approach for accessing the proximal right subclavian vasculature. The top section is a clinical photograph showing a median sternotomy coupled with a right supraclavicular transverse incision. A heavy-duty sternal retractor is in place, widely separating the divided sternum to expose the superior mediastinum. The surgical field reveals transected cervical musculature (sternocleidomastoid and anterior scalene muscles) and various surgical instruments, including forceps and clamps, providing exposure to the innominate and subclavian vessels. The lower section is a corresponding anatomical diagram depicting the median sternotomy approach. The diagram shows the positioning of the sternal retractor and the resulting visibility of the mediastinal contents, including the heart and the great vessels. Together, these images demonstrate the specific surgical trajectory and anatomical landmarks required to achieve proximal control and repair of a transected right subclavian artery following blunt trauma.

The composite image illustrates an open surgical approach for accessing the proximal right subclavian vasculature. The top section is a clinical photograph showing a median sternotomy coupled with a right supraclavicular transverse incision. A heavy-duty sternal retractor is in place, widely separating the divided sternum to expose the superior mediastinum. The surgical field reveals transected cervical musculature (sternocleidomastoid and anterior scalene muscles) and various surgical instruments, including forceps and clamps, providing exposure to the innominate and subclavian vessels. The lower section is a corresponding anatomical diagram depicting the median sternotomy approach. The diagram shows the positioning of the sternal retractor and the resulting visibility of the mediastinal contents, including the heart and the great vessels. Together, these images demonstrate the specific surgical trajectory and anatomical landmarks required to achieve proximal control and repair of a transected right subclavian artery following blunt trauma.

Reading File
Reading File
Reading Web Page

https://www.ncbi.nlm.nih.gov/books/NBK539819

Superior mediastinum

The superior mediastinum is the upper part of the mediastinum. It acts as a passage between the neck and thorax for major blood vessels, nerves, airway, food passage, and lymphatics.

Boundaries

BoundaryDescription
SuperiorThoracic inlet, an oblique plane from the jugular notch to the upper border of T1
InferiorTransverse thoracic plane from sternal angle to the T4-T5 intervertebral disc
AnteriorManubrium sterni
PosteriorBodies of T1-T4 vertebrae
LateralMediastinal pleura on each side
It is continuous with the neck above and the inferior mediastinum below. The sternal angle is an important surface landmark because it marks the plane separating superior from inferior mediastinum. Gray's Anatomy for Students, p. 252.

Contents

The contents can be recalled from anterior to posterior:
  1. Thymus or its fatty remnant in adults
  2. Veins
    • Right and left brachiocephalic veins
    • Upper half of superior vena cava
    • Arch of azygos vein entering the SVC
    • Left superior intercostal vein
  3. Arteries
    • Arch of aorta
    • Its branches, from right to left:
      • Brachiocephalic trunk
      • Left common carotid artery
      • Left subclavian artery
  4. Nerves
    • Right and left phrenic nerves
    • Right and left vagus nerves
    • Left recurrent laryngeal nerve
    • Cardiac nerves and cardiac plexus
  5. Trachea
  6. Oesophagus
  7. Thoracic duct and mediastinal lymph nodes
A useful order is: Thymus - Veins - Arteries - Nerves - Trachea - Oesophagus - Thoracic duct.
Diagram of structures in the superior mediastinum

Important relations

  • The left brachiocephalic vein crosses obliquely from left to right, anterior to the branches of the aortic arch.
  • The arch of aorta passes upward, backward, and to the left over the root of the left lung.
  • The left vagus nerve crosses the left side of the arch of aorta.
  • The left recurrent laryngeal nerve hooks under the arch of aorta, just posterolateral to the ligamentum arteriosum, then ascends in the tracheo-oesophageal groove.
  • The right vagus passes posterior to the root of the right lung, while the left vagus passes posterior to the root of the left lung.
  • Both phrenic nerves pass anterior to the root of the lung.
  • The trachea lies anterior to the oesophagus.
  • The thoracic duct ascends into the superior mediastinum on the left and terminates at the left venous angle.
The anterior-to-posterior arrangement is thymus, brachiocephalic veins/SVC, aortic arch, trachea, oesophagus, and lymphatic trunks. Fischer's Mastery of Surgery, p. 2511.

Applied anatomy

1. Superior mediastinal syndrome

A mass, enlarged lymph nodes, retrosternal goitre, lymphoma, thymoma, or aneurysm may compress structures in this confined space.
Compressed structureClinical feature
Superior vena cavaFacial and upper-limb swelling, cyanosis, dilated superficial veins over chest wall, headache
TracheaDyspnoea, stridor, cough
OesophagusDysphagia
Recurrent laryngeal nerveHoarseness due to ipsilateral vocal-cord paralysis, usually left-sided
Phrenic nerveRaised hemidiaphragm and dyspnoea from diaphragmatic palsy
Sympathetic chain, if extension occursHorner syndrome

2. Aortic arch aneurysm

An aneurysm of the arch of aorta may compress:
  • Left recurrent laryngeal nerve causing hoarseness, known as Ortner syndrome
  • Trachea causing cough, wheeze, or stridor
  • Oesophagus causing dysphagia
  • Left main bronchus in larger aneurysms

3. Left recurrent laryngeal nerve palsy

The left recurrent laryngeal nerve is especially vulnerable because it loops under the aortic arch. Hoarseness can therefore be a presentation of:
  • Aortic arch aneurysm
  • Enlarged mediastinal lymph nodes
  • Bronchogenic carcinoma
  • Left atrial enlargement or other cardiovascular enlargement

4. Retrosternal goitre

An enlarged thyroid may extend through the thoracic inlet into the superior mediastinum and compress the trachea, oesophagus, or great veins. It may present with positional dyspnoea, stridor, dysphagia, or SVC obstruction.

5. Thymic lesions

The thymus lies anteriorly in the superior mediastinum. Thymoma is classically associated with myasthenia gravis. Thymic enlargement or tumour may cause local pressure symptoms.

6. Central venous access

During internal jugular or subclavian venous catheterization, the catheter passes through the brachiocephalic vein into the SVC. Knowledge of the long, oblique course of the left brachiocephalic vein helps explain why left-sided central venous access can be technically more difficult.

7. Mediastinal widening on chest radiograph

Widening of the superior mediastinal shadow may result from:
  • Aortic aneurysm or dissection
  • Mediastinal haemorrhage after trauma
  • Retrosternal goitre
  • Lymphadenopathy
  • Mediastinal tumour
Because it contains great vessels, airway, and major nerves, trauma or penetrating injury in this region can be rapidly life-threatening, as summarized in the NCBI mediastinum anatomy review.
This is a shared conversation. Sign in to Orris to start your own chat.