Mediastinum

The mediastinum is a central compartment in your chest, located between your lungs. It houses many vital organs and structures, including your heart, major blood vessels, windpipe (trachea), food pipe (esophagus), and thymus gland. This important space protects these organs and serves as a pathway for structures connecting different body regions.

What is the Mediastinum?

The mediastinum is a crucial space in the middle of your chest, situated between your two lungs. It contains essential organs like your heart, the large blood vessels connected to it, your windpipe (trachea), and food pipe (esophagus). This central area provides protection and a pathway for structures that extend from your neck to your abdomen.

The mediastinum is not an organ itself, but rather a flexible, central region within your chest cavity. It is bordered by the breastbone (sternum) in the front, the spine (vertebral column) in the back, and the diaphragm (the main breathing muscle) below. On each side, your lungs enclose this space. This arrangement means the mediastinum is well-protected by bone and muscle. This central chest area is further divided into two main parts: the superior (upper) mediastinum and the inferior (lower) mediastinum. The superior mediastinum is located above an imaginary line drawn from the breastbone to the fourth thoracic vertebra in the spine. It contains structures passing between the neck and the chest. The inferior mediastinum, below this line, is then subdivided into three smaller compartments: the anterior (front), middle, and posterior (back) mediastinum. The anterior mediastinum is the smallest part, located behind the breastbone. The middle mediastinum is the largest and most important subdivision, as it contains your heart, the protective sac around it (pericardium), and the roots of the great blood vessels. The posterior mediastinum is located behind the heart and in front of the spine, housing structures like the esophagus and major blood vessels.

Function

The mediastinum serves as a vital protective enclosure for many of your body's most important organs, including your heart and major blood vessels. It also acts as a crucial passageway, allowing structures like the windpipe (trachea) and food pipe (esophagus) to travel between your neck and abdomen. This central space ensures these organs are cushioned and supported.

One primary function of the mediastinum is to protect the delicate and vital organs it contains. The bony cage of the ribs, breastbone, and spine surrounds this area, offering significant physical protection against external injury. Inside this protective shell, the mediastinum holds the heart, which continuously pumps blood, and the large arteries and veins that carry blood to and from the heart. Beyond protection, the mediastinum acts as a central highway for many essential tubes and vessels. For example, the windpipe (trachea) passes through the mediastinum to reach the lungs, allowing air to enter and exit your body. Similarly, the food pipe (esophagus) travels through this space, carrying food from your throat to your stomach. Nerves that control various bodily functions also pass through the mediastinum. The loose connective tissue within the mediastinum is also important. This tissue allows the organs within the space to move and change shape as needed. For instance, your heart needs to beat freely, your lungs expand and contract during breathing, and your esophagus needs to stretch as you swallow food. This flexibility is crucial for the normal functioning of these dynamic structures.

Related conditions

Several medical conditions can affect the mediastinum, often due to its central location and the many organs it contains. These include the growth of abnormal tissue (mediastinal masses or tumors), inflammation of the space (mediastinitis), or the presence of air where it shouldn't be (pneumomediastinum). Symptoms vary depending on the specific condition and its location.

One common issue affecting the mediastinum is the development of a mediastinal mass or tumor. These can be benign (non-cancerous) or malignant (cancerous) and may originate from any of the structures within the mediastinum, such as the thymus gland, lymph nodes, or nerves. The specific location of a mass often helps doctors narrow down the possible causes. For example, masses in the anterior mediastinum are often related to the thymus, while those in the posterior mediastinum might involve nerves or the esophagus. Another condition is mediastinitis, which is inflammation of the tissues within the mediastinum. This can be a serious condition, often caused by an infection. It may occur after chest surgery, such as heart surgery, or if there is a tear in the esophagus, allowing contents to leak into the mediastinal space. Symptoms can include severe chest pain, fever, and difficulty swallowing. Pneumomediastinum occurs when air leaks into the mediastinal space. This can happen due to trauma to the chest, a severe coughing fit, or a rupture in the windpipe or esophagus. While sometimes harmless and resolving on its own, it can also indicate a more serious underlying injury. Symptoms might include chest pain, shortness of breath, or a crackling sensation under the skin of the neck or chest. Mediastinal widening, seen on a chest X-ray, is not a condition itself but a sign that the mediastinum appears broader than usual, which can be caused by various issues like tumors, enlarged lymph nodes, or bleeding.

Related tests

Diagnosing conditions affecting the mediastinum often involves various medical tests to identify the problem's nature and exact location. Common approaches include imaging studies like X-rays, CT scans, and MRI scans, which provide detailed views of the chest. Sometimes, more invasive procedures like a biopsy are needed to examine tissue samples.

When a doctor suspects a problem in the mediastinum, they will typically start with imaging tests. A chest X-ray is often the first step, as it can show if the mediastinum appears wider than normal or if there are any obvious masses. However, X-rays provide limited detail. For a more comprehensive view, a computed tomography (CT) scan is frequently used. A CT scan uses X-rays from different angles to create detailed cross-sectional images of the mediastinum and its contents, helping to pinpoint the exact location and size of any abnormalities. Magnetic resonance imaging (MRI) may also be used, especially when doctors need to differentiate between different types of soft tissues or to evaluate blood vessels without using radiation. MRI provides very detailed images that can help characterize masses or inflammation within the mediastinum. These imaging tests are crucial for planning further diagnostic steps. If imaging tests reveal a suspicious mass or abnormality, a doctor might recommend a biopsy. This procedure involves taking a small tissue sample from the affected area for examination under a microscope. A mediastinoscopy is one way to perform a biopsy; a small incision is made in the neck, and a thin, lighted tube (mediastinoscope) is inserted to visualize and sample tissues from the mediastinum. Other methods include bronchoscopy (inserting a scope into the airways) or esophagoscopy (inserting a scope into the esophagus) to reach certain parts of the mediastinum for biopsy or examination. These tests help confirm a diagnosis and guide treatment decisions.

Frequently asked questions

What is the difference between the mediastinum and the lungs?

The mediastinum is the central space in your chest, located between your two lungs. Your lungs are the primary organs for breathing, situated on either side of the mediastinum. While the mediastinum contains many vital structures, the lungs themselves are not part of the mediastinum but border it.

Can problems in the mediastinum cause breathing difficulties?

Yes, problems in the mediastinum can certainly cause breathing difficulties. If a mass or inflammation in the mediastinum grows large enough, it can press on your windpipe (trachea) or major airways, making it harder to breathe. Conditions like pneumomediastinum can also directly affect breathing.

Is the mediastinum part of the circulatory system?

The mediastinum itself is a space, not an organ system. However, it contains major components of the circulatory system, most notably your heart and the large blood vessels (like the aorta and vena cava) that carry blood to and from the heart. So, while not part of the system, it houses critical parts of it.

What are the common symptoms of a mediastinal tumor?

Symptoms of a mediastinal tumor can vary widely depending on its size and location. Common symptoms may include chest pain, shortness of breath, a cough, or difficulty swallowing if the tumor presses on the windpipe or esophagus. Some tumors might not cause any symptoms until they grow quite large.

Is mediastinitis always a serious condition?

Mediastinitis is generally considered a serious medical condition. It involves inflammation, often due to infection, within the central chest space. It can be life-threatening, especially if it develops after surgery or from a tear in the esophagus, requiring prompt medical attention and treatment.

How is a mediastinal mass usually discovered?

A mediastinal mass is often discovered incidentally during imaging tests like a chest X-ray or CT scan performed for other reasons. If symptoms are present, such as persistent cough or chest pain, these tests are specifically ordered to investigate the cause and can reveal the presence of a mass.

Sources

• MedlinePlus — Mediastinum
• Mayo Clinic — Mediastinum
• Cochrane Library — Mediastinum