Mediastinoscopy is a surgical procedure that allows physicians to view areas of the mediastinum, the cavity behind the sternum (breastbone) that lies between the lungs. The organs in the mediastinum include the heart and its vessels, the lymph nodes, trachea, esophagus, and thymus.
Mediastinoscopy is most commonly used to detect or stage cancer. It is also ordered to detect infection, and to confirm diagnosis of certain conditions and diseases of the respiratory organs. The procedure involves insertion of an endotracheal (within the trachea) tube, followed by a small incision in the chest. A mediastinoscope is inserted through the incision. The purpose of this equipment is to allow the physician to directly see the organs inside the mediastinum, and to collect tissue samples for laboratory study.
Mediastinoscopy is often the diagnostic method of choice for detecting lymphoma, including Hodgkin's disease. The diagnosis of sarcoidosis (a chronic lung disease) and the staging of lung cancer can also be accomplished through mediastinoscopy. Lung cancer staging involves a determination of the level or progression of the cancer into stages. These stages help a physician study cancer and provide consistent cancer definition levels and corresponding treatments. They also provide some guidance as to prognosis. The lymph nodes in the mediastinum are likely to reveal if lung cancer has spread beyond the lungs. Mediastinoscopy allows a physician to observe and extract a sample from the nodes for further study. Involvement of these lymph nodes indicates the diagnosis and stage of lung cancer.
Mediastinoscopy may also be ordered to verify a diagnosis that was not clearly confirmed by other methods, such as certain radiographic and laboratory studies. Mediastinoscopy may aid in some surgical biopsies of nodes or cancerous tissue in the mediastinum. In fact, a surgeon may immediately perform a surgical procedure if a malignant tumor is confirmed while the patient is undergoing mediastinoscopy. In these cases, the diagnostic exam and surgical procedure are combined into one operation.
Mediastinoscopy provides a diagnosis in 10–75% of cases, depending on histology, location, and size of cancer. The false positive rate, however can be as high as 20%.
Approximately 130,000 new pulmonary nodules are diagnosed each year in the United States. Of those, half are malignant. The majority of pulmonary nodules are diagnosed via mediastinoscopy.
Mediastinoscopy is usually performed in a hospital under general anesthesia. Before the general anesthesia is administered, local anesthesia is applied to the throat while an endotracheal tube is inserted. Once the patient is under general anesthesia, a small incision is made, usually just below the neck or at the notch at the top of the sternum. The surgeon may clear a path and feel the person's lymph nodes first to evaluate any abnormalities within the nodes. Next, the physician inserts the mediastinoscope through the incision. The scope is a narrow, hollow tube with an attached light that allows the surgeon to see inside the area. The surgeon can insert tools through the hollow tube to help perform biopsies. A tissue sample from the lymph nodes or a mass can be removed and sent for study under a microscope, or to a laboratory for further testing.
In some cases, tissue sample analysis that shows malignancy will suggest the need for immediate surgery while the person is already prepared and under anesthesia. In other cases, the surgeon will complete the visual study and tissue removal, and stitch the small incision closed. The person will remain in the surgerical recovery area until the effects of anesthesia have lessened and it is safe to leave the area. The entire procedure should require about an hour, not counting preparation and recovery time. Studies have shown that mediastinoscopy is a safe, thorough, and cost-effective diagnostic tool with less risk than some other procedures.
Because mediastinoscopy is a surgical procedure, it should only be performed when the benefits of the exam's findings outweigh the risks of surgery and anesthesia. Individuals who previously had mediastinoscopy should not receive it again if there is scarring from the first exam.
Several other medical conditions, such as impaired cerebral circulation, obstruction or distortion of the upper airway, or thoracic aortic aneurysm (abnormal dilation of the thoracic aorta) may also preclude mediastinoscopy. Certain structures in a person's anatomy that can be compressed by the mediastinoscope may complicate these pre-existing medical conditions.
Patients are asked to sign a consent form after reviewing the risks of mediastinoscopy and known risks and reactions to anesthesia. The physician will normally instruct the patient to fast from midnight before the test until after the procedure is completed. A physician may also prescribe a sedative the night before the exam and again before the procedure. Often a local anesthetic will be applied to the throat to prevent discomfort during placement of the endotracheal tube.
Following mediastinoscopy, patients will be carefully monitored and watched for changes in vital signs , or symptoms of complications from the procedure or anesthesia. The patient may have a sore throat from the endotracheal tube, experience temporary chest pain, and have soreness or tenderness at the incision site.
Complications from the actual mediastinoscopy procedure are relatively rare. The overall complication rates in various studies have been reported in the range of 1.3–3%. However, the following complications, in decreasing order of frequency, have been reported:
The usual risks associated with general anesthesia also apply to this procedure.
In the majority of procedures performed to diagnose cancer, a normal result indicates the presence of small, smooth lymph nodes, and no abnormal tissue, growths, or signs of infection. In the case of lung cancer staging, results are related to the severity and progression of the cancer.
Abnormal findings may indicate lung cancer, tuberculosis, the spread of disease from one body part to another, sarcoidosis (a disease that causes nodules, usually affecting the lungs), lymphoma (abnormalities in the lymph tissues), and Hodgkin's disease.
Complications of mediastinoscopy include bleeding, pain, and post-procedure infection. These are relatively uncommon. Mortality is extremely rare.
A less invasive technique is ultrasound. However, it is not as specific as mediastinoscopy, and the information obtained is not as useful in making a diagnosis.
Although still performed, there is a decline in the use of mediastinoscopy as a result of advancements in computed tomography (CT), magnetic resonance imaging (MRI), and ultrosonography techniques. In addition, improved fine-needle aspiration (withdrawing fluid using suction) results of and core-needle biopsy (using a needle to obtain a small tissue sample) investigations, along with new techniques in thoracoscopy (examination of the thoracic cavity with a lighted instrument called a thoracoscope) offer additional options in examining masses in the mediastinum. Mediastinoscopy may be required when other methods cannot be used or when they provide inconclusive results.
See also Lung biopsy ; Thoracic surgery .
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A mediastinoscopy procedure is usually performed by a thoracic or general surgeon in a hospital setting.