Mediastinoscopy is a major method to clarify mediastinal lesions and their nature. A mediastinoscope is placed through small incisions in the neck and parasternal area to directly visualize, palpate and remove diseased tissue or enlarged lymph nodes around the trachea, under the tracheal bulge and in the bronchial region.
I. Application scope of mediastinoscopy
1. Staging of lung cancer: clarifying the TNM stage of lung cancer patients is important for determining the treatment plan and judging the prognosis. Among them, for patients with non-small cell lung cancer who may be operated, it is even more important to clarify whether there is metastasis in mediastinal lymph nodes before surgery. Neoadjuvant therapy for lung cancer has been agreed by most scholars and is gradually becoming the standardized treatment for stage IIIa lung cancer. Neoadjuvant therapy requires accurate pathological assessment of mediastinal lymph node status before treatment, however, traditional diagnostic methods (CT, MRI) are less accurate and have high false positive and false negative rates. Positron emission computed tomography (PET) imaging exceeds CT in terms of accuracy and specificity in lung cancer staging, but still has certain false positives and false negatives, and is too expensive to be widely used at present. It has been reported in the literature that the diagnostic criteria of CT for metastatic mediastinal lymph nodes is >l cm in diameter, and its sensitivity is 64% and specificity is 94%; the sensitivity of PET is 88% and specificity is 86%, and the negative predictive value is high. In contrast, mediastinoscopy was 96% and 100%, respectively. Therefore, mediastinoscopy is the most accurate method to determine whether the mediastinal lymph nodes of lung cancer are metastatic or not. Yang Yulun, Department of Thoracic Surgery, Zhengzhou People’s Hospital
2. Diagnosis of difficult mediastinal diseases: Due to the special location of the mediastinum, the diagnosis of mediastinal diseases is often difficult, especially the enlarged mediastinal lymph nodes or masses, which have many causes, and there are great differences or even contradictions in the treatment of different causes, such as nodular disease requiring radical therapy, tuberculosis requiring anti-tuberculosis treatment prohibiting hormones, lymphoma requiring radiotherapy, and tracheal cysts and teratomas requiring surgical resection. The traditional treatment mode is mostly based on imaging and clinical symptoms and experimental treatment for more likely diagnoses. It is undeniable that some patients may receive correct treatment, but a significant proportion of patients may lead to misdiagnosis, misdiagnosis, delay or even deterioration of the disease.
The emerging CT-mediated transthoracic aspiration cytology examination in recent years has provided a more accurate basis for definite diagnosis to a certain extent, but due to the small amount of tissue obtained by this method and the drawbacks of cytology examination itself, its accuracy is far from satisfactory, with a reported confirmation rate of 78%. Mediastinoscopy directly observes the lesion and takes enough tissues for pathological examination, which has a high diagnostic accuracy and avoids unnecessary surgery and wrong experimental chemotherapy.
3. Compared with traditional mediastinoscopy, TV mediastinoscopy can also complete surgical resection treatment. For isolated lesions around the trachea with a diameter of <3cm and cysts in the anterior and middle mediastinum with a diameter of <5cm, when the adhesions are not serious, they can be resected directly under the mediastinoscope, avoiding conventional open chest, which not only reduces the pain of patients but also saves hospitalization costs. It can also replace thoracoscopy for esophageal cancer resection, ligation of large pulmonary alveoli, treatment of malignant pleural effusion, hand sweating, etc.
4. With the accumulation of surgical experience, the success of some exploratory surgeries has broken the confines of some mediastinoscopic surgeries. For example, it is used for the diagnosis of superior vena cava obstruction, and mediastinoscopy also has higher sensitivity, specificity and safety.
II. Mediastinoscopic procedures
1. Standard mediastinoscopy: It is the most common method for upper mediastinal exploration and mass biopsy. The patient is under general anesthesia, the neck is hyperextended, a 3-cm transverse incision is made on the sternal notch, the tracheal cartilage ring is separated, the anterior trachea, the anomalous artery and vein, and the posterior space of the aortic arch are separated to the level of the aorta with the index finger to make a posterior thoracic vascular tunnel, and then the mediastinoscope is inserted for operation. Care should be taken not to damage the laryngeal recurrent nerve on the left side of the trachea and to exclude vessels when biopsying lymph nodes. The lymph nodes of groups 1, 2L, 2R, 4R, 4L, and 7 can be removed by standard mediastinoscopy, but the posterior ramus and groups 8, 9, 5, and 6 cannot be examined. Enlarged peritracheal lymph nodes are the most common in clinical practice and the best area for standard mediastinoscopy.
2. Expanded cervical mediastinoscopy: It is mainly used in patients with left upper lobe lung cancer with a main pulmonary window and/or anterior lymph node diameter of the aortic arch >l cm. The method is to complete the standard mediastinoscopy, then use the index finger to bluntly separate the loose connective tissue between the aorta and the common carotid artery to reach the aortic arch, and at the angle between the aorta and the aorta, a tunnel is separated anteriorly and inferiorly to the subaortic arch and the lymph nodes of the ascending aortic group, and the mediastinoscope is placed along this tunnel.
3. Parasternal mediastinoscopy: It is mainly used for biopsy of enlarged group 5 and 6 lymph nodes and assessment of resectability of the hilum, diagnosis of anterior mediastinal masses with failed puncture biopsy and superior vena cava obstruction syndrome. A 5-cm transverse incision is made next to the sternum at the 2nd or 3rd intercostal space, and a mediastinoscope is placed via extrapleural separation to the lesion for operation.
Common complications of mediastinoscopic surgery and prevention
Mediastinoscopic surgery is safe and reliable with low complication rate, and the most serious complication is hemorrhage. Some scholars reported that the complication rate of mediastinoscopic surgery is less than 2.3%. 240 cases of mediastinoscopy were performed by Venissac, etc. There were no surgical deaths, and the complications accounted for 0.8%. 936 cases of mediastinoscopic surgery were performed by Weissberg, with one death and no other serious complications.
1. bleeding: the mediastinum has more large blood vessels, the space is narrow, the operation is inconvenient, bleeding is mostly caused by accidental injury to large vessels, especially the odd vein. Therefore, the biopsy must be punctured with a needle before the biopsy, and the tissue can be bitten only when there is no returning blood. For small bleeding can be hemostatic by electrocoagulation or compression with gelatin sponge; for severe hemorrhage need open-chest treatment.
2. Tracheal and esophageal injury: mostly caused by unskilled operation and rough force. Once it occurs, the chest needs to be opened to repair.
3. Pleural injury: mostly due to blunt finger separation or biopsy accidental injury to the pleura, can be found in the bubble overflow. A small amount of pneumothorax can generally be absorbed by itself without special treatment. More pneumothoraces should be drained by chest puncture or chest tube.
4. Infection: Mediastinoscopic surgery is a class I incision, and infection is caused by surgical contamination. If the incision is infected or mediastinitis, antibiotics treatment and local treatment should be given, and if necessary, incision or mediastinal drainage should be performed.
In conclusion, mediastinoscopic surgery is a rather safe and effective clinical diagnostic and therapeutic tool, and is one of the important techniques that modern thoracic surgeons should master.