Overview
Definition:
Mediastinoscopy is a minimally invasive surgical procedure used to visualize and obtain biopsy samples from the mediastinum, particularly mediastinal lymph nodes and masses
It involves inserting a mediastinoscope (a rigid or flexible lighted tube) through an incision, typically in the suprasternal notch or parasternal region, allowing direct inspection and biopsy of structures within the mediastinal compartments.
Epidemiology:
Mediastinoscopy is primarily indicated for staging lung cancer, diagnosing indeterminate mediastinal masses (e.g., sarcoidosis, lymphoma, granulomatous disease), and evaluating suspected infections
Its utility is widespread in centers managing thoracic malignancies and complex mediastinal pathology.
Clinical Significance:
Accurate staging of lung cancer is crucial for determining the optimal treatment strategy
Mediastinoscopy provides direct access to mediastinal lymph nodes (stations 2, 3, 4, and 7) which are common sites of metastasis
It is also invaluable for obtaining tissue diagnosis of mediastinal lesions when non-invasive methods are inconclusive, thereby guiding appropriate medical or surgical management and improving patient outcomes.
Indications
Lung Cancer Staging:
Diagnostic mediastinoscopy is indicated for T1 or T2 non-small cell lung cancer without evidence of distant metastasis, especially when mediastinal involvement is suspected based on imaging (e.g., CT scan, PET-CT)
It is also used to assess N2 disease for potential surgical resection
Cervical mediastinoscopy is the standard for evaluating paratracheal and subcarinal nodes.
Mediastinal Masses:
When imaging reveals mediastinal masses of uncertain etiology, mediastinoscopy allows for tissue diagnosis
This is particularly relevant for suspected lymphoma, germ cell tumors, thymoma, and granulomatous diseases like sarcoidosis or tuberculosis.
Pulmonary Sarcoidosis:
In cases of suspected stage II or III pulmonary sarcoidosis with significant hilar or mediastinal lymphadenopathy, mediastinoscopy can provide tissue for definitive diagnosis and guide management decisions.
Other Indications:
Less common indications include evaluation of suspected mediastinal infections (e.g., tuberculosis, fungal infections) and rare instances of mediastinal cysts or neurogenic tumors where percutaneous biopsy is not feasible or diagnostic.
Contraindications
Absolute Contraindications:
Known unresectable metastatic disease (M1 disease)
Significant coagulopathy that cannot be corrected
Severe cardiopulmonary compromise that makes general anesthesia unsafe.
Relative Contraindications:
Previous mediastinal radiation therapy or surgery (increases risk of adhesions and scarring)
Extensive mediastinal fibrosis
Presence of a mediastinal mass that is predominantly posterior or encroaches on vital structures like the aorta or great vessels, making biopsy difficult or unsafe.
Anesthetic Considerations:
The procedure is typically performed under general anesthesia with endotracheal intubation
Careful anesthetic management is required due to the proximity of mediastinoscopic instruments to major airways and vascular structures.
Technique
Preoperative Preparation:
Informed consent is obtained
Preoperative imaging (CT chest with contrast, PET-CT if indicated) is reviewed to delineate the mass and lymph node stations
Blood tests, including coagulation profile, are performed
Patients are counselled regarding the procedure, risks, and expected outcomes.
Surgical Approach Cervical:
A horizontal or vertical incision (typically 3-5 cm) is made in the suprasternal notch
The pretracheal fascia is dissected, and the mediastinoscope is advanced into the anterior mediastinum
Carefully, the instrument is used to explore lymph node stations 2R, 2L, 4R, 4L, and sometimes 7 (subcarinal)
Specialized instruments (biopsy forceps, graspers, scissors) are used to obtain tissue samples
Hemostasis is meticulously maintained.
Surgical Approach Parasternal:
An anterior parasternal incision may be used for better access to anterior mediastinal masses or lymph nodes (e.g., station 8, 9)
This approach is less common than cervical mediastinoscopy for routine staging.
Completion Of Procedure:
After adequate biopsy samples are obtained from all relevant stations, the mediastinoscope is withdrawn
The wound is closed in layers, and a drain may be placed if significant dissection or oozing occurred
Specimens are sent for histopathological examination.
Complications
Early Complications:
Bleeding (most common, can be immediate or delayed)
Injury to major blood vessels (brachiocephalic artery, aorta, pulmonary artery) requiring urgent intervention
Laryngeal nerve injury (recurrent laryngeal nerve) leading to hoarseness
Tracheal or esophageal injury
Pneumothorax
Infection
Hematoma formation.
Late Complications:
Chronic pain
Scarring
Persistent hoarseness (rare)
Fistula formation (rare)
Obstruction of airways due to hematoma or edema (rare).
Prevention Strategies:
Meticulous surgical technique and careful dissection
Adequate visualization and illumination
Thorough understanding of mediastinal anatomy
Use of cautery for hemostasis
Careful handling of instruments to avoid injury to adjacent structures
Judicious use of drains
Close postoperative monitoring for signs of bleeding or respiratory distress.
Postoperative Care And Follow Up
Postoperative Care:
Patients are monitored in the recovery room for vital signs, oxygen saturation, and signs of bleeding or airway compromise
Pain management is provided
Chest X-ray is usually obtained postoperatively
Patients are typically discharged within 1-2 days if no complications arise.
Pathological Analysis:
Biopsy specimens are sent for urgent intraoperative assessment (frozen section) and definitive histopathological examination, including immunohistochemistry if indicated, to establish a diagnosis and guide further management.
Follow Up:
Follow-up is tailored to the diagnosis
For lung cancer staging, results are integrated into the treatment plan
For other diagnoses, follow-up includes monitoring for resolution of symptoms and progression of disease
Regular clinical assessment and imaging may be required.
Key Points
Exam Focus:
N2 disease is a critical indication for mediastinoscopy in lung cancer staging
The specific lymph node stations accessible via cervical mediastinoscopy (2, 3, 4, 7) are frequently tested
Complications like bleeding and recurrent laryngeal nerve injury are high-yield.
Clinical Pearls:
Always confirm the patient has had adequate bowel preparation if a subcarinal biopsy (station 7) is anticipated, as this station is best accessed with the patient in a slightly head-down position
Intraoperative frozen section is invaluable for immediate diagnostic confirmation and to guide further sampling.
Common Mistakes:
Inadequate exploration of all relevant lymph node stations
Failure to achieve adequate hemostasis, leading to delayed bleeding
Misidentification of anatomical structures, potentially causing injury
Not obtaining sufficient tissue for definitive histopathology, especially for suspected lymphoma or granulomatous disease.