For the paravertebral approach, the patient is generally placed in the prone position; patients who are unable to lie prone may be placed in a prone oblique or lateral decubitus position. The needle is advanced immediately lateral to the vertebral body between the endothoracic fascia and the parietal pleura. The endothoracic fascia, located outside the parietal pleura, lines the walls of the thorax and merges with the prevertebral fascia posteromedially. In some patients, the paravertebral extrapleural space may be wide enough to allow needle biopsy without traversing the pleura. However, in most patients, an injection of saline solution or a dilute iodinated contrast medium is required to displace the mediastinal parietal pleura and gain extrapleural access (Fig. 10.9) [5, 9].

An 18-gauge blunt-tip needle or cannula is used for creation of the extrapleural window; the same needle can be used as the guide needle for performing the biopsy with a coaxial technique (Fig. 10.10). Alternatively, a 22-gauge needle may be introduced initially to inject fluid and subsequently be exchanged for an 18-gauge needle to perform the biopsy [9]. In most patients, injection of 10–20 mL of saline solution is sufficient to achieve adequate mediastinal widening; however, larger volumes may be required [18]. Insufficient widening can occur when the needle tip lies outside the endothoracic fascia, in a blood vessel, or in the pleural space. The injection of saline solution also displaces mediastinal structures, such as the azygos vein, esophagus, nerves, and vertebral blood vessels, from the needle’s path, thereby reducing the risk of inadvertent injury to these structures. Needle advancement and biopsy must be performed expeditiously because the mediastinal widening regresses along with the redistribution of fluid. The needle should be inserted medial to the pleural surface at the head of the ribs. Administration of saline through a needle placed lateral to the transverse process may not achieve mediastinal widening because of the fixation of the endothoracic fascia and parietal pleura at this location [5, 9]. The biopsy needle should be placed along the superior edge of the rib and above the transverse process to avoid injury to the intercostal nerve and artery. Some investigators recommend oral administration of a contrast medium if the esophagus is not identified on non-contrast-enhanced CT scans [5, 9]. In some patients, the presence of large osteophytes or the orientation of the transverse process may preclude paravertebral extrapleural access [19].

The paravertebral approach allows access to posterior mediastinal lesions and is used mostly for biopsy of subcarinal lesions from the right side (Fig. 10.10). Occasionally, a saline injection may cause sufficient displacement of the descending aorta to allow retroaortic access from the left side (Fig. 10.11) for biopsy of subcarinal, periesophageal, or left paratracheal masses. To avoid inadvertent injury to the aorta, only a blunt-tip guide needle should be used with this approach. The right paravertebral approach can also sometimes be used for accessing middle mediastinal lesions located in the pre- or paratracheal spaces, especially cranial to the level of the arch of the azygos vein [19].

The transsternal approach involves needle placement through the sternum (Fig. 10.12). Any of the commonly available 18-gauge guide needles (Chiba [Cook Inc., Bloomington, IN] or Hawkins-Akins [Meditech, Westwood, MS]) are adequate to penetrate the sternum. Although an 18-gauge hypodermic needle can also be used to penetrate the sternum, it precludes the insertion of a coaxial 20-gauge core-biopsy needle to obtain larger specimens when needed [8]. If necessary, larger-caliber bone biopsy systems and drill bits can be used to gain transsternal access.

Transsternal needle insertion performed with local anesthesia and intravenous sedation is well tolerated by most patients. Injection of a local anesthetic into the periosteum of the anterior and posterior sternal cortices minimizes the discomfort associated with the procedure. A non-contrast-enhanced CT study obtained immediately before the procedure should be sufficient for safe biopsy planning in most patients who have had previous diagnostic contrast-enhanced CT scans; rarely, intravenous administration of a contrast agent may be needed during the procedure to help differentiate among mediastinal structures.

The transsternal approach is used for biopsy of lesions that are not safely accessible by the parasternal approach. The transsternal approach is usually used for biopsy of anterior mediastinal masses (Fig. 10.13) [6, 13] but also allows access to middle or posterior mediastinal masses (Fig. 10.14) [8]. Traversal of a brachiocephalic vein with 22-gauge needles for biopsy of middle or posterior mediastinal masses has been shown to be safe (Fig. 10.15) [8]. A curved 22-gauge Chiba needle can also be used to compensate for minor discrepancies in the trajectory of the guide needle (Fig. 10.16) [8]. Saline administration can be used to increase the contact between the mediastinum and the sternum to avoid pleural traversal as in the parasternal technique (Fig. 10.16).