The classic approach for most posterior mediastinal masses is a lateral or posterolateral thoracotomy.3 A double-lumen endotracheal tube is used to obtain lung isolation for exposure. Preoperative bronchoscopy or esophagoscopy is considered when the tumor may involve aerodigestive structures, although, in practice, this is a rare necessity. Because of the predominance of benign neurogenic tumors in the adult population, en bloc resection of major adjacent structures (e.g., vertebral body or chest wall) is not usually required. Rather, the mass is enucleated from its subpleural origin. The site of the thoracotomy is determined by the level of the tumor. In cases of neurilemmomas, the nerve root may be preserved with careful dissection of the tumor after incising the epineurium, but this is often not possible. Neurofibromas are intercalated with the nerve fibers, and thus the nerve root is taken en bloc with the tumor.63
Dumbbell tumors pose a special challenge for complete resection because of extension into the neural foramen and spinal canal. Approximately 10% of benign nerve sheath tumors have this type of anatomy.13 Complications such as hemorrhage within the spinal canal leading to neurologic deficits or dural leak can arise with improperly approached dumbbell tumors secondary to excessive traction on the nerve root or improper control of vascular structures (see Fig. 162-3).2,64,65 In addition, thoracotomy alone may provide only enough exposure for an incomplete resection, leaving tumor in the foramen and spinal canal, with the consequences of continued tumor progression and eventual spinal cord compression.3 Various approaches have been described for resection. The degree of foraminal involvement dictates the need for a spinal approach in addition to the transthoracic resection. In some cases, the tumor simply may extend to the distal aspects of the neural foramen, where it widens the foramen but does not truly extend into the spinal canal. Such tumors still may be resected solely via a thoracic approach, taking care not to avulse the nerve root and injure the spinal cord by using meticulous dissection and control of any incised dura to prevent cerebrospinal fluid leak.66 For true dumbbell tumors with intraspinal extension, some have advocated removal of the intraspinal portion via laminectomy for immediate decompression of the spinal cord and relief of symptoms, followed by resection of the intrathoracic portion as a second procedure.67,68 Grillo et al.69 removed dumbbell tumors via a single posterolateral thoracotomy with a “hockey-stick” extension that extended vertically over the middle of the spinous processes. The vertical aspect of the skin incision traversed 5 cm superior and inferior to the level of the involved foramen, and thus a skin flap was created to access the desired site of thoracotomy superior to the level of the horizontal skin incision. An update on this technique reported minimal morbidity, and it was noted that the order of the thoracotomy and intrathoracic tumor mobilization and laminectomy or hemilaminectomy for the intraspinal resection was not fixed. Rather, it depended on surgeon preference.38 In general, a full laminectomy is not necessary to mobilize a unilaterally oriented tumor (Fig. 162-5).70 Whether a single incision or combined chest and back approach is used, the goal of obtaining a complete resection with minimal risk of bleeding and cerebrospinal fluid leak is paramount.
Approach for dumbbell tumors. A. Hemilaminectomy (black arrow). B. Resection of intraspinal component of tumor prior to thoracic approach.
In the last 20 years, video-assisted thoracic surgery (VATS) has been used to resect posterior mediastinal neurogenic tumors.66,71–73 Conversion rates of thoracoscopy to open thoracotomy for resection of neurogenic tumors had been reported to be as high as 17% in early series, but the more modern series note rates around 2% to 4%.71–76 Although the operative time is longer, the advantages of the thoracoscopic approach include quicker recovery, as evidenced by a shorter length of stay and quicker return to work.77 A prospective trial comparing the two techniques has not been done. Long-term freedom from recurrence has been reported with the thoracoscopic technique.76
The camera and port sites are similar to those used for standard thoracoscopic lung resection (Fig. 162-6). The videoscope generally is introduced into the chest in the seventh interspace in the middle to posterior axillary line. A port is placed anteriorly to retract the lung away from the paravertebral space. One or two additional ports then are placed for dissection, with the locations determined by the level of the tumor. The resected tumor is removed in a specimen bag to avoid contamination of the port site. This technique has been used for resection of dumbbell tumors as well, in conjunction with a spinal approach either before or after the thoracic dissection.78,79
Ideal port placement for access to posterior mediastinal compartment.
The advent of robotic-assisted thoracoscopic surgery has seen several reports that have described successful robotic thoracoscopic resection of neurogenic tumors.80–83 The ports may be placed in a similar fashion to those used for robotic-assisted thoracoscopic lobectomy,84 or may be triangulated using the camera port at the inferior apex.85 In either case, inferior and superior posterior mediastinal tumors require different robot docking angles to maximize robot-arm mobility. The largest series of robotic posterior mediastinal neurogenic tumor resections (41 cases) was included in a recent report on robotic use for posterior mediastinal pathology. There were no conversions to thoracotomy, significant bleeding, or other operative morbidity noted.84
Patients undergoing neurogenic tumor resection are managed similarly to any patient who has undergone thoracotomy or thoracoscopy. Chest drains are removed early (i.e., on the day of surgery or postoperative day 1) based on output and re-expansion of the lung. Patients are extubated in the OR, and early mobilization is advocated. The performance of a hemilaminectomy in patients with dumbbell tumors should not dissuade this practice. Diet may be resumed in short order as tolerated. Analgesia is delivered via patient-controlled analgesia devices or orally in VATS patients. Discharge on the day of the surgery or postoperative day 1 is anticipated.
The management of patients with paragangliomas warrants special attention to heart rate and blood pressure because doses of pharmacologic agents may be reduced or withdrawn preoperatively. For example, because of its prolonged half-life, the dose of the α-blocker phenoxybenzamine usually is reduced immediately prior to surgery to prevent postoperative hypotension. Although β-blockers may be continued through the perioperative period for cardioprotective effects, the dose likewise may be reduced.
Hemorrhage requiring spinal cord decompression has been described.2,64 Postoperative assessment after resection of a neurogenic tumor should include a detailed neurologic examination, even with a purely thoracic (i.e., nondumbbell) tumor resection. Of note, the preoperative physical assessment also should document the neurologic examination in detail to distinguish preoperative deficits from the untoward sequelae of resection.
Management of the dura when tumor invades the neural foramen requires meticulous dissection and attention to the possibility of a dural leak. A cerebrospinal fluid leak into the chest, necessitating a pleural drain, can add to the already negative intrathoracic pressures of inspiration and may be difficult to manage conservatively. Thus, the sleeve on the nerve root should be controlled with a hemoclip or suture before the proximal margin of resection is divided. Intraoperatively, if any cerebrospinal fluid is detected, further application of suture, clips, fibrin glue, or a fascial patch may be used to control the leak.66 In the immediate postoperative interval, chest drains are placed on water seal as opposed to suction. In some patients, a lumbar drain can be used to reduce the potential flow gradient of cerebrospinal fluid into the pleural space.66 If the dural leak is noted postoperatively, reoperation and laminectomy will be required occasionally to close the dural defect.5
Other complications are related to the extent of resection, and these possibilities should be conveyed when obtaining the preoperative informed consent. Depending on the scope of the intended resection, these may include recurrent nerve palsy (vagus), Horner syndrome (sympathetic chain), neuralgia/paresthesia/hypesthesia/neuropraxia (nerve root, brachial plexus), and dyspnea (lung, phrenic nerve).1–3,5 Other complications, such as wound infection, atelectasis, post-thoracotomy or post-thoracoscopic port neuralgia, and chylothorax, are managed with standard measures.