Surgery is performed with the patient under general anesthesia, with double-lumen endotracheal intubation. The patient is positioned on the operative table as for standard posterolateral thoracotomy and is prepared for a videothoracoscopic approach through three 10-mm access ports. A 25° to 30° endoscope is introduced into the midaxillary line, usually between the VIII–IX intercostal space, and two working 10-mm ports are used for insertion of the dissecting instruments, which are directed toward the location of the tumor.
Once the tumor has been identified, the pleura is incised circumferentially around the surface of the lesion with either an electrocautery hook or endoscopic bipolar forceps. The lesion is then mobilized and lifted up with a blunt-tipped instrument to expose the vessels. Intercostal and vertebral vessels are clipped with a clip applier. In cases of tumors of nerve sheath origin, the peripheral section of the involved intercostal nerve is sectioned after clipping. The tumor is extracted with the aid of an endoscopic bag through one of the port sites, which can be enlarged, depending on the dimension of the tumor. A 32F chest tube is left in place, and, after reinflation of the lung under direct visualization, the trocars are removed and the incisions are closed.
Dumbbell-type tumors are removed through the combined neurosurgical approach, as described by Vallières et al.5 Dissection of the intraspinal part is performed first through a posterior approach, with the patient in the thoracotomy position. This is followed by a unilateral laminectomy and a wide foraminectomy. Part of the adjacent intervertebral facet and of the transverse process is then removed. The use of the neurosurgical operating microscope facilitates the procedure. After dural opening, the intraspinal component is removed. The dural tube is sutured in a watertight manner. The patient is then ready for the thoracoscopic stage.
Preoperative symptoms were observed in seven cases (23%), including back pain in three, chest pain in two, dyspnea in one, and radicular symptoms in one. Twenty-five tumors developed in the costovertebral sulcus, and five were dumbbell-type. Nineteen tumors (63%) were located on the right side and 11 (37%) on the left side. Mean tumor size was 5.6 ± 1.4 cm (range, 4 to 11). Videothoracoscopic resection was possible in 26 patients, of whom 5 were dumbbell-type, requiring a combined neurosurgical approach. Reasons for conversion to thoracotomy were pleural adhesions in one case and bleeding in three. The operative procedure was radical tumor extirpation in all cases. Mean operative time was 140 ± 55 minutes (range, 95 to 230) for non–dumbbell-type tumors and 215 ± 42 minutes (range, 180 to 280) for dumbbell-type tumors. No operative and/or postoperative complications occurred. The chest tube remained in place for an average of 1.5 days. Final histology showed 25 schwannomas, 4 ganglioneuromas, and 1 neurofibroma. Mean postoperative stay was 6.5 ± 1 day for patients with dumbbell-type tumors and 4 ± 1 day for those without.
Neurogenic tumors of the posterior mediastinum arise from a spinal nerve root but may involve any thoracic nerve. They are benign in 70% to 80% of the cases, and almost half of the patients are asymptomatic.1,7,10 Only 23% of our patients were symptomatic, most of them having pain, but other series report respiratory symptoms in up to 45% to 50% of their patients and neurologic symptoms ranging from 6% to 13%.1,11,12 Tumor finding is often incidental, but surgery is the treatment of choice because both benign and malignant neurogenic tumors may look alike, and they tend to grow slowly.10
Accurate preoperative diagnosis is essential to define the appropriate surgical strategy. Suzuki et al13 and Naidich et al14 reported a 60% to 79% sensitivity of CT scan in detecting chest wall invasion. Most series report a 72% to 90% diagnostic yield of percutaneous needle biopsy.15 In our series, however, a biopsy was needed in only a minority of patients because the CT scan was able to exclude local invasion in 73% of cases and provided detailed information on the feasibility of a radical excision of the lesion.
Nuclear magnetic resonance appears to be highly effective in accurately diagnosing neurogenic tumors of the mediastinum.16 In our series, it proved to be particularly useful in confirming the presence of suspected dumbbell-type tumors because it was able to identify spinal cord involvement of the tumor in all five cases.6
Spinal angiography is indicated if the tumor is located near the site of the Adamkiewicz artery, which, when present, usually originates from the aorta or from an intercostal artery on the left side between T9 and L2. Injury to this artery should be avoided during surgery because it leads to serious spinal cord ischemia.
Benign neurogenic tumors of the posterior mediastinum can be removed by means of thoracotomy or videothoracoscopy.1,2,7,10 Videothoracoscopy minimizes the trauma of incision, reduces hospital stay, and provides an appropriate view of the posterior mediastinum.6,10 On the other hand, removal of tumors lodged within the superior sulcus, large tumors, and dumbbell-type tumors might be challenging.1 Moreover, the presence of dense pleural adhesions or bleeding often requires conversion to thoracotomy. These factors prompted conversion to thoracotomy in four patients in our series. When the tumor was close to the stellate ganglion, we avoided the use of monopolar electrocautery and carried out dissection with bipolar forceps. Large tumors over 7 to 8 cm in size may also be removed thoracoscopically and extracted by enlarging the thoracoscopic access. The use of an endoscopic bag facilitates the passage through the incision. The largest tumor (11 cm in diameter) in our series was removed through a small thoracotomy mainly because of the onset of bleeding.
Different surgical approaches have been described to remove dumbbell-type tumors.3–5 The favorable results achieved with videothoracoscopic resection of non–dumbbell-type tumors prompted Vallèries et al5 to extend the use of this technique to the thoracic phase of treatment of the dumbbell type. Our experience with this combined neurosurgical and thoracic approach6 has shown that an accurate neurosurgical dissection associated with a wide foraminotomy makes the subsequent thoracoscopic approach brief and easy.6 Controversies regarding the thoracoscopic phase concern the possible damage that might occur to the spinal cord as the result of traction on the tumor during dissection.17 In our experience, this can be obviated by leaving a patch of lyophilized dura mater in situ on the dural sac during the neurosurgical phase. The patch can be easily identified in the thoracoscopic phase and provides a guide for the depth limit of the thoracoscopic dissection. Another useful maneuver is to leave a portion of parietal pleura around the border of the tumor to allow the mass to be grasped and dissected with greater precision. In cases of dumbbell-type tumors with a very small paravertebral portion, the posterior approach may suffice.17
In conclusion, our experience confirms that videothoracoscopy represents a safe and effective alternative to thoracotomy in managing benign neurogenic tumors of the posterior mediastinum. Videothoracoscopy can also be useful in resecting dumbbell-type tumors through a combined thoracoscopic-neurosurgical approach.5 Preoperative evaluation is crucial to determine the appropriate surgical strategy. Conversion to thoracotomy may be necessary because of pleural adhesions, bleeding, and large tumor size.
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Keywords:© 2006 Lippincott Williams & Wilkins, Inc.
Neurogenic tumor; Videothoracoscopy; Mediastinum