There are several methods of performing thymectomy that are classified by the Myasthenia Gravis Foundation of America (MGFA) according to the approach and extent of resection. The transsternal extended thymectomy (T3-b thymectomy) is the most commonly adopted among them for patients with MG with or without thymoma.1 Other techniques include the transcervical approach,2 the combined median sternotomy with a transcervical incision (T-incision), and the partial sternotomy (involving either the upper3 or lower4 sternum).
The thoracoscopic approach to thymectomy was first reported by Landreneau and colleagues.5 It has subsequently evolved into the following variants: the unilateral video-assisted thoracic surgery (VATS) approach that uses three ports6,7 and the simple bilateral thoracoscopic approach (one side after the other, within the same session) followed by a cervical incision (VATS extended thymectomy).8 More recently, endoscopic robot-assisted thymectomy has also been reported, with good immediate results; however, long-term data are still pending.9
Minimally invasive alternatives have become increasingly popular because of their low procedural morbidity and mortality, improved cosmesis, lesser degree of access trauma and postoperative pain, and equivalent efficacy compared with conventional open techniques.10 However, they have not been extensively evaluated for this disease process because data regarding the long-term oncologic effectiveness of these techniques remain to be established. Therefore, no consensus has been universally adopted with regard to the optimal surgical approach for thymectomy as part of the treatment in MG. Furthermore, a unilateral approach may compromise the extent of the resection and may cause irreversible damage to the phrenic nerve on the opposite side. We evaluated the clinical feasibility and safety of a concomitant bilateral approach with the implementation of a contralateral surveillance camera in patients undergoing thymectomy for thymoma.
PATIENTS AND OPERATIVE TECHNIQUE
Four patients (3 females, 1 male) were diagnosed as having MG. The diagnosis of MG was based on a history of fatigable extremities, weakness associated with ptosis, a positive response to the anticholinesterase test, and abnormal repetitive nerve stimulation or electromyography studies. An anticholinesterase receptor antibody assay was routinely performed, and it was found positive in all the patients. The MGFA clinical classification was used for clinical assessment of disease severity. The quantitative MG scoring system (QMG score) was applied for objective evaluation of MG treatment11 (data not presented).
All patients had been previously treated in the neurologic department of our institution. They were referred for surgery because of failure of other optional treatments.
The preoperative MGFA therapy status was recorded as were the current doses of all pertinent medications. Patients with severe weakness were treated with five courses of plas mapheresis before being sent for surgery. Preoperative diagnostic tests included spirometry and chest computed tomographic (CT) scans. A well-defined solitary lesion was found at the anterior mediastinal tissue in the CT scans of all the patients, and these lesions were diagnosed as thymomas (Fig. 1).
The study patients were operated on at our institution between January 2010 and September 2011. The surgical technique was as follows. Under general anesthesia with double lumen endotracheal intubation, the patients were placed in the supine position with inflatable pillows under each hemithorax, allowing tilting of the table to the right or to the left, with some degree of reverse Trendelenburg positioning according to surgical needs.
With the patient under one-lung ventilation, a 5-mm 30-degree lens thoracoscope was inserted into the left pleural space through the sixth intercostal space at the anterior axillary line. Two other sealed 10-mm trocars were applied under direct vision: one at the third intercostal anterior axillary line and the second at the eighth intercostal space at the mid-axillary line. En bloc thymectomy and anterior mediastinal exenteration were performed under clear vision of the thymic tissue. Dissection included the mediastinal pleura from the level of the thoracic inlet to the diaphragm, the pericardial fat pad, and all the mediastinal fat. The left innominate vein was identified, and branches of the thymic vein were divided with ultrasonic scissors. While traversing the midline, another 5-mm thoracoscope was inserted into the right hemithorax (Fig. 2A, B). Close surveillance of the extension and safety of the resection could be maintained through the right-sided camera.
A slight inflation of the right-sided inflatable bag was necessary for the primary insertion of the thoracoscope into the pleural cavity. Once inserted, however, the bag could be deflated to the normal position. After completion of the dissection, the entire resected thymic tissue was placed into the Endobag and removed. In cases of large thymomas, the incision was extended 3 to 5 cm according to the size of the thymoma for mass evacuation without capsular breakage. Carbon dioxide insufflation and valved ports were used for the left resection, but they were not required for the right side, and so the right lung could be ventilated continuously.
Complete resection was achieved in all four patients without any nerve injury that could be easily identified and protected from the right side.
The duration of the operation was about 100 minutes. There was no surgical mortality or major morbidity, such as pneumonia, wound infection, or postoperative bleeding necessitating reoperation. No patient experienced transsternal conversion or postoperative MG crises.
Gradual remission from proximal muscle weakness followed by improvement in ocular signs and other myasthenic symptoms were achieved after recovery in three of the four patients.
The mean ± SD weight of the retrieved specimens was 72.5 ± 58.8 g. The characteristics of the excised tumors are described in Table 1.
The thymus has a major role in the autoimmune pathogenesis of MG, and thymectomy is an established therapeutic method that can yield improvement of symptoms and complete remission of MG.12 We demonstrated that bilateral concomitant VATS thymectomy is a feasible and safe procedure in experienced hands and should be considered as a surgical treatment for MG. Considerable uncertainties remain over the optimal surgical treatment of MG, and the best surgical approach for thymectomy remains controversial. Regardless of the technique, it is generally agreed on that a thymectomy for MG should be complete13 to achieve en bloc thymectomy and anterior mediastinal exenteration. This includes removing the mediastinal pleura from the level of the thoracic inlet to the diaphragm, the pericardial fat pad, and all the mediastinal fat. Although it may seem intuitive to remove as much mediastinal soft tissue as possible to avoid leaving behind ectopic thymus material, these remnants have never been conclusively shown to be clinically relevant, and even the most radical surgical approach does not result in a complete remission rate greater than 40%.14 Most centers prefer the “remove it all” strategy, thereby precluding widespread adoption of a minimally invasive approach.
There are basically two minimally invasive approaches to thymectomy thus far: the VATS approach and the transcervical approach with or without video assistance. The VATS approach is similar to the transcervical approach in that both are associated with minimal chest wall trauma, low postoperative morbidity, shorter hospital stay,14,15 and, perhaps more importantly, improved patient acceptance for surgery earlier in the course of the disease compared with the transsternal approach.15 However, there is controversy—even among surgeons who perform VATS thymectomy—over the exact technique and, in particular, whether the thymus should be approached from the left, the right, or from both sides one side after the other.
The unilateral VATS approach offers a panoramic view of the hemithorax and creates ample room for dissection, but there may be undesired thymic tissue or damage to the contralateral phrenic nerve if it is performed from only one side either right or left.
There are advantages to each side. The left-sided approach is safer because the superior vena cava lies out of the surgical field, thus reducing the risk of accidental injury or bleeding. The removal of perithymic fatty tissue around the left pericardiophrenic angle and aortopulmonary window can also be performed more readily from the left.16 On the other hand, the right-sided approach benefits from the fact that the superior vena cava is easily identified, thus providing a clear landmark for further dissection of the innominate veins.17
The complete bilateral approach may benefit both sides but results in extensive and longer procedural time because of the three larger ports from either side.
Our approach offers better visualization than the unilateral approach and less invasiveness than the traditional bilateral approach by introducing only a single thoracoscopic 5-mm port into the right hemithorax. There seems to be no need to resect the thymus from both sides because close monitoring can be done using the right-sided thoracoscope. Only rarely is conversion from VATS to sternotomy required (2.6%–5.5%).10 We assume that, with our approach, these rates will decrease even further.
The cosmetic appearance of the surgical scars is seldom used to argue for a particular surgical approach. However, thymectomy may be a notable exception because most patients are young females for whom the enhanced cosmetic appearance of VATS should be taken into consideration. In addition, the results of a recent small randomized prospective study showed that the pulmonary function is significantly better preserved in the immediate postoperative period followed by a faster recovery after VATS compared with the median sternotomy approach to thymectomy for MG.18 Such an advantage may contribute toward earlier extubation and a potential reduction in the incidence of postoperative pulmonary infections.
The ultimate surgical goal of thymectomy is to completely remove the gland and the anterior mediastinal tissue without causing neurological injury. Our technique allows complete thymectomy to be performed at least as well as the transsternal approach because of lateralization of the resection. Bilateral concomitant VATS thymectomy was demonstrated as being a feasible and safe operation in experienced hands and represents an alternative approach for patients with MG. Given the capability of our technique to perform a complete and extensive thymectomy, there seems to be a role for it in the treatment of thymoma.
1. Gronseth GS, Barohn RJ. Practice parameter: thymectomy for autoimmune myasthenia gravis (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology
. 2000; 55: 7–15.
2. Calhoun RF, Ritter JH, Guthrie TJ, et al.. Results of transcervical thymectomy for myasthenia gravis in 100 consecutive patients. Ann Surg
. 1999; 230: 555–559.
3. Milanez de Campos JR, Filomeno LTB, Marchiori PE, Jatene FB. Parietal sternotomy approach to the thymus. In: Yim APC, Hazelrigg SR, Izzat MB, Landreneau RJ, Mack MJ, Naunheim KS, eds. Minimal Access Cardiothoracic Surgery
. Philadelphia, PA: WB Saunders; 2000: 205–208.
4. Granone P, Margaritora S, Cesario A, Galetta D. Thymectomy in myasthenia gravis via video assisted infra-mammary cosmetic incision. Eur J Cardiothorac Surg
. 1999; 15: 861–863.
5. Landreneau RJ, Dowling RD, Castillo WM, Ferson PF. Thoracoscopic resection of an anterior mediastinal tumor. Ann Thorc Surg
. 1992; 54: 142–144.
6. Yim AP. Paradigm shift in surgical approaches to thymectomy. ANZ J Surg
. 2002; 72: 40–45.
7. Yim AP, Low JM, Ng SK, Ho JK, Liu KK. Video-assisted thoracoscopic surgery in the pediatric population. J Paediatr Child Health
. 1995; 31: 192–196.
8. Novellino L, Longoni M, Spinelli L, et al.. “Extended” thymectomy without sternotomy, performed by cervicotomy and thoracoscopic techniques in the treatment of myasthenia gravis. Int Surg
. 1994; 79: 378–381.
9. Augustin F, Schmid T, Sieb M, Lucciarini P, Bodner J. Video-assisted thoracoscopic surgery versus robotic-assisted thoracoscopic surgery thymectomy. Ann Thorac Surg
. 2008; 85: S768–S771.
10. Yim AP, Kay RLC, Ho JKS. Video-assisted thoracoscopic thymectomy for myasthenia gravis. Chest
. 1995; 108: 1440–1443.
11. Lee Y, Kim DJ, Lee JG, Park IK, Bae MK, Chung KY. Bilateral video-assisted thoracoscopic thymectomy has a surgical extent similar to that of transsternal extended thymectomy with more favorable early surgical outcomes for myasthenia gravis patients. Surg Endosc
. 2011; 25: 849–854.
12. Jaretzki A III. Thymectomy for myasthenia gravis: analysis of controversies—patient management. Neurologist
. 2003; 9: 77–92.
13. Jaretzki A III, Penn AS, Younger DS, et al.. “Maximal” thymectomy for myasthenia gravis: results. J Thorac Cardiovasc Surg
. 1988; 95: 747–757.
14. Pompeo E, Nofroni I, Iavicoli N, Mineo TC. Thoracoscopic completion thymectomy in refractory nonthymomatous myasthenia. Ann Thorac Surg
. 2000; 70: 918–923.
15. Meyer DM, Herbert MA, Sobhani NC, et al.. Comparative clinical outcomes of thymectomy for myasthenia gravis performed by extended transsternal and minimal invasive approaches. Ann Thorac Surg
. 2009; 87: 385–391.
16. Shrager JB, Nathan D, Brinster CJ, et al.. Outcomes after 151 extended transcervical thymectomies for myasthenia gravis. Ann Thorac Surg
. 2006; 82: 1863–1869.
17. Mineo TC, Pompeo E, Lerut TE, Bernardi G, Coosemans W, Nofroni I. Thoracoscopic thymectomy in autoimmune myasthenia gravis: results of left sided approach. Ann Thorac Surg
. 2000; 69: 1537–1541.
18. Yim APC. Thoracoscopic thymectomy: which side to approach? [Letter]. Ann Thorac Surg
. 1997; 64: 584–585.
Most reports of thymectomy, even minimally invasive techniques, demonstrate low complication rates, including phrenic nerve injury. During the last decade, many surgical teams have placed a contralateral videoscope to obtain an additional view of the surgical resection, but none have reported it in the literature.
The team from Tel-Aviv Sourasky Medical Center has presented a small series of patients with thymomatous myasthenia gravis in which they used a contralateral videoscope and they believe that it improves the safety of their procedure. This technique may offer the novice minimally invasive thymectomy surgeons a potential means to improve their visibility.