Review Article Page 1 of 6 Bilateral VATS thymectomy in the treatment of myasthenia gravis Bianca Bromberger, Joshua Sonett Department of Surgery, Columbia University Medical Center, Columbia University, New York 10032, USA Contributions: (I) Conception and design: All authors; (II) Administrative support: All authors; (III) Provision of study materials or patients: All authors; (IV) Collection and assembly of data: All authors; (V) Data analysis and interpretation: All authors; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors. Correspondence to: Joshua Sonett. The Herbert Irving Pavilion, 161 Fort Washington Avenue, 3rd Floor, New York 10032, USA. Email: [email protected]. Abstract: Surgical removal of the thymus is an important tool in the treatment of myasthenia gravis. While there exist a number of different surgical approaches, the optimal thymectomy removes the most amount of thymic tissue in the least invasive manner, allowing for rapid recovery from the procedure and providing the best chance of remission of disease. The purpose of this paper is to review bilateral video- assisted thoracoscopic thymectomy with regard to both relevant anatomy and surgical technique, as well as in comparison to other existing methods of thymectomy in terms of safety, recovery and outcomes. Bilateral video-assisted thoracoscopic thymectomy appears to have improved recovery time and comparable rates of remission to more invasive approaches, though more high-quality long-term outcomes studies are needed. Keywords: Thymectomy; video-assisted thoracoscopic surgery; myasthenia gravis Received: 30 November 2016; Accepted: 05 January 2016; Published: 21 March 2017. doi: 10.21037/vats.2017.02.02 View this article at: http://dx.doi.org/10.21037/vats.2017.02.02 Introduction achieved until 5 to 10 years after surgery (4). A number of issues regarding thymectomy in myasthenia Myasthenia gravis (MG) is an autoimmune disorder gravis remain unresolved, including optimal surgical characterized by skeletal muscle weakness, most commonly approach. The purpose of this paper is to provide an due to antibodies directed against acetylcholine receptors. overview of bilateral video-assisted thoracic surgery (VATS) The thymus is an immunogenic organ located in the thymectomy in patients with myasthenia gravis, including anterior mediastinum and believed to be key to the a review of anatomic considerations, surgical technique, pathogenesis of MG as a location of origin of these and evaluation of operative risk and disease outcomes in autoantibodies. Thymic abnormalities are prevalent in comparison to alternative methods of resection. patients with MG; approximately 70% of patients have thymic hyperplasia and 15% have thymomas (thymic epithelial cell tumors that tend to be slow growing but have Anatomy the potential to become invasive) (1). The thymus is a butterfly-shaped gland located in the Though still a source of debate, thymectomy is anterior mediastinum. It reaches its maximal weight of indicated for patients with myasthenia gravis with a approximately 30 to 40 gm during puberty, but subsequently thymoma and in non-thymomatous MG associated with involutes and eventually weighs between 20 to 28 gm in certain autoantibodies (2,3). The purpose of thymectomy the normal adult. It is thought to be composed of multiple is to remove as much thymic tissue as possible in order lobules, but typically maintains a distinct right and left to achieve remission and prevent tumor invasion in the bi-lobar shape. The upper left and right poles usually lie setting of thymomas. However, the benefit of thymectomy anterior to the brachiocephalic veins and have fibrous for symptom remission is not immediate and may not be thyrothymic attachments at their superior ends. However, © Video-Assisted Thoracic Surgery. All rights reserved. vats.amegroups.com Video-assist Thorac Surg 2017;2:12 Page 2 of 6 Video-Assisted Thoracic Surgery, 2017 the operation, in which only peri-thymic tissue is grasped during the dissection. Capsular transgression of a thymoma should be considered a never event in any surgical approach. Video 1. Bilateral VATS thymectomy in the treatment of myasthenia▲ gravis Positioning and port placement Bianca Bromberger, Joshua Sonett* Patient is placed in the supine position and prepped such that both left and right sides may be accessed. The left The Herbert Irving Pavilion, 161 Fort Washington Avenue, 3rd Floor, New York 10032, USA side is accessed first with the left arm extended overhead. Once the left-sided portion of the operation is complete, the left arm is lower and the right arm extended, all Figure 1 Bilateral VATS thymectomy in the treatment of while maintaining a sterile field. This avoids any brachial myasthenia gravis (7). plexopathy from positioning. Additionally, the head is flexed Available online: http://www.asvide.com/articles/1417 so as to move the thymus inferiorly out of the cervical neck. Three 5mm ports are placed on each side and 8 to 10 mmHg is used for insufflation. The initial port is placed in the thymic horns may be found under the brachiocephalic the mid-axillary line 2–3 ribs inferior to the inframammary vein. The superior poles of the thymus may lie in close crease, permitting direct visualization of the placement of proximity to the recurrent laryngeal nerves as they course the caudal-most port, located at the mid-axillary line at in the tracheoesophageal grooves. Inferiorly, the thymic the level of the insertion of the diaphragm. The location lobules rest on the anterior aspect of the pericardium. of this second port facilitates dissection of mediastinal fat The phrenic nerves run laterally to the thymus in the and allows for improved access to the cervical neck superior anterior mediastinum; thymic tissue may extend deep to to the brachiocephalic vessels. The third port is placed is these nerves, resting on the pericardium (5). Importantly, placed laterally and mid-way between the initial two. extracapsular islands of thymic tissue are found embedded in peri-thymic fat throughout the mediastinum and neck. Procedure overview (Figure 1) Ectopic thymic tissue was found in the mediastinum and cervical neck in 98% and 32% of thymectomy specimens, Step 1: Release from diaphragm, sternum and pericardium respectively (6). Thymic tissue is dissected free from attachments to the Arterial blood supply to the thymus is primarily derived diaphragm inferiorly, sternum anteriorly and pericardium from branches of the internal mammary arteries, but posteriorly until the right lung is visualized. Dissection is superior portions may also be supplied by branches of the extended until the left internal mammary vein is identified inferior thyroid arteries. Venous drainage is predominantly and traced until it enters the inferior aspect of the left achieved via a large draining vein on the posterior side of brachiocephalic vein. the thymus that enters the left brachiocephalic vein. Step 2: Release of left phrenic nerve The left phrenic nerve should be visualized coursing on along Surgical technique in bilateral VATS thymectomy the left lateral aspect of the pericardium; visceral pleural overlying the nerve is incised and thymic and peri-thymic General principles tissue are resected deep to the phrenic nerve. The goal of thymectomy in MG is to remove as much thymic tissue as is safely possible so as to reduce the number Step 3: Release from left brachiocephalic vein of immunogenic thymic cells responsible for the production Dissection is then continued laterally to medially along the of pathogenic antibodies, as well as achieving complete inferior side of the left brachiocephalic vein, with continued mass resection in cases associated with a thymoma. Care removal of thymic and peri-thymic tissue anteriorly and is taken to avoid directly grasping thymic tissue so as to posterior side of the brachiocephalic vein. A large venous reduce the risk of capsular disruption and spillage of thymic branch draining the thymus is usually encountered on the tissue. Thus, a “touch-free” approach is utilized throughout inferior aspect of the brachiocephalic vein and may be © Video-Assisted Thoracic Surgery. All rights reserved. vats.amegroups.com Video-assist Thorac Surg 2017;2:12 Video-Assisted Thoracic Surgery, 2017 Page 3 of 6 clipped and transected. cervical thymic tissue, but minimize the risks associated with cervical neck dissection (such as recurrent laryngeal Step 4: Cervical neck dissection nerve injury) (9,10). Dissection is then continued superiorly into the Within videoscopic-assisted thymectomy (T-2), there cervical neck until the thyrothymic ligaments are freed. exists a range of surgical approaches, including unilateral Given the location of the thymic horn adjacent to the (right or left) VATS (T-2a), bilateral VATS (T-2b), and tracheoesophageal groove, care is taken to avoid injury robot-assisted thymectomy (T-2c-d). While the T-2b to the recurrent laryngeal nerve, which runs in the same bilateral VATS, also known as “video-assisted thoracoscopic location. Additionally, inferior thyroid veins draining into extended thymectomy” or VATET, is classically defined as a the brachiocephalic vein may be identified and ligated. bilateral approach with a cervical neck incision to facilitate cervical lobe excision, the term is inconsistently used in the Step 5: Release from right phrenic nerve and removal literature and may refer to a bilateral VATS thymectomy of specimen with or without additional cervical neck incision