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Ann Thorac Surg 2001;72:1902-1905
© 2001 The Society of Thoracic Surgeons
a Department of Surgery and Oncology, Graduate School of Medical Sciences, Fukuoka, Japan
b Department of Endoscopic Diagnostics and Therapeutics, Faculty of Medicine, Fukuoka, Japan
c Department of Neurology, Neurological Institute, Kyushu University, Fukuoka, Japan
Accepted for publication August 8, 2001.
* Address reprint requests to Dr Uchiyama, Department of Surgery and Oncology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan
e-mail: uchiyama{at}surg1.med.kyushu-u.ac.jp
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Abstract |
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Methods. We evaluated this new approach in 23 patients with myasthenia gravis who underwent total thymectomy assisted by infrasternal mediastinoscopy between 1998 and 2000. The results were analyzed with special reference to morbidity and short-term improvement of the disease severity determined according to quantitative myasthenia gravis (QMG) scores.
Results. Complete removal of the thymic gland with the pericardial adipose tissue was accomplished through an infrasternal mediastinoscopic approach in 21 of the 23 (91.3%) patients. The remaining 2 patients required conversion to sternotomy, the one for insufficient sternal lifting with vascular tape and the other for invasion of a thymoma to the innominate vein. There was no related mortality and only one complication, a phrenic nerve injury in 1 patient (4.3%). Significant clinical improvement of disease was achieved in the short term and several advantages were apparent.
Conclusions. Infrasternal mediastinoscopic thymectomy is safe and feasible for patients with myasthenia gravis.
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Introduction |
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Material and methods |
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The diagnosis of myasthenia gravis was confirmed on the basis of both clinical presentation and neurologic examinations including the edrophonium chloride (Tensilon) test, electromyographic study, and serum acetylcholine receptor antibody assay. Preoperative grading of the disease was based on the Osserman classification system [10]. Classifications were grade I (n = 3), grade IIA (n = 16), and grade IIB disease (n = 4). The grade I patients were unique in that 1 was intolerant to drugs due to liver damage (patient 4), 1 preferred surgical treatment (patient 12), and 1 had a thymoma (patient 22). A total of 4 patients had a thymoma. The maximal diameter of the thymomas ranged from 25 to 43 mm. Thymoma was not considered a contraindication to mediastinoscopic thymectomy.
Surgical techniques
Infrasternal mediastinoscopic thymectomy was performed under general anesthesia. Patients were placed in the supine straddle position with their neck extended. In the first 18 patients, a transverse incision of 3 cm was made above the sternal notch. The anterior cervical muscles were divided at the midline and the upper portion of the thymus was dissected free. In the most recent patients (patients 19 to 23), the operation was performed without the cervical incision. An arc-shaped incision of 3 cm was made just below the xiphoid process. The rectus abdominis muscle was divided and the xiphoid process was excised. Laparofan (Origin Co, Ltd, Menlo Park, CA) was inserted beneath the lower part of the sternum and the sternum was lifted with the use of a Laparolift (Origin Co, Ltd). In the first 4 patients the sternum was lifted with vascular tape. The infrasternal incision was used for insertion of a grasping forceps and ultrasonic coagulating shears (Harmonic scalpel; Ethicon Endo-Surgery, Inc, Cincinnati, OH). A 30-degree angled telescope was inserted through a trocar placed below the surgical wound (Fig 1). The anterior mediastinal tissue including the thymus was dissected free from the pericardium. The anterior mediastinal space was well visualized by pushing the ventilated lungs aside with either a lung spatula (Karl Storz GmBH & Co, Tuttlingen, Germany) or an original device (Fig 2). After the innominate vein was identified, the thymic veins were clipped and divided. In cases without cervical incision (in patients 19 to 23), each of the upper poles of the thymus was dissected free from the thyroid gland using blunt dissection from below. The small blood vessels feeding the thymus were divided with a Harmonic scalpel. The superior poles of the thymus were then well visualized from below (Fig 3). The thymus together with the adipose tissue was removed through the abdominal incision (Fig 4). Complete dissection of the lateral adipose tissue along the phrenic nerves was confirmed at the end of surgery. A drainage tube was placed in the anterior mediastinal space. After surgery all patients were monitored in the intensive care unit for at least 1 night.
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Outcome measures
Clinical improvement subsequent to surgery was evaluated on the basis of the quantitative myasthenia gravis (QMG) score [11] in 15 patients followed up for more than 5 months at our institution. The average period from the operation to the date of clinical evaluation of these patients was 15.5 months (range 6 to 27). Scored items included ptosis, diplopia, facial weakness, dysphagia, dysarthria, neck muscle strength, bilateral arm muscle strength, bilateral hand grips, bilateral leg muscle strength, and vital capacity. Each item was graded on a scale of 0 to 3 (0 = normal, 1 = mild, 2 = moderate, and 3 = severe). The scores were added together for an aggregate QMG score. Data are expressed as mean ± SD. The presurgery and postsurgery QMG scores were compared. The Wilcoxon signed-ranks test was applied to determine statistical significance. A probability value less than 0.05 was considered significant.
The surgical outcomes were graded according to the criteria used by DeFilippi and associates [4]: 1 = complete remission off all medication, 2 = asymptomatic on decreased medication, 3 = improved with decreased medication, 4 = no change, and 5 = worsening symptoms.
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Comment |
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Video-assisted mediastinoscopic thymectomy is a new alternative to thoracoscopic surgery for patients with myasthenia gravis. Kido and coworkers [9] recently applied this technique in 3 patients with anterior mediastinal masses. We employed this procedure for total thymectomy because it allowed for equal bilateral dissection of the pericardial adipose tissue through one incision, and differential lung ventilation was not always necessary. The thoracoscopic approach employed in most institutions is usually conducted from either the left or right side. In the unilateral approach, dissection of the pericardial adipose tissue on the opposite side is a problem still debated [12, 13]. The mediastinoscopic approach allows us to perform thymectomy from both sides. Since both phrenic nerves can be clearly identified during this procedure, dissection of the pericardial adipose tissue can be performed safely. In addition the adipose tissue on the cardiophrenic angles can be removed directly through the abdominal incision.
Another advantage of mediastinoscopic thymectomy is that it can be performed with bilateral lung ventilation. The mediastinoscope and the operative instruments can be used easily when the ventilated lungs are pushed aside with lung retractors. Avoidance of one-lung ventilation should decrease the risk of pulmonary complications. In addition mediastinoscopic thymectomy is applicable to patients with thoracotomy, a history of pleuritis, or with poor pulmonary function.
Our quantitative analysis of the short-term change in the clinical status of patients showed the therapeutic effectiveness of mediastinoscopic thymectomy. The postoperative medications used in our institution for myasthenia gravis routinely include steroids. As no patient in this series received steroids preoperatively, the surgical benefit in patients who do receive postoperative steroids should be carefully evaluated. Although there may be some modification of clinical status with the use of steroids, our overall results suggest that mediastinoscopic thymectomy is a clinically acceptable surgical procedure for the treatment of myasthenia gravis.
There may be some disadvantages to this approach versus the transsternal or transcervical approach. One is the longer operation time although this will likely be shortened with experience. The average operation time for the first 17 patients was 293 minutes but that for the next 4 patients was 197 minutes. Another is the equipment required for lifting the sternum. If the Laparolift system is not available, use of vascular tape is another option.
After our experience with the first 18 patients we speculated that cervical incision might not always be necessary. As expected we found that the upper portion of the thymus could be clearly visualized and dissected without cervical incision. Avoidance of the cervical incision provides a clear cosmetic benefit and shortens the operation time. Granone and coworkers [14] have recently demonstrated the use of inframammary cosmetic incision for thymectomy in cases of myasthenia gravis. Their incision is similar to ours but they performed a total median sternotomy through the inframammary incision.
This procedure can also be applied to patients with a thymoma. Macroscopic invasion of the thymoma can be observed through mediastinoscopy. If the thymoma is encapsulated, video-assisted thymectomy should not be difficult. If the thymoma invades to the surrounding organs and endoscopic resection is considered difficult, conversion to sternotomy should ensue. In patient 22 preoperative computed tomography showed that the innominate vein was pressed by a thymoma. After direct invasion was confirmed by mediastinoscopy, sternotomy was performed by extending the abdominal incision. With this approach conversion to sternotomy was not difficult. The current study and our recent experience show that mediastinoscopic thymectomy is technically difficult when a thymoma more than 5 cm in diameter is located above the innominate vein or when a thymoma invades major vessels. If preoperative computed tomography shows one or the other of these conditions, sternotomy is recommended.
Infrasternal mediastinoscopic thymectomy has cosmetic benefits compared with the transsternal and transcervical approaches. It also has some advantages over a unilateral thoracoscopic approach. Clearly long-term follow-up is necessary for precise evaluation of this procedure. Our results are promising and we anticipate prospective studies comparing this procedure with the other approaches.
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This article has been cited by other articles:
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  A. Manlulu, T. W. Lee, I. Wan, C. Y. Law, C. Chang, J. C. Garzon, and A. Yim Video-Assisted Thoracic Surgery Thymectomy for Nonthymomatous Myasthenia Gravis Chest, November 1, 2005; 128(5): 3454 - 3460. [Abstract] [Full Text] [PDF]
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F. Rea, G. Marulli, and L. Bortolotti Robotic video-assisted thoracoscopic thymectomy MMCTS, March 24, 2005; 2005(0324): 422. [Abstract] [Full Text] [PDF]
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M. B. Marshall Invited commentary Ann. Thorac. Surg., August 1, 2004; 78(2): 409 - 410. [Full Text] [PDF]
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M. Zielinski, J. Kuzdzal, A. Szlubowski, and J. Soja Comparison of late results of basic transsternal and extended transsternal thymectomies in the treatment of myasthenia gravis Ann. Thorac. Surg., July 1, 2004; 78(1): 253 - 258. [Abstract] [Full Text] [PDF]
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M. Ohta, H. Hirabayasi, M. Okumura, M. Minami, and H. Matsuda Thoracoscopic thymectomy using anterior chest wall lifting method Ann. Thorac. Surg., October 1, 2003; 76(4): 1310 - 1311. [Abstract] [Full Text] [PDF]
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C.-P. Hsu, C.-Y. Chuang, N.-Y. Hsu, and S.-E. Shia Subxiphoid approach for video-assisted thoracoscopic extended thymectomy in treating myasthenia gravis Interactive CardioVascular and Thoracic Surgery, September 1, 2002; 1(1): 4 - 8. [Abstract] [Full Text] [PDF]
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A. Jaretzki III Injury to the phrenic and recurrent nerves needs to be avoided in the performance of thymectomy for myasthenia gravis Ann. Thorac. Surg., August 1, 2002; 74(2): 633 - 633. [Full Text] [PDF]
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A. Uchiyama, S. Shimizu, and M. Tanaka Reply Ann. Thorac. Surg., August 1, 2002; 74(2): 634 - 634. [Full Text] [PDF]
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