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Ann Thorac Surg 2002;74:633
© 2002 The Society of Thoracic Surgeons
a Columbia Presbyterian Medical Center, PO Box 365, Essex, CT 06426 USA
e-mail: alfred.jaretzki{at}snet.net
To the Editor
In a recent issue of this journal, Uchiyama and colleagues reported their experience with a substernal thoracoscopic approach to thymectomy for myasthenia gravis (MG) in 23 patients, 4 of which also had a thymoma [1]. An additional cervical incision was used in the first 18 patients. The authors’ state that this new thymectomy technique: (a) accomplishes a total thymectomy more effectively than unilateral thoracoscopy, (b) avoids the problems associated with a median sternotomy, and (c) produces excellent "short-term" results. They use cautery in the dissection and report an incidence of 4% phrenic nerve injury.
Although the authors are to be congratulated for continuing the search for a resectional technique that removes the entire thymus with results equal to the more aggressive resections and with reduced morbidity, there are several problems with the present report.
Based upon the known anatomy of the thymus and descriptions of the more aggressive thymectomy techniques, this procedure probably does not assure a total thymectomy. It appears to be greater than the standard transsternal but less than the extended transsternal resections and it does not remove extra-lobar tissue in the neck that may contain small amounts of thymus [2]. Although this technique does avoid some of the problems associated with a transsternal median-sternotomy, phrenic nerve injury appears to be at risk. Since phrenic, recurrent, and left vagus nerve injuries compromise respiratory and oropharyngeal function, such injuries can be devastating in a patient with MG. Accordingly, nerve injury should be avoided if at all possible. For this reason, cautery should not be used in the vicinity of these nerves and, as emphasized by those advocating aggressive transsternal thymic resections for MG, such injury must be avoided even if some thymic tissue is thereby not removed [3].
Although a 2% incidence of nerve injury has been reported [4], by employing direct vision and careful dissection, Mulder had no nerve injuries in 333 "extended" transsternal thymectomies [3], and I had a similar experience with over 200 "maximal" thymectomies [5, 6]. Accordingly, a 0% incidence of nerve injury is achievable and should be the goal of all thymic resections for autoimmune nonthymomatous MG.
The demonstrated postoperative improvement cannot be attributed to the thymectomy alone. Only 15 of the 23 patients were evaluated, "short-term" is not defined, and, most importantly, all patients received immunosuppressive therapy postoperatively. When patients receive immunosuppressive medications after thymectomy, it is not possible to infer retrospectively the effects of thymectomy itself without appropriately controlled studies [7].
The consensus continues to indicate that wide local excision is required for all thymic neoplasms whether they appear "benign" or not. To accomplish this, a formal median-sternotomy (with the occasional addition of a posterolateral thoracotomy) is required. Accordingly, the approach described is thought to be inappropriate for the resection of these tumors [8].
References
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