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J Thorac Cardiovasc Surg 1998;115:252-254
© 1998 Mosby, Inc.
BRIEF COMMUNICATIONS |
Rome, Italy
Supported by a grant from MURST 60%.
Received for publication August 26, 1997 Accepted for publication Sept. 3, 1997. Address for reprints: Tommaso Claudio Mineo, MD, Cattedra di ChirurgiaToracica, Universitá Tor Vergata di Roma, Ospedale S. Eugenio, P.leUmanesimo, 10—00144 Rome, Italy.
Thymectomy is an effective surgical therapy complementing the medicalcare of patients with myasthenia gravis. Residual thymic tissue is present in 64%up to 70% of patients showing partial improvement or no response afterthymectomy.
1 Either it is dueto a remnant of the original gland missed during the operation or it developsfrom ectopic thymic tissue. 2,3 Completion thymectomy, carried outby the extended transsternal 2,3 or the maximaltranssternal-transcervical 4approaches, has been advocated after unsuccessful transcervical thymectomy.Video-assisted thymectomy is being investigated in the belief that thisprocedure may also allow a complete removal of the thymus and the anteriormediastinal and lower cervical perithymic adipose tissue. 5,6We have adopted the video-assisted approach as a less invasive modality toreoperate on patients with nonthymomatous refractory myasthenia who did notundergo extended thymectomy initially.
Between December 1995 and December 1996, four patients with myastheniagravis, three women and one man with a mean age of 41 years, underwentvideo-assisted completion thymectomy. The mean duration of myasthenia gravisbefore the initial operation was 21 months, ranging from 12 to 38 months. Theinitial operation was transcervical thymectomy performed by one of the authors(T.C.M.) in three patients and sternal-splitting thymectomy performed in adifferent institution in one. No patient underwent extended thymectomyoriginally. The mean interval between operations was 120 months, ranging from 72to 180 months. Informed consent was obtained from all patients. They were giventhe main information regarding the different approaches and the possiblecomplications. Worthy of note, results of preoperative computed tomography andmagnetic resonance imaging were deemed negative or inconclusive regarding theidentification of residual or ectopic thymus. Three patients had elevated serumtiters of antibody to the acetylcholine receptor, and all had a positiveedrophonium test and characteristic decreasing responses to low-frequencyrepetitive nerve stimulation. At admission, every patient was completelydisabled. Three patients were receiving large doses of pyridostigmine bromide(mean dose 560 mg/day) in combination with prednisone (mean dose 45 mg/d), andone patient was receiving prednisone and azathioprine (Table I).All attempts to taper medication were unsuccessful because of increasedfatigue. Three patients were receiving long-term maintenance plasma exchangewith a mean of 6.25 cycles/year (Table I). Each patientunderwent four exchange cycles over the last two preoperative weeks to stabilizethe clinical condition and reduce postoperative morbidity. Adjuvantpneumomediastinum was always induced within the last 24 hours to facilitate thesubsequent visualization of the thymic tissue and the dissection maneuvers. 5 The operation was performed afterdouble-lumen intubation by a four-trocar access and with the patient lying in a45-degree off-center position. Thymectomy routinely included en bloc removal ofthe residual thymus, if present, or all of the mediastinal-lower cervicalperithymic adipose tissue (Fig. 1). Thymic tissue was identified athistologic examination by the presence of Hassal's corpuscle or afterimmunohistochemical staining with cytokeratin and T-cell markers. Thetherapeutic effect of completion thymectomy was established for each patient bycomparing the preoperative clinical status with the status at the most recentfollow-up examination. Completion thymectomy was performed by the leftvideo-assisted approach in three patients and by the right approach in onepatient because of diffuse pleural adhesions on the left side. Mean operativetime was 136 minutes, ranging from 90 to 210 minutes. In all the patients thymicremnants were found below the left innominate vein. Mean weight of the removedtissue was 22.7 gm (Table I). No operative deaths normajor morbidity occurred. Mean hospital stay was 3.25 days (range 2 to 5 days).Mean follow-up was 15.0 months (Table I). Postoperatively,one patient required further plasma exchange treatment because of a myastheniccrisis, which occurred at 6 months. At the most recent follow-up examination,although no patient was in complete remission, three had significant improvementin bulbar and limb function, needing substantially lower doses ofcorticosteroids and anticholinesterase drugs (Table I).Both patients who had removal of the gross thymic tissue improved aftercompletion thymectomy.
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2-4 In these cases completionthymectomy carried out by the extended transsternal 2,3or maximal transsternal-transcervical approaches 4 proved effective in ameliorating theeffects of refractory myasthenia gravis. Similarly we noted that video-assisted completion thymectomy providedclinical improvement in three of four patients. In our experience clinicalimprovement clearly correlated with the reoperation, because symptoms eased soonafter the operation and the improvement persisted during the follow-up period.We have always intentially performed an extended dissection of the residualthymus and adipose perithymic tissue, and we have found residual thymic tissuein all our patients.
We believe that the video-assisted approach might be considered areliable alternative to the transsternal or the combined approach for a numberof reasons. First, it is minimally invasive, which however does not seem tocompromise either a complete anatomic thymectomy or a wide dissection of theanterior mediastinal and lower cervical adipose tissue. Second, patients withchronic refractory myasthenia are often receiving high doses of steroids, whichexposes them to an increased risk of wound healing problems if the transsternalapproach is used. Third, the transsternal reexploration of the anteriormediastinum after transcervical or transsternal thymectomy might be particularlydemanding because dense adhesions might be found at the site of the innominatevein. On the other hand, the surgical reexposure of the anterior mediastinum canbe facilitated by using a different route, such as the transpleural route.Finally, the magnified video imaging may allow better visualization of thevascular and nervous structures and may help reduce the risk of injuring themduring the dissection maneuvers. To date the combined transsternal-transcervicalthymectomy represents the gold standard in terms of extent of dissection andremoval of ectopic thymic tissue in patients with myasthenia. 4 However, many patients andneurologists are reluctant to accept it because of its invasiveness and becauseits superiority over other approaches has not yet been demonstrated. Thisinitial experience suggests that completion thymectomy is not a contraindicationfor the video-assisted approach, which might prove as effective as openapproaches. The role of the video-assisted thymectomy is evolving and seems tohold unsuspected potentiality. More detailed studies based on a wider accrual ofpatients and longer follow-up are needed to confirm these findings.
Footnotes
J Thorac Cardiovasc Surg 1998;115:252-4
References
This article has been cited by other articles:
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  F. Rea, G. Marulli, L. Bortolotti, P. Feltracco, A. Zuin, and F. Sartori Experience With the "Da Vinci" Robotic System for Thymectomy in Patients With Myasthenia Gravis: Report of 33 Cases Ann. Thorac. Surg., February 1, 2006; 81(2): 455 - 459. [Abstract] [Full Text] [PDF]
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 H. K. Kolski, P. C.W. Kim, and J. Vajsar Video-Assisted Thoracoscopic Thymectomy in Juvenile Myasthenia Gravis J Child Neurol, August 1, 2001; 16(8): 569 - 573. [Abstract] [PDF]
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E. Pompeo, I. Nofroni, N. Iavicoli, and T. C. Mineo Thoracoscopic completion thymectomy in refractory nonthymomatous myasthenia Ann. Thorac. Surg., September 1, 2000; 70(3): 918 - 923. [Abstract] [Full Text] [PDF]
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T. C. Mineo, E. Pompeo, T. E. Lerut, G. Bernardi, W. Coosemans, and I. Nofroni Thoracoscopic thymectomy in autoimmune myasthenia: results of left-sided approach Ann. Thorac. Surg., May 1, 2000; 69(5): 1537 - 1541. [Abstract] [Full Text] [PDF]
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