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Ann Thorac Surg 1998;65:1520-1522
© 1998 The Society of Thoracic Surgeons

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Original articles: general thoracic

Long-Term Clinical Outcome After Transcervical Thymectomy for Myasthenia Gravis

^a Division of Neurology, The Toronto Hospital, General Division, Toronto, Ontario, Canada

Accepted for publication December 18, 1997.

Address reprint requests to Dr Bril, The Toronto Hospital, General Division, EN11-209, 200 Elizabeth St, Toronto, Ont Canada M5G 2C4
e-mail: (vera.bril{at}utoronto.ca)

	Abstract

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Background. We reviewed the long-term clinical outcome after transcervical thymectomy for generalized myasthenia gravis without thymoma in 52 patients who had this procedure at The Toronto Hospital between 1977 and 1986, and compared the results with those reported after more radical surgical approaches.

Methods. Preoperative and postoperative patient evaluations were based on a modified Osserman classification. We defined complete remission as asymptomatic with normal strength and without medications for myasthenia gravis. The complete remission rate was selected as the best measure for comparison between different surgical approaches.

Results. The 52 patients were followed up for a mean of 8.4 years (±6.1 years [standard deviation]). The preoperative mean Osserman grade was 2.7 compared with 0.4 at final follow-up. Complete remission occurred in 44.2% of patients. Similar results are reported after transsternal thymectomy.

Conclusions. Comparable results after transcervical and transsternal thymectomy favor the use of the less radical approach.

	Introduction

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Thymectomy is recognized currently as standard effective therapy complementing the medical management of patients with generalized myasthenia gravis (MG), but the optimal surgical approach remains controversial. Transcervical, transsternal, and combined exposures of the anterior mediastinum are alternatives advocated by different authors [1–6]. In 1988, Cooper and colleagues [6] reported the results of transcervical thymectomy in 65 patients at The Toronto Hospital. These patients were followed up for at least 1 year, with a mean follow-up of 3.6 years. Their outcome compared favorably with outcomes reported after more invasive surgical approaches. Critics of transcervical thymectomy question whether the long-term outcome after this procedure would be as good as with other exposures, as the thymus might not be visualized and resected completely with this approach. We present our long-term results with transcervical thymectomy and compare them with outcomes reported for other surgical approaches (transsternal or combined transsternal and transcervical).

	Material and methods

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We reviewed the clinical outcomes of 52 patients who had transcervical thymectomy for generalized MG without thymoma at The Toronto Hospital between 1977 and 1986. The 52 patients, all of whom returned for follow-up, were included in this review. Patients with thymoma demonstrated radiographically underwent transsternal thymectomy and were excluded from this series.

All patients underwent evaluation at The Toronto Hospital Neuromuscular Clinic by one of us who is a neurologist specializing in the care of patients with MG (V.B.). Clinical assessments were done at variable intervals depending on patient status, but the interval was not longer than 12 months and could be as frequent as every 1 month to 3 months. Assessments addressed symptoms, medications used, state of general health, medication side effects, and ability to work. A standard neurologic examination assessed strength in all muscle groups. Staging preoperatively and at follow-up visits was done with a modified Osserman classification [6]: 0 = asymptomatic; 1 = ocular signs and symptoms only; 2 = mild generalized weakness; 3 = moderate generalized weakness; and 4 = severe generalized weakness, respiratory dysfunction, or both.

Surgical intervention was done by one of us (J.C.) as soon as possible after clinical evaluation in The Toronto Hospital Neuromuscular Clinic. The technique of transcervical thymectomy has been described previously [6]. Patients considered at risk for postoperative respiratory insufficiency had plasma exchange prior to operation. Immunosuppressive medications were not started until after operation. Anticholinesterase medications were given as needed both before and after the surgical procedure.

We used definitions similar to those in other published series to be able to compare our results with theirs, as the operative approach used in The Toronto Hospital for patients with generalized MG and without thymoma was strictly transcervical.

The definitions were as follows: complete remission = asymptomatic without weakness and without any MG medications, and remission = asymptomatic with normal strength or minimal ocular findings (slight ptosis) without any MG medications or with only pyridostigmine bromide. The palliation rate included all patients with minimal to no weakness with or without MG medications. The improvement rate included all patients who improved by at least one grade, although the patients could still have more than minimal weakness, therefore not fitting into the palliation category. The improvement rate included all patients with complete remission, remission, and palliation. We compared the follow-up visit rates to those in studies reporting follow-up rates after other surgical approaches [7, 8].

Statistical analyses of means, standard deviations, and percentages were done using Statview IV (Abacus Concepts, Berkeley, CA) for the Macintosh computer (Apple, Cupertino, CA). Numbers of returning patients were compared using the Fisher exact statistical method.

	Results

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The study population consisted of 52 patients, 15 male and 37 female. Age ranged from 14 to 50 years with a mean age of 28.4 years. The mean follow-up period after thymectomy was 8.4 ± 6.1 years (± the standard deviation). The preoperative mean Osserman grade was 2.7 and the mean Osserman grade at last follow-up, 0.4. None of the patients sustained phrenic nerve injuries or other major surgical morbidity.

The improvement rate (at least one grade) was 90.4%, with palliation (minimal or no residual symptoms) in 82.7%. Remission was noted in 59.6% of patients, with complete remission in 44.3%. The complete remission rate for transcervical thymectomy compared with other surgical approaches is shown in Table 1. The rate does not differ between these approaches.

	Comment

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We considered complete remission the best measure for comparison with other reported series but had difficulties making exact comparisons because of the lack of standard definitions, assessments, and classifications in the reports. Selection of different outcome measures or different lengths of follow-up could readily introduce a bias into the results.

One interesting observation from this review of different series is that patients who undergo transcervical thymectomy return for fewer follow-up visits than those who have extended and transsternal thymectomy [7, 8]. This different rate of follow-up was noted even when transsternal thymectomy and transcervical thymectomy were done in the same institution [7]. We speculate that the patients who do not return for follow-up may have a better remission rate and do not think it necessary to return. Other outcomes are possible (death, care at another institution). Our observation that the complete remission rate at last follow-up for patients not returning for more than 5 years was higher than that for the total group lends support to the concept that the patients not returning were doing well.

In summary, we conclude that the long-term clinical outcome after transcervical thymectomy is the same as that after more radical surgical approaches. However, transcervical thymectomy carries a lower morbidity [4, 6], a briefer hospitalization, and a faster patient recovery. Our equivalent clinical outcome supports the contention that the transcervical approach is optimal for patients with generalized MG.

	References

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1. Masaoka A., Yamakawa Y., Niwa H., et al. Extended thymec-tomy for myasthenia gravis patients: a 20-year review. Ann Thorac Surg 1996;62:853-859.[Abstract/Free Full Text]
2. DeFilippi V.J., Richman D.P., Ferguson M.K. Transcervical thymectomy for myasthenia gravis. Ann Thorac Surg 1994;57:194-197.[Abstract]
3. Mulder D.G., Graves M., Herrmann C. Thymectomy for myasthenia gravis: recent observations and comparisons with past experience. Ann Thorac Surg 1989;48:551-555.[Abstract]
4. Papatestas A.E., Genkins G., Kornfeld P., et al. Effects of thymectomy in myasthenia gravis. Ann Surg 1987;206:79-88.[Medline]
5. Jaretzki A., Penn A.S., Younger D.S., et al. "Maximal" thymectomy for myasthenia gravis. J Thorac Cardiovasc Surg 1988;95:747-757.[Abstract]
6. Cooper J.D., Al-Jilaihawa A.N., Pearson F.G., Humphrey J.G., Humphrey H.E. An improved technique to facilitate transcervical thymectomy for myasthenia gravis. Ann Thorac Surg 1988;45:242-247.[Abstract]
7. Papatestas A.E., Genkins G., Kornfeld P. Comparison of the results of the transcervical and transsternal thymectomy in myasthenia gravis. Ann NY Acad Sci 1981;377:766-781.[Medline]
8. Masaoka A., Monden Y. Comparison of the results of the transsternal, transcervical and extended thymectomy. Ann NY Acad Sci 1981;377:755-765.[Medline]

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Joel D. Cooper Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Bril, V. Articles by Cooper, J. D. Search for Related Content PubMed PubMed Citation Articles by Bril, V. Articles by Cooper, J. D.