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Eur J Cardiothorac Surg 2006;30:411-412
© 2006 Elsevier Science NL

Letter to the Editor

Can we consider thymectomy before pregnancy in female patients with myasthenia gravis?

Department of Neurology, National Institute of Medical Sciences and Nutrition "Salvador Zubirán", Mexico City, Mexico

Received 9 February 2006; accepted 19 April 2006.

^_* Corresponding author. Tel.: +52 55 56430741; fax: +52 55 56430741. (Email: jftellez{at}yahoo.com).

Key Words: Myasthenia gravis • Pregnancy • Prognosis • Transient neonatal myasthenia gravis • Thymectomy

I have read with interest the article by Roth et al. [1] reporting the course of a group of patients with myasthenia gravis (MG) during pregnancy. Roth et al. [1] analyzed retrospectively the outcome in eight patients with MG with a previous thymectomy and seven patients without thymectomy, reporting a better outcome during the pregnancy in thymectomized mothers and also in the babies. Recently our group reported the prognosis of 18 pregnant women with MG during the pregnancy [2]. The majority of the patients in our study had a thymectomy before the pregnancy (17 of 18 patients) and the prognosis was similar to the classical series of myasthenia gravis [3,4], 11% improved, 39% had worsening and 50% remained clinically unchanged. Our study contains patients with a previous thymectomy [2], and the trend demonstrated in the study by Roth et al. [1] at least in this group was not observed. This study was not considered in the analysis of this article [1].

Djelmis et al. [4] reviewed 69 pregnancies among 65 women. Twenty-five percent showed improvement, 45% did not change and 30% suffered exacerbations. Twenty-five patients (38.5%) had a previous thymectomy before the pregnancy. This study suggested that thymectomy before the pregnancy can minimize the likelihood of neonatal myasthenia. Batocchi et al. [3] evaluated the course of 47 females with MG who became pregnant. During pregnancy 41% had no change, 39% improved and 19% got worse. They concluded that the course during pregnancy is highly variable and unpredictable. Forty-two patients had thymectomy before the pregnancy. Both studies did not analyze the prognosis according to the thymectomy status.

The suggestion of Roth et al. [1] that thymectomy can improve the prognosis during the pregnancy is good but the evidence to support this idea is not solid. In our institution, we empirically recommend the thymectomy in the majority of the patients before the pregnancy. We do not have strong basis to support this recommendation but we have the same idea as Roth et al. [1] that thymectomy before the pregnancy can improve the evolution of MG during the pregnancy. The most important limitation of the study of Roth et al. [1] is the sample size and due to the unpredictable course of myasthenia gravis during pregnancy the observation about a better prognosis in thymectomized mothers could be obtained only by chance. The second observation in this study about a better prognosis in babies of mothers with myasthenia gravis should be taken carefully. The prevalence of transient neonatal myasthenia gravis is highly variable in reports, going from 5 to 30% and mainly explained by the different methods to perform the diagnosis but potentially a genetic variation has been suggested [5]. In the study by Roth et al. [1], two newborns had symptoms after the delivery and both belonged to the nonthymectomized group of mothers. Again this observation could be derived only due to the small sample size of the study and not related directly with thymectomy status of the mother. Overall, this study has an interesting observation but more investigation is required.

References

1. Roth TC, Raths J, Carboni G, Rosler K, Schmid RA. Effect of pregnancy and birth on the course of myasthenia gravis before or after transsternal radical thymectomy. Eur J Cardiothorac Surg 2006;29(2):231-235.[Abstract/Free Full Text]
2. Tellez-Zenteno JF, Hernandez-Ronquillo L, Salinas V, Estanol B, da Silva O. Myasthenia gravis and pregnancy: clinical implications and neonatal outcome. BMC Musculoskelet Disord 2004;5(1):42.[CrossRef][Medline]
3. Batocchi AP, Majolini L, Evoli A, Lino MM, Minisci C, Tonali P. Course and treatment of myasthenia gravis during pregnancy. Neurology 1999;52(3):447-452.[Abstract/Free Full Text]
4. Djelmis J, Sostarko M, Mayer D, Ivanisevic M. Myasthenia gravis in pregnancy: report on 69 cases. Eur J Obstet Gynecol Reprod Biol 2002;104(1):21-25.[CrossRef][Medline]
5. Papazian O. Transient neonatal myasthenia gravis. J Child Neurol 1992;7(2):135-141.[Abstract/Free Full Text]

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