Thymectomy For Ocular Myasthenia In China: A Systematic Review

BackgroundApproximately50%of people with myasthenia gravis present with purely ocular symptoms, so called ocular myasthenia. Of these between50to60percent become generalized disease, most within two years. Self-healing tendencies present on20to30percent of people with ocular myasthenia.Thus, with the complexity of the natural course of the disease, their management remains controversial. The effect of surgical treatment of ocular myasthenia gravis and the need for them is controversial especially. Systematic review and meta-analysis are used more widely about clinical studies during the era of evidence-based medicine. Through systematic reviews of the literatures, it is possible to increase the credibility of some conclusions, and to provide direction for further research. The systematic review about the treatment for ocular myasthenia has been performed, but the reasearches in China were not involved.ObjectivesTo perform a systematic review of the literatures about thymectomy for ocular myasthenia in China. To evaluate the validity of thymectomy in ocular myasthenia gravis.To provide reference for clinical practice, and new ideas for further clinical studies.MethodsTrials were located through electronic searches of CBM, CNKI, VIP, Wanfang Database, Cochrane Library. Manual search was performed for other literature. Where necessary, some authors were contacted for further information. A detailed analysis of the references was done.The randomized controlled trials as well as case-control or cohort studies were selected. Inclusion required meeting the criteria which is performed in advance. The risk of bias of these studies were assessd. Data regarding the risk of progression to generalized myasthenia gravis, complete remission of ocular symptoms were collected. And the meta-analysis were conducted by the Revman5.2software.Results1. No randomized controlled studies met the preset selection criteria. Only five retrospective controlled study were included in the review. Original data about complete remission rate can be obtained from all of the five studies. Original data about conversion rate can be obtained from two of the five studies.2. A systematic review of available retrospective controlled study were performed. Results are as follows:(1) Thymectomy can reduce the conversion rate of ocular myasthenia in China(RR=0.20,95%CI:0.10-0.40, P<0.00001).It can not be determined that thymectomy can reduce the complete remission rate of ocular myasthenia in China (RR=1.06,95%CI:0.79-1.44, P=0.69);(2) Confounding differences in baseline characteristics of prognostic importance between thymectomy and nonthymectomy patient groups exist in all studies;(3) The results as mentioned before remain unchanged after controlling for single confounding variables such as the duration of follow-up,with or without thymoma,the use of steroids;(4) Only one study performed multivariate analysis,it shows that thymectomy can reduce the conversion rate of ocular myasthenia.Conclusions1. There is no available evidence from randomized controlled trials regarding the efficacy of thymectomy for people with ocular myasthenia with respect to the outcome measures of complete remission of ocular symptoms and the risk of progression to generalized MG in China.2. The data from several observational studies favor the validity of thymectomy for people with ocular myasthenia with respect to the outcome measures of the risk of progression to generalized MG. However, compared to non-surgical treatment, the thymectomy can not improve the strict complete remission rate of ocular myasthenia gravis patients in China.But the uncontrolled nature of these reports limits the ability to draw any firm conclusions.3. Recommendations for future research:There is a need for well-designed, prospective, randomized studies about the efficacy of thymectomy. These studies should employ clinically relevant outcome measures such as improvement or resolution of ocular symptoms and the risk of progression to generalized MG In the absence of randomized controlled trials, well-designed observational studies may shed light on the efficacy of thymectomy.These studies should control adequately for potentially confounding factors, and should ensure that the outcome measure is ascertained in a blinded fashion in order to minimize bias.