Corticosteroids for myasthenia gravis

Background

Although widely accepted as an appropriate immunosuppressive therapy, the efficacy of glucocorticosteroid treatment has only rarely been tested in controlled studies.

Objectives

To assess the efficacy of glucocorticosteroids or adrenocorticotrophic hormone (ACTH) medication in autoimmune myasthenia gravis.

Search strategy

We searched the Cochrane Neuromuscular Disease Group Trials Register in July 2004 and updated in September 2007, MEDLINE (from January 1966 to September 2007) and EMBASE (from January 1980 to September 2007). We also checked the bibliographies in reviews and the randomised trials and contacted their authors to identify additional published and unpublished data.

Selection criteria

From the articles identified we selected those open or controlled studies which allowed us to assess the outcome of treated and untreated patients at definite endpoints.
Types of studies: quasi-randomised or randomised controlled trials.
Types of participants: patients with myasthenia gravis of all ages and all degrees of severity.
Types of interventions: any form of glucocorticosteroids or adrenocorticotrophic hormone treatment.
Types of outcome measures:

Primary outcome
1. improvement after at least three months in either the weakest muscles or all muscles.

Secondary outcomes
1. proportion of patients improved after at least six months
2. proportion of patients in remission
3. number of episodes of worsening during the first six months
4. acetylcholine receptor antibody titres after at least three months of therapy.

Data collection and analysis

Three authors extracted the data from the selected articles and one other checked them.

Main results

A trial of adrenocorticotrophic hormone (43 patients) did not show any advantage compared with placebo for the treatment of ocular myasthenia gravis. Two double-blind trials compared prednisone with placebo for generalised myasthenia gravis. In the first (13 patients), the improvement was slightly greater in the prednisone group at six months. In the second (20 patients) which was a short-term trial, the improvement was significantly greater at two weeks. Two trials compared glucocorticosteroids with azathioprine (41 and 10 patients respectively). In one of these the rate of treatment failure was greater in the prednisone group. In a trial of glucocorticosteroids versus intravenous immunoglobulin (33 patients) no differences in treatment responses were encountered during a treatment period of 14 days. An open trial (39 patients) evaluating different corticosteroid doses revealed a shorter time to improvement in the high-dose group. However only limited evidence can be drawn from the available randomised controlled trials due to numerous and important methodological flaws.

Authors' conclusions

Limited evidence from randomised controlled trials suggests that corticosteroid treatment offers significant short-term benefit in myasthenia gravis compared with placebo. This supports the conclusions of observational studies and expert opinion. Limited evidence from randomised controlled trials does not show any difference in efficacy between corticosteroids and either azathioprine or intravenous immunoglobulin.