Abstract: The review authors discovered no new trials in the new searches in June 2009, November 2011, or January 2016. Six trials with 587 participants provided data for the primary outcome. According to moderate quality evidence, the disability grade change after four weeks in the corticosteroid groups was not significantly different from that in the control groups, mean difference (MD) 0.36 less improvement (95% confidence intervals (CI) 0.16 more to 0.88 less improvement). In four trials of oral corticosteroids with 120 participants in total, there was very low quality evidence of less improvement after four weeks with corticosteroids than without corticosteroids, MD 0.82 disability grades less improvement (95% CI 0.17 to 1.47 grades less). In two trials with a combined total of 467 participants, there was moderate quality evidence of no significant difference of a disability grade more improvement after four weeks with intravenous corticosteroids (MD 0.17, 95% CI -0.06 to 0.39). According to moderate quality evidence, there was also no significant difference between the corticosteroid treated and control groups for improvement by one or more grades after four weeks (risk ratio (RR) 1.08, 95% CI 0.93 to 1.24) or for death or disability after one year (RR 1.51, 95% CI 0.91 to 2.5). We found high quality evidence that the occurrence of diabetes was more common (RR 2.21, 95% CI 1.19 to 4.12) and hypertension less common (RR 0.15, 95% CI 0.05 to 0.41) in the corticosteroid-treated participants. According to moderate quality evidence, corticosteroids given alone do not significantly hasten recovery from GBS or affect the long-term outcome. According to very low quality evidence, oral corticosteroids delay recovery. Diabetes requiring insulin was more common and hypertension less common with corticosteroids based on high quality evidence.

Plain-language summary: There were eight clinical trials with altogether 653 participants. Only six trials with altogether 587 participants gave information about the primary outcome measure for this review, which was change in a seven-point disability scale. Financial support came from Baxter Bioscience for one trial, research councils for two trials, the National Institutes of Health for one trial, and unstated sources for the others. According to moderate quality evidence, when we pooled the results of the six trials with the necessary information there was no significant difference in change in disability grade after four weeks. Also according to moderate quality evidence, there was no difference in the percentage of participants who died or were left disabled after one year. We considered the evidence about disability unreliable because of marked variations between the trials. In four small trials of oral corticosteroids, with 120 participants, there was significantly less improvement after four weeks with corticosteroids than without corticosteroids but we considered the evidence quality very low. By contrast, according to moderate quality evidence, in two large trials of intravenous (injected into a vein) corticosteroids with a combined total of 467 participants, there was a slight improvement in disability after four weeks, but the results allowed for the possibility of no effect. Corticosteroids were not associated with a significant increase in harm except that diabetes was significantly more common than with placebo or supportive treatment alone. Although high blood pressure is a known harmful effect of corticosteroids, high blood pressure was unexpectedly much less common in the corticosteroid-treated participants. The lack of benefit from corticosteroids is not understood but might be because the drugs have a harmful effect on muscles which counteracts the benefit from reducing inflammation in nerves. The review is assessed as up to date to January 2016.