Meta-analyses in the wonderl and of neurology

Meta-analyses are often misused and underused in neurology. This editorial provides some comments on the role of meta-analyses in neurological research.Recently, a huge increase in the number of metaanalyses and systematic reviews has been observed in neurological journals. The major strengths of metaanalyses are the increase of statistical power. However, as for any other investigative tool, meta-analytic research is a research method itself which can produce severe shortcomings. Specifically, the issues of search terms, time periods of published studies, databases used for searching, the definitions of inclusion and exclusion criteria for papers(which greatly affect clinical heterogeneity), publication bias; and the statistical methods used, dramatically influence the results of metaanalyses. The main problem of meta-analyses is that they cannot be expected to overcome the limitations of the studies they include(the so-called "garbage in,garbage out" phenomenon). Furthermore, most systematic reviews in the neurological literature lead to the unsatisfying and clinically frustrating statement "further studies are needed". However it is much more frustrating to see how the gaps in scientific knowledge identified by meta-analyses have not been translated into serious efforts to fill them. Besides their role in evaluating efficacy and tolerability of drugs, meta-analyses may be used to assess diagnostic values of debatable clinical findings, as they represent powerful tools to try to answer questions not posed by individual studies and to settle controversies arising from conflicting claims.