Its typical of CRPS research that very small sample sizes are used, especially for initial research studies - its cheaper, saves you wasting a lot of time and effort on a hypothesis that turns out to be pointless and (cynically) it lets researchers do a second, larger study which then counts as two research projects and two published journal articles.

Usually if there is any value in the initial research a larger study is done with an attempt to correct any methodological flaws or inadequacies. That said, many times in the history of CRPS, policies about treatment options have often been made on the back of very small studies. It is always going to be an issue with CRPS that sample sizes will be small for much of the research work - even with international multi-centre trials its exceptionally difficult to recruit enough consistent, definitively diagnosed patients so that comparisons and conclusions are valid. The alternative is that you recruit over 5 or 10 years to get the numbers and by then your research will be out of date!!