The negative outcome of a trial of fetal stem cells in patients with Parkinson's disease is likely to provide fodder to opponents of fetal stem cell therapy. But the methods used in the trial differed substantially from those used by other groups doing fetal neuron transplants, indicating that changes in protocols can substantially affect patient outcomes.

A placebo-controlled trial reported last week in The New England Journal of Medicine demonstrated a lack of efficacy compared to previous, open-label studies of the procedure. Particularly disturbing was that 15 percent of the young patients who had showed improvement developed severe dyskinesias (involuntary abnormal movements) after the first year of observation.