In 2001, Freed et al1 reported that human embryonic dopamine-neuron transplants survive in patients with severe Parkinson disease (PD) and do result in some clinical benefit in younger but not in older patients, those older than 60 years. In a similar study in 2003 with bilateral human embryonic dopamine-neuron implants in the putamen in patients with PD, Olanow et al2concluded that transplantation offered no significant improvement and could not be recommended. Both studies were unable to achieve their primary objective of major clinical improvement despite increased striatal F-18 fluorodopa uptake with positron emission tomography and data showing maintenance of transplanted neurons at postmortem examination.1,2 Freed et al1 did find improved motor function in a subset of patients younger than 60 years; Olanow et al did not find similar evidence but did note improvement in patients with milder disease at baseline. Of note, both studies reported disabling dyskinesia while not receiving medication in patients who received a transplant.
Rosenberg RN. Positive Potential of Fetal Nigral Implants for Parkinson Disease. Arch Neurol. 2004;61(6):837-838. doi:10.1001/archneur.61.6.837