Neural transplantation for Parkinson's disease: a critical appraisal.

The medical treatment of severe Parkinson's disease is presently problematical and neural transplantation has been proposed as an additional therapy. While functional improvement in animal models of Parkinson's disease has been reported following neural grafting, the treatment of human Parkinsonian patients by adrenal medulla autografting into the neostriatum has produced little clinical improvement overall, and is associated with significant morbidity. Although recent grafting of human foetal dopaminergic neurons has shown more promise, many of the case reports lack rigorous assessment and long term follow-up. Further laboratory experimentation in animal models, particularly primates, to ascertain the mechanism of action of the grafts, the optimal sites for grafting, and the immunological responses to grafting, is essential. The future success of neural transplantation for Parkinson's disease may depend on the development of novel strategies such as the use of growth factors to aid cell survival, regulate neurotransmitter levels and promote connectivity. However, at present, the clinical application of neural transplantation for Parkinson's disease is premature.