The case for neural tissue transplantation as a treatment for Parkinson's disease.

Neural tissue grafting can be highly effective and constitutes a potentially curative approach for progressive neurodegenerative disorders such as PD. Virtually all signs and symptoms of PD have been shown to improve after grafting but not necessarily simultaneously in one patient. Several technical aspects require improvement before widespread use of neural tissue implants can be recommended. These include better definition of donor tissue in terms of infectious risks, the need and duration of immunosuppressive treatment, and the minimal amount of tissue needed for definite benefit. Somatotropism within the basal ganglia system (with specific targeted grafts) aimed at relieving certain symptoms need to be elucidated experimentally. Interaction with the underlying disease process is also important to consider, and the role of intracerebral grafts in differing patterns of parkinsonism needs to be addressed. Grafting is potentially a very powerful therapeutic approach that may evolve to be the ideal treatment for patients with young-onset disease who, when starting to experience fluctuations, may have a life expectancy of 25 years with the disease. For these patients, grafting is likely to be both effective and long-lasting. For these patients, it is likely to become an efficient and also economically sound treatment for the patients and society. Provided that the transplantation procedure is performed judiciously and with strict adherence to basic principles defined from animal and human experimentation, more patients are likely to benefit from the procedure.