Current issues in neural transplantation.

Neural transplantation research has resulted in many important advances in neurobiology in the last hundred years. Neural transplantation for Parkinson's disease (PD) has developed since 1985, but the overall results of autogenous adrenal medulla transplantation have been disappointing. Graft survival is poor, benefits transient and morbidity high. Peripheral nerve is a rich source of nerve growth factor (NGF) and has been co-grafted with adrenal medulla in an attempt to improve these results. Foetal tissue grafting has shown more promise with sustained clinical improvements noted, and some evidence of graft survival noted on Positron emission tomography (PET) scans. The optimal technique is to use three to four foetuses from induced abortions of 6.5 to eight weeks gestation with multiple stereotaxic implants into the putamen and caudate nucleus. Most investigators recommend immunosuppression post-operatively. Host tissue recovery appears to be an important mechanism for this clinical improvement. Foetal neural grafting has also been performed for Huntington's disease, diabetes insipidus, and hereditary cerebellar ataxia. Although foetal forebrain cholinergic and spinal grafts have been performed in animals, these have not yet been attempted for Alzheimer's disease, or spinal cord damage respectively in humans. Neural transplantation as a therapy for human central nervous system disease is at an early stage of development, but holds much promise for the future. It should only be undertaken by multidisciplinary groups, using strict research protocols.