New strategies for the treatment of Parkinson's disease hold considerable promise for the future management of neurodegenerative disorders.

Neurodegenerative diseases are often considered incurable with no efficient therapies to modify or halt the progress of disease, and ultimately lead to reduced quality of life and to death. Our knowledge of the nervous system in health and disease has, however, increased considerably during the last fifty years and today, neuroscience reveals promising new strategies to deal with disorders of the nervous system. Some of these results have been implemented with success in the treatment of Parkinson's disease, a common neurodegenerative illness affecting approximately 1% of the population aged seventy or more. Parkinson's disease is characterized by a massive loss of dopaminergic neurons in the substantia nigra, leading to severe functional disturbance of the neuronal circuitry in the basal ganglia. A thorough description of basal ganglia circuitry in health and disease is presented. We describe how the functional disturbances seen in Parkinson's disease may be corrected at specific sites in this circuitry by medical treatment or, in advanced stages of Parkinson's disease, by neurosurgical methods. The latter include lesional surgery, neural transplantation and deep brain stimulation, together with future treatment strategies using direct or indirect implantation of genetically modified cell-lines capable of secreting neurotrophic factors or neurotransmitters. Advantages and disadvantages are briefly mentioned for each strategy and the implications for the future and the possible use of these interventions in other neurodegenerative diseases are discussed, with special emphasis on deep brain stimulation.