Using newly developed technologies, scientists from diverse fields and disciplines are in a position to make significant progress in understanding the critical issues raised by the neurodegenerative disorders and the mechanisms of the selective vulnerability of cells of the central nervous system. Although the pathway of cell death may be common, these disorders are associated with a variety of risk factors including genetic and environmental events. Still, except for HD, most cases of these disorders have not been shown to be of genetic origin. Exogenous agents including neuroleptic drugs used in the treatment of schizophrenia can cause tardive dyskinesia with PD-like symptoms. While the etiology of many neurodegenerative disorders is unknown, the mechanisms by which the neurons die may be similar.
Neurodegenerative diseases occur when a significant proportion of neurons die.
The cause of the selective vulnerability of these cells is not known. Implicated in this destruction as well as in destruction of neurons following neuronal injury are oxidative stress by free radical damage, defective energy metabolism, external or internal toxins, genetic factors, and aging. Altered regulation of programmed cell death during development may be involved in the etiology of specific mental disorders. Alone or in combination, these factors could lead to necrotic or apoptotic cell death. Changes in mitochondrial function with age or injury can alter cellular energetics, free radical metabolism, and vulnerability to further harm.