Diagnostic aspects of early Parkinson's disease.
Insidious onset of mild, unspecific, sensitive, vegetative, psychopathological, cognitive and perceptive disturbances, i. e., visual and olfactory dysfunction, with a resulting change of personal behavior, i. e., reduced stress tolerance, precede the initially intermittently occurring motor symptoms in patients with Parkinson's disease (PD). Novel neuropathological findings suggest an expansion pattern of the neurodegenerative process beyond the nigral dopaminergic neurons with the initial event located outside the brain. This underlines the clinical concept of an initial premotor phase, which starts in nondopaminergic areas in PD. Moreover a more global general understanding of chronic neurodegeneration enables the performance of clinical trials on neuroprotection, since there is increasing evidence that diagnosis of PD at the threshold of onset of motor symptoms or cognitive symptoms in Alzheimer's disease is too late. Such an earlier diagnosis of chronic neurodegeneration will allow a more convincing demonstration of the efficacy of a neuroprotective or disease modifying compound. It will also support the concept of a clinically effective pharmacological intervention on a disease process, which is also more and more demanded by the health authorities for drug approval.