Early detection of Parkinson's disease. Implications for treatment.

Parkinson's disease (PD) is the second most common neurodegenerative disorder worldwide and is characterised by cardinal clinical features and specific pathological findings. It is possible to detect PD early on in the course of the disease, and certain laboratory studies may identify preclinical stages. Based on this information, and the hypothesis that there is a long preclinical period, there appears to be a window of opportunity to influence the natural course of the disease. Postulates regarding pathogenesis, such as oxidative stress and excitotoxicity, have led to the discovery of abnormal mitochondrial function in PD and a search for biochemical markers. Functional imaging studies have detected subclinical nigral dopaminergic dysfunction in individuals at risk of developing PD. Current symptomatic therapies are aimed at enhancing dopaminergic transmission. However, some commonly used PD medications may have alternative actions with both symptomatic and neuroprotective consequences. Bromocriptine has been postulated to have antioxidant effects and amantadine to have N-methyl-D-aspartate (NMDA) receptor antagonistic properties. Both have been reported to be associated with improved survival in PD. Additionally, monoamine oxidase type B inhibitors may provide neuroprotection. Recent new medications are also under study with regard to neuroprotection. Despite these advances, until there is a better understanding of the aetiology and pathogenesis of PD, there will be no definitive long-term benefit of early diagnosis and treatment of PD.