Parkinson's disease: imaging update

We aim to review recent neuroimaging contributions to our understanding of the cause and pathogenesis of Parkinson's disease, as well as treatment-related complications of disease, with a focus on functional anatomy and neurochemistry.

Recent reports describe altered dopaminergic activity in extrastriatal regions, as well as changes in other monoaminergic systems, such as serotonin. Attempts to correlate altered dopaminergic function with personality traits have also been described in the last year. The role of different markers of presynaptic dopaminergic integrity in the assessment of disease progression is discussed, as is the role of biomarkers in detection of preclinical disease. Cerebral activation studies not only confirm altered function of cortico-striatal-thalamo-cortical loops in Parkinson's, but also emphasize the importance of networks involving the cerebellum. The ability to detect changes in synaptic availability of dopamine using positron emission tomography with [(11)C]raclopride is reviewed, including the application to detect altered levels of dopamine in response to pharmacological, mechanical and behavioral stimuli. Such studies have been used to identify altered patterns associated with the development of motor fluctuations, as well as a biochemical substrate underlying the placebo effect in Parkinson's.

Functional imaging studies can provide novel insights into the etiopathogenesis of Parkinson's disease, as well as the mechanisms that contribute to complications of long-term therapy. They also shed light on the mechanisms that may underly behavioral changes and benefit derived from surgical interventions.