Neurodegenerative movement disorders: the contribution of functional imaging

Functional imaging such as positron emission tomography and single-photon emission computed tomography provide sensitive tools to assess functional brain abnormalities associated with neurodegenerative disease. This review discusses recent findings in this field, with a focus on the detection and characterization of receptor binding and presynaptic dopamine changes in movement disorders.

The classical role of positron emission tomography and radioligands such as F-dopa and C-raclopride for investigating abnormalities of the presynaptic and postsynaptic dopaminergic system underlying Parkinson's disease, Parkinsonism and Huntington's disease has recently been made more powerful by the application of statistical mapping to localize changes in dopamine storage capacity and receptor binding across the whole brain at a voxel level. C-raclopride positron emission tomography provides an indirect marker of changes in levels of dopamine in the synaptic cleft. The application of this model in assessing dopamine changes in response to pharmacological, behavioural, motor task and magnetic stimulation in normal individuals and Parkinson's disease patients is reviewed. Recent studies using positron emission tomography and single-photon emission computed tomography to discriminate Parkinson's disease from essential tremor and Parkinsonism, the involvement of non-dopaminergic systems in Parkinson's disease and the role of cell transplantation in Parkinson's disease and Huntington's disease are also discussed.

Functional imaging techniques provide insight into the pathophysiology of Parkinson's disease, Parkinsonism, and Huntington's disease and the mechanisms of the progression of these diseases. They also play a role in assessing the efficacy of putative neuroprotective and restorative therapy, such as striatal infusions of neurotrophic factors and implants of fetal cells.