References for this Review were found through a search of PubMed using the terms “PET” or “SPECT” and “Parkinson*” from 1980 to August, 2011, and “MR spectroscopy”, “MR imaging”, “Parkinson's disease”, and “iron” from 1993 to August, 2011, and from a search of Google Scholar using the terms “MRI”, “shape analysis”, “segmentation”, and “Parkinson's disease” from 2008 to August, 2011. Only reports published in English were included. Additional searches were done as needed for specific topics.
ReviewAdvances in imaging in Parkinson's disease
Introduction
The past 25 years have seen extensive developments in imaging approaches to the study of CNS disorders. Although diagnosis of Parkinson's disease remains clinical, advances in functional and structural imaging have improved the capacity to differentiate between Parkinson's disease and essential tremor, and between different akinetic-rigid syndromes. Recent advances in our understanding of the pathogenesis of Parkinson's disease have stimulated greater interest in the development of potential disease-modifying therapies, and, therefore, a more urgent need to detect early disease and identify biomarkers to assess the results of interventions.
Here, we review applications of imaging as a biomarker for early disease detection and for the study of disease progression. Imaging studies of animal models provide important complementary information on pathogenesis and for assessment of novel therapies, but are currently in their infancy. Imaging can provide significant insights into the basis of motor and non-motor complications of Parkinson's disease and its therapy, and the role of dopamine in normal brain function. Novel markers might permit in-vivo assessment of processes contributing to disease pathogenesis, such as inflammation and abnormal protein deposition. Although much of the interest in imaging approaches in Parkinson's disease has focused on PET or SPECT imaging using radionuclide scanning or on functional MRI, novel magnetic resonance approaches, including anatomical studies of connectivity and shape analysis, and the ability to measure iron deposition in vivo are all potentially relevant to Parkinson's disease and are reviewed here. Novel technologies are emerging that can draw on the strengths of radionuclide imaging and MRI. Some approaches, such as transcranial sonography, have been previously reviewed1 and are not considered further here.
Section snippets
Human radionuclide studies
The most widely accepted application of PET and SPECT in Parkinson's disease is the assessment of dopamine function (figure 1). Presynaptic dopamine integrity can generally be assessed in one of three ways: 18F-fluoro-L-dopa (18F-FDOPA) is taken up by L-aromatic amino acid decarboxylase (AAAD), converted to 18F-fluorodopamine, and packaged in synaptic vesicles from which it ultimately leaves and is subject to enzymatic degradation; 11C-dihydrotetrabenazine or its 18F-labelled analogue2 labels
Magnetic resonance techniques
The role of MRI in the diagnosis and monitoring of parkinsonian syndromes has progressed from excluding conditions that result in parkinsonism to distinguishing idiopathic Parkinson's disease from atypical parkinsonian disorders such as PSP, MSA, and corticobasal syndrome.115 Advances in hardware allow, for example, direct visualisation of the substantia nigra at high field strengths,116 but most of the recent advances have been in quantitative analyses of the images.
Conclusions and future directions
Radionuclide imaging is exquisitely sensitive for the assessment of neurochemical function, including the synthesis, storage, release, and reuptake of neurotransmitters. Radionuclide imaging can also be used to assess altered metabolism and functional connectivity. These properties are beneficial for the study of conditions such as Parkinson's disease, in which functional changes are of greater magnitude than anatomical changes, which are somewhat limited and difficult to detect. Thus,
Search strategy and selection criteria
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2019, Behavioural Brain ResearchCitation Excerpt :Data from neurophysiological and functional neuroimaging studies have revealed a complex relationship between cortico-subcortical pathology and motor timing deficits in PD. While most studies have suggested that PD is associated with decreased subcortical activities in subthalamic nucleus (STN) of the basal ganglia, the pattern of cortical response modulation has yielded conflicting results as some studies have reported hypo-activation whereas others reported hyper-activation of cortical neural responses during different motor timing tasks [14–18]. When PD patients were compared with neurologically intact matched control individuals, modulation (i.e. hypo-activation or hyper-activation) of cortical neural responses was localized to areas within the premotor and primary motor cortex (M1), supplementary motor area (SMA), inferior parietal cortex (IPC), and superior parietal lobule (SPL) [19].