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Dopamine transporter imaging

SPECT imaging of the nigrostriatal dopaminergic system is proving to be the first functional imaging technique of practical application to movement disorder specialists. The authors of this Movement Disorders supplement attended a small educational workshop in London on dopamine transporter (DAT) imaging under the auspices of the European Section of the Movement Disorder Society. A logical progression from anatomical and functional considerations through clinical diagnostic and research evidence for the technique leads to an assessment of DAT imaging as a surrogate marker in therapeutic trials for Parkinson’s disease. Reference to positron emission tomography (PET) is made where appropriate because these studies provide a “jump start” to the understanding of DAT SPECT and its potential application in clinical practice. The fundamental tools in assessing DAT SPECT are also addressed. For readers new to the topic or with mainly a clinical interest, the description of the DAT system (Piccini, p S3) and the two practical clinical guides are recommended as the starting point (Oertel et al., p S9; Poewe and Scherfler, p S16). These provide a description of the DAT system and neuroimaging, where neurotransmitter and transporter concepts are introduced, the evolution of PET and SPECT ligands is reviewed, and potential drug interactions are considered (Piccini). The article by Wolfgang Oertel and colleagues takes a case example approach, to illustrate potential applications for DAT imaging in general neurological practice. Professor Poewe and his colleagues from Innsbruck, Austria then provide an overview of clinical application from early diagnosis, through atypical presentations, and thence to measuring progression. Atypical tremor is analysed as a component of benign tremulous PD and of pseudoparkinsonism, such as is found in elderly patients, and is an important cause of misdiagnosis of PD in general practice (Marshall and Grosset, p S22). Drug-induced parkinsonism is reviewed and the time course and clinical features of an evolving parkinsonism that could represent a potentially reversible drug effect, or an unmasking effect of drug treatment on subclinical PD, are discussed (Tolosa et al., p S28). Psychogenic parkinsonism is rare but its investigation and management may be assisted by DAT imaging (Tolosa et al.). The distinction between dementia with Lewy bodies and Alzheimer’s disease may be difficult, especially when parkinsonism is not present. Professor Costa (p S34) reports encouraging early results with DAT scanning in dementia with Lewy bodies (DLB), suggesting that this may be a helpful ancillary aid to clinical diagnosis in difficult cases. In each of these clinical articles the main focus is on presynaptic DAT imaging but pointers are provided to the additional use of postsynaptic imaging. Postsynaptic dopamine receptor imaging is covered in detail by Leenders (p S39) and potential clinical uses are highlighted. The inquiring patient frequently asks if the DAT image predicts or correlates with symptom severity, to which a summary answer might be, “to some extent.” A more informed reply comes from the reflection on basic science knowledge (Uhl, p S79), and then on clinicalimaging correlates (Pirker, p S43). Healthcare management considerations follow, with the definition of a framework and methodology that can be adapted according to the clinical practice environment (Dodel et al., p S52). Finally, there is a critical review of recent clinical trial application of DAT imaging as a marker for disease progression (Morrish, p S63). We hope that this supplement introduces readers of Movement Disorders to the potential of dopamine transporter SPECT imaging in neurological practice and helps to answer some of the questions posed by clinicians, researchers, managers, and patients about the appropriate use of DAT imaging. Clinical diagnosis is difficult even for the expert in the Parkinsonian syndromes and tremors and any new investigation that helps to improve accuracy is to be welcomed. However, one must guard against DOI 10.1002/mds.10570 Published online in Wiley InterScience (www.interscience.wiley. com). Movement Disorders Vol. 18, Suppl. 7, 2003, pp. S1–S2 © 2003 Movement Disorder Society