The introduction of first 18 F-dopa ( fluorodopa) positron emission tomography (PET) and then DaTSCAN scanning into clinical trial work has even led to a new class of “parkinsonian” patient termed a subject with a scan without evidence of dopaminergic deficits (SWEDDs).
Furthermore, caution should be exercised when interpreting an abnormal DaTSCAN result and scan findings should be compared to clinical signs to determine whether or not they are congruous. Care is required in the analysis of DaTSCAN scans, which can be reported visually semiquantitatively, using a region of interest approach or quantitatively, using statistical parametric mapping. The new millennium has seen the introduction of single photon emission CT (SPECT) imaging techniques, particularly 123 I-FP-CIT (iodine 123-labelled N-ω-fluoropropyl-2β-carbomethoxy-3β-nortropane) SPECT (DaTSCAN), into routine clinical practice as a means of assessing the integrity of the nigrostriatal dopaminergic system in patients with tremor. Standard magnetic resonance (MR) and CT imaging has had a limited role in the routine management of tremulous patients except mainly for people with Holmes tremor syndrome and other secondary causes of tremor (multiple sclerosis or Wilson disease). The routine use of single photon emission CT technology to image the nigrostriatal dopaminergic system is proving helpful in distinguishing essential and dystonic tremors from neurodegenerative forms of parkinsonism and in improving our understanding of the pathophysiology of rarer tremors. The role for neuroimaging in the management of patients with tremor is gradually increasing, particularly with respect to stereotactic neurosurgery and deep brain stimulation where less than 2-mm tolerance is required for accurate electrode placement.
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