Dopamine transporter (DAT) imaging is a sensitive method to detect presynaptic dopamine neuronal dysfunction, which is a hallmark of neurodegenerative parkinsonism. DAT imaging can therefore assist the differentiation between conditions with and without presynaptic dopaminergic deficit. Diagnosis of Parkinson disease or tremor disorders can be achieved with high degrees of accuracy in cases with full expression of classical clinical features; however, diagnosis can be difficult, since there is a substantial clinical overlap especially in monosymptomatic tremor (dystonic tremor, essential tremor, Parkinson tremor). The use of DAT-SPECT can prove or excludes with high sensitivity nigrostriatal dysfunction in those cases and facilitates early and accurate diagnosis. Furthermore, a normal DAT-SPECT is helpful in supporting a diagnosis of drug-induced-, psychogenic- and vascular parkinsonism by excluding underlying true nigrostriatal dysfunction. This review addresses the value of DAT-SPECT and its impact on diagnostic accuracy in movement disorders presenting with tremor and/or parkinsonism.

/pdf/the-role-of-dat-spect-in-movement-disorders-3r60el8q04.pdf

The role of DAT-SPECT in movement disorders

Purpose of review Marked olfactory dysfunction (hyposmia) is a frequent and early abnormality in Parkinson's disease. We review recent advances related to its cause and its clinical relevance with respect to the differential diagnosis of Parkinsonian syndromes.Recent findings Marked olfactory dysfunction occurs in Parkinson's disease and dementia with Lewy bodies but is not found in progressive supranuclear palsy and corticobasal degeneration. In multiple system atrophy, the deficit is mild and indistinguishable from cerebellar syndromes of other aetiologies, including the spinocerebllar ataxias. This is in keeping with evidence of cerebellar involvement in olfactory processing, which may also help to explain recent findings of mild olfactory dysfunction in essential tremor. Smell testing remains, however, a clinically relevant tool in the differential diagnosis of indeterminate tremors. Intact olfaction has also been reported recently in Parkin disease (PARK 2) and vascular Parkinsonism. The relevance of sniffing ability to olfaction and a possible role of increased tyrosine hydroxylase and dopamine in parts of the olfactory bulb are issues of current interest with respect to pathophysiology. The early or 'pre-clinical' detection of Parkinson's disease is increasingly recognized as an area in which olfactory testing may be of value.Summary Research findings have confirmed a role for olfactory testing in the differential diagnosis of movement disorders, and suggest that this approach is currently underused in clinical practice. Validated test batteries are now available that may prove to be of practical use in the differential diagnosis of Parkinsonian syndromes and indeterminate tremors.

Olfaction and Parkinson's syndromes: its role in differential diagnosis.

In vivo imaging of synaptic function in the central nervous system: I. Movement disorders and dementia.

Orthostatic tremor (OT) is a condition described as high-frequency tremors predominantly in the legs and trunk, which are present not only in the standing position but also during isometric contraction of the limb muscles. This report is one of the largest OT series describing clinical and neurophys- iologic findings in 26 subjects with OT. The main findings included 13.0 to 18.6 Hz leg tremors while standing with varied patterns of phase relationships between the antagonists of the ipsilateral leg and between the homologous muscles of the contralateral leg, short latency tremor onset upon standing with abrupt cessation after sitting, coexistence of tremors in the cranial structures and the arms, and sense of unsteadiness without actual falls. Although the oscillator of OT is most likely located in the brainstem, cerebral cortex, basal ganglia, and cere- bellum may also be involved in its pathogenesis. © 2005 Move- ment Disorder Society

/pdf/clinical-and-neurophysiologic-spectrum-of-orthostatic-tremor-1ngiyfasto.pdf

Clinical and neurophysiologic spectrum of orthostatic tremor: case series of 26 subjects.

Patients with Parkinson's disease (PD) often complain of unsteadiness. This can occur as the result of various neurological dysfunctions, including changes in postural adjustments, loss of postural reflexes, axial akinesia and rigidity, freezing and/or postural hypotension. In some cases these symptoms remain unexplained, and rare cases of unsteadiness have been attributed to tremor on standing. To delineate this condition, we investigated 11 consecutive PD patients with unexplained unsteadiness because of tremor on standing, seen in our department over a 6-year period. All the patients had detailed clinical and electrophysiological investigations based on surface polygraphic electromyographic recordings. Four patients had fast orthostatic tremor (13-18 Hz), one had intermediate orthostatic tremor (8-9 Hz), and three had slow orthostatic tremor (4-6 Hz). The remaining 3 patients had orthostatic myoclonus, a condition that has not previously been reported in PD. Patients with fast tremor improved on clonazepam. Patients with slow tremor and myoclonus improved on levodopa and sometimes benefited further when clonazepam was added. These observations show the usefulness of neurophysiological investigations for diagnosing and treating unexplained unsteadiness in Parkinson's disease.

Myoclonus or tremor in orthostatism: an under-recognized cause of unsteadiness in Parkinson's disease.

There is increasing evidence of a potential role of the dopaminergic system in orthostatic tremor (OT): Association with parkinsonism and treatment effects of L-dopa and dopamine agonists have been reported. Eleven patients with isolated OT had single-photon emission computed tomography (SPECT) using (123)I-FP-CIT ([(123)I]-2 beta-carbomethoxy-3beta-(-4-iodophenyl)-N-(3-fluoropropyl)-nortropane) as dopamine transporter tracer. Results were compared with 12 age-matched normal controls and 12 patients with Parkinson's disease (PD). A marked reduction in striatal tracer binding was found in OT compared to normal controls (p < 0.001). Tracer uptake was significantly higher and more symmetrical than in PD, and caudate and putamen were equally affected. L-dopa challenges, performed in seven patients, showed a small but non-significant improvement on EMG and a small but significant improvement in clinical parameters on blinded video rating. Two-month open-label L-dopa treatment (600 mg/day) led to a small improvement in two of five patients but no significant overall change. Olfactory function on University of Pennsylvania Smell Identification Test was normal. Our finding of a marked tracer uptake reduction on dopamine transporter SPECT supports a role of the dopaminergic system in OT. Lack of evidence of a clinically relevant therapeutic response to L-dopa suggests that other mechanisms must also be involved in the pathogenesis.

[123I]-FP-CIT-SPECT demonstrates dopaminergic deficit in orthostatic tremor.

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[123I]-FP-CIT-SPECT demonstrates dopaminergic deficit in orthostatic tremor.