Clinical Indications for the Use of Dopaminergic Functional Imaging
Dopaminergic functional imaging has been shown to be a useful adjunct to the clinical diagnosis of movement disorders in some settings. In general, the risk of functional imaging is justified when the outcome of the examination will help to dictate clinical management. Accurate diagnosis can prevent exposure to inefficacious treatments, improve prognostic abilities and improve cost efficiency. Dopaminergic functional imaging has not been shown to be helpful in differentiating between different Parkinsonian syndromes (e.g. Parkinson’s disease, progressive supranuclear palsy, multiple system atrophy, corticobasal degeneration). Decisions on whether or not to conduct scans for a given clinical scenario should also be guided by relevant sensitivity and specificity data as well as the recognition that there is some inter-rater variability in the interpretation of scans. Scenarios in which the result of dopaminergic functional imaging may prove helpful in determining therapeutic interventions include:
1) Patients with tremor that is not clearly differentiated into either essential tremor or Parkinsonian tremor.
2) Patients with tremor or other features of Parkinsonism in the context of treatment with dopamine-blocking medications known to induce Parkinsonism to determine if the Parkinsonism is likely to be purely drug-induced or if there is an underlying neurodegenerative condition.
3) Patients with possible psychogenic Parkinsonism.
4) Patients with tremor of unclear etiology that is not responsive to dopaminergic replacement therapies and who are being considered for deep brain stimulation therapy to help guide target selection.