Diagnostic Imaging for Parkinsonian Syndromes

Introduction to Diagnostic Imaging

The American College of Radiology recommends DaTscan (I-123 ioflupane SPECT/CT) as the gold standard for clinical use in differentiating Parkinsonian syndromes from essential tremor and drug-induced tremor 1, 2, 3
DaTscan binds to presynaptic dopamine transporters (DAT) on dopaminergic neurons, showing decreased radiotracer uptake in the striatum, typically progressing from putamen to caudate nuclei 1, 2

The American College of Radiology suggests ordering DaTscan when clinical diagnosis is uncertain to differentiate true Parkinsonian syndromes from essential tremor or drug-induced tremor 1, 3
DaTscan cannot differentiate between different types of Parkinsonian syndromes, and is not indicated for monitoring disease progression in established Parkinson's disease 1, 2, 4

The American College of Radiology recommends starting with MRI brain without contrast as the optimal initial imaging modality before any nuclear medicine study 2, 5, 6
MRI rules out structural causes, focal lesions, vascular disease, and regional atrophy patterns, and is superior for soft-tissue characterization and sensitivity to iron deposition 2, 5, 6
DaTscan should be considered only after MRI and when clinical uncertainty persists, for differentiating Parkinsonian syndromes from essential tremor or drug-induced causes 1, 3, 5

TRODAT and DOPA PET are not available for routine clinical use in most U.S. centers, and if dopamine transporter imaging is needed, DaTscan should be ordered specifically 1, 2, 3
Never order DaTscan without first obtaining MRI brain, as structural imaging may reveal vascular parkinsonism, normal pressure hydrocephalus, or space-occupying lesions that mimic PD 3, 5
DaTscan is not indicated for patients with established Parkinson's disease experiencing worsening symptoms, as it does not help monitor progression or guide treatment adjustments 4