Introduction Dopamine transporter (DaT) scans are used in the investigation of clinically uncertain Parkinsonian syndromes (CUPS). Presently, bilateral abnormal DaT scans are diagnostic of Parkinson’s disease and degenerative Parkinsonism, while normal scans suggest non-degenerative causes. However, the clinical significance of unilateral abnormal scans remains ambiguous. Therefore, we aimed to determine their relevance in CUPS, and hypothesised that they may presage Parkinson’s disease and degenerative Parkinsonism.

Methods A retrospective analysis was performed for patients with CUPS within a tertiary institution who had undergone DaT scans. Demographic data, clinical features, imaging and diagnoses were collected. In patients with unilateral scans, follow-up assessments, further imaging and diagnostic changes were also recorded.

Results A total of 200 DaT scans were performed from 1 January 2008 to 1 January 2017. There were 100 (50.0%) with normal scans, 77 (38.5%) with bilateral scans, and 23 (11.5%) with unilateral scans. Of the latter group (n=23), 8 (34.8%) underwent follow-up DaT imaging in a mean period of 31.9±12.6 months from baseline, with 4 (17.4%) now reported as bilateral, although 2 (8.7%) remained unilateral and 2 (8.7%) were reported as normal.

Conclusion Unilateral DaT scans can serve as a predictive factor for development of Parkinson’s disease and degenerative Parkinsonism.