Quantitative analysis of striatal subregional asymmetry on 99mTc-TRODAT-1 SPECT and clinical correlations with UPDRS subscales in Parkinson's disease.

OBJECTIVE

To investigate the relationship between striatal asymmetry indices-namely the High/Low Ratio and Asymmetry Index (AI)-derived from dopamine transporter single-photon emission computed tomography (DAT-SPECT) using 99mTc-TRODAT-1, and the subscale scores of the Unified Parkinson's Disease Rating Scale (UPDRS), with the aim of evaluating their utility in clinical phenotyping and symptom assessment in Parkinson's disease (PD).

METHODS

Fifty-six patients with clinically diagnosed PD underwent 99mTc-TRODAT-1 SPECT imaging and UPDRS evaluation. Radiotracer uptake in the caudate nucleus, putamen, and whole striatum was quantified bilaterally, and corresponding High/Low Ratios and AIs were calculated. These asymmetry measures were analyzed in relation to UPDRS subscale scores and Hoehn-Yahr stages.

RESULTS

Putaminal asymmetry was significantly greater in early-stage PD patients (Hoehn-Yahr ≤ 2; p = 0.010), suggesting early lateralized dopaminergic degeneration. The AI of the caudate nucleus was strongly correlated with UPDRS Part I (non-motor symptoms; r = 0.690, p < 0.001), while putaminal asymmetry was significantly associated with UPDRS Part III (motor symptoms; r = 0.497, p < 0.001).

CONCLUSION

Region-specific DAT-SPECT asymmetry shows domain-specific correlations in PD (caudate-non-motor; putamen-motor). These findings may support the use of TRODAT-1-based imaging biomarkers for precision assessment and individualized management; however, they are hypothesis-generating and require confirmation in larger, better-balanced prospective cohorts.