Visual assessment of degeneration pattern in 123I-FP-CIT SPECT differentiates patients with atypical parkinsonism and Parkinson's disease

Purpose: To investigate the abilitiy of visual assessment and quantitative analysis of 123I-FP-CIT SPECT to differentiate idiopathic Parkinson disease (PD) and atypical parkinsonian syndromes (APS).

Methods: 165 patients with a clinical diagnosis of PD (n=120) or APS (n=45) underwent 123I-FP-CIT SPECT and were included in the current study. 123I-FP-CIT SPECT results were analysed visually and quantitatively and compared for PD and APS and for the subgroup of patients with early PD and APS (disease duration < 5 years). Quantitative assessment was performed with a 2D manual and a 3D automated approach. Visual assessment was performed according to predefined visual patterns of dopaminergic degeneration and the results were graded as normal (grade 5) or abnormal (grade 1–4).

Results: Quantitative analysis of striatal binding ratios with both applied mehtods failed to depict these different degeneration patterns in PD and APS patients. In contrast, visual assessment showed significant different dopaminergic degeneration patterns for PD and APS patients. A grade 1 (“burst striatum”) degeneration pattern was predominantly associated with APS patients. A grade 2 (“egg shape”) degeneration pattern was the characteristic finding in PD patients. In the subgroup of patients with early disease visual assessment with identification of the "burst striatum" degeneration pattern provided 90% positive predictive value and 99% specificity for the diagnosis of APS.

Conclusion: Visual assessment of the pattern of dopaminergic loss in 123I-FP-CIT SPECT shows different patterns of dopaminergic degeneration for PD and APS patients. Therefore, it could provide valuable information to distinguish APS from PD patients, especially in early stages of disease. Within the first five years of disease, the occurrence of a “burst striatum” degeneration pattern has a high positive predictive value of APS.