Comparison of diffusion‐weighted imaging and [123I]IBZM‐SPECT for the differentiation of patients with the Parkinson variant of multiple system atrophy from those with Parkinson's disease

Both dopamine D2 receptor (D2R) binding single‐photon emission computed tomography (SPECT) with [123I]iodobenzamide (IBZM) and diffusion‐weighted imaging (DWI) have been shown to contribute to the differential diagnosis of patients with the Parkinson variant of multiple system atrophy (MSA‐P) and Parkinson's disease (PD). We aimed to compare these two routinely available functional imaging modalities in differentiating patients with MSA‐P from PD. For this purpose, results obtained by DWI and IBZM‐SPECT were intraindividually compared in a cross‐sectional study of 15 MSA‐P and 17 PD patients matched for age and disease duration. The activity ratios of striatal to frontal cortex uptake (S/FC ratio) were used as a semiquantitative measure of the relative density of basal ganglia dopamine receptors labeled by IBZM. Regional apparent diffusion coefficients (rADC) were determined in the striatum. MSA‐P patients had significantly lower S/FC ratios and significantly higher striatal rADCs than both PD patients and healthy volunteers. There were no significant differences in S/FC ratios and striatal rADC between PD patients and healthy volunteers. Sensitivity of IBZM‐SPECT versus DWI for the differentiation of MSA‐P from PD was 80% versus 93%, specificity 71% versus 100%, the predictive accuracy 75% versus 97%, the positive predictive value 71% versus 100%, and the negative predictive value 80% versus 94%. Striatal rADCs had a significant higher overall predictive accuracy than D2R binding with IBZM. In summary, our data suggest that DWI may be more accurate compared to IBZM‐SPECT in the differential diagnosis of MSA‐P versus PD. © 2004 Movement Disorder Society