123I-MIBG cardiac uptake, smell identification and 123I-FP-CIT SPECT in the differential diagnosis between vascular parkinsonism and Parkinson's disease.

UNLABELLED: Vascular parkinsonism (VP) may occur as a distinct clinicopathological entity but the comorbid presence of vascular damage in Parkinson's disease (PD) is very frequent too. This differential diagnosis has therapeutic and prognostic implications but remains challenging as the usefulness of a number of supporting tools is still controversial.

OBJECTIVE

To ascertain the clinical value of cardiac (123)I-meta-iodobenzylguanidine ((123)I-MIBG) SPECT, olfactory function and (123)I-FP-CIT SPECT as supporting tools in the differential diagnosis between VP and PD.

METHODS

Cross-sectional study of 15 consecutive patients with suspected VP, 15 PD patients and 9 healthy subjects. Cardiac (123)I-MIBG SPECT (heart-to-mediastinum ratio) and olfactory testing (University of Pennsylvania Smell Identification Test-UPSIT) were performed in all of them. (123)I-FP-CIT SPECT was performed in VP-suspected patients.

RESULTS

Heart-to-mediatinum ratio was significant lower in suspected VP (mean 1.45) and PD (mean 1.16) compared to control group (mean 1.69) (p = 0.017 and p < 0.0001). VP patients presented a higher ratio than PD patients (p = 0.001). Control group presented a significant higher UPSIT score (mean 30.71) when compared to both VP (mean 18.33) and PD (mean 15.29) (p = 0.001 for both groups). Those VP with a cardiac (123)I-MIBG non suggestive of PD were more likely to have a higher UPSIT score (p = 0.006). (123)I-FP-CIT SPECT imaging was heterogeneous (7/15 VP normal, 3/15 abnormal suggestive of PD and 5/15 abnormal but atypical for PD).

CONCLUSIONS

The use of cardiac (123)I-MIBG SPECT and to a lesser extent UPSIT could assist the differential diagnosis between VP and PD in subjects in which the diagnosis remains uncertain despite (123)I-FP-CIT SPECT imaging.