Differentiation of idiopathic Parkinson's disease from striatonigral degeneration and progressive supranuclear palsy using iodine-123 meta-iodobenzylguanidine myocardial scintigraphy.

Iodine-123 meta-iodobenzylguanidine ([123I]MIBG), an analogue of norepinephrine, is a tracer for functioning of sympathetic neurons. To investigate cardiac sympathetic function in PD, SND, and PSP, [123I]MIBG myocardial scintigraphy was performed in 25 patients with PD, 15 patients with SND, 14 patients with PSP, and 20 control subjects. In planar imaging studies, the heart-to-mediastinum average count ratio (H/M) was calculated for both early and delayed images. The mean value of H/M in patients with PD was significantly lower than those with SND, PSP, or no disease. Regardless of disease severity or intensity of anti-Parkinsonian pharmacotherapy, mean values for H/M were always low in patients with PD. The mean value of H/M in SND with orthostatic hypotension (OH) was lower than that in SND without OH. Although the mean value of H/M in PSP with amitriptyline treatment was significantly lower than that in PSP patients without amitriptyline treatment, there was no significant difference between the mean value of H/M in PSP patients without amitriptyline treatment and that in control. Thus, PD may have a abnormality of cardiac sympathetic function which has not been detected by previous cardiovascular autonomic studies. Moreover, particularly in early stages, [123I]MIBG myocardial scintigraphy may provide helpful diagnostic information in these akinetic-rigid syndromes.