[Iodine-123-labeled meta-iodobenzylguanidine myocardial scintigraphy evaluation of Machado-Joseph disease].

Iodine-123-labeled meta-iodobenzylguanidine ([123I]MIBG), an analogue of guanetidine, is used as a tracer for evaluation of the function of sympathetic neurons. To investigate cardiac sympathetic function in Machado-Joseph disease (MJD), [123I] MIBG myocardial scintigraphy was performed in 12 patients with MJD and 20 controls. In planar imaging studies, the heart to the mediastinum of the average count ratio (H/M) was calculated for both early and delayed images. The mean values of H/M in delayed images of MJD was lower than those of controls (p < 0.01), but this did not correlate with duration of the illness. The mean values of H/M in MJD patients with abnormal sympathetic skin response (SSR) was lower than that with normal SSR (p < 0.05). The decrease of H/M in delayed image is more sensitive than abnormal SSR. The increase of heart rate after standing in the patients with low H/M was lower than those with normal H/M. Abnormal cardiac sympathetic function revealed by [123I]MIBG myocardial scintigraphy in MJD can be seen earlier than abnormal sudomotor system detected by SSR.