MIBG Scintigraphy in Parkinsonian Syndromes

Summary

Active uptake of [¹²³I] metaiodobenzylguanidine (MIBG) reflects localisation and functional integrity of postganglionic adrenergic neurons. There is accumulating evidence, that in patients with Parkinson’s disease MIBG uptake into cardiac sympathetic neurons is selectively and grossly reduced. Currently there are studies available on 239 patients with idiopathic Parkinson’s disease (IPD), 73 patients with MSA and 14 with progressive supranuclear palsy (PSP) in comparison to 78 healthy controls. The overall mean heart/mediastinum ratio of MIBG uptake was 1.29 in IPD, 2.13 in MSA, 1.89 in PSP and 2.24 in controls. The sensitivity to identify IPD patients correctly by their very low cardiac MIBG uptake appears to be higher than 95% and the specificity is 100%, if Hoehn and Yahr stage is II or higher, if no interacting medication is given and if there is no additional polyneuropathy. This significant reduction of uptake is independent of duration of Parkinsonian or autonomic symptoms and the degree of abnormality in cardiovascular function tests. Although it remains to be cleared whether the findings in IPD represent true postganglionic damage or a functional neuronal deficit, in clinical practice cardiac MIBG scintigraphy allows an early discrimination of IPD in relation to MSA and PSP, which appears to be more reliable and less expensive compared to PET and SPECT imaging of the brain.