Reduced cardiac MIBG uptake is observed in Lewy body disease, PD associated with α–synuclein mutation, PD associated with α–synuclein multiplication, some cases of PD associated with LRRK2 mutation with Lewy bodies in the brain, and various disorders with Lewy body disease or iLBD, as mentioned above. These disorders have Lewy bodies or Lewy neurites in the central nervous system and/or peripheral autonomic nervous system. In contrast, Lewy bodies and Lewy neurites are usually not found in MSA, progressive supranuclear palsy (PSP), CBD, Alzheimer disease (AD), frontotemporal dementia (FTD), parkin disease, and PD associated with LRRK2 mutation without Lewy bodies in the brain. Figure 19.1 shows the TH- and NF-immunoreactive nerve fibers of epicardial nerve fascicles in a wide range of neurodegenerative disorders. In two cases of iLBD (b, c, I, j), PD (d, k), DLB (e, l), PD associated with α–synuclein duplication (f, m), PD associated with LRRK2 mutation with Lewy bodies in the brain (g, n), and TH- and NF-immunoreactive nerve fibers were mildly to markedly decreased. In contrast, in MSA (o, v), PSP (p, w), CBD (q, x), AD (r, y), FTD (s, z), parkin disease (t, A), and PD linked to LRRK2 mutation without Lewy bodies in the brain (u, B), TH- and NF-immunoreactive nerve fibers were well preserved. In neurodegenerative disorders and familial PD, degeneration of the cardiac sympathetic nerve was closely related to the presence of Lewy bodies. As previously mentioned, degeneration of the cardiac sympathetic nerve can cause a reduction in the cardiac sympathetic nerve. Therefore, reduced cardiac MIBG uptake can be a potential biomarker for the presence of Lewy bodies. MIBG cardiac scintigraphy can allow us to estimate the presence of Lewy bodies. However, attention needs to be paid to the interpretation of cardiac MIBG scintigraphy results, because some medications, peripheral autonomic neuropathies, and congestive heart failure can affect cardiac MIBG uptake. MIBG cardiac scintigraphy should be used as a supportive tool for differentiating parkinsonism or dementia.