Pathological Background of Reduced Cardiac MIBG Uptake

Abstract

Cardiac MIBG uptake is reduced in Lewy body diseases, including Parkinson’s disease (PD), dementia with Lewy bodies, and pure autonomic failure. It is useful to differentiate Lewy body diseases from other related disorders. Postmortem studies have shown that tyrosine hydroxylase (TH)-immunoreactive axons in the heart are decreased, primarily due to degeneration of the cardiac sympathetic nerve in pathologically confirmed Lewy body disease but not in other related disorders. This supports the findings that reduced cardiac MIBG uptake is found in Lewy body disease. In incidental Lewy body disease (iLBD), TH-immunoreactive axons are relatively preserved, while α-synuclein aggregates accumulate in the heart in abundant numbers. In PD, α-synuclein aggregates are reduced in the heart but are increased in the mother neurons of the cardiac sympathetic nerve in the paravertebral sympathetic ganglia. This distal-dominant degeneration of the cardiac sympathetic nervous system may represent the pathological mechanism underlying the common degenerative process in PD. Furthermore, degeneration of the cardiac sympathetic nerve can occur in familial PD due to PARK1, PARK4, and PARK8 with Lewy bodies in the brain. Therefore, degeneration of the cardiac sympathetic nerve is closely related to the presence of Lewy bodies in a wide range of neurodegenerative processes.