Different histopathology accounting for a decrease in myocardial MIBG uptake in PD and MSA

Differential diagnosis between PD and multiple-system atrophy (MSA) is often difficult, especially in early disease stages. Recent studies have shown that [123I]metaiodobenzylguanidine (MIBG) myocardial scintigraphy is useful to separate PD from MSA; MIBG uptake in PD is significantly lower than in MSA.1-3⇓⇓ However, a pathophysiologic mechanism for the decrease in myocardial MIBG uptake in PD and MSA remains to be elucidated. We describe a patient with PD and a patient with MSA. Postmortem examination revealed a severe loss of myocardial sympathetic nerve fibers in the former but not in the latter. ### Patient 1. An 80-year-old woman developed bradykinesia and gait disturbance, followed by right dominant resting hand tremor and rigidity, postural instability, severe constipation, and orthostatic hypotension. Dopaminergic therapy such as levodopa/carbidopa was given and effective for bradykinesia, rigidity, and tremor. She was diagnosed as having PD at the age of 82 years. Her condition deteriorated; she occasionally experienced syncope. She died of bronchopneumonia at 84 years old. MIBG myocardial scintigraphy, at the age of 83 years, showed …