Brain monoamine systems in multiple system atrophy: a positron emission tomography study

Post-mortem studies of multiple system atrophy (MSA) patients have shown widespread subcortical neurodegeneration. In this study, we have used 18F-dopa PET, a marker of monoaminergic nerve terminal function, to explore in vivo changes in striatal and extrastriatal dopamine, noradrenaline, and serotonin transmission for a cohort of patients with MSA with predominant parkinsonism. Fourteen patients with MSA, ten patients with idiopathic Parkinson's disease (PD) matched for disease duration, and ten healthy controls were studied with 18F-dopa PET. Regions of interest (ROIs) were placed to sample 18F-dopa uptake in thirteen structures and mean activity was compared between groups. The MSA patients showed significantly decreased 18F-dopa uptake in putamen, caudate nucleus, ventral striatum, globus pallidus externa and red nucleus compared to controls, whereas PD patients only had decreased 18F-dopa uptake in putamen, caudate nucleus, and ventral striatum. MSA cases with orthostatic hypotension had lower 18F-dopa uptake in the locus coeruleus than patients without this symptom. In conclusion, 18F-dopa PET showed more widespread basal ganglia dysfunction in MSA than in PD with similar disease duration, and extrastriatal loss of monoaminergic innervation could be detected in the red nucleus and locus coeruleus. In contrast to PD, there was no evidence of early compensatory increases in regional 18F-dopa uptake.