Cardiac noradrenergic deficiency revealed by 18F-dopamine positron emission tomography identifies preclinical central Lewy body diseases

In the Lewy body diseases (LBDs) Parkinson's disease (PD) and dementia with Lewy bodies (DLB), by the time parkinsonism or cognitive dysfunction manifests clinically substantial neurodegeneration has already occurred. Biomarkers are needed to identify central LBDs in a preclinical phase, when neurorescue strategies might forestall symptomatic disease. This phase may involve catecholamine deficiency in the autonomic nervous system. We analyzed data from the prospective, observational, long-term PDRisk study to assess the predictive value of low vs. normal cardiac 18F-dopamine positron emission tomography (PET), an index of myocardial content of the sympathetic neurotransmitter norepinephrine, in at-risk individuals.Participants self-reported risk factor information (genetics, olfactory dysfunction, dream enactment behavior, orthostatic intolerance or hypotension) at a protocol-specific website. Thirty-four with ≥ 3 confirmed risk factors underwent serial cardiac 18F-dopamine PET at 1.5-yearly intervals for up to 7.5 years or until PD was diagnosed.Nine participants had low initial myocardial 18F-dopamine-derived radioactivity (<6,000 nCi-kg/cc-Ci) and 25 normal radioactivity. At 7 years of follow-up, 8 of 9 with low initial radioactivity and 1 of 11 with normal radioactivity were diagnosed with a central LBD (LBD+) (P = 0.0009 by Fisher's exact test). Conversely, all of 9 LBD+ participants had low 18F-dopamine-derived radioactivity before or at the time of diagnosis of a central LBD, whereas among 25 participants without a central LBD only 1 (4%) had persistently low radioactivity (P < 0.0001 by Fisher's exact test).Cardiac 18F-dopamine PET highly efficiently distinguishes at-risk individuals who are diagnosed subsequently with a central LBD from those who are not.