Locus coeruleus degeneration is associated with orthostatic hypotension in Parkinson's disease and multiple system atrophy.

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PurposeWe compared locus coeruleus (LC) structural integrity, as measured by neuromelanin-sensitive magnetic resonance imaging (NM-MRI), between patients with Parkinson's disease (PD) and those with multiple system atrophy (MSA) and tested whether orthostatic hypotension (OH) impacted differences in LC volume between PD and MSA. Substantia nigra (SNc) volumes were compared between these groups to determine whether effects observed in LC were specific to that structure. Last, we tested whether LC integrity is associated with orthostatic hemodynamic responses.MethodsPresence or absence of (±)OH was determined with active stand testing. Automated segmentation of LC and SNc volumes took place using NM-MRI. Structural volumes were first compared between PD and MSA groups and, second, after stratification by OH status. Last, correlations between LC volumes and orthostatic vitals were calculated.ResultsOf 71 patients with PD, 19 were (+)OH. Of 19 patients with MSA, 12 were (+)OH. LC volumes were larger in PD than MSA (p = 0.002), and LC volumes in PD(-)OH were larger than PD(+)OH and MSA(±)OH (p ConclusionsSimilar levels of LC neurodegeneration were observed in PD(+)OH and MSA(±)OH. Therefore, LC measurement may be useful to differentiate PD(-)OH from MSA. Lower LC volumes additionally correlated with greater drops in MAP in both PD(+)OH and MSA(+)OH, suggesting that LC neurodegeneration may contribute to OH in both conditions.

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