Abstract
(18)F-Florbetaben is a tracer used to evaluate the metabolic activity of and amyloid accumulation in the brain when measured in early- and late-phase, respectively. The metabolism of neural substrates could be viewed as a network and might be an important factor in cognition. Orthostatic hypotension (OH) might play an indirect moderating role in cognition, and its latent influence could modify the inherent cognitive network. This study aimed to identify changes of cognitive connectivity according to orthostatic stress in patients with early Parkinson's disease (PD). This study included 104 early PD patients who were evaluated with a head-up tilt-test and(18)F-Florbetaben positron emission tomography (PET). Cognition was assessed with a comprehensive neuropsychological battery that gauged attention/working memory, language, visuospatial, memory, and executive functions. PET images were analyzed visually for amyloid deposits, and early-phase images were normalized to obtain standardized uptake ratios (SUVRs) of pre-specified subregions relevant to specific cognitive domains. The caudate nucleus was referenced and paired to these pre-specified regions. The correlations between SUVRs of these regions were assessed and stratified according to presence of orthostatic hypotension. Among the patients studied, 22 (21.2%) participants had orthostatic hypotension. Nineteen patients (18.3%) were positive for amyloid-β accumulation upon visual analysis. Moderate correlations between the caudate and pre-specified subregions were observed (Spearman's rho, range [0.331-0.545]). Cognition did not differ, but the patterns of correlation were altered when the disease was stratified by presence of orthostatic stress. In conclusion, cognition in early PD responds to hemodynamic stress by adapting its neural connections between regions relevant to cognitive functions.