Dopaminergic Correlates of Orthostatic Hypotension in de novo Parkinson's Disease.

BACKGROUND: Orthostatic hypotension (OH) at an early stage of Parkinson's disease (PD) predicts poor prognosis, which may suggest degeneration of dopaminergic neurons affects sympathetic function, causing OH. OBJECTIVE: We tested the hypothesis that striatal dopaminergic depletion is associated with OH in PD. METHODS: Out of 99 patients with newly diagnosed untreated PD, 81 patients were enrolled according to our selection criteria. All patients underwent head-up tilt-table testing and striatal 123I-2ß-carbomethoxy-3ß-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (123I-FP-CIT) dopamine transporter single photon emission computed tomography (DAT-SPECT). DaTQUANT software (GE Healthcare) was used as a semi-quantitative tool to analyze DAT-SPECT data. The association between hemodynamic changes and 123I-FP-CIT uptake was examined. RESULTS: 123I-FP-CIT uptake in the putamen, especially the anterior part and left side, was related not only to motor severity but also to OH. Change in systolic blood pressure correlated negatively with 123I-FP-CIT uptake in bilateral anterior putamen (left: p < 0.01, right: p < 0.05) and left posterior putamen (p < 0.05). Patients with OH had more severe dopamine depletion in left anterior (p = 0.008) and posterior (p = 0.007) putamen at a similar motor severity than did patients without OH even though both groups have similar baseline characteristics. An analysis of asymmetry index showed patients with OH had symmetrically decreased dopamine levels in anterior putamen when compared to those without OH (p = 0.024). CONCLUSION: OH is closely related to striatal dopamine depletion in PD. This relation may help to account for the prognostic value of OH.