Abstract
Background: Neurogenic orthostatic hypotension (NOH), defined as a drop in systolic blood pressure (SBP) ≥30mmHg on standing or head-up tilt, is associated with autonomic dysfunction. The cortical autonomic network (CAN) is a network of brain regions associated with autonomic function. Our aim was to investigate CAN activation patterns in NOH patients during autonomic testing. Methods: Fifteen controls (61±14 years) and 13 NOH patients (68±6 years;p=0.1) completed: 1)Deep Breathing (DB), 2)Valsalva maneuver (VM) and 3)Lower-body negative pressure (LBNP) during a functional MRI. Blood-oxygen level dependent (BOLD) contrasts were obtained and contrasted. Results: Compared to controls (C), patients (NOH) had significantly smaller heart rate (HR) responses to DB (C:15.3±9.6 vs.NOH:6.0±2.2) and VR’s (C:2.1±0.47 vs.NOH:1.2±0.1;p<0.001). Patients had larger SBP drops during LBNP (C: -22.3±6 vs.NOH: -61±22) with -significantly smaller compensatory tachycardias (19±8.5 vs.7.6±4.3)(p<0.001). BOLD response: During VM, controls had greater activation in the right (R) hippocampus (T-value:7.34), left (L) posterior cingulate (T-value:7.22) bilateral mid-cingulate (TR-value:5.76; TL-value:6.84) and bilateral thalamus (TR-value:7.23, TL-value:8.16)(pFWE<0.001). Following subtraction analysis, brain activation patterns showed no significant differences in the regions of interest in response to DB and LBNP. Conclusions: During tests of autonomic function, NOH patient had different cortical activation patterns during VM only. Cortical activation pattern during DB and LBNP showed similar patterns to that of controls.
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