Assessing changes in pial artery resistance and subarachnoid space width using a non-invasive method in healthy humans during the handgrip test.

The aim of this study was to assess the influence of the handgrip test (HGT) on: (1) pial artery pulsation (cc-TQ), (2) subarachnoid space (SAS) width (sas-TQ) and (3) the relationship between peripheral blood pressure (BP), heart rate (HR), cerebral blood flow velocity (CBFV), resistive index (RI), cc-TQ and sas-TQ. The study was performed on 29 healthy volunteers (11 men and 18 women) with a mean age of 29.3 ± SE 4.0. HGT was performed in the sitting position at 30% of maximal voluntary contraction. cc-TQ and sas-TQ were registered using near-infrared transillumination/backscattering sounding (NIR-T/BSS); BP and heart rate (HR) were measured using a Finapres monitor. CBFV and RI were recorded using a transcranial Doppler. A significant reduction in cc-TQ (-34.3%, P<0.0001) and sas-TQ (-12.9%, P<0.001) were observed, while mean arterial pressure and HR increased (+34.8%, P<0.0001 and +7.9%, P<0.0001, respectively). There was no significant change in CBFV (+1.0 percent) while RI increased (+12.0 percent, P<0.05). Correlation and regression analysis did not reveal any interdependencies between the investigated variables. HGT evoked a significant increase in pial artery resistance, with a simultaneous decrease in the width of the SAS. A decrease in pial artery compliance should be seen as protective mechanism against acute BP elevation, most likely mediated by sympathetic activation. NIR-T/BSS recordings allowed for non-invasive assessments of changes in pial artery compliance, and were consistent with data from the literature and physiological knowledge.