Biomechanical properties of porcine cerebral bridging veins with referenceto the zero-stress state

Passive mechanical and morphometric properties of porcine cerebral bridging veins were studied. Fifteen cerebral bridging veins were obtained from 7 p igs. The superior sagittal sinus, bridging veins and the meninges were exci sed and placed in aerated calcium-free Krebs solution. The outflow cuff seg ment is a narrow region at the junction of the cerebral bridging veins and superior sagittal sinus. The principal direction of collagen fibres was lon gitudinal in the bridging vein and circumferential in the cuff region. The diameter was smaller in the outflow cuff segment than in the cerebral bridg ing veins in the pressure range studied (0-23 mm Hg) whereas the thickness was highest in the outflow cuff seg ment (p < 0.01). The circumferential st ress-strain analysis showed that the outflow cuff seg ment was extensible u p to a strain of 0.25. At hi gh er strains the outflow cuff segment was pro gressively stiffer than the cerebral bridging vein (p < 0.05). The longitud inal stress-strain relation for the cerebral bridging vein was shifted to t he left compared to the outflow cuff segment (p < 0.05). When compared to t he stress-strain properties in the circumferential direction, the outflow c uff segment was more extensible and the cerebral bridging vein stiffer in l ongitudinal direction (p < 0.05). The opening angle of the outflow cuff seg ment and the cerebral bridging vein was 115 +/- 4 and 120 +/- 4 (means +/- SE) without statistical difference between the two regions. In conclusion t he difference in biomechanical properties between the outflow cuff segment and the cerebral bridging vein was associated to their difference in histol ogy and fibre arrangement. This indicates that the function of the outflow cuff segment is to act as a flow-limiting resistance to the outflow from th e cerebral circulation. Copyright (C) 2001 S. Karger AG, Basel.