Circulatory disturbance of the venous system during experimental intracranial hypertension

✓ The venous drainage system during increased intracranial pressure (ICP) was studied in dogs. The ICP was gradually increased to the level of the systemic blood pressure while related arterial and venous pressures were monitored. The blood flow through the parasagittal intradural venous channels (lateral lacuna) was also measured to test the collapsibility of these vessels. The cortical venous pressure was constantly 50 to 200 mm H2O higher than the ICP regardless of the degree of elevation, while the sagittal sinus pressure remained at 50 to 75 mm H2O unless the central venous pressure was elevated by respiratory disturbance. Flow through the lateral lacuna decreased as the ICP was increased. The authors conclude that the low pressure in the sinus and the consistency of the walls of the lateral lacuna allow gradual stenosis of the lacuna during increased ICP.