[Circulatory disturbance of the venous system under intracranial hypertension (3rd report)-an experiment using primates (author's transl)].

Although many authors suggested vascular compression of venous system under increased intracranial pressure, the exact site and mechanism of the compression are still obscure. By the previous reports obtained in mongrel dogs, we clarified that a vascular stenosis took place 1-2 mm lateral to the junction between the lateral lacuna and the superior sagittal sinus as the intracranial pressure (ICP) was elevated. The present study was designed to reinvestigate the internal pressure of the intracranial venous pathways using crab-eating monkeys under gradually increasing ICP. (1) METHODS: Using crab-eating monkeys, pressure of the cortical veins and the superior sagittal sinus was measured by cannulating small calibred (0.4 - 0.5 mm in outer diameter) polyethylene tube. The ICP was elevated by inflating rubber balloon placed in the epidural space. Pressure of the above mentioned vessels, systemic blood pressure and ICP were measured with a standard pressure transducer. Pressure gradient between the lateral lacuna and the superior sagittal sinus was measured by moving to and fro the tip of small calibred tube which was inserted into the lacuna under operation microscope. (2) RESULTS: The pressure of the cortical vein was constantly 50 - 250 mmH2O (4-18 mmHg) higher than the ICP in monkeys, regardless of the level of ICP (Fig. 1, 2 & 3). Pressure of the superior sagittal sinus was quite stable at the low level untill the ICP was elevated up to 500mmH2O (36 mmHg) and more or less increased thereafter (Fig. 1 & 2). The pressure in the parasagittal venous pathways presented abrupt alterations between the lacuna and the superior sagittal sinus in monkeys (Fig. 6). (3) CONCLUSIONS: It was concluded that a gradual stenosis of parasagittal venous pathways took place 1-2 mm lateral to the junction between the lateral lacuna and the superior sagittal sinus in monkeys when the ICP was gradually elevated. This result suggests that also in humans a gradual stenosis occurs in a similar fasion as the ICP is elevated. The results of the experiment obtained in monkeys were almost the same as those previously obtained in dogs.