Brain Tissue Pressure

The changes in regional cerebral blood flow observed in diseased areas of the brain when arterial PCO2 and/or arterial blood pressure are altered have been attributed to variations in local tissue perfusion pressure (TPP) [1] and to pressure gradients within the brain [2, 3, 4]. Conclusions drawn from “cerebral” perfusion pressure (CPP) calculations appear to possess only a restricted value for the analysis of local circulatory phenomena since CPP is an overall value. Local brain tissue perfusion pressure, however, can only be determined if the blood pressure within the small intraparenchymatous brain vessels and the “interstitial” pressure of the brain tissue are known. While recent papers [5, 6] contain quantitative data on blood pressure in small vessels of the brain, no satisfactory method has hitherto permitted the measurement of brain tissue pressure. Implantable capsules [7] and balloons filled with saline [8] are inappropriate for this purpose since they involve excessive damage to the brain tissue.