to the cerebral perfusion pressure (CPP) divided by the cerebrovascular resistance (CVR): CBF = CPP / CVR Control of CBF is considered in terms of the factors affecting CPP and the factors affecting CVR. CVR is controlled by four major mechanisms: Metabolic control (or 'metabolic autoregulation') Pressure autoregulation Chemical control (by arterial pCO2 and pO2) Neural control Role of intracranial pressure Increased intracranial pressure (ICP) causes decreased blood perfusion of brain cells by mainly two mechanisms: Increased ICP constitutes an increased interstitial hydrostatic pressure that, in turn, causes a decreased driving force for capillary filtration from intracerebral blood vessels. Increased ICP compresses cerebral arteries, causing increased cerebrovascular resistance (CVR). Cerebral perfusion pressure Cerebral perfusion pressure, or CPP, is the net pressure gradient causing cerebral blood flow to the brain (brain perfusion). It must be maintained within narrow limits; too little pressure could cause brain tissue to become ischemic (having inadequate blood flow), and too much could raise intracranial pressure (ICP). Imaging Arterial spin labeling (ASL), phase contrast magnetic resonance imaging (PC-MRI), and positron emission tomography (PET) are neuroimaging techniques that can be used to measure CBF. ASL and PET can also be used to measure regional CBF (rCBF) within a specific brain region. rCBF at one location can be measured over time by thermal diffusion References External links Computer Model of the Cerebral Circulation for Training and Education Neurology Cardiology