Cerebral perfusion<unk>  (CPP), the<unk>  of blood flowing to the brain, is normally fairly constant due to autoregulation, but for abnormal mean arterial<unk>  (MAP) or abnormal<unk>  the cerebral perfusion<unk>  is calculated by subtracting the<unk>  from the mean arterial<unk> : CPP = MAP −<unk>  . One of the main dangers of increased<unk>  is that it can cause ischemia by decreasing CPP. Once the<unk>  approaches the level of the mean systemic<unk> , cerebral perfusion falls. The body's response to a fall in CPP is to raise systemic blood<unk>  and dilate cerebral blood vessels. This results in increased cerebral blood volume, which increases<unk> , lowering CPP further and causing a vicious cycle. This results in widespread reduction in cerebral flow and perfusion, eventually leading to ischemia and brain infarction. Increased blood<unk>  can also make<unk>  hemorrhages bleed faster, also increasing<unk> . Severely raised<unk> , if caused by a unilateral space-occupying lesion (e.g. a hematoma) can result in midline shift, a dangerous sequela in which the brain moves toward one side as the result of massive swelling in a cerebral hemisphere. Midline shift can compress the ventricles and lead to hydrocephalus. Monro–Kellie hypothesis The<unk> –volume relationship between<unk> , volume of CSF, blood, and brain tissue, and cerebral perfusion<unk>  (CPP) is known as the Monro–Kellie doctrine or hypothesis. The Monro–Kellie hypothesis states that the cranial compartment is inelastic and that the volume inside the cranium is fixed. The cranium and its constituents (blood, CSF, and brain tissue) create a state of volume equilibrium, such that any increase in volume of one of the cranial constituents must be compensated by a decrease in volume of another. *This concept only applies to adults, as the presence of fontanelles and open suture lines in infants that have not yet fused means there is potential for a change in size and<unk>  volume. The principal buffers for increased volumes include CSF and, to a lesser extent, blood volume. These buffers respond to increases in volume of the remaining<unk>  constituents. For example, an increase in lesion volume (e.g., epidural hematoma) will be compensated by the downward displacement of CSF and venous blood. The Monro–Kellie hypothesis is named after Edinburgh doctors Alexander Monro and George Kellie.
Intracranial pressure
Cerebral perfusion pressure
Cerebral autoregulation
Mean arterial pressure
Intraocular pressure
Blood volume
Segmental blood pressure
Blood pressure