Brain tissue, blood volume and CSF are the three main elements contributing
to the generation of ICP. The Monroe-Kellie doctrine11 says an
increase in the volume of one of these must be countered by a decrease
in the other components to maintain normal ICP. The volume of brain
tissue in a healthy adult is constant, while volumes of blood and CSF
within the cranial cavity are tightly controlled to prevent fl uctuations in
ICP. Damage arises when the regulatory mechanisms designed to protect
the brain and maintain normal ICP become overwhelmed. Aside from the
initial injury, secondary damage occurs, due to hypoxia and displacement
of brain structures