Alterations in Cerebral Homeostasis
- Increased intracranial pressure may result from edema, excess cerebrospinal fluid, hemorrhage, or tumor growth. When intracranial pressure approaches arterial pressure, hypoxia and hypercapnia produce brain damage.
- Cerebral edema is an increase in the fluid content of the brain resulting from infection, hemorrhage, tumor, ischemia, infarct, or hypoxia.
- The shifting or herniation of brain tissue from one compartment to another disrupts the blood flow of both compartments and damages brain tissue.
- Supratentorial herniation involves temporal lobe and hippocampal gyrus shifting from the middle fossa to posterior fossa; transtentorial herniation involves a downward shift of the diencephalon through the tentorial notch; and shifting of the cingulate gyrus can occur under the falx.
- The most common infratentorial herniation is a shift of the cerebellar tonsils through the foramen magnum.
- Hydrocephalus comprises a variety of disorders characterized by an excess of fluid within the cranial vault, subarachnoid space, or both. Hydrocephalus occurs because of interference with cerebrospinal fluid flow caused by increased fluid production or obstruction within the ventricular system or by defective reabsorption of the fluid.