cerebral edema
an abnormal accumulation of fluid in the intercellular or intracellular spaces of brain tissues, which may be caused by injury, disease, cerebrovascular accident, or tumor (see also acute mountain sickness). The condition results in swelling and a rise in intracranial pressure; if uncorrected, this may be followed by herniation of cerebral tissue through weakened areas. It may be reversible unless the damage extends to the brainstem, where the effects can be fatal. The increase in intracranial pressure may result in headaches and visual disorders. Cerebral edema can also cause cognitive dysfunction that recedes when the defect is corrected.