Cerebral Edema

Excerpt

The most basic definition of cerebral edema is swelling of the brain. It is a relatively common phenomenon with numerous etiologies. Cerebral edema categorizes into either vasogenic, cellular, osmotic, and interstitial causes. It can arise from a variety of causes, including head trauma, vascular ischemia, intracranial lesions, or obstructive hydrocephalus resulting in interstitial edema. The consequences of cerebral edema can be devastating, even fatal, if untreated.

The explanation of the mechanism of injury arising from cerebral edema comes via the Monroe-Kellie doctrine. The Monroe-Kellie doctrine states that space of the cranial cavity is fixed in volume and contains fixed proportions of brain matter (approximately1400 ml), blood (approximately 150 ml) and cerebrospinal fluid (approximately 150 ml). Because of this fixed space, an increase in the volume of one of these components must, therefore, result in the loss of another component in equal amounts. In cerebral edema, the relative volume of brain tissue increases as the brain tissues swells with edema. This increased relative brain volume decreases perfusion (blood) to the brain, and the pressure can cause further damage to both the edematous and non-edematous brain. Clinical presentation of cerebral edema is variable, ranging from asymptomatic to severe autonomic dysregulation, coma, and death. Symptoms appear as the intracranial pressure (ICP) rises above 20 cm H2O in most patients. Treatment for cerebral edema targets the underlying cause and any life-threatening complications. Treatments include hyperventilation, osmotherapy, diuretics, corticosteroids, and surgical decompression.