Cerebral edema
From Wikipedia, the free encyclopedia
| ICD-10 | G93.6 |
|---|---|
| ICD-9 | 348.5 |
| DiseasesDB | 2227 |
Cerebral edema is an excess accumulation of water in the intra- and/or extracellular spaces of the brain. Edema can occur as the result of many things, including head injury, allergic reaction, stroke, acute liver disease, cardiac arrest or from the lack of proper altitude acclimatization.
Symptoms of cerebral edema include headaches, decreased level of consciousness, loss of eyesight, hallucinations, psychotic behavior, memory loss and coma. If left untreated, it can lead to death - Bruce Lee's death is a famous example.
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[edit] Different Forms
[edit] Vasogenic cerebral oedema
Due to a breakdown of tight endothelial junctions which make up the blood-brain barrier (BBB). This allows normally excluded intravascular proteins and fluid to penetrate into cerebral parenchymal extracellular space. Once plasma constituents cross BBB the oedema spreads, this may be quite fast and widespread. As water enters white matter it moves extracellularly along fibre tracts and can also affect the grey matter. This type of oedema is seen in response to trauma, tumors, focal inflammation, late stages of cerebral ischemia and hypertensive encephalopathy.
Some of the mechanisms contributing to BBB dysfunction are: physical disruption by arterial hypertension or trauma, tumour-facilitated release of vasoactive and endothelial destructive compounds (eg arachidonic acid, excitatory neurotransmitters, eicosanoids, bradykinin, histamine and free radicals).
[edit] Cytotoxic cerebral oedema
In this type of edema the BBB remains intact. This oedema is due to the derangement in cellular metabolism resulting in inadequate functioning of the sodium and potassium pump in the glial cell membrane. As a result there is cellular retention of sodium and water. There are swollen astrocytes in grey and white matter. Cytoxotic oedema is seen with various intoxications (dinitrophenol, triethyltin, hexachlorophene, isoniazid), in Reye's syndrome, severe hypothermia, early ischemia, encephalopathy, early stroke or hypoxia, cardiac arrest, pseudotumour cerebri, and cerebral toxins.
[edit] Osmotic oedema
Normally cerebral-spinal fluid (CSF) and exocoelomic fluid (ECF) osmolality of the brain is slightly greater than that of plasma. When plasma is diluted by excessive water intake (or hyponatremia), syndrome of inappropriate antidiuretic hormone secretion (SIADH), hemodialysis, or rapid reduction of blood glucose in hyperosmolar non-ketotic acidosis (HONK), the brain osmolality will then exceed the serum osmolality creating an abnormal pressure gradient down which water will flow into the brain causing oedema.
[edit] Hydrostatic oedema
This form of cerebral edema is seen in acute, malignant hypertension. It is thought to result from direct transmission of pressure to cerebral capillary with transudation of fluid into the ECF.
[edit] Interstitial cerebral oedema
Occurs in obstructive hydrocephalus This form of oedema is due to rupture of CSF-brain barrier: permits CSF to penetrate brain and spread in the extracellular space of white matter. Differentiated from vasogenic oedema in that fluid contains almost no protein
[edit] High Altitude Cerebral Edema
High Altitude Cerebral Edema (or HACE) is a severe (usually fatal) form of altitude sickness. HACE is the result of swelling of brain tissue from fluid leakage. Symptoms can include headache, loss of coordination (ataxia), weakness, and decreasing levels of consciousness including disorientation, loss of memory, hallucinations, psychotic behaviour, and coma. It generally occurs after a week or more at high altitude. Severe instances can lead to death if not treated quickly. Immediate descent is a necessary life-saving measure (2,000 - 4,000 feet). There are some medications (e.g. dexamethasone) that may be prescribed for treatment in the field, but these require proper medical training in their use. Anyone suffering from HACE must be evacuated to a medical facility for proper follow-up treatment. A gamow bag can sometimes be used to stabilize the sufferer before transport or descending.
Climbers may also suffer high altitude pulmonary edema (HAPE), which affects the lungs. While not nearly as life threatening as HACE in the initial stages, failure to descend to lower altitudes or receive medical treatment can also lead to death.
