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Definition: increase in the water content of the brain

Several forms

• most common form
• due to a breakdown of tight endothelial junctions which make up the BBB. This allows normally excluded intravascular proteins and and fluid to penetrate into cerebral parenchymal extracellular space
• once plasma constituents cross BBB the oedema spreads. May be quite fast and widespread as oedema enters white matter and moves extracellularly along fibre tracts
• mechanisms contributing to BBB dysfunction: 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
• accompanies traumatic injury, inflammatory disease, brain tumours and hypertensive encephalopathy. Also late stages of brain infarction

• BBB intact
• due to encephalopathy, early stroke or hypoxia, cardiac arrest, pseudotumour cerebri, cerebral toxins
• another form of cytotoxic oedema occurs when brain osmolality exceeds serum osmolality and water passes into brain eg after water intoxication or rapid reduction of blood glucose in HONK

• occurs in obstructive hydrocephalus
• 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

© Charles Gomersall December 1999

©Charles Gomersall, May, 2008 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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