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Cerebral oedema

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Cerebral oedema

Definition: increase in the water content of the brain

Several forms

Vasogenic cerebral oedema

  • 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

Cytotoxic cerebral oedema

  • 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

Interstitial cerebral oedema

  • 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

Site of herniation

Structures involved


Lateral tentorial (uncal)

Cerebral peduncle
Posterior cerebral artery

Ptosis, mydriasis, lateral deviation of eye

Posterior tentorial (tectal)

Tectal plate (post commissure, sup colliculi)

Bilateral ptosis, failure of upgaze

Central tentorial
(axial brainstem)

Reticular formation
Corticospinal tracts
Midbrain and pons


¯ consciousness
Decerebrate rigidity
¯ or absence of eye movement reflexes, irregular respiration
­ BP, ¯ HR, irregular respiration, apnoea

Foramenal (tonsillar)



Subfalcine (cingulate)

Cingulate gyrus, anterior cerebral artery

Leg weakness

Further reading

Shapiro HM, Drummond JC. Neurosurgical anesthesia. In Millar RD (ed), Anesthesia, 4th ed, 1994

© Charles Gomersall December 1999


©Charles Gomersall, February, 2015 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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