Intracranial Hypertension

Posted by e-Medical PPT
Monroe-Kellie Doctrine
Skull is a rigid structure (except in children with fontanels)
3 components:
Brain:  80% of total volume, tissues and interstitial fluid
Blood: 10% of total volume = venous and arterial
CSF: 10% of total volume
Vintracranial = Vbrain + VCSF + Vblood
An increase in one component occurs in the compression of another

Brain
80% of intracranial space = 80% water
Cell types
Neurons: Cell body, dendrites, axon, pre-synaptic terminal-neurotransmission
Astrocytes/Pericytes
Support the neurons & other glial cells by isolating blood vessels, sypnapses, cell bodies from external environment
Endothelial cells
Joined a tight junctions  form BBB
Oligodendrocytes
Myelin sheath around axons  propagates action potential  efficient transmission of information
Microglia
Phagocytes, antigen-presenting cells, secrete cytokines

CSF
10% of total volume
Choroid plexus > 70 % production
Transependymal movement fluid  from brain to ventricles ~30%
Average volume CSF in child is 90cc (150cc in adult)
Rate of production: 500cc/d
Rate production remains fairly constant
w/ increase ICP it is absorption that changes  (increase up to 3X via arachnoid villa)

Blood
10% of intracranial volume
Delivered to the brain via the Circle of Willis  course through subarachnoid space before entering brain
Veins & sinuses drain into jugular veins
Cerebral blood volume (CBV)
Contributes to ICP
Cerebral blood flow (CBF)
Delivers nutrients to the brain

Cerebral Edema
Vasogenic
Increased capillary permeability disruption BBB
Tumors/abscesses/hemorrhage/trauma/ infection
Neurons are not primarily injured
Cytotoxic
Swelling of the neurons & failure ATPase Na+ channels
Interstitial
Flow of transependymal fluid is impaired (increased CSF hydrostatic pressure..

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