Revision 22 for 'Blood-brain barrier'

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Blood brain barrier

The blood brain barrier (BBB) forms a physical resistance to the passage of lipophobic substances from cerebral capillaries into the brain and is a key reason why there is no CSF enhancement following IV contrast media in CT and MR imaging.

Gross anatomy

The BBB is formed by a combination of endothelial cells, pericytes, and astroglial and perivascular macrophages along the cerebral capillary walls.

In general, capillary walls in the human body can comprise of three different types:

  • continuous: present in areas which have a BBB
    • continuous interendothelial tight junctions
    • no pinocytosis
    • no fenestrations
  • fenestrated: present in areas which lack the BBB
  • sinusoidal: not found in the brain

In the brain, the majority of capillary walls are of the continuous type with tight junctions and a continuous basement membrane

Areas which have fenestrated capillaries and thus lack the blood brain barrier are:

Generally lipophilic solutes can cross the BBB which include:

  • caffeine
  • ethanol
  • radiopharmaceuticals used in PET and SPECT imaging
  • CO2
  • O2
  • nicotine

Hydrophilic solutes in general on the other hand are unable to cross it, e.g. water soluble CT/MR contrast media. 

Related pathology

There are a multitude of conditions that are associated with disruption of the BBB:

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