Blood-brain barrier

Last revised by Yvette Mellam on 1 Mar 2023

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 intravenous contrast media on CT and MRI.

The blood-brain barrier 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 consist of three different types:

  • continuous: present in areas which have a blood-brain barrier

    • continuous interendothelial tight junctions

    • no pinocytosis

    • no fenestrations

  • fenestrated: present in areas which lack the blood-brain barrier

  • 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 contain fenestrated capillaries, and thus lack the blood-brain barrier, are:

Generally, lipophilic solutes can cross the blood-brain barrier, including:

Hydrophilic solutes, in general, are unable to cross it, e.g. water soluble CT/MRI contrast media. 

There are a multitude of conditions associated with disruption of the blood-brain barrier:

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Cases and figures

  • Case 1: radionecrosis : enhancment from BBB disruption
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  • Case 2: breakdown following infarct
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