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 intravenous contrast media on CT and MRI.

Gross anatomy

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:

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

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

Related pathology

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

See also

  • blood-ocular barrier
Siehe auch:
und weiter: