Natural waste removal system drives acute tissue swelling in the brain after a stroke
Cerebral oedema – the swelling of the brain following a stroke – can be triggered by the glymphatic system, according to scientists at the University of Rochester (Rochester) in New York, US. The glymphatic system is used by the brain to clear away waste – during sleep, cerebrospinal fluid (CSF) is usually pumped through brain tissue to flush out toxic proteins, dead cells and other unwanted items. In cerebral oedema, the CSF uncharacteristically fills in some of the gaps created when blood vessels in the brain become blocked, essentially drowning the organ in its own fluids.
Using magnetic resonance imaging and radio-labeled tracers, the scientists observed that when the brain cells of their animal subjects were denied nutrients and oxygen due to vessel blockage, they create a “depolarisation” effect in which the muscle cells lining the vessel walls seizes up and stops blood flow, a process called spreading ischemia. The CSF is then free to flow into the vacuum, drowning already vulnerable brain cells and causing the organ to swell.
Lead author Humberto Mestre said, “The double hit of the spreading depolarisation and theischemia makes the blood vessels cramp, resulting in a level of constriction that is completely abnormal –like a battery, you basically discharge the entire brain surface in one fell swoop.”
However, with this new understanding of cerebral oedema, the Rochester team sees several new therapeutic targets that “could improve stroke outcomes” – drugs could be used to restore lagging blood flow to the brain, or block specific receptors on nerve cells to slow the spread of depolarisation.
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