glymphatic system of the brain

Introduction

discovered in 2012, the glymphatic system is a “pseudo-lymphatic” perivascular network distributed throughout the brain, responsible for replenishing as well as cleansing the brain.
glymphatic clearance is the macroscopic process of convective fluid transport in which harmful interstitial metabolic waste products are removed from the brain intima
sleep is a primary driver of glymphatic clearance
- there appears to be a 90% reduction in glymphatic clearance during wakefulness, and twice the amount of protein clearance from the brain intima during sleep - and it appears that the majority of glymphatic clearance activity occurs during N3 sleep which occurs in non-REM deep sleep and glymphatic transport is most efficient in the right lateral sleeping position, with more CSF clearance occurring compared to supine and prone. ¹⁾
- two main flow processes²⁾:
  - fast flow:
    - fluid moves at a few microns per second around the brain's open regions such as the surface between the skull and the brain
  - slower flow:
    - fluid trickles through the brain's deep tissue at a rate about 50 times slower
it appears to reduce in efficiency as we age
low doses of alcohol (0.5 g/kg) appears to increase glymphatic clearance but higher levels reduce it
glymphatic clearance can be manipulated by sleep deprivation, cisterna magna puncture, acetazolamide or genetic deletion of AQP4 channels
it has been proposed that glymphatic dysfunction is the central cause of delirium³⁾

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