cerebrospinal fluid

Function

• 70% secreted by choroid plexus, 30% from brain parenchyma.
• CSF is absorbed into the systemic circulation through the arachnoid villi
• >80% of the protein in CSF originates from plasma, the remainder from intrathecal synthesis
• pulsatility of the brain's arteries creates a convective force that draws CSF into the brain from the space around its arterial walls & back out again along its veins, facilitating penetration of CSF into the brain parenchyma
• CSF exchanges with brain parenchymal interstitial fluid, percolating through & around astroglial end-feet toward nearby veins, along which it then exits the brain thus taking with it neuronal waste products
• the veins must propel CSF toward the arachnoid villi where it is absorbed into the systemic circulation
• the process is termed glymphatic clearance
• waste products such as beta-amyloid & other aggregation-prone proteins are cleared not only alongside veins but also across the blood-brain barrier into the systemic circulation

Structure

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Pathology

• pulsatility of the small penetrating arteries in the brain declines with age
• reduction of CSF influx into brain parenchyma with age

Laboratory

CSF protein electrophoresis (after concentration)

• ultrafiltrate of plasma
• all proteins visible on electrophoresis are <150 kD
• prominent prealbumin band
• 2 transferrin bands
  • beta-1 transferrin
  • beta-2 transferrin
• used largely to detect intrathecal production of IgG
  • IgG/albumin ratio < 0.27 considered normal ,

Total volume (adult): 150 mL (100-160 mL)

CSF: production: 0.35 mL/min, 500 mL/day ,

Also see CSF analysis

Comparative biology

• distribution of the aquaporin receptor changes with age in mice
  • normally, aquaporin receptors are located on astrocytic end-feet facing the arteries, where they facilitate uptake of fluid from the peri-arterial space & drive glymphatic flow toward nearby veins
  • with age, aquaporin receptors redistribute more uniformly facilitating fluid retention within astrocytes more than directing flow from arteries to veins

More general terms

• extracellular compartment (extracellular space)
• body fluid

Additional terms

• cerebrospinal fluid (CSF) protein electrophoresis
• cerebrospinal fluid analysis
• intracranial pressure (ICP)
• lumbar spinal puncture (LP, Quincke puncture, spinal tap, rachicentesis, rachiocentesis)
• reference values for CSF constituents