Cerebrospinal Fluid

Monoamine pathways | Main Anatomy Index

Robinson, S. (1998) The Hippocampus and Cerebrospinal Fluid [Lecture]. University of NSW, 12 October, 1998.

• Cerebrospinal fluid (CSF) is formed mainly by the choroid plexuses of the lateral, third and fourth ventricles.

• Choroid plexus is highly folded sheet of pia mater.
• It contains wide capillaries and a surface layer of cuboidal epithelium.
• The anterior and posterior choroid arteries supply it.

• This involves the active transport of sodium and other ions, and the passive diffusion of water.
• Other components of CSF come from metabolites secreted by neurons and glia into the extracellular space of the brain (continuous with CSF via the ependymal lining of the ventricles).

• The adult CNS contains 80-140 mL of CSF.
• Production is at a rate so that there is a complete turnover roughly ever 6 hours.

• After flowing to the 4th ventricle, CSF exits via:

1. The foramen of Magendie (midline);
2. Or the foramina of Luschka (laterally).

• Some CSF then flows in the subarachnoid space surrounding the spinal cord.
• It then pools in the lumbar cistern and is resorbed into the venous supply via arachnoid villi.

• The remaining CSF passes through a series of subarachnoid cisterns that surround the brain.
• This CSF is "pumped" by the throbbing of the vessels in the subarachnoid space.
• It is resorbed into the venous supply of the arachnoid villi projecting into the superior sagittal sinus.

• All constituents of CSF are resorbed, including small molecules, proteins, microorganisms and red blood cells.
• Arachnoid villi become hypertrophied and calcified with age (arachnoid granulations).

1. Buffers the extracellular fluid and maintains a constant ionic environment.
2. Provides a reservoir of oxygen and glucose.
3. A conduit for removal of waste metabolites.
4. A rout for the spread of neuroactive hormones.
5. Cushions the brain from impact with the skull.
6. Allows the brain to float, reducing the effective brain weight from 1400 g to 50 g.
7. Serves as a heat sink.

• A needle is inserted between the 4th and 5th lumbar vertebrae.
• This allows the collection of CSF with minimal risk of damaging the spinal cord.
• Normal CSF does not contain red or white blood cells and contains little protein.

1. The presence of leukocytes indicates infection. Levels are particularly high with bacterial meningitis.
2. Presence of RBCs indicates bleeding (e.g., stroke).
3. Elevated protein levels can indicate necrosis or breakdown of the blood-brain barrier (e.g., albumin). Some proteins are secreted into the CSF in certain diseases (e.g., tau protein in Alzheimer's disease).
4. Decreased glucose levels indicate a fungal or yeast infection, or a meningeal tumour.

• The central artery and vein of the retina pass through the subarachnoid space or the optic nerve.
• Thus, increased CSF pressure slows the return of venous blood, causing oedema of the retina and swelling of the optic nerve head (papilledema).

• Excess CSF in subarachnoid space, due to brain atrophy (e.g., in senile dementia).

• Dilation of the ventricles due to occlusion of flow from the 4th ventricle (congenital abnormality; sequelae of meningitis), or cerebral aqueduct (pinealoma).

• External and internal hydrocephalus due to obstruction of the arachnoid villi after a subarachnoid haemorrhage.

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