Friday, February 8, 2008
CSF outflow isn't only through the arachnoid granulations
We teach our medical students that CSF outflow is through the arachnoid granulations into the venous sinuses. That's true, and good enough for a second year medical school curriculum. But we should keep in mind that some CSF appears to be absorbed by the ependymal lining of the ventricles, as well as in the spinal subarachnoid space and through the walls of the capillaries in the pia mater. Additionally, to quote my source on all of this (Clinically Oriented Anatomy, 2nd edition, by Keith Moore), "some CSF is probably absorbed into the lymphatics adjacent to the subarachnoid space around cerebrospinal nerves (e.g., the optic nerves)."
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The following is adapted from a respected researcher:
(All names are omitted to protect the innocent.)
"There is a fundamental change in the doctrine of CSF reabsorption. At least in several mammalian models, more than half the CSF drains via the olfactory nerves into the nasal submucosa, then into cervical lymph. CSF flow through the arachnoid villi seems to be minimal, except perhaps under elevated ICP. Granted, the human situation needs to be documented. Some scientists still cling to the older, more traditional model. Other scientists are spearheading the new model.
Most neuroscientists and neurosurgeons do not appreciate the new CSF drainage model. That is why review articles need to be written to educate neuro-oriented people."
Now THAT is interesting. If you have any references for that, please post them.
Addendum:
"CSF reabsorption across the ependyma would occur only in high-pressure hydrocephalus. Under normal CSF pressure, brain extracellular fluid would flow from brain across ependyma into the ventricles or subarachnoid space."
The reference for both posts is a chapter in a not-yet-published book.
Nursing jobs in Hawaii are being advertised now on here! Top pay and benefits, free private housing.
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