34 CSF & INTRACRANIAL PRESSURE Flashcards
Two types of meninges
Pachymeninges and leptomeninges
Describe the pachymeninges
Dura mater. Two layers periosteal layer and meningeal layer.
Where do the venous sinus’s form
In between the two layers of the pachymeninges
Describe the leptomeninges
Arachnoid mater and pia mater. Separted by subarachnoid space which contains CSF and blood vessels
What are the falx cerebri and tentorium made from
Inner folds of the meningeal layer of the Pachymeninges
What are Virchow-Robinson spaces
As blood vessels enter or leave the brain/spinal cord the pia mater invaginates into the brain or sc to form perivascular spaces
Where is CSF produced
In the chorioid plexus mostly in the lateral ventricles some in 3rd and fourth ventricles
Describe the chorioid plexus
Bundles of fenestrated capillaries surrounded by ependymal cells (glial cells)
Two processes of CSF production
Mainly through filtration of choroidal blood some through secretion from ependymal cells
Typical total volume of CSF
150ml. 600ml created daily. Total volume replaced 4-5 times daily. Clinical relevance LP volume quickly replace
Major route of CSF absorption
Via arachnoid villi and arachnoid granulations which are invaginations of the pia mater into venous sinuses. Unidirectional bulk flow
Changes to CSF in disease states
Meningitis- increased WBC, protein and possibly glucose
SAH- RBC, xanthochromia
Functions of the CSF
Mechanical protection, homeostasis, counter changes in ICP, conduit for hormones
What may increases in ICP be caused by
Increase in brain volume (tumour, haemorrhage, hydrocephalus, abscess), increase in CSF volume (obstruction to flow, increased production, reduced absorption, increased blood flow)
Three kinds of cerebral herniations
Midline shift
Middle temporal lobe through tentorial notch
Inferior cerebellum through posterior fossa into SC
