CSF and Meninges Flashcards
What is the main function of the meninges?
PROTECTION
What are the two layers of the dura mater?
Periosteal layer
inner meningeal layer
stuck together and very tightly tacked onto the skull
Special places where two dura layers come apart to form?
sinuses
What forms falx and tentorium dural infoldings?
meningeal layer
Which mater layer is trabecular?
Arachnoid! Contains projections and space that contains CSF
What is the pia layer consisted of?
Single layer of cells that wrap around entire brain…single of layer of epithelium
Where does the dural layers end?
periosteal ends at foramen magnum
meningeal continues to go down with spinal cords
Spinal cord ends? Dural sac?
Spinal ends at L1
dural sac ends around S2 (contains nerves that have come out of spinal cord but haven’t exited vertebral column…cauda equina)
What does the epidural space along vertebrae contain and why is it importance?
Nerves leaving spinal cord, important for placement of epidural anesthesia and good place for spinal tap
Names and number of ventricles?
Lushka (2 lateral)
megendi (1 medial)
all 3 communicate with cisterna magna
Functions of CSF
- provides buoyancy to brain (less traction on nerves and vessels)
- dampens effects of trauma
- provides stable ionic environment
- removes metabolites from brainn extracellular fluid
composition of CSF
150 cc present, about 500 cc/day made,
clear low viscosity
very little protein
less glucose than serum
acellular
THINK CLEAR AND LOW, like water…can get headaches of too much drained after LP
What makes the CSF?
Choroid plexus. Little stringy fronds of vascularized tissue that are present in ventricles Leaky fenestrated capillaries that uses CARBONIC ANHYDRASE for production…actively transports ions
What is the blood CSF barrier?
Tight junctioned epithelium that filters large molcules like proteins
Flow of CSF starting from lateral ventricles
lateral ventricles > foramen of Monro (2) > 3rd ventricle > cerebral aqueduct > 4th ventricle > magendie and luschka (2) > cisterna magna > cortex, spinal canal > along nerve sleeves > arachnoid villi granulations > superior saggital sinus >jugular veins
What moves CSF?
ependymal cilia
target of LP
L3/L4/L5
Path of needle in LP?
Skin > subcutaneous > supraspinous ligament > ligamentum flavum (stop here for epidural anesthesia) > dura/arachnoid (stop here for CSF drainage)
Meningitis?
Inflammation or infection of meninges
What is aseptic meningetis?
Non-bacterial/non neutrophilic meningitis
Signs of meningitis?
Headache, fever, neck stiffness, photophobia, encephalopathy
How to Dx meningitis?
LP to analyze CSF and see a high WBC count and protein in CSF
Features of meningiomas?
Benign, slow growing, asymptomatic, generally good prognosis
Types of meningeal bleeds
epidural, subdural, subarachnoid
Features of epidural hematoma
bleed in between skull and periosteal layer of dura. Consequence of traumatic rupture of MENINGEAL ARTERIES…acute
Features of subdural bleed
Occur under dura, outside arachnoid. consequence of trauma to bridging VEINS (but can be chronic also , can be acute or chronic
Features of subarachnoid bleeds?
occurs deeper in brain substance, can happen traumatically but usually due to ANEURYSMAL rupture of cerebral arteries. (Associated with thunderclap headache), acute
What is hydrocephalus?
Obstructive process that results in dilation of CSF spaces (dilated ventricles or anywhere where CSF travels)
Water. Head. Get it.
Communicating vs non-communicating hydrocephalus?
communicating - all places carrying CSF are still normally connected, but have problem draining (i.e. scarring of arachnoid villi)
non communicating - doesn’t communicate with rest of CSF
I.e. scarring of aqueduct while ventricles keep making CSF
What can increase intracranial pressure?
Diffuse, focal edema (brain)
hydrocephalus, meningitis (CSF)
blood, venous clot (blood)
extra stuff (tumor or abess)
Signs of increased intracranial pressure
headache, vomiting, bradycardia and hypertension, papilledma
What does elevated protein in CSF indicate?
infection or inflammation, Guillan Barre syndrome, MS
What do elevated WBCs and low glucose indicate?
infection, inflammatoin, neutrophils in bacterial meningitis, aseptic process
What do elevated RBCs indicate?
Subarachnoid hemorrhage, hemorrhagic meningitis
Normal color of CSF?
clear
Xanthochromia
yellow CSF, old blood (Hb turned into bilirubin)
Functions of blood-brain-barrier (BBB)
- keep plasma toxins out of brain
- block tiny oscillations of plasma ions
- keep plasma proteins and growth factors out
- keep NTs from going in or out of brain
GANDALF WITH STAFF YOU SHALL NOT PASS
What forms BBB?
unique capillaries. Tight junctions in endothelial cell, processes of ASTROCYTES, capillary basement membrane
What parts of brain lack BBB?
Area postrema - needs to sense toxins so you can vomit
OVLT - needs to sense ions and osmolar changes in order to influence ADH production
What determines what passes through BBB?
Lipid solubility (hydrophobicity)…
if too fast, carrier mediated transport
if too slow, albumin bound
