2. Meninges and CSF Flashcards
What does the dura cover?
Brain, spinal cord, cranial nerves, optic chiasm
Where are sinuses located?
Within the dura mater
Where do the sinuses drain venous blood?
Jugular veins –> SVC
What landmark distinguishes the end of the brainstem and the beginning of the spinal cord?
Foramen Magnum
Falx cerebri
Attached to skull, goes down to corpus callosum
Separates brain into two hemispheres
Where is the superior sagittal sinus?
Top of falx cerebri
Tentorium cerebelli vs falx cerebelli
Tentorium cerebelli covers the top of the cerebellum, separates it from the occipital lobe
Falx cerebelli divides the cerebellum into two hemispheres
What is the tentorium notch?
It is the space in the tentorium cerebelli through which the brainstem passes
What happens during uncal herniation?
Increased intracranial pressure (ICP) causes the uncus to herniate and get stuck under the tentorial notch
Epidural space in brain vs spinal cord
In brain, it is a potential space
In SC, it is a real space
Space between skull and dura; space between dura and vertebrae
Is the subdural space a real space or a potential space?
Potential space. Dura and arachnoid are usually fused
In which meningeal space is the CSF?
Subarachnoid space
In what cases do epidural hematomas occur? Describe what happens
Tearing of middle meningeal artery or tearing of venous sinus –> quick bleeding –> accumulation of blood –> rapid rise of pressure (dura can dissect off bone)
Where does the bleeding occur with an epidural hematoma vs subdural hematoma?
Epidural = above dura; subdural = inbetween dura mater and arachnoid
Consequences of epidural hematoma?
Compression and midline shift of brain
Can effect/damage optic chiasm (dilated pupil that doesn’t constrict)
Coma and death can result
Consequences of subdural hematoma?
Dissect arachnoid off dura; blood distributed throughout entire hemisphere
Can also lead to brain compression, similar symptoms as epidural
Slower onset than epidural since it involves brain
Subdural hematoma involves damage to what structure(s)? Significance of this?
Cerebral vein; bleed is lower pressure and occurs more slowly
Why does the risk of tearing increase as we age?
Brain shrinks, pulls away from sinus –> greater risk for tears
Younger people and more susceptible to _________ hematomas, and elderly are more susceptible to ______________ hematomas.
Younger people –> epidural hematomas
Elderly –> subdural hematomas
Composition of CSF
little glucose/protein/cells, chloride
What happens to CSF with meningitis?
CSF may be cloudy with presence of bacteria (also notable difference in composition of CSF)
Functions of CSF (6)
Bouyancy and support
Cushion and protect
Nourishment
Reservoir and regulation of the contents of skull
Removes metabolites
Pathway for pineal secretions to reach pituitary gland
Where is choroid plexus located?
In all of the four ventricles
Describe the flow of CSF
lateral ventricles –> interventricular foramin of Monroe –> 3rd ventricle –> cerebral aqueduct –> 4th ventricle
If it goes through foramin of magendie (median aperture) –> flows up around the brain into subarachnoid space
If it goes through the foramen of luschka (lateral aperture)–> flows in and around SC