Session 3 - Meninges Flashcards
What are the 3 membranous layers that surround and protect the brain and spinal cord from external to internal
Dura mater - sole covering and does not go in fissures or rolls
Arachnoid - only dip into fissures not gyre
Pia matar - like visceral pleura and follows every crevice
All go down into spinal column
What are the leptomeninges and what is their significance
Pia matar and arachnoid matar
Get swollen in meningitis
What are the “spaces” of the brain layers called and what fills them
Space between arachnoid and pia matar is subarachnoid space filled with cerebral spinal fluid and cerebral vessels
Sub dural - The pressure of CSF presses the arachnoid matar against the dura so this “space” is potential (like it times of bridging vein hemorage)
What are the 3 membranous sacs that surround and protect brain and spinal cord
Dura - doesn’t even go around fissures only surface
Arachnoid matar - only goes into deep fissures not grooves
Pia matar - around every groove and fissure of brain
What are the two layers of the dura
Periosteal (outer layer which lines inner skull bone)
Meningeal layer which lines the surface connnecting with arachnoid
What does the separation of the dura create
Can create dural folds and dural venous sinuses
What are the names of the main dural folds
Midline - falx cerebri (sits on top of lateral)
Lateral - tentorium cerebelli
Why are dural folds important
Help stabilise brain and act as rigid dividers
Why can they be a common site for herniation
A rise in intracranial pressure pushes contents underneath fold (herniation) or compress parts of brain under dural folds or through foramen magnum
Where are dural venous sinuses found
Between the periosteal and meningeal layer of the dura
Why are the dural venous sinuses different from normal veins
They DO NOT HAVE VALVES
Where do dural venous sinuses receive blood from
Cerebral veins (to drain the brain) and eventually into the IJV
What is an anatomical landmark for when DVS becomes the IJV
Foramen magnum
Where do the inferior and superior sagittal sinuses lay
SSS in falx cerebri
ISS in inferior falx cerebri (met by great cerebral vein and unite to form straight sinus)
What are arachnoid kid granulations
Arachnoid projections through meningeal layer found is SSS and allow CSF can be transported back into venous system
What is the main insertion point for all DVS and where does the blood go from there
Occipital protuberance (confluence of sinuses) where blood can go left or right into transverse sinus (mainly left) then sigmoid sinus after crossing parietal bone
Sigmoid run across temporal until IJV forms
Where is the cavernous sinus and where does it drain
Lateral to sella turcica
Drain into sigmoid sinus via superior petrousal sinus along tentoum cerebelli or straight to IJV by inferior petrousal sinus (first tributary of IJV(
What does the cavernous sinus drain
Cranial nerves
Internal carotid artery
Opthalmic veins
What are bridging veins
Veins formed as tributaries from cranial veins (in subarachnoid) that drain into DVS by traversing subdural space
What are emissary veins
Veins that connect the scalp to DVS (go through the bone) extracranial to intracranial
What are the 3 times of intracranial hemorrage
Extradural - outside dura, pressure strips periosteum off inner bone so must have run under scalp (middle meningeal artery laceration) eventually get pinched due to sutures stopping stripping
Subdural - potential space filled with blood due to weakness in spot where bridging veins connect to dural wall
Subarachnoid - secondary to trauma or spontaneous rupture (aneurysm) and usually is a branch of the circle of Willis blood leaks into subarachnoid space mixing with CSF also causes meningitis like symptoms
What is the difference between intracerebral and intracranial
Intracranial is bleeding in the meningeal layers and scalp whereas intracerebral is bleeding due to brain tissue itself (tearing etc)
Why do elderly need to be so cautious with even minor head injuries
As you grow older, cerebral atrophy occurs as a natural process and the distance between the sub arachnoid space and dura causes tension in the bridging veins making them even more prone to injury
What do the different bleeds look like on a CT and secondary measures for subarachnoid bleeding is CT inconclusive
Sub dural - Banana at side of brain
Extradural - mango
Subarachnoid - circle, if inconclusive do lumbar puncture to see if CSF have blood (specifically haemoglobin degradation products)
