Session 3 - Meninges

Question 1

What are the 3 membranous layers that surround and protect the brain and spinal cord from external to internal

Answer 1

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

Question 2

What are the leptomeninges and what is their significance

Answer 2

Pia matar and arachnoid matar

Get swollen in meningitis

Question 3

What are the “spaces” of the brain layers called and what fills them

Answer 3

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)

Question 4

What are the 3 membranous sacs that surround and protect brain and spinal cord

Answer 4

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

Question 5

What are the two layers of the dura

Answer 5

Periosteal (outer layer which lines inner skull bone)

Meningeal layer which lines the surface connnecting with arachnoid

Question 6

What does the separation of the dura create

Answer 6

Can create dural folds and dural venous sinuses

Question 7

What are the names of the main dural folds

Answer 7

Midline - falx cerebri (sits on top of lateral)

Lateral - tentorium cerebelli

Question 8

Why are dural folds important

Answer 8

Help stabilise brain and act as rigid dividers

Question 9

Why can they be a common site for herniation

Answer 9

A rise in intracranial pressure pushes contents underneath fold (herniation) or compress parts of brain under dural folds or through foramen magnum

Question 10

Where are dural venous sinuses found

Answer 10

Between the periosteal and meningeal layer of the dura

Question 11

Why are the dural venous sinuses different from normal veins

Answer 11

They DO NOT HAVE VALVES

Question 12

Where do dural venous sinuses receive blood from

Answer 12

Cerebral veins (to drain the brain) and eventually into the IJV

Question 13

What is an anatomical landmark for when DVS becomes the IJV

Answer 13

Foramen magnum

Question 14

Where do the inferior and superior sagittal sinuses lay

Answer 14

SSS in falx cerebri

ISS in inferior falx cerebri (met by great cerebral vein and unite to form straight sinus)

Question 15

What are arachnoid kid granulations

Answer 15

Arachnoid projections through meningeal layer found is SSS and allow CSF can be transported back into venous system

Question 16

What is the main insertion point for all DVS and where does the blood go from there

Answer 16

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

Question 17

Where is the cavernous sinus and where does it drain

Answer 17

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(

Question 18

What does the cavernous sinus drain

Answer 18

Cranial nerves
Internal carotid artery
Opthalmic veins

Question 19

What are bridging veins

Answer 19

Veins formed as tributaries from cranial veins (in subarachnoid) that drain into DVS by traversing subdural space

Question 20

What are emissary veins

Answer 20

Veins that connect the scalp to DVS (go through the bone) extracranial to intracranial

Question 21

What are the 3 times of intracranial hemorrage

Answer 21

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

Question 22

What is the difference between intracerebral and intracranial

Answer 22

Intracranial is bleeding in the meningeal layers and scalp whereas intracerebral is bleeding due to brain tissue itself (tearing etc)

Question 23

Why do elderly need to be so cautious with even minor head injuries

Answer 23

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

Question 24

What do the different bleeds look like on a CT and secondary measures for subarachnoid bleeding is CT inconclusive

Answer 24

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)