Meninges

Question 1

describe the layers of the brain

Answer 1

Dura mater (tough fibrous bridges attached to skull) bridges over fissures and sulci
Arachnoid (delicate sealed bag for CSF)
–arachnoid trabeculae (ropes)
Pia mater (delicate, dips into crevices)
CEREBRAL ARTERY BRANCH

Question 2

what is found embedded within the pia mater

Answer 2

cerebral artery branch

Question 3

what helps position the brain in one place

Answer 3

arachnoid trabeculae

Question 4

what arteries are found within the dura mater

Answer 4

branches of the middle meningeal artery
which courses close to pterion

Question 5

what happens if the middle meningeal artery is damaged

Answer 5

extradural haemorrhage

Question 6

what are the different cisterns found in the brain
what are cisterns

Answer 6

2 AT FRONT:
interpeduncular cistern
-central part of midbrain
-in between peduncles

cisterna pontis
-junction of pons and medulla

2 AT BACK:
superior cistern
-behind midbrain
-behind superior and inferior colliculus

cisterna magna
-junction between cerebellum and brainstem

SPACES FILLED WITH CSF

Question 7

what is the clinical significance of the cisterna magna

Answer 7

accessible by a neurosurgeon (v delicate)
vital centres in brainstem- so dangerous
rare times to sample csf under radiographic control

Question 8

where does the arterial circle of Willis lie
what is the clinical significance of this

Answer 8

in subarachnoid space

can cause a subarachnoid haemorrhage
it can swell (BERRY ANEURYSM) and burst– thunderclap headache– unconsciousness

90% occur in anterior circulation

a frequent site is where posterior communicating artery arises from the ICA

if there was a venous bleed around brain- subdural haem evolves over days

Question 9

what are pia denticulate ligaments

Answer 9

position mechanism supporting spinal cord in meningeal system
NOT ARACHNOID TRABECULAE
tooth like

Question 10

where is a good place to sample csf

Answer 10

cauda equina collection of roots good place to sample csf

Question 11

why are the roots long at the cord end

Answer 11

early- S1 root origin close to S1 vertebra

vertebral column grows faster than spinal cord during development

S1 roots exits well below the origin in the cord

spinal cord tapers off to form conus medullaris

Question 12

what is special about the veins in the brain

Answer 12

they have thin walls and NO VALVES
they emerge from the brain and lie in the subarachnoid space

drain into cranial venous sinuses

grouped into EXTERNAL (variable) and INTERANAL cerebral veins

Question 13

what is the point of the dural folds
what are the dural folds

Answer 13

dura compartmentalises the brain
good protection mechanism
decreases the energy (if trauma) minimises these effects

dural folds
FALC CEREBRI with a free edge
divides posteriorly to form TENTORIUM CEREBELLUM

cerebral veins join into superior sagittal sinus
drains posteriorly and joins straight sinus

Question 14

what is in the floor of the lateral ventricle

Answer 14

top thalamus (is floor of LV)- next to third ventricle

caudate nucleus (pair of LV)

Question 15

what does the great vein of galen do

Answer 15

drains deep structures via internal cerebral vein and basal vein

Question 16

what do the deep veins above the thalamus do

Answer 16

great cerebral vein (vein of galen) drains deep structures via internal cerebral vein and basal vein

internal cerebral vein has thalamostriate vein- drains caudate nucleus and putamen

choroidal vein drain choroid plexus of lateral ventricle

Question 17

what sits in the tentorium notch
what is clinical significance

Answer 17

midbrain/ brainstem
midbrain = 2 big bulges and an aqueduct

so if there is a space occupying lesion from eg. herniating temporal lobe pushes into this space is dangerous
forces bit of brain into this “space”
CONING
-vital centres are particularly sensitive

Question 18

what is csf
how much produced

Answer 18

clear colourless fluid which fills the ventricles of the brain surrounds the brain and spinal cord

150ml produced at 0.5ml/min
turns over 4 times a day
production about 500ml

75ml in cisterns
50ml in subarach space
25ml in ventricles

Question 19

how is csf formed

Answer 19

formed in the choroid plexus
specialised ependymal cell on surface
adapted to make csf in all ventricles
core of vascular tissue in pia

also made from blood vessels around ventricles

Question 20

how does csf flow

Answer 20

csf flows out of ventricle system in subarachnoid space via apertures in fourth ventricle
choroid plexus is in lateral ventricle, roof of 3rd and 4th ventricles

continually produced and nudged along due to pulsation of arteries and access subarachnoid space through 3 apertures

3 apertures in 4th ventricle to allow subarachnoid space
SINGLE MEDIAN
- Magendie
PAIRED LATERAL APERTURES
-Luschka

Question 21

what happens to csf after ventricles

Answer 21

flows to cistern/ subarachnoid space and exits to arachnoid granulations

interfacing with venous system
therefore csf to venous blood

uptake of csf from subarachnoid space in arachnoid granulations and then superior sagittal sinus

Question 22

what is a singular arachnoid granulation and how does it bridge through dura

Answer 22

arachnoid villus

bridging in superior sagittal sinus
therefore movement of csf into venous system

Question 23

what is hydrocephalus

Answer 23

due to blocked transport (non-communicative)/ overproduction/ blocked absorption (communicative) of CSF

blocked exits eg. meningitis, congenital

if fused sutures
get brain compression

brain box extension if sutures not fused

catheter (shunt) in ventricular system -CSF into peritoneal to decompress system