what are the order of meninges from brain towards skull?
(brain) pia arachnoid dura (skull)
which meningeal layer can be described as a tough fibrous membrane?
dura
which meningeal layer can be described as a soft translucent membrane?
arachnoid
where is the subdural space?
space between arachnoid and dura/below the dura (very thin)
falx cerebri and tentorium cerebelli are extensions of which meninges layer?
dura
what is the name of extension of dura matter that forms a partition between the right and left hemispheres?
falx cerebri
which meningeal layer can be described as microscopically thin, delicate membrane?
pia
which meningeal layer is tightly adhered to the surface of the brain, following all cavities?
pia
what is considered a real space? Give examples.
a space that normal exists - subarachnoid space in the skull and spine - epidural space in the spine
what is considered a potential space? Give examples.
not a space - but can become a space in pathological conditions (eg brain bleed) - epidural space in the skull - subdural space in the spine and skull
is the epidural space, real or potential?
potential in the skull real in the spine
what are the real spaces in the skull?
subarachnoid space
what are the real spaces in the spine?
epidural space subarachnoid space
what are the potential spaces in the skull?
epidural space subdural space
what are the potential spaces in the spine?
subdural space
is the subdural space, real or potential?
potential
is the subarachnoid space, real or potential?
real
what is the blood supply of the dura matter?
middle meningeal artery
what are the twi layers if the dura?
outer layer adhered to skull: periosteal inner layer which forms falx cerebral: meningeal
the two layers of the dura matter are tightly fused together except for where?
dural venous sinuses various infoldings
where is the middle meningeal artery? Why is it prone to injury in this position?
- lies below pterion (region where the frontal, parietal, temporal, and sphenoid bones join together. It is located on the side of the skull, just behind the temple.) - most fragile part of the skull and so if it fractures/breaks = middle meningeal artery bleeds
where does venous blood of the brain drain?
into dural sinuses (e.g superior sagittal sinus) and then into the internal jugular vein
where will you find the falx cerebri dural folding?
between cerebral hemispheres
where will you find the tentorium cerebelli dural folding?
between occipital lobes and cerebellum
where will you find the falx cerebelli dural folding?
between cerebellar hemispheres
what is the function of dural infoldings? (e.g falx cerebri)
act as shelves to stabilise brain
where are the venous (dural) sinuses located?
within the dural inholdings
what is the function of the venous (dural) sinuses?
they receive venous blood from the brain and drain into the internal jugular vein
what do superficial veins of the brain drain into?
superior sagittal sinus
what do deep veins of the brain drain into?
internal cerebral veins
what do internal cerebral veins of the brain drain into?
great vein (of Galen)
what does the great vein (of Galen) drain into?
straight sinus
what does the straight sinus and superior sagittal sinus drain into?
confluence of sinuses which drains into the transverse sinuses
what does the transverse sinus drain into?
sigmoid sinus
what does the sigmoid sinus drain into?
internal jugular vein
what percentage of oxygen consumption does the brain use?
20% (high)
what condition is a persistent neurological deficit of vascular origin?
stroke
what are the two arteries that supply the brain?
vertebral artery (posteriorly) internal carotid (anteriorly)
the vertebral artery is a branch of what vessel?
subclavian artery
where does the vertebral artery enter the skull?
foramen magnum
where do the two vertebral arteries join?
two pairs of VA join at the basilar artery at the base of the brain stem
The internal carotid artery is a branch of what vessel?
common carotid artery
the common carotid artery bifurcates into internal and external carotid arteries, what do each arteries supply?
internal supplies brain external supplies face, scalp, neck
where does the internal carotid artery enter the skull?
carotid canals NB: and passes OVER (not through) foramen lacerum
the carotid canal is a boney feature, what is the clinical relevance of this?
If the bone was to fracture, the fractured bone would puncture the ICA
in the ventral brainstem how many arteries supply the cerebellar?
3 pairs (6 arteries) - Post. Inf. Cerebellar - Ant. Inf. Cerebellar - Sup. Cerebellar
in the ventral brainstem how many arteries supply the cerebrum?
3 pairs (6 arteries) - Post. Cerebral - Middle Cerebral - Ant. Cerebral
what are the branches of the vertebral artery?
- anterior spinal (unpaired) - posterior spinal (paired) - inf. post. cerebellar arteries (PICA)
the basilar artery is formed by the joining of which two arteries?
two vertebral arteries
the anterior spinal artery is formed by the joining of which two arteries?
formed by *branches* from both vertebral arteries
what are the branches of the basilar artery?
- anterior inferior cerebellar arteries (AICA) - pontine arteries - superior cerebellar arteries - posterior cerebral arteries
what are the branches of the internal carotid?
- middle cerebral artery - anterior cerebral artery
which artery runs lateral to the optic chiasm?
internal carotid artery
what forms the vertebrobasilar system?
vertebral and basilar arteries
what does the vertebrobasilar system supply?
cerebellum and brain stem
what causes locked in syndrome?
pontine arteries damage causing lack of blood supply to the pons
why is eye movement possible in locked in syndrome but no other movement is?
Eye movement is possible as the oculomotor nerve is above this blood supply
why does pontine arteries damage lead to locked in syndrome?
Pons contain descending motor fibres for movement, which are supplied by the blood vessel running aside them.
what interconnects the internal carotid and vertebrobasilar system?
arterial circle of willis
what artery system surrounds the optic chiasm and hypothalamus?
arterial circle of willis
what is the function of the arterial circle of willis?
allows collateral circulation – if an artery is blocked, blood can still get through
What is a berry aneurysm?
abnormal dilations around the circle of willis or at points of arterial branching in the brain
what is a saccular aneurysm?
which is sac-like dilation on a weak part of the arterial wall. (a berry aneurysm is the most common type of saccular aneurysm)
what happens if a berry aneurysm ruptures?
allows blood to enter the subarachnoid space = sub-arachnoid haemorrhage
what does the anterior cerebral artery (ACA) supply?
- superior and medial areas of frontal and parietal lobes - corpus callosum
what does the medial cerebral artery (MCA) supply?
- lateral areas of frontal, temporal and parietal lobes
what does the posterior cerebral artery (PCA) supply?
- occipital lobe - inferior and medial surface of temporal lobe
what cortical area does the ACA supply?
motor and sensory cortices for the lower limb
what cortical area does the MCA supply?
primary motor and sensory cortices for the whole body (excluding lower limb) and the auditory cortex
what cortical area does the PCA supply?
the visual cortex
which artery supplies the visual cortex?
PCA
which artery supplies the auditory cortex?
MCA
which artery supplies the primary motor and sensory cortices for the whole body (except the lower limb)?
MCA
which artery supplies the motor and sensory cortices of the lower limb?
ACA
what do deep/perforating arteries off the arterial circle of willis supply?
structures inside hemisphere (deep nuclei) - deep grey matter - internal capsule
what are striate arteries?
arise from the middle cerebral artery and supply deep structures in the cerebrum, including the internal capsule (deep/perforating arteries)
what causes an epidural haemorrhage?
torn meningeal artery
how would a epidural haemorrhage present on an MRI?
hemispheres pushed away from the skull
what causes a subdural haemorrhage?
torn briding veins
How would a subdural haemorrhage present on an MRI?
dura still applied to the skull but the hemispheres are squished = ventricles pushed away
what causes a subarachnoid haemorrhage?
torn cerebral arteries
how would a subarachnoid haemorrhage present on an MRI?
bleeding in the grooves of the brain itself
what type of haemorrhage is shown here, and what causes it?
epidural haemorrhage
caused by torn meningeal arteries
what type of haemorrhage is shown here, and what causes it?
subdural haemorrhage
torn bridging veins
what type of haemorrhage is shown here, and what causes it?
subarachnoid haemorrhage
torn cerebral arteries
watershed areas of the brain are more susceptible to what?
ischaemia (watershed stroke)