Cerebral Blood Supply Flashcards
The anterior circulation is governed by the…
Internal carotid artery
The posterior circulation is governed by…
Vertebral artery
Where does the internal carotid artery originate from?
Common carotid artery at the carotid bifurcation (C4 - upper border of thyroid cartilage)
What is the path of the internal carotid artery?
i. Passes upwards in the carotid sheath (with IJV and CN10)
ii. Enters carotid canal
iii. s-shaped course through the canal in petrous part of temp bone
iv. passes superior to foramen lacerum
v. along carotid groove in the cavernous sinus
vi. winds around anterior clinoid process –> forward under dura mater of cavernous sinus
Identify the branches of the internal carotid artery.
i. Opthalmic artery
ii. Anterior choroidal artery
iii. Anterior cerebral artery
iv. Posterior communicating artery
v. Anterior communicating artery
Outline key features of the opthalmic artery.
- Path: branches off from the ophthalmic segment (C6) of the ICA passes through the optic canal into the orbit
- Supplies: the eye and orbital contents
Outline key pathway of the anterior choroidal artery.
A) Path: communicating segment (C7) of ICA –> passes backwards with optic tract –> around cerebral peduncles and reaches lateral geniculate body –> above uncus to enter inferior horn of lateral ventricle where it passes choroid plexus
What does the anterior choroidal artery supply?
a. optic tract
b. choroid plexus of lateral ventricles
c. deep structures of the cerebral hemisphere (i.e. basal ganglia, posterior limb + retrolenticular + sublenticular parts of internal capsule)
What happens following an occlusion of the anterior choroidal artery?
Major effects related to motor pathways and movement – internal capsule affected
Does the anterior choroidal artery have any branches?
Gives off very slender perforating branches that are vulnerable to rupture
What is the path of the anterior cerebral artery (ACA)?
a. Above the optic nerve longitudinal fissure
i. Near the genus of the corpus callosum, it gives of the callosomarginal artery that runs on and above the cingulate gyrus
ii. The remaining part of the ACA passes above the corpus callosum as the pericallosal artery
What does the ACA supply?
- Anterior cerebral artery superficial branches supply medial surface of frontal & parietal lobes
Functional areas supplied: - Medial aspects of primary motor &
somatosensory cortices (contralateral
lower limbs) – i.e. paracentral lobule - Ventromedial prefrontal cortex
- Unimodal motor + somatosensory
association areas - Limbic lobe (cingulate gyrus)
What is the effect of an ACA occlusion?
Paralysis + sensory loss to the contralateral lower limb
Identify branches of the ACA.
a. Medial striate artery (Recurrent artery of Huebner): arising from the A2 segment. joins the anterolateral central arteries to supply parts of the basal ganglia
b. Anteromedial central arteries supply the anterior limb of internal capsule
What does the anterior communicating artery do?
Unites the 2 ACA just before entering the longitudinal fissure
What does the posterior communicating artery do?
Connects the anterior and posterior circulation
What is the path of the Middle Cerebral Artery (MCA)?
Lateral sulcus –> superolateral surface of the brain + Insula
Emerges onto lateral surface of
cortex
What does the MCA supply?
- Lateral aspect of primary motor & primary somatosensory cortices (contralateral head, upper limb, trunk)
- Broca & Wernicke’s areas (dominant
hemisphere only) - Primary (and association) auditory area
- Dorsolateral prefrontal cortex
- Unimodal motor + somatosensory
association areas - POT association area
What are the branches of the MCA?
Anterolateral group. (aka.
lenticulostriate/lateral striate/middle
striate aa.)
What is the origin of the vertebral artery?
Subclavian artery
What is the path of the vertebral artery?
i. Passes through successive transverse foramina C6-C1 vertebrae
ii. At C1, it pierces the dura mater to enter the cranial cavity through the foramen magnum
iii. R + L vertebral arteries pass the anterior surface of the medulla and unite to form the basilar artery at the pontomedullary junction
How is the basilar artery formed?
R + L vertebral arteries pass the anterior surface of the medulla and unite to form the basilar artery at the pontomedullary junction
How does the basilar artery terminate?
Terminates by dividing into posterior cerebral arteries
Identify branches of the vertebral artery from inferior to superior.
Posterior inferior cerebellar artery (PICA), posterior spinal artery, anterior spinal artery, meningeal branch of vertebral artery, labyrinth artery
Identify branches of the basilar artery.
Pontine arteries, AICA, superior cerebellar artery (SCA), posterior cerebral arteries
Identify key features of the Posterior Inferior Cerebellar Artery (PICA).
- Path: arises from the vertebral arteries (largest branch) tortuous course over the olive + inferior cerebellar peduncle pass between medulla and cerebellum
- Supplies: inferior surface of cerebellum + posterolateral medulla + choroid plexus of 4th ventricle
- Occlusion: lateral medullary (Wallenberg’s) syndrome: vertigo, dizziness, nystagmus, ataxia, nausea and vomiting, dysphagia, and hiccups
Outline key features of the posterior spinal artery.
- Path: branches off the vertebral artery/PICA runs on the posterior spinal cord
- Supplies: posterior part of medulla and spinal cord
Outline key features of the anterior spinal artery.
- Path: formed by union of a branch from the R + L vertebral arteries pass downwards in the anterior median fissure of the medulla and spinal cord
- Supplies: cervical spinal cord + medial part of medulla
What does the meningeal branch of the vertebral artery do?
Supply the dura of the posterior cranial fossa + falx cerebelli
Outline key features of the AICA.
- Path: arises near the origin of the basilar artery passes posterolaterally anterior surface of cerebellum
- Supplies: anterior + inferior surface of cerebellum
Outline key features of the labyrinth artery.
- Path: branches off the basilar artery after the anterior spinal artery enters internal acoustic meatus
- Supplies: inner ear
What are the pontine branches?
Numerous fine branches supplying the pons
Outline key features of the superior cerebellar artery.
- Path: arises immediately before the basilar artery terminates as the posterior cerebral artery winds around the cerebral peduncle superior surface of the cerebellum
- Supplies: superior surface of the cerebellum
Outline key features of the posterior cerebral artery.
- Path: curves around the cerebral peduncle (midbrain) pass between the cerebrum and cerebellum occipital lobe
- Supplies: Inferior surface of temporal lobe + occipital lobe (inc. primary visual cortex + visual association areas)
- Occlusion: loss in vision in the contralateral half of the visual field (hemianopia)
- Branches: supply the midbrain + diencephalon + choroid plexus of lateral ventricles
a. Posteromedial central arteries including the thalamoperforating artery
b. Posterolateral central arteries including the thalamogeniculate artery
Which arteries supply different parts of the medulla?
A) Vertebral artery –> Directly supply lateral aspect of entire medulla
B) Anterior spinal artery –> Supplies anterior aspect of entire medulla (before descending anterior spinal cord)
C) Posterior spinal artery –> Supplies posterior aspect of caudal medulla
D) Posterior inferior cerebellar artery –> Supplies posterolateral aspect of rostral medulla
Which arteries supply different aspects of the pons?
A) Pontine arteries –> Paramedian branches supply medial pons
* Circumferential branches supply lateral pons
B) AICA –> Supplies posterolateral aspect of caudal pons
C) Superior cerebellar artery –> Supplies posterolateral aspect of rostral pons
Which artery supplies the midbrain?
Posterior cerebral arteries:
- Posterior medial group/branches supply medial midbrain
- Posterior lateral group/branches supply lateral midbrain
- Collicular branches supply
posterior aspect of midbrain
Which arteries supply different aspects of the cerebellum?
Superior Cerebellar artery:
* Supplies superior region of cerebellum
Anterior Inferior Cerebellar artery:
* Supplies anterior (inferiorly) region of cerebellum
Posterior Inferior Cerebellar
artery:
* Supplies posterior (inferiorly) region of cerebellum
What is the circle of Willis?
- Group of arteries that form
anastomotic ring on ventral aspect
of brain - Links anterior circulation with
posterior circulation - Allows equalization of blood flow
between both sides of brain - Permits anastomotic circulation in
case of occlusion within circulation
Which arteries comprise the circle of willis?
- Internal carotid arteries (L+R)
- Anterior cerebral arteries (L+R)
- Anterior communicating artery
(single) - Posterior communicating artery
(single) - Posterior cerebral arteries (L+R)
Which deep structures do branches of the CoW supply?
Anterior Choroidal a (ICA): choroid plexus,
internal capsule (posterior limb, retrolenticular,
sublenticular), hippocampus
Anteromedial group (ACA): anterior hypothalamus
* Medial striate artery: caudate (head),
internal capsule (anterior limb)
Anterolateral group (MCA): caudate, putamen,
internal capsule (posterior limb, genu)
Posteromedial group (PCA): medial midbrain, medial thalamus, posterior hypothalamus
Posterolateral group (PCA): posterolateral midbrain, lateral thalamus
What is the internal capsule?
- Condensed bundle of afferent/efferent fibres
passing from cortex to subcortical structures - ‘Sandwiched’ between caudate + thalamus
(medially) and lentiform nucleus (laterally) - Supplied by small groups of end-arteries ,
susceptible to occlusion & haemorrhage
What are the 5 parts of the internal capsule?
A) Anterior limb: between caudate and lentiform
B) Genu: between anterior and posterior limbs
C) Posterior limb: between thalamus and lentiform
D) Sublenticular part: beneath the lentiform
E) Retrolenticular part: behind the lentiform
Which arteries supply different aspects of the internal capsule?
Medial striate artery (ACA):
* Anterior limb (limbic/prefrontal fibres)
Anterolateral group (MCA):
* Posterior limb (corticospinal,
corticobulbar spinothalamic, dorsal
columns)
* Genu (corticobulbar)
Anterior Choroidal artery (ICA):
* Posterior limb (Corticospinal,
spinothalamic, dorsal columns)
* Retrolenticular limb (optic radiation)
* Sublenticular limb (auditory radiation)
How is the cerebral venous system structured?
- System of veins that drain brain,
located in the subarachnoid space - Do not even remotely follow the
arterial system and are highly
variable - Superficial veins drain cortex, deep
veins draining internal (deeper)
structures - Ultimately, all cerebral veins drain
into a nearby dural venous sinus
What are dural venous sinuses?
- Channels of venous blood in space
between dural layers - Modified veins ‘trapped’ between
layers of dura dura - Associated with dural folds
- Form major drainage pathway of brain
- Predominantly drain venous blood to
internal jugular veins (which exit skull
& course toward heart)
Where is the superior sagittal sinus?
superior margin of falx cerebri
Where is the inferior sagittal sinus?
inferior margin of falx cerebri
Where is the straight sinus?
Along junction of falx
cerebri & tentorium cerebelli
Where are the confluence of sinuses?
Junction of falx cerebri, tentorium cerebelli & falx cerebelli
Where are the transverse sinuses?
Along outer margins of tentorium cerebelli
Where is the sigmoid sinus?
on surface of
temporal/occipital bone
Outline the venous sinus drainage pathway.
What are some additional sinuses that drain into main flow pathway?
- Sphenoparietal sinus: On edge/rim of lesser wing (sphenoid)
- Occipital sinus: at base of falx cerebri
- Basilar plexus: on clivus/base of
occiput - Cavernous sinus: On either side of
pituitary fossa
What is the cavernous sinus and what does it contain?
Venous sinus on either side of pituitary fossa
Contents (“O TOM CAT”):
* Oculomotor nerve (CN III)
* Trochlear nerve (CN IV)
* Ophthalmic nerve (CN V1)
* Maxillary nerve (CN V2)
* Internal Carotid artery
* Abducens nerve (CN VI)
How does the cavernous sinus drain into main flow pathway?
Superior petrosal sinus:
* Runs along superior aspect of petrous temporal bone
* Drains into sigmoid sinus
Inferior petrosal sinus:
* Runs along inferior aspect of petrous temporal bone
* Drains directly into internal jugular vein
