S4 L2 Blood supply to the brain Flashcards
Where does the arterial supply to the brain come from?
Two sources:
- Anterior circulation - IC and supplies most of the cerebral hemisphere
- Posterior circulation- Vertebral arteries supplies the brainstem, cerebellum, some of the temporal and the occipital lobe
How is the posterior circulation created?
- Left and right vertebral arteries ascend through the transverse foramina enters the skull through the foramen magnum
- Join to form the basilar artery → midline artery
- Gives rise to the posterior cerebral artery
Important branches
→ Posterior inferior cerebellar arteries
→ Anterior spinal artery
→Anterior inferior cerebellar arteries
(from the VA)
→ Pontine arteries
→ Superior cerebellar arteries
(from basilar artery)
How is the anterior circulation created?
- Internal carotid arteries enters the base of the skull through the carotid canal
- Gives rise to the middle cerebral artery and anterior cerebral artery
Branches
→ Posterior communicating artery
→ Anterior communicating artery
How does the internal carotid artery enter the skull?
- Enters the base of the skull through the carotid canal in petrous part of the temporal bone
- Turns medially and horizontally,
- Enters the cranium makes an S shape bend moves through the cavernous sinus
What is the circle of Willis?
Refers to the circle of BV around the pituitary gland Includes the - Posterior cerebral artery - Posterior communicating artery - Anterior cerebral artery - Anterior communicating artery
Why is the circle of Willis clinically important?
Blockage in one area
Blood can flow in the retrograde direction
Bypass blockage
What is the middle cerebral artery?
Continuation of the internal carotid artery
Runs laterally → over insula cortex → through sylvian fissure and lateral fissure onto cortex → superior and inferior branches onto cerebral hemisphere
Gives of lenticulostriate branches
What does the middle cerebral artery supply?
- Large area on the lateral aspect of cerebral hemisphere mainly frontal lobe
- Some of the parietal lobe and superior temporal lobe
- Also deep structures of cerebral hemisphere
What is the lenticulostriate arteries?
aka lateral striate
Supplies deep matter structures including the lentiform nucleus and caudate nucleus as well as the internal capsule
What happens in middle cerebral artery occlusion?
Motor function: proximal to lenticulostriate vessels - weakness of face, arms and legs to opposite side of occlusion
Sensory function: sensory changes on opposite side to occlusion
Visual system: Right homonymous hemianopia due to involvement of both superior and inferior optic radiations
Speech: Global Aphasia
What is the anterior cerebral artery?
Branch of the internal carotid
Left and right anastomose via the anterior communicating artery
Vessels loop over corpus callosum and send branches to the adjacent cortex
Cortical branches supply the medial aspect of the frontal and parietal lobes (not the occipital lobe)
Branches also go into the corpus callosum itself
What is the effect of an occlusion to the anterior cerebral artery?
Motor: leg weakness (contralateral side to opposite CC)
Sensory: Leg sensory loss
Visual system: none
Other: frontal lobe syndrome
What is the posterior cerebral artery?
Bifurcation of basilar artery
Loops around the midbrain, and along the inferior surface of posterior hemisphere, supplies the occipital lobe and inferior aspect of temporal lobe
Supplies the occipital lobe, inferior temporal lobe, and thalamus (via thalamoperforator and thalamogeniculate branches)
Supplies midbrain as it passes
Connects to the anterior cerebral artery via the posterior communicating artery
How does the posterior circulation relate to the brainstem?
Vertebral arteries run along the ventral surface of the medulla oblongata
→ Branches of VA supplies the medulla
→ Posterior inferior cerebellar artery - medulla and cerebellum
Basilar artery along the midline of the pons
→ Anterior inferior cerebellar artery - onto cerebellum
→ Pontine arteries - supplies pons including the corticospinal tract
→ Superior cerebellar artery- superior cerebellum
Posterior cerebral artery loops around midbrain
What is the arterial supply to the spinal cord?
Anterior and posterior spinal artery
- Anterior spinal artery → Anterior 2/3
→ Receives blood from the segmental arteries and branches of vertebral arteries
→ Grey matter of ventral horn and STT and CST
→ Blockage: midline vessel so bilateral problems, loss of STT modalities below the level of the blockage + upper motor neurone signs due to CST
- Posterior spinal artery → Posterior 1/3
→ Grey matter of dorsal horn and dorsal columns
→ Blockage: most commonly unilateral, paired arteries, ipsilateral loss of dorsal column modalities below level of lesion
