6/10- Cerebrovascular Anatomy Flashcards
What is a stroke?
Damage to the brain due to vascular causes; interruption of blood flow in a cerebral vessel
What are the 2 different types of strokes?
- Ischemic (decreased flow)
- Hemorrhagic
Cerebrovascular disease tends to produce ____ (gradual/rapid), ____ (focal/generalized) neurologic deficit
Cerebrovascular disease tends to produce rapid, focal neurologic deficit
What is the main source for anterior circulation?
What areas does this cover?
Internal carotid arteries
Most of cerebral hemispheres
- Cortex
- White matter
- Diencephalic structures
What is the main source for posterior circulation?
What areas does this cover?
Vertebral arteries
- Brainstem
- Cerebellum
- Occipital
- Mesial temporal lobe
What connects the anterior and posterior circulation?
Posterior communicating arteries
(provide collateral circulation; variable amounts)
Picture of vasculature
Dotted lines = Circle of Willis
FACTS:
- Vertebral arteries ascend in bony cervical vertebrae
- PICA come off single vertebral a’s
- Vertebral a’s joint to form basilar a.
- Basilar branches = AICA and SCA before it terminates as PCA
- Smaller basilar branches = Labyrinthine (internal auditory) a, pontine arteries (variable)
- Post communicating comes off PCA to connect into internal carotids
- Internal carotids give off MCA and ACA (connected by ant communicating)
- Smaller carotid branch = ophthalmic a.
- Branches off MCA = anterior choroidal a, lenticulostriate a’s
- Branches off ACA = medial striate a. (Recurrent a. of Heubner)
What provides circulation to the brainstem?
- Medial arteries (midline parts of medulla, pons, and midbrain)
- Lateral arteries (lateral parts of medulla, pons, and midbrain)
What provides circulation to the cerebellum? Defects from occlusion?
- Posterior and anterior inferior arteries supply inferior cerebellum
- Superior cerebellar a. supplies superior cerebellum
Defects: Ipsilateral ataxia/hypotonia
What does posterior cerebral artery supply?
Defects from occlusion?
- Occipital lobe: visual field defect/complex visual agnosia
- Inferior medial temporal lobe: defects in recognition of things and people (prosopagnosia- facial recognition)
What is the most common stroke of posterior circulation?
Lateral medullary infarct (Wallenberg syndrome)
- Brown, cystic area in left medulla from lack of circulation in one of the lateral arteries (branches of vertebral or posterior cerebellar, possibly)
What is this?
Medial pontine infarct
- Cystic area in midline area (right side of the picture)
- Affected basilar perforating arteries
What is the order of severity/”badness” of arteries in anterior circulation (ICA, ACA, MCA, branches)?
In order of severity:
Internal carotid > Ant/middle cerebral > branch occlusion of ACA/MCA
What is the most detailed way to image these arteries?
Cerebral arteriogram
- Femoral catheter run up to aortic arch to inject the carotids (although, can also inject vertebrals)
How can you differentiate internal and external carotids on arteriogram?
Internal is relatively straight/smooth running up to brain (may see sinus)
External has many branches (recall: head and neck)
What is another (non-arteriogram) method of imaging these arteries?
Carotid ultrasound
- Structural imaging
- Flow imaging (velocity; laminar vs. turbulent)
(Can see plaque on the wall inducing slow flow and turbulence)
Where does the anterior cerebral artery go? Branches? Supplies?
Anterior cerebral artery goes up/around corpus callosum (“pericallosal a”) and supplies superior, mesial lobes
Branches:
- Orbital
- Frontopolar a. (rostral end of cerebral hemisphere)
- Callosomarginal a. (big branch off pericallosal a.)
- Pericallosal a. (big terminal branch)
Big deficits due to loss of anterior cerebral artery?
Contralateral UMN disorder, especially of leg
Big deficits due to loss of middle cerebral artery?
Contralateral UMN disorder, especially of face and arm
What is the most common source of anterior strokes?
Middle cerebral artery
Branches of middle cerebral artery?
(Deep)
- Lenticulostriate arteries (supply striatum)
- Temporal branches
(Superficial)
- Precentral (pre-Rolandic a.)
- Central (Rolandic) a.
- Parietal branches
What is this? What is biggest artery?
Cerebral angiogram (contrast injected into artery from femoral threaded up to internal carotid)
- Largest here is internal carotid
(Structures seen depends on length of time after injection)
Risks of angiogram procedure?
- Hemorrhage at catheter site
- Dislodgment of atherosclerotic plaque (-> stroke)
What is this?
CT angiogram (CTA)
- Not quite as good of detail as angiogram, but good
- Arch M bit is the posterior cerebral arteries
- Can’t visualize posterior communicating
- Middle cerebral arteries coming off each side
What is this?
What key features allow you to identify?
Proximal MCA infarct
- ACA territory spared
- Internal carotid occlusion would involve both territories (anterior cerebral artery as well as middle)
- Area infarcted is darker than normal
- Can see cracking (split in living/dead white matter)
What symptoms would be seen with a proximal MCA infarct?
- Contralateral UMN weakness affecting face and arm
- Aphasia if in left hemisphere
- Possible contralateral visual field issues (clipping visual radiations)- homonomous heminaopsia and possible dysfunction of higher visual function
What is this? Results in (broadly)?
CTA showing MCA occlusion (causes ischemic stroke)
Branches of middle cerebral artery (superficial)?
- Anterior temporal a.
- Middle temporal a.
- Posterior temporal a.
- Orbitofrontal a.
- Precentral (pre-Rolandic) a.
- Central (Rolandic) a.
- Anterior parietal a.
- Posterior parietal a.
- Angular a.
What is this?
Multiple emoblic hemorrhagic infarcts due to branch occlusions
- Most likely have cardiac source (bad valve, ventricular assist device)
- May not occur all at the same time
Branches of posterior cerebral a?
- Anterior temporal branches (supply mesial temporal lobe)
- Posterior temporal branches
- Parieto-occipital branch
- Calcarine branch
What is this?
Acute posterior cerebral artery stroke (territory infarcts)
Acute stroke on CT looks ___ (bright/dark)?
Acute stroke on CT looks dark
Brain vascular regions (picture)- LEARN
What areas are susceptible to poor perfusion (as opposed to actual occlusion of artery)?
Watershed areas
- Parts of the brain between ACA, MCA, and PCA; these are perfused poorly by several arteries (“last meadow” or end of the garden hose territory)
What causes Watershed infarcts?
Hypoperfusion
- Cardiac arrest
- Inadequate perfusion during cardiopulmonary bypass
Describe venous drainage of the brain
- Lateral portion of the hemispheres drain to the superior sagittal sinus
- Posterior fossa structures drain to transverse sinus, which drains into internal jugular vein
- Medial hemisphere and deep structures drain to straight sinus to confluence of sinuses to transverse sinuses to IJV
Another pic of venous drainage (just look)
What do hypercoaguable states cause?
Venous sinus thrombosis; variable symptoms
What supplies circulation to the spinal cord? Defects cause what?
Spinal arteries
- Anterior spinal a. (causes anterior spinal a. syndrome)
- Posterior spinal a. (usually no infarct)
Spinal veins
- Similar organization to arteries
Picture of spinal veins (just look)
