CNS Blood Supply Flashcards
What blood vessels of the brain are part of the anterior blood supply?
- middle cerebral artery
- anterior cerebral artery
off of the ICA
What blood vessels of the brain are part of the posterior blood supply?
posterior cerebral artery
off of vertebral-basilar artery
What structures of the brain get blood supply from the middle cerebral artery?
lateral areas of brain
- broca’s area
- wernicke’s area
- primary motor and somatosensory cortex
What structures of the brain get blood supply from the anterior cerebral artery?
supplementary motor area
leg of somatosensory and motor
What structures of the brain get blood supply from the posterior cerebral artery?
medial-lower supply
- temporal lobe
- occipital lobe (calcarine fissure)
- medial temporal memory system
- visual system
What is the role of the anterior spinal artery?
supply blood to the anterior 2/3 of spinal cord
What is the role of the 2 posterior spinal arteries?
supply blood to the posterior 1/3 of spinal cord
What does ischemia mean?
to keep back blood
What is cerebrovascular disease?
any disease that affects the blood vessels of the brain
What is ischemic stroke?
stroke resulting from insufficient blood flow that causes tissue death
80% of all strokes
What is hemorrhagic stroke?
rupture of blood vessel causing bleeding effect
What is FAST when it comes to stroke?
- the faster someone gets medical attention better the outcome
Face
Arm
Speech
Time needed to act
What are the risk factors to ischemic stroke?
- age
- cardiac disease
- hypertension
- blood lipids
- diabetes mellitus
- smoking
- obesity
- excessive alcohol consumption
How does a stroke work?
- lack of oxygen due to obstruction preventing blood supply distally
What is ischemic necrosis?
neuronal death caused by lack of blood flow
What is an infarct?
area of death brain tissue
What is a thrombus?
blood clot attached to the wall of an artery
What is a embolus?
fragment of thrombus that has become loose and traveled to another area
What is a factor unique to the cerebral arterial supply that helps mitigate stroke?
- anastomoses help redirect blood if there is an occlusion, stopping a stroke
What is important when it comes to the speed of an occlusion?
if a an occlusion forms slowly, it allows for more time for circulation to redirect
What artery connects the ICA and ECA in the skull?
opthalmic artery
How can thrombosis cause vascular problems?
- decrease blood flow
- fragment off and become embolus
- hemorrhaging center of thrombus creating high pressure, hard for blood to pass
What is cerebral embolism the result of?
most often cardiovascular disease
75% of cardiac emboli become lodged in the brain
What is a transient ischemic attack?
a “mini stroke” that lasts 2-15 min, rarely 30 min, resolves on its own
strong predictor or stroke
What are the symptoms of ischemic attack?
- numbness, tingling, weakness in face, arm, or leg one side of the body
- difficulty walking
- difficulty talking or understanding what others say
- confusion
- difficulty with vision in one/both eyes
- dizziness
How does the anatomy of arteries impact the effect of stroke?
ACA, MCA, PCA have a stem that if occlusion lies there, affects will happen in areas supplied by penetrating and cortical branches
What is important to remember about the location of occlusion?
the more proximal the location of occlusion, more widespread and severe the deficits
What artery in the brain is most common to suffer and ischemic stroke?
Middle cerebral artery
Why does infarction of the cortical branches of a vessel cause contralateral sensory loss and weakness of the UMN?
b/c it primarily supplies primary motor and somatosensory parts
What are the effects of dominant and on-dominant hemispheres suffering ischemic stroke of the MCA?
dominant (left): aphasia
non-dominant (right): problems wit prosody and unilateral visuospatial deficits
What is prosody?
ability to interpret the meaning behind tone of voice (produce or understand)
How does occlusion of the ACA affect the brain?
may cause no symptoms due to collateral circulation
What does ischemic stroke of the ACA affect the most?
UMN weakness and sensory deficits of contralateral lower extremity and bowel and bladder dysfunction
How does a bilateral ACA infarction occur?
- anomaly in circle of willis
- sensory motor syndrome involving both LEs due to no collateral circulation (causing occlusion of both ACAs
What does unilateral occlusion of the PCA cause?
contralateral hemianopsia
What is bilateral PCA infarction?
- when single embolic or thrombotic occlusion of upper basilar artery
What is the result of bilateral PCA infarction?
bilateral homonymous hemianopsia (cortical blindness)
What happens when the inferomedial temporal lobes are infarcted?
severe memory problems
if also affecting occipital lobe, can’t interpret visual info and memorize who someone is
How much of the internal carotid artery must be occluded to produce a carotid-border zone syndrome?
70%
What is important about carotid-border zone syndrome?
max ischema occurs in watershed areas there is not enough pressure in ICA to get to distal cortical branches
What causes Lacunar syndrome?
occlusion of small, deep, penetrating vessels
What are the symptoms of lacunar syndrome?
sensory and/or motor deficits occur without cognitive deficits
face, leg, arm are typically affected equally
When do 1/3 of thrombotic strokes occur?
during sleep
What is important about the timing of catching a stroke?
decision if ischemic or hemorrhagic must be made within 2-4.5 hours
How are ischemic strokes treated?
anticoagulation, while hemorrhagic cannot
How does prognosis look if someone survives a stroke?
favors long term improvement
related to edema 3-4 days after
What is the prognosis of ischemic stroke syndromes?
severe to least severe
- large strokes
- presence of edema or hemorrhage
- stroke in many territories
- single territory MCA > ACA > PCA
What is a hemorrhagic stroke?
Avery rupture and blood flows into intracranial structures, brain tissue, ventricles, subarachnoid space
What are the types of hemorrhagic stroke?
- primary hemorrhagic stroke
- rupture of aneurysms
- arteriovenous malformations
What are the risk factors of a hemorrhagic stroke?
hypertension
anticoagulation
inherited coagulation deficits (hemophilia)
How does hemorrhagic stroke work?
escaped blood fills intracranial space, increasing pressure and obstructing structures
a once broken vessel is likely to break again
When do hemorrhagic strokes occur?
mostly in wakefulness and activity
as time increases, symptoms worsen
usually without headache
What is the mortality rate of primary intracerebral hemorrhage?
30-35%
if they survive they can have considerable recovery
What is primary intracerebral hemorrhage?
occurs when brain penetrating artery is damaged or ruptures
higher incidence with those with hypertension
can displace and compress adjacent brain tissue
can result in coma or death
What is a ruptured intracranial aneurysm?
- second most common cause of hemorrhagic stroke
- small, localized ballooning of vessel wall
Where do most aneurysms occur?
90-95% in circle of willis
When do aneurysm ruptures occur?
waking hours with sudden and severe headache, neck pain, and stiffness, altered consciousness and neurological deficits
are unruptured aneurysms asymptomatic?
yes
What is an arteriovenous malformation?
tangle of dilated blood vessels that form abnormal communications between arteries and veins
Where do arteriovenous malformations occur?
brain, brainstem, spinal cord
Can arteriovenous malformations be dangerous?
- often asymptomatic, produce symptoms in 30+ year olds
- when large can be life threatening
What does UMN injury lead to?
lack of descending control, lead to:
- spasticity
- clonus
- hyper reflexia
- hypertonia
- primitive reflexes
- synergies
- weakness
What is the course of MCA stroke on the left side?
- flaccid hemiparesis, no reflex
- after a couple months you could have stiff extremities on the right, high reflex activity
- drooping eyelid and lips on the right side
What are the characteristics of Broca’s aphasia?
broken choppy speech
intelligence still intact
What are the characteristics of fluent aphasia (wernicke’s)?
smooth speech that lacks intelligence and coherence
