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BB1 > Blood Supply to the Brain > Flashcards

Blood Supply to the Brain Flashcards

1
Q

What are the main blood vessels in/to the brain?

A

See diagram in lecture notes

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2
Q

What percentage of your body mass is the brain and what percentage of cardiac output does it receive? What percentage of total body oxygen and glucose?

A
  • ~ 2% of body weight

- Receives 15% of cardiac output and uses 20% of total body O2 and 25% of total body glucose

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3
Q

What is the average value of brain blood flow?

A
  • Average brain blood flow = 46mL/100 grams of brain per minute
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4
Q

How long would anoxia to the brain need to last to lead to unconsciousness? What about permanent unconsciousness?

A
  • 20 secs of anoxia lead to unconsciousness

- > 5 mins permanent unconsciousness

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5
Q

How is brain blood flow regulated?

A
  • Flow regulated by auto-regulation
    o Normotensive cerebral blood flow = ~50mL per 100g of brain tissue per min if cerebral perfusion pressure between 60-160mmHg
    o ↓O2, ↑CO2 = ↑flow
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6
Q

What are the arteries and veins like in the brain?

A
  • Arteries, thin walled, easily blocked, distorted or ruptured
  • Veins, no valves, thin walled, no muscles or elasticity to help return
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7
Q

Below what PO2 will blood flow increase and by how much?

A
  • Blood flow does not change until PO2 falls below ~50mmHg when cerebral blood flow increases if hypoxia decrease PO2 further then cerebral blood flow can increase up to 400% above resting levels.
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8
Q

What effect does CO2 have on blood flow and by how much?

A
  • CO2 has a profound effect – hypercapnia causes marked dilation of cerebral arteries and increased blood flow hypocapnia constriction and decreased blood flow. 5% CO2 inhalation increases cerebral blood flow by 50%, 7% CO2 increases cerebral blood flow by 100%.
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9
Q

What percentage each do the internal carotids and vertebral arteries provide of the cerebral blood flow?

A
  • Internal carotids = 80% of total cerebral blood flow to anterior 2/3rd of cerebral cortex
  • Vertebral arteries = 20% of total cerebral blood flow to posterior 1/3rd of cerebral cortex, brainstem and spinal cord

See diagrams in lecture notes

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10
Q

What are the components of the circle of Willis?

A

See diagrams and angiograms in lecture notes

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11
Q

What would the Circle of Willis look like in a normal angiogram? In what percentage of the population can a classic Circle of Willis be seen?

A
  • Under normal situations anterior communicating and posterior communicating closed
  • Classic Circle of Willis seen in only 34.5% of population
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12
Q

When only should the collateral circulation be open? What does this mean?

A
  • Collateral circulation should only open when there is a pressure difference
  • Collateral circulation opens in pathologies
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13
Q

What do variants in cerebral arterial circle look like on an angiogram?

A

See diagrams in lecture notes

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14
Q

What are the main branches of the internal carotid artery (ICA) in the anterior circulation? What do they supply?

A
  • Ophthalmic
    o Orbit and retina – connects to external carotid artery
  • Posterior communicating
    o Connects carotid and vertebral artery system
  • Middle cerebral artery
    o Basal ganglia and internal capsule (striate arteries), lateral 2/3rds of cortex
  • Anterior cerebral
    o Internal capsule, medial side of frontal and parietal lobes.
    o Anastomose with MCA

See diagram and angiograms in lecture notes

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15
Q

Which artery supplies each part of the cerebral cortex?

A

See diagrams in lecture notes

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16
Q

What are the main branches of the posterior circulation?

A 
-	Vertebral
o	Spinal cord
o	Dorsal medulla of brainstem - PICA
-	Basilar
o	Pons
o	cerebellum
-	Posterior cerebral artery
o	Inferior and medial aspects of temporal and occipital cortex
o	Thalamus and posterior internal capsule
o	Midbrain
o	Anastomose with MCA
17
Q

What are the abbreviations for the components of the posterior circulation?

A
  • ASA = anterior spinal artery
  • AICA = anterior inferior cerebellar artery
  • PICA = posterior inferior cerebellar artery
  • VA = vertebral artery
  • BA = basilar artery
  • VI = abducents
  • OMN = oculomotor nerve
  • MB = mammillary body
  • PCA = posterior cerebral artery
  • V3 = floor of 3rd ventricle
  • SCA = superior cerebellar artery

See diagrams in lecture notes

18
Q

Where are the superficial cerebral veins and what allows the CSF to flow into them? How is backflow prevented?

A
  • Superficial cerebral veins cross the subarachnoid space
  • Bridging veins pierce dura as they enter intracranial (dural) venous sinuses
  • Mainly superior sagittal sinus
  • Arachnoid granulations allow CSF to flow into venous blood of sinuses but prevent backflow of blood into sub-arachnoid space
19
Q

What is the cavernous sinus? When can they be seen?

A
  • Large collection of thin walled veins
  • Only place where an artery travels through a venous structure
  • ICA make acute bends and can be seen twice
20
Q

What is the blood supply to the spinal cord?

A

See diagrams in lecture notes

(Great segmental medullary artery (artery of Adamkiewicz) on left in 65% of population reinforces circulation to 2/3rds of spinal cord)

21
Q

What may happen during surgery for an aortic aneurysm? What can cause these problems and what may be the effects?

A

Ischaemia of spinal cord

  • Patients undergoing surgery for an aortic aneurysm may lose all sensation and voluntary movement inferior to level of occlusion
  • Severe drop in BP for 3-6 mins may be reduce or stop blood flow from the segmental medullary to anterior spinal artery
22
Q

What are the major causes of stroke?

A 
-	Major causes of stroke
o	Atherosclerosis
o	Hypertension
o	Aneurysm
o	Elderly
o	Head injury (trauma)
o	Alcoholics
o	Arteriovenous malformation
23
Q

What are the most common non-traumatic causes of intracerebral haemorrhage?

A

Hypertension (36%)
Aneurysm (36%)
AV Malformation (11%)
Other (17%)

24
Q

What are the 2 types of brain aneurysm? What is the likelihood of developing one and who is most at risk? When do they become dangerous?

A 
-	2 types
o	Saccular (berry is a subtype)
o	Fusiform
-	1:15 people develop a brain aneurysm
-	Women at higher risk 3:2
-	Danger comes if it ruptures
25
Q

Where can an middle cerebral artery (MCA) stroke occur and what does it cause?

A 
-	MCA stroke
o	Dominant hemisphere (Left)
	Global aphasia
	Sensorimotor loss on contralateral face, upper limb and trunk
o	Striate arteries often involved
o	Non-dominant (R.parietal lobe)
	Neglect syndrome
-	Unilateral neglect are able to describe only the parts of a mental scene represented by the undamaged cortex. Both left and right parietal damage will result in hemispatial neglect, but patients with L parietal damage tend to recover quickly
26
Q

What effects can an ACA stroke cause?

A

o Contralateral sensorimotor loss below waist
o Urinary incontinence
o Personality defects
o Split-brain syndrome

27
Q

What effects can a PCA stroke cause?

A

o Contralateral homonymous hemianopsia
o Reading and writing deficits
o Impaired memory

28
Q

What are the characteristics and symptoms of lateral medullary syndrome (Wallenberg syndrome) PICA?

A

o Vertigo, nystagmus, nausea and vomiting, dysarthia, dysphonia, loss of pain and temp in body (contralateral), loss of pain and temp in face (ipsilateral), loss of gag reflex (nucleus ambiguus)
o Horner syndrome (ipsilateral)

29
Q

What is a transient ischaemic attack (TIA)? What are its symptoms

A
  • “A transient episode of neurologic dysfunction caused by focal brain, spinal cord, or retina ischemia, without acute infarction”
  • Diagnosis based on symptoms alone
  • Warning sign of heart attack or stroke
    o 5% in 1st 48 hours
    o 10% within 90 days
    o 30-40% in 3-5yrs
  • TIA symptoms
    o Anterior circulation
     Motor weakness
     Hemi-sensory loss
     Dysarthria
     Transient monocular blindness
    o Posterior circulation
     Vertigo
     Diplopia
     Ataxia
     Amnesia

BB1 (28 decks)

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