Neurology 4 - Anatomy of blood flow in CNS Flashcards
What proportion of CO, O2 and glucose does the brain use?
- 10-20% cardiac output
- 20% of body O2 consumption
- 66% liver glucose
List the sources of blood supply to the brain
- Internal carotid arteries (pair at front)
- Vertebral arteries (pair at back)
- These 4 arteries form the circle of Willis together, and coming off that there are the cerebral arteries going into the brain
List the veins draining the brain
- Cerebral veins
- Venous sinuses
- Dura mater
- Internal jugular vein
Define stroke and give it another name
- Cerebrovascular accident
- Rapidly developing focal disturbance of brain function of presumed vascular origin and of more than 24 hours duration
What are the two types of stroke?
85% infarction
15% haemorrhage
Define transient ischaemic attack
- Rapidly developing focal disturbance of brain function of presumed vascular origin that resolves completely within 24 hours
- Where something causes a temporary blockage of a blood vessel - a warning sign
Define infarction
- Degenerative changes which occur in tissue following occlusion of an artery
- An area of dead tissue which has lost its blood supply
Define cerebral ischaemia
- Lack of sufficient blood supply to nervous tissue resulting in permanent damage if blood flow is not restored quickly
- Hypoxia or anoxia
List the causes of occlusions
- Thrombosis (formation of a blood clot)
- Embolism (plugging of small vessel by material carried from a larger vessel, eg.atherosclerosis)
Describe the epidemiology of stroke
- 3rd commonest cause of death
- 100000 UK deaths/year
- 50% survivors permanently disabled
- 70% show obvious neurological deficit
List the main risk factors for stroke
- Age
- Hypertension (hemorrhagic stroke)
- Cardiac disease
- Smoking
- Diabetes mellitus
List the result of occlusion of anterior cerebral artery
- Paralysis of contralateral leg or arm (most likely the leg)
- Disturbance of intellect, executive function and judgement
- Loss of appropriate social behaviour
List the results of occlusion of middle cerebral artery
- Contralateral hemiplegia - paralysis on other side of body (mainly arm, can be leg)
- Contralateral hemisensory deficits (loss of sensation down one side of the body)
- Hemianopia (blindness of half the vision)
- Aphasia (expressive speech issues)
List the results of occlusion in the posterior cerebral artery
Visual defects
- Homonymous hemianopia (loss of the visual field on the same side in both eyes)
- Visual agnosia (unable to identify something)
List the characteristics of lacunar infarcts
- Lacune is a small cavity representing small strokes that happened during life
- Appear in deep structures due to small vessel occlusion
- Deficit is dependent on anatomical location
- Hypertension
- Often no visual symptoms
List the types of haemorrhagic stroke
- Extradural (trauma, immediate effects due to pressure on the brain due to middle meningeal artery)
- Subdural (trauma with delayed effects)
- Subarachnoid (ruptured aneurysms)
- Intracerebral (spontaneous hypertensive)
Describe the pathway of the common carotid artery
Common carotid splits in to external and internal common carotid at the level of the adams apple
Describe the pathway of the vertebral artery
It is the first branch off the subclavian artery, and goes up through the foramen amgnum
Describe the blood flow through the basilar artery
- Vertebral arteries come together to form the basilar artery
- Basilar artery spits to form the posterior cerebral artery
- Middle cerebral artery splits to form the anterior cerebral artery and posterior communicating artery
- Anterior communicating artery at the top
- Internal carotids are at the front
How can an infarction be identified post mortem?
The grey/white matter border is unclear, and there is asymmetry in the brain
What is supplied by the middle cerebral artery?
- The lateral parts of the brain
- Most of the temporal lobe
What is supplied by the anterior cerebral artery?
- Supplies the cortex along the midline to the parietal-occipital sulcus
- Supplies the motor cortex of the lower limb
- Supplies the frontal cortex
What is supplied by the posterior cerebral artery?
- Occipital lobe
- Inferior part of the temporal lobe
Compare the effects of cerebrovascular accident in the cerebral cortex with those in the brainstem
A stroke affecting the brainstem affects cranial nerves:
- Altered smell, taste, hearing, or vision
- Drooping of eyelid (ptosis) and weakness of ocular muscles
- Decreased reflexes
- Decreased sensation and muscle weakness of the face
- Balance problems and nystagmus
- Altered breathing and heart rate
- Weakness in sternocleidomastoid muscle with inability to turn head
- Weakness in tongue
An occlusion in the cerebral cortex is more likely to cause
- Aphasia
- Apraxia
- Memory defects
- Confusion and hypersexual gestures
