3: Blood supply of the brain Flashcards
For which percent of the body weight and cardiac output does the brain makes up?
Only 2% of body weight but
10- 20% of cardiac output
Which two major arteries supply the brain with blood?
- Internal carotid artery
- Vertebral arteries
What is the circle of Willis?
Anastomosis of arteries supplying the brain
–> allows collater circulation in the cerebral circulation
Summarise the overall venous drainage of the brain
Cerebral veins
–> Venous sinuses (in subarachidonic space) –>
–> Dura mater
Internal jugular vein
What is a Cerebrovascular accident (CVA)?
A Stroke
rapidly developing focal disturbance of brain function of presumed vascular origin and of >24 hours duration
–> 85% infarction, 15% hemmorage
What is a Transient Ischaemic Attack (TIA)?
rapidly developing focal disturbance of brain function of presumed vascular origin that resolves completely within 24 hours
–> warning sign: patients are at hight risk of getting a stroke!
What is an infarction?
Degenerative changes which occur in tissue following occlusion of an artery
What is cerebral ischemia?
Lack of sufficient blood supply to nervous tissue resulting in permanent damage if blood flow is not restored quickly
hypoxia/anoxia
What are posiible causes for an occlusion
- Thrombus (blood cloth at site of formation)
- Embolus (any other substance or other blood cloth formed in another place)
What are the main risk factors for stroke?
- Age
- Hypertension
- Cardiac disease
- Smoking
- Diabetes mellitus
Which part of the brain is supplied by the anterior cerebral artery?
Medial two thirds of the Cortex
- Medial prtions of frontal lobes
- Superior medial parietal lobes
Which part of the brain is supplied by the middle cerebral artery?
Lateral 2/3 of cortex + forebrain
Which part of the brain is supplied by the posterior cerebral artery?
The occipital lobe (posterior part)
Which symptoms might occur when ther is a blockage to the anterior cerebral artery?
Paralysis of
- contralateral leg (more than arm)
- face
Disturbance of intelect, executive function and judgement (–>abulia)
Loss of appropirate social behaviour
Which symptoms might occur when there is a occlusion of the middle cerebral artery?
“Classic stroke”
- Contralateral hemiplegia (=hemiparesis): arm rather than leg
- Contralateral hemisensory (=altered sensation) deficits
- Hemianopia (optical disturbance (blurred/blindness)
- Aphasia (L sided lesion) (loss of speach)
What is hemiplegia?
Hemiparesis
(half sided paralysis)
What is hemianopia?
Visual field loss in a vertical line
What is Aphasia
Loss of speach (can also be eiter efferent (understanding) or afferent (speaking))
What is Broca’s aphasia?
It is expressice loss of speach
due to damage to the broca region
What is Wernicke’s aphasia?
Receptive aphasia
- loss of understnading of speech
–> due to damage to the Wernicke region of the brain
How does a paitent with blockafe of the posterior cerebral artery might present?
Visual deficits
- homonymous hemianopia (hemianopic visual field loss on the same side of both eyes)
- visual agnosia (impaired visual perception)
What is a Lacunar Infarct?
- Lacune is a small cavity formed by tissue loss due to former strokes
- Appear in deep structures as a result of small vessel occlusion
- Deficit is dependent on anatomical location
- Main risk factor: Hypertension
What are the characteristice of a subarachnoid hemorrhage?
Usually ruptured aneurysm
- Rupture can be due to trauma
- or spontaneous
What are the characteristics of a intercerebral hemorrhage?
Usually spontaneous
- closely linked to hypertension
Explain the organisation of the dura mater in relation to the cerebral sinuses?
Dura surrounds the sinuses
Compare a subdural vs. an extradural (epidural) haematoma
Subdural:
- venous
- slow
- can be traumatic or spontaneous (more common in eldrely)
Extradural
- arterial
- quicker
- usually traumatic (more common in young patients)
Which symptoms would you expect with and occlusion of the anterior cerebral artery?
Supplies part of motor cortex to legs:
- paralysis/weakness in contralateral leg
- loss of sensation in contralateral leg
- Abulia –> no motivation
- inability to initiate the process of walking (gait appraxia)
- urinary incontinence
Where would you suspect someone to have a leasion if one presents with following symptoms:
- paralysis/weakness in contralateral leg
- loss of sensation in contralateral leg
- Abulia –> no motivation
- inability to initiate the process of walking (gait appraxia)
- urinary incontinence
In the anterior cerebral artery
Which symptoms would a patient present with when having an occklusion in the basilar artery?
Present with locked-in syndrome
Which part of the brain dos the middle cerebral artery supply?
- A lot of the lateral surface of the hemisphere
- (location of Broca’s area i.e. language expression)
- Inferior division supplies lateral temporal lobe (location of Wernicke’s area i.e. language comprehension)
- Deep branches supply the basal ganglia as well as the internal capsule
Which symptoms might someone present when there is an occlusion of the middle cerebral artery?
- Paralysis + sensory loss of contralateral face and arm
- Aphasia (dependant of side of brain if Broca of Wernicke) –> usually left
- contralateral neglect syndrome
- Contralateral homonymous hemianopsia is often present
When someone presents with following symptoms: Where would you supect a leasion to be?
- Paralysis + sensory loss of contralateral face and arm
- Aphasia (dependant of side of brain if Broca of Wernicke) –> usually left
- contralateral neglect syndrome
- Contralateral homonymous hemianopsia is often present
Middle cerebral artery
When someone is haveing an occulusion in the posterior cerebral artery, what do you expect the symptoms to be?
Supplies the: Occipital lobe, Basal ganglia in temporal lobe, Thalamus, lateral+3rd ventricle
- Contralateral loss of pain and temperature sensations.
- Visual field defects (contralateral hemianopia with macular sparing).
- Prosopagnosia –> no recognition of faces
- Ipsilateral deficits of oculomotor nerve,
- Contralateral deficits of facial nerve (only lower face, upper face receives bilateral input), vagus nerve and hypoglossal nerve
Someone presenting with following symptoms:
Where do you expect the leasion to be?
- Contralateral loss of pain and temperature sensations.
- Visual field defects (contralateral hemianopia with macular sparing).
- Prosopagnosia –> no recognition of faces
- Ipsilateral deficits of oculomotor nerve,
- Contralateral deficits of facial nerve (only lower face, upper face receives bilateral input), vagus nerve and hypoglossal nerve
Posterior cerebral artery
What is a Berry aneurism?
What does it cause?
It is a saccular aneurism in the brain
- most common cause for sub-arachnoid haemorrhage
