Blood supply Flashcards
What % of the following does the brain use
a) Cardiac output
b) total body oxygen
c) total body glucose
a) 15%
b) 20%
c) 25%
What is average brain blood flow
46ml/100g/min
How many seconds of anoxia lead to unconciousness
20
Describe structure of arteries in the brain
Thin walled so easily blocked distorted or ruptured
Describe structure of veins in the brain
Thin walled so no muscles or elasticity to help return
What causes increased flow to the brain
Increased CO2
Reduced 02
What % change in CO2 is needed to double blood flow to the brain
70
Which arteries provide cerebral blood flow and in what proportion
80% from carotids
20% from vertebrals
2 common variations of the circle of willis
One posterior communicating small, one large
Anterior communicating large
What artery do striate come off and what do they supply
Internal capsule, lentiform nucleus etc
Come off middle cerebral
What artery supplies majority of lateral surface of brain
Middle cerebral artery
What does the basilar artery supply
Pons and cerebellum
What does the posterior cerebral artery supply
Inferior and medial aspects of temporal and occipital cortex
Thalamus and posterior internal capsule
Midbrain
What does the vertebral artery supply
Spinal cord
Dorsal medulla of brainstem (PICA)
Where do superficial cerebral veins cross
Subarachnoid space
What is the function of arachnoid granulations
Allow CSF to flow into venous blood of sinuses but prevent backflow of blood into sub arachnoid space
Causes of ischaemic strokes
Atherosclerosis
Embolism
Causes of cerebral haemorrhage
Trauma
Spontaneous (haemorrhagic shock)
What happens in an MCA stroke, dominant hemisphere
Global aphasia
Sensorimotor loss on contralateral face, upper limb and trunk
What happens in an MCA stroke non dominant hemisphere
Neglect syndrome
What happens in a stroke that affects ACA
Contralateral sensorimotor loss below waist
Urinary incontinence
Personality defects
What happens in a stroke that affects PCA
Contralateral homonymous hemianopsia
Reading and writing defects
Impaired memory
What is transient ischaemic attack
Temporary loss of brain function <30 minutes
What are TIA symptoms if it affects anterior circulation
Motor weakness
Hemi-sensory loss
Dysarthria
Transient monocular blindness
What are TIA symptoms if it affects posterior circulation
Vertigo
Diplopia
Ataxia
Amnesia
How does extra/ epi dural haematoma present?
May present with lucid period immediately after trauma followed by unconciousness
Symptoms of epidural bleed (explain them)
- Blood collects in compresses intracranial structures
- Compress cranial nerve III
- Weakness of extremities on opposite side of lesion
- Loss of visual field opposite to the lesion
Symptoms of subarachnoid haemotoma
Severe headache
Vomiting
Confusion
Lowered level of conciousness
What can be seen on CT scan of subarachnoid haemotoma
White signal diffuse over sulci on both sides
Name the 3 forms of cerebral aneurysms
Saccular
Fusiform
Berry
