Cerebrovascular accident (Stroke)

  • Described by the side of the brain affected
    • not the side of the clinical signs
    • Eg. left cerebral infarct leads to right hemiparesis
      and dysphasia

Types of stroke

  • Infarction
    • embolic
    • hypotensive
  • Haemorrhage
    • aneurysm

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Revision of basic anatomy of the brain

Vascular supply of the brain

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  • Anterior from
    • common carotids
    • internal carotids
    • then form the Anterior and Middle cerebral arteries.
  • Posterior from
    • vertebral arteries
    • merging into the basilar artery
    • forming the Posterior cerebral arteries

Circle of Willis

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  • connection of the anterior and posterior circulations around the optic chiasma
  • Consist of:
    • Anterior communicating artery
    • 2 anterior cerebral arteries
    • 2 internal carotid arteries
    • 2 posterior communicating arteries
    • 2 posterior cerebral arteries

Gross functional anatomical areas of the cortex

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Arterial territories and functional areas:

  • Anterior cerebral arteries
    • primary motor cortex
    • primary somatosensory cortex (hips to feet)
  • Middle cerebral artery
    • frontal primary motor cortex (hips to head)
    • parietal cortex primary somatosensory cortex (hips to head)
    • temporal lobe (auditory and olfactory cortex)
    • dominant hemisphere language centres
  • Posterior cerebral artery
    • visual cortex
    • hippocampus (long term memory)
    • thalamus
    • hypothalamus

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Somatosensory map with superimposed homunculus

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Motor map with superimposed homunculus

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Stroke: Cerebral infarction

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Pathogenesis

  • lack of blood supply
    • causes ischaemia –> resulting in tissue hypoxia
  • Brain requires high oxygen supply
    • brain tissue dies
    • cerebral infarction

Causes of infarction

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  • Narrowing of blood vessels by atheromatous plaques
    • results in decreased blood supply
    • infarction
  • Embolism
    • more common than atheromatous narrowing
    • embolism from
      • vegetation of heart valve
      • atheroma in aorta
      • atheroma in cerebral circulation
  • Hypotension
    • decreased blood flow in boundary zones (watershed regions) of the cerebral circulation
    • (picture) above
  • Liquefactive (colliquative) necrosis
    • focal bacteria/fungal infection
      • tissue digested by hydrolytic enzymes
      • resulting in soft, circumscribed lesion
        • consisting of pus and fluid remains of necrotic tissue
      • after removal of cell debris by WBC, fluid filled space is left – abscess formation
    • apopleptic cyst formation

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Types of ischaemic stroke

  • Total anterior circulation infarct (TACI)
    • occlusion of internal carotid or MCA on one side
    • Clinical features
      • Drowsy/unconscious
      • Complete hemiparesis
      • Dysphasia (L) or neglect (R>L)
      • Incontinence
      • Hemianopia and deviation of eyes to side of stroke
      • Poor prognosis
  • Partial anterior circulation infarct (PACI)
    • smaller wedge shaped infarct variable signs, less severe
    • Clinical features
      • Good recovery
      • Likely to have further stroke
  • Lacunar stroke (LACI)
    • small discrete infarcts, often multiple
    • associated with hypertension
  • Posterior circulation infarct (POCI)
    • vertebrobasilar infarction
    • Brainstem damage
      • so mortality high
      • but good functional recovery if survive

Types of haemorrhagic stroke

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  • Intracerebral Haemorrhage
    • Microaneurysm formation in hypertensive patients
      • Aneurysm forms on the penetrating vessels in the basal ganglia and internal capsule
    • Vascular malformation
    • Haemorrhage into tumours
  • Intracranial Haemorrhage
    • Subarachnoid haemorrhage
      • Caused by rupture of saccular (berry) aneurysm
      • Sites of aneurysm formation on the Circle of Willis
      • Defect in the middle layer at bifurcation of vessel
        • 1-2% adult population
        • 10-15% multiple
        • women > men
        • ‘congenital’

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Transient Ischaemic Attack

  • Known as mini strokes
  • Pathogenesis
    • change in the blood supply to a particular area of the brain
      • resulting in brief neurologic dysfunction that persists, by definition, for less than 24 hours.
    • If symptoms persist longer, then it is categorized as a stroke
    • A cerebral infarct that lasts longer than 24 hours, but less than 72 hours is termed a reversible ischaemic neurologic deficit (RIND)
  • Symptoms
    • Temporary loss of vision
      • Typically amaurosis fugax
        • Amaurosis fugax is loss of vision in one eye due to a temporary lack of blood flow to the retinal
        • artery
    • Dysphasia/aphasia weakness
    • Weakness on one side of the body
    • Numbness or tingling (paraesthesia)
      • usually on one side of the body.
    • Impairment of consciousness
      • very uncommon
    • Dizziness, lack of coordination or poor balance
      • may vary in severity
  • Symptoms of a TIA are short lived and usually last a few seconds to a few minutes and most symptoms disappear within 60 minutes.
    • Some individuals may have a lingering feeling that something odd happened to the body

Vertebro-basillar insufficiency

  • Known as ‘hair saloon stroke’
    • a type of transient ischaemic attack
    • resolves within 24 hours
  • Pathogenesis
    • Hyperextending the neck can damage an artery
    • Tearing of the artery lining
      • blood starts flowing between layers of tissue and that can cause blood clots to start building up, leading to a stroke
    • decreased blood flow in the posterior circulation of the brain
      • medulla
      • cerebellum
      • pons
      • midbrain
      • thalamus
      • occipital cortex
  • Symptoms
    • vertigo
    • diplopia
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Terri is obsessed with making medical school as painless as possible. She studies and compiles medical school notes in a concise, easy-to-understand format. She also enjoys reading contributions by others. She is an investor in sustainability projects. Her ideal weekend is wine tasting and experimenting on bread-making. She has yet to master the art of Sourdough baking.

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