Cerebrovascular disorders

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

• 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

• 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

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

Somatosensory map with superimposed homunculus

Motor map with superimposed homunculus

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Stroke: Cerebral infarction

Pathogenesis

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

Causes of infarction

• 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

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

• 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