Introduction to stroke (NEEDS IMPROVING)

Question 1

Define an ischemic stroke

Answer 1

• Blockage of an artery within the brain
• Accounts for 80% of strokes
• Embolic stroke occurs when blood clot forms outside brain
• Thrombotic stroke occurs when clot forms within a brain artery

Question 2

Define a hemorrhagic stroke

Answer 2

• Aneurysm within brain vasculature burst. Commonly caused by small-vessel disease
• 20% of all strokes
• Intracerebral occurs when blood enters the substance of the brain
• Subarachnoid occurs when blood enters various spaces around the brain

Question 3

What are the early symptoms of a stroke?

Answer 3

• Numbness, hemiplegia and or inability to move one side of the body or face
• Difficulty in speaking or understanding speech
• Severe headache
• Loss of vision
• Problems with walking or co-ordination
• Any sudden neurological change (can vary widely depending on the location of the stroke)

Question 4

What is the ischemic penumbra?

Answer 4

A region of functionally impaired, but structurally intact tissue surrounding the ischemic core. It has the potential to be recovered. It can be identified by comparing perfusion weighted images and diffusion weighted images.

Question 5

What is the cascade of events occurring in the ischemic core which may spread to the penumbra?

Answer 5

Within the ischemic core there is a necrotic core infarct, representing the end stages of the cascade. tissues become unsalvagable.

Ischemia due to oxygen depletion 
Energy depletion
Disruption of ion homeostasis (energy required for
70mV potential) 
Glutamate release due to depolarisation
Ca2+ rising
Mitochondrial damage 
Free radical release 
Cell death by apoptosis/necrosis 
Inflammation

Question 6

What are the risk factors for stroke?

Answer 6

• AGE
• Gender. Men at higher risk until 55
• Family history
  -ethnic origin (stroke is more common in African-Caribbean
  people)
  • high blood pressure/cholesterol
  • diabetes (doubles the risk)
  • smoking
  • obesity and an inactive lifestyle
  • heavy alcohol use and binge drinking

Question 7

What molecular events follow stroke injury?

Answer 7

• Hours: excitotoxicity and free radicals
• Days: Necrosis, apoptosis, inflammation, remodelling
• Weeks: Plasticity

Question 8

What are some mechanisms of inducing a stroke in animal models?

Answer 8

• Proximal middle cerebral artery occlusion using a thread
• Distal middle cerebral artery occlusion (closer to the capillary bed) using electrocoagulation. Small and reproducible lesions
• Photothrombotic ischemia: Injects Rose Bengal into brain and shines light in specific area to induce photochemical reaction producing a clot
• Embolic ischemia: Injecting pre-clotted emboli. Representative of clinical stroke but highly variable

Question 9

How can you measure stroke recovery in animal models?

Answer 9

Limb function

Imaging or staining to measure size of the injury

Question 10

Recombinant tPA

Answer 10

• tissue plasminogen activator
• acute stroke intervention
• usually given <6hr after stroke
• converts plasminogen to plasmin to break down clots
• symptomatic intracerebral hemorrhage is a major side effect

Question 11

What are some acute stroke interventions?

Answer 11

• Recombinant tPA / combined with ultrasound to mobilize endogenous tPA
• Aspirin, inhibiting clot formation
• Thrombectomy to remove clots mechanically
• Carotid stent