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WHO DEFINITION OF STROKE

"Rapidly developing clinical signs of focal (or global) disturbance of cerebral function, with symptoms lasting 24 hours or longer or leading to death, with no apparent cause other than of vascular origin."

By this definition ,TIA, which lasts < 24 hours, and patients with stroke symptoms caused by subdural haemorrhage, tumours, poisoning, or trauma are excluded.

 

GLOBAL EPIDEMIOLOGY OF STROKE

  • Annually, 15 million worldwide suffer a stroke-5 million die and 5 million are permanently disabled 

  • WHO estimates a stroke occurs every 5 seconds 

  • Stroke related disability is the 6th most common cause of reduced DALYs

  • Accounts for 10% of all deaths worldwide

  • Globally, stroke is the 2nd leading cause of death 

ISCHEMIC STROKE - 3 SUBTYPES(87%)

  • Thrombosis: In situ obstruction of an artery.

  • Embolism: Particles of debris originating elsewhere that block arterial access to a particular brain region.

  • Systemic hypoperfusion: More general circulatory problem, manifesting itself in the brain and perhaps other organs.

Hemorrhagic Stroke due to intracerebral hemorrhage or subarachnoid haemorrhage.

Data compiled by AHA show that strokes due to ischemia, intracerebral haemorrhage and subarachnoid haemorrhage are 87%, 10%, and 3 % respectively.

CONSEQUENCES OF REDUCTION IN CBF DURING STROKE

  • Brain contains little or no energy stores and relies on blood for their delivery.

  • During stroke, reduction of blood flow to brain results in a deprivation of glucose and oxygen.

  • Region directly surrounding vessel is most affected.

  • Central core irreversibly damaged and necrosis if ischemia is long enough. (Infarct), brain blood flow is reduced

  • Cells which receive oxygen and glucose by diffusion from collaterals are viable. (Penumbra), 20 -30 ml/100gr/min

  • Experimental studies report that the infarct is formed 3-12 h after initiation of ischemia and continues to develop even after 24h, although in a much slower rate.

By definition, neuroprotection is an effect that may result in salvage, recovery or regeneration of the nervous system, its cells, structure and function.

Neuroprotection Is specifically defined as the "protection of neurons" and is a strategy used to potentially protect the brain in a number of different cerebral conditions including Parkinson’s disease, traumatic brain injury and ischemic stroke.

Neuroprotection Is perhaps best exemplified by strategies designed to prevent cells undergoing apoptosis

There are currently no approved treatments for the myriad of damaging pathological processes that persist in the brain long after the acute stage.

  • Inflammation,

  • Excitotoxicity,

  • Oxidative stress,

  • Apoptosis, and

  • Odemaresulting from disruption of the blood brain barrier.

A common feature evident in most neuroprotection studies is that beneficial outcomes are far greater when the therapy is commenced earlier in the disease process.

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