I am interested to know whether or not the actual brain cell damage is more severe at the point of stroke or further along the arterial path?
I know the amount of damage depends on various factors, such as duration of ischemia, size of occlusion etc.
http://stroke.ahajournals.org/content/30/6/1190.short
The whole arterial territory beyond the site of occlusion is damaged, but not all to the same extend at first. Having in mind the penumbra-hypthesis, there is a core of parenchyma that goes under the vital perfusion limits and dies instantly. Around this core there is a penumbra where the perfusion is above the vitality level but under the level to let the parenchyma function properly, ensuing in neurological symptoms, but without killing the neurons. This penumbra has a chance of survival and recuperation if temporarely kept on collateral flow and eventually reperfused timely. If not, then the secondary processes of cell necrosis and longer lasting ischemia turn this penumbra into infarction as well, so enlarging the initial core of dead tissue and forming the final infarct size.
Cells of ischemic core die anyway through necrosis. However, as Geert pointed, reperfusion in a time manner (less than 3 hours with tPA treatment) is important to perserve penumbra. Clinically, reperfusion brings better outcome, but from studies on animals, researchers believe that reperfusion cause more stressor factors and result in a bigger infract size. On point of my view, I think the cells in point of ischemia will die, but dependent on ischemic insult intensity/time of ischemia/reperfusion onset time, penumbra tissue will have different responses.
Depending of duration of the ischemia:
Short, the site will be the more severe.
Long period, along the arterial route will be more affected.
At the point, blood will cause damage
Along the arterial route, after a period of stunning, collateral formation, the dammage will be more severe.
You may compare the difference of area of image between Diffusion weighted and perfusion weighted MRI for objective study
You are right in pointing out that the DWI/PWI mismatch is theoretically a marker for the potentially salvageble brain tissue. This concept of mismatch concurs with the penumbra, I mentionned earlier. This measurement is based on MRI imaging. There is a lot of discussion still going on about the interpretation and the clinical use of this DWI/PWI mismatch. On top of that, perfusion CT techniques, have also been develloped to try to discern the same penumbra-tussue (which is in fact a concept coming from PET-imaging). These CT-techniques are potentially even more discutable, mainly because of perfusiontreshold technical issues.
So in conclusion. imaging can illustrate the uneven distribution of ischemic damage in a hypoperfused arterial territory, but the clinical use in decission support for reperfusion has not been definitively established.
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