I explain the penumbra after stroke fully here (with pictures!) and explain how important it is after stroke.
But a question kept coming up in my clinical talks: Do hemorrhagic strokes have a penumbra?
Just some quick background:
After a block (ischemic) stroke, there is an area that the stroke kills (infarct) ("Stroked" in the image below).
Then there's another LARGE area that, hopefully, comes back on line: The penumbra.
But what about a bleed stroke:? There is no penumbra in bleed (hemorrhagic) stroke.
There was a long debate about this, but as more experimentation was done, and as brain scanning has gotten better: Bleed stroke: No penumbra.
If you'd like a more science-y take:
The first thing to make clear is that hemorrhagic stroke is different to ischaemic stroke. In ischaemic stroke, all the fuss... is about perfusing and salvaging the penumbra of ischaemic brain tissue, surrounding the dead central tissue. This penumbra doesn’t exist around hemorrhagic tissue.
Or even nerdier!: