Quick back story: Back in February I had a dissection in my vertebral artery which lead to a cerebellar stroke. The doctors didn’t realize it was a stroke until 2 or 3 days later, so I didn’t really have much intervention and they said that basically the left half of my cerebellum is dead.
A question I asked the doctors and never got a clear response is, what happens to all the dead brain tissue? Does it just shrivel up and hang out for the rest of my life? Does it get broken down and I have a void in my skull? The still-living parts of my brain want to know!
I’ve tried googling, but my google-fu is weak on this one. All I get are sites talking about how the brain can regenerate somewhat after a stroke (which I don’t understand, I thought once a brain cell was dead, it was dead).
Sort of both. On MRI scans it’s possible to tell how long ago an infarction may have occurred by the stages of healing / scarring.
Long term you end up with “scar tissue”, and that tissue takes up less volume, so adjacent areas might expand slightly.
Not necessarily; in most strokes some tissue is damaged only temporarily/incompletely due to hypoxia. There is often an “umbra” in which tissue damage is irreversible and a “penumbra” in which there is compromised function that may return in time.
ETA: IANA doctor, I just have a neuroscience master’s
To add to this, in one documentary I saw, a neurologist was talking about the brain “healing” after a TBI (traumatic brain injury). He said that in our minds we think of the brain healing like a wound, but in actuality, it’s closer to look at it this way: After a TBI, you have a different brain from the one you had previously. The “healing” process is actually getting the new brain to start relearning the functions that the old brain did.
Not a doctor just another person with a MSc in Neuroscience.
In the Central Nervous System (CNS) dead neuronal tissue would be broken down by a specialized Glial cell called Microglia; whose job is to circulate the CNS and swallow up/destroy odd bits of foreign/non-functional matter. The “empty space” left by those deconstructed cells would be replaced by other various glial cells (probably astrocytes through scarring).
Fun fact: glial cells make up ~90% of our brain, and work to support the function of our neurons.
We were told by a leading neurologist from Albert Einstein College of Medicine last year that the newest school of thought believes that there is some new cell growth in brains (after trauma or not?), but how much and to what extent it is useful is still unknown. He stressed that doctors used to believe we never made any more brain cells beyond the ones we are born with and that this is irrefutably not the case.
I’ve heard this too. Supposedly our brain does indeed have stem cells available to reconstruct a certain amount of damage, in addition to the rewiring. From what I understand, it’s also a factor of time, not age - that is to say, if you’re 50 and live to be 100, you’ll heal as much as a 20 year old who lives to be 70. Read it in some medical journal, not sure which one, it was a while ago, so I don’t have a cite. But if it’s requested, I can try looking for it again.
From a previous Cecil column (too lazy to cite now) - we have extra brain cells that have just been sitting there doing nothing. When needed, like after a stroke, they can be pressed into service to relearn to walk, talk, juggle, etc. The proof is that some people recover completely from strokes; this wouldn’t be possible if every cell had to be accounted for. The column topic was something like ‘what do they mean when they say we only use 10% of our brains?’. The thrust of the answer was that we simply got extra cells that in ordinary circumstances would never be used.
Yeah but as I said before, after a stroke a lot of tissue may only have temporarily impaired function anyway. Paralysis down much of one side of the body, then recovering much of the original movement within weeks, is fairly common.
If it were a matter of rewiring, neurogenesis or forming new connections, it would not happen this fast.
Possibly true but of course it would not be anything like 90% of cells being surplus.
I read about this earlier this year, here’s a blurb:
“Researchers at Lund University in Sweden have discovered a new stem cell in the adult brain. These cells can proliferate and form several different cell types—most importantly, they can form new brain cells.”
Brain tissue after infarction does not undergo scarring as in organs like the heart.
Instead, it commonly breaks down, liquifies while macrophages remove debris and ultimately a cavity is left behind. More on liquefactive necrosis here.
Of course it’s an entirely separate issue as to what rewiring can be accomplished so that functions can be performed without the affected tissue.