So, say my arm gets sliced through, from between my middle and ring fingers, all the way to my elbow. Now, assuming I get prompt enough medical attention and I don’t bleed to death, how much is medical science going to be able to do for my arm? Am I definately going to lose it, or is there any chance of regaining any useful function with the limb and hand—and if so, how much?
Granted, I imagine a vague hypothetical injury probably isn’t the best thing to base concrete medical opinion. But I’m just looking for a “ballpark estimate.”
If the cut is sharp and clean, you might be able to recover nearly normal function. There will be a period of numbness while the repaired nerves have their axons grow back.
If the cut is dirty or crushed or repair is delayed, it might be nearly useless and chronically annoying.
In both cases you’ll have some long-term joint problems. The joint surfaces aren’t going to heal cleanly.
Huh. For some reason I was under the impression that nerves didn’t grow back once damaged. Dumb question: Is this impression more a question of degree of regrowth?
It depends on where and it depends on what nerves. If the neuron in question didn’t experience retrograde degeneration (i.e., the cell body didn’t die when the axon was cut), and if the myelination isn’t so dense that the regrowing axon can’t find its way through, it can regrow.
So odds are that a clean cut of a peripheral nerve would be regrowable (myelination via Schwann cells), while a cut of a central nerve probably wouldn’t (myelination via oligodendrocytes, much denser tissue).
Additionally, the axon will only regrow along the path of the nerve. You need both ends of the nerve to be cleanly cut, and very carefully reconnected by surgery.
I accidentally chopped a tree with an ax at the wrong angle when I was ten years old. The ax struck my knee instead disabling me completely from walking or running or even standing. I was pouring blood. I tried to get back home to get help. I did the very slow army crawl instead and my mother took me to the emergency room where it turned out that, besides the acute trauma injury, there was nothing left they could do except for many stitches. However my entire knee remained numb as well as my leg three inches above and below
They said it would remain numb for 3 - 4 years in the emergency room while it healed. That was wildly optimistic. The situation improved in 4 years but it literally took about 20 years before both legs felt the same when aggressively touched from top to bottom. I just did my own test and I think the problem finally healed. It was hard dealing with a knee that was completely numb all the time.