r ranson wrote the following in the "dailyish":
My cut healed beautifully well, but it was bone-deep, and now that the bandages are off, I find there's some severe nerve damage.
Not really enough detail, but I thought a quick primer on nerves might help:
Picture a "nerve" like a big phone cable coming into an office building. It has one wire (nerve cell) surrounded by insulation (myelin sheath) in a bundle with a whole bunch more each going to an individual phone.
If you squish the big wire (bruise or compress a nerve) you can damage both the insulation and the wire. This can stop the messages from getting through totally if there's a lot of damage, or partially if some wires are working and others aren't, or can cause cross-connections if wires are touching due to damaged insulation (that's where the "electric shocks" may be coming from that people have commented on), but more or less, since nerves are living, if you get the pressure off, provide all the necessary building blocks (nutrition) there will hopefully be primary healing of the nerves and everything will start working again. If only real life was that simple!
If some of those wires got squished to the point that the wire is broken, but the insulation is still intact, since we're dealing with magical human wires here, the tip of the wire can re-grow, and since it's got a nice myelin tube to follow, with good nutrition it should grow right on back down that tube. Unfortunately, they only grow at 1-5mm/day so if they've got a long way to grow the results may be complicated.
If the big wire got totally cut through (what r ranson probably did no her finger) the myelin sheath tubes need to be lined up to give the nerve cell a scaffold to grow down. Doctors can stitch nerves back together (assuming they're smart enough to ignore the blood during an emergency and *realize* a nerve's been cut - they didn't in a cut my mom had at the base of her thumb), but simply aligning the sides of even a sharp cut will *not* likely have aligned the nerve endings. If r ranson has a large/critical area of numbness, it's probably time for a consult with a reliable Plastic Surgeon who may feel it's worth re-opening the wound and aligning the "ends of the wires". *Even* if they do this though, they're *only* aligning the ends
- the insides won't line up to the phones they used to, so the regrown nerves still won't "feel" the same way they used to. But human brains are awesome, so you can "train the brain" to where the new phone patterns are (mostly through use, but there are extra tricks if people are interested.)
Lastly, also because nature is awesome, if an area is numb, nerves in the surrounding area will/may grow toward the damaged area to a small degree. (greater in the under 2 year old department, but that's not what we're working with here.)
Warning: the area that is numb will be more likely to suffer damage from both heat and cold, even if the surrounding finger is fine. How much that is really due to the numbness, or whether because blood vessels were also damaged and are also operating sub-optimally is a good question that don't have an answer to. It was a *long* time ago that I took an anatomy course!