I recently cut my left thumb across the pad on a very sharp knife last week. It was a very deep cut requiring 5 stitches. They stitches came out today and I told the doctor that most of the pad of my thumb is still numb. He is going to refer me to a hand specialist because he thinks there might be some nerve damage.
My question is do nerves that are damaged like this grow back or repair themselves? I’ve been told that nerve tissue doesn’t grow back, but I’ve also been told by a few people that it will grow back, but very very slowly. I’ve tried looking this up on the net and found nothing that really relates to my question.
So which is it? Do I have any hope of getting the feeling back in the tip and pad of my left thumb?
(Disclaimer: I am not a doctor and I start this thread with the knowledge that people here are not medical professionals. I fully intend on seeing my hand specialist on this and doing what he recommends.)
If the body of the nerve cell is not damaged, the axon can grow back, though there may be impaired conduction. It all depends on the type and size of the cut.
I cut the ever living shit out of my left index finger back in 1994. The cut was near (but below) the last joint before the tip. It went to the bone.
I had no feeling starting at the point of the cut extending to the exact middle of the tip. I found it damn near impossible to do things like start a bolt or a nut.
However as the years have moved on, I have regained feeling in my finger. I have a slight tingly feeling near the cut, otherwise normal amounts of feeling in that finger.
So no guarantees, but good luck.
I had a softball accident, which tore the tendon in my right ring finger (hammer finger). Unlike when I was a kid, the injury required surgery this time. They put a pin in, and when it was time to remove it, they took a scalpel across the fingertip to get it out. The fingertip was numb for a long time (maybe as long as a year…it’s been 1.5 years now since the accident), but I probably have about 95%-99% of the feeling back now.
Another anecdote: I had my wrist pinned after a break in '94. After they took out the pin, about 50% of the middle of my palm was pretty much numb.
Feeling has gradually returned, but there’s a bit in the centre about a finger-width wide that’s never properly got better - I’d say it’s currently at about 80 - 90% of the feeling of the other hand. So yeah it got better - but Very Very Slowly and I don’t think it will ever be as good as the other.
That is almost exactly where my cut is, but on the left thumb and just a bit above the joint. The numbness is from the cut straight up to the tip of the thumb. I’m finding it nerve wracking (no pun intended) to use that thumb for every day tasks.
The digital nerves which supply the thumb run in two main bundles along the volar (underside) aspect of the the thum on each side. A cut does not have to be particularly deep to cut one of the digital nerve bundles.
When a digital nerve is severed, the digit involved loses sensation along that side of the digit; innervation to the pad is shared by nerves which cross over from each side. One of the ways we tell how severe the injury to the nerve is is by testing your ability to discriminate one point from two.
Ideally, digital nerves severed fairly near the base of the digit are repaired within a few days of the injury. Under a microscope, the nerve bundle is sewed up like putting together the two walls of a severed cylinder. Inside of this, the nerve itself will still degenerate–perhaps all the way back to the spinal column. However the nerve cells themselves do not die, and they will grow new axons to the right place as long as the channel–the bundle shell–has been repaired. This may take several months because the nerves regenerate their axons slowly, on the order of a millimeter a day.
Without a proper repair, the extent and quality of re-innervation is variable, and heavily dependent on how severe the transection of the digital nerve bundle was. The outside of the thumb is slightly more critical than the side of it next to the index finger, because this helps remind the hand and thumb where it has been placed.
A hand doctor is the right place to be, so you are in good hands.
One more thing–if all you have cut are some small cutaneous nerves (unfortunately we use the term “nerve” to mean both an individual cell and a whole bundle of them) they will be too small to repair and everything will be left alone. It is only a transection of the main digital nerve bundles that gets repaired, and then only if the cut is fairly near the origin of the digit. Distal to that the nerves branch too much and they are too small to bother repairing.
Anecdote: Cut my left index finger (palm-side, at the “proximal interphalangeal joint”) quite deep in October 2006. I partially severed both flexor tendons (one 80/20, one 20/80) and severed the thumb-side nerve. I had absolutely no sensation on that side of my finger from the cut to the tip; the other side was fine. During the surgery to repair my tendons, the surgeon also repaired the nerve (as well as he could). Now, it’s still numb and tingly, though I do have sensation. My hand surgeon had, coincidentally, had exactly the same injury about ten years earlier, and he told me his finger still had limited sensation. (Though good enough, obviously, to be a hand surgeon!)
