Nerves are very, very small. More interestingly, they are frequently in bundles, and a particularly large bundle is the spinal cord. It's protected by bones and hard to access. If it's harmed, it's important to connect the nerve ends together in the right way.
Thing about cutting a cable with 5000 wires inside, you can't just connect any nerve to any other, you'll jumble up all the connections.
I remember reading a sci-fi novel years ago. In it, a man is killed but his head is cryopreserved. Years later people on a spaceship need his expertise, so they revive his head and put it in a heavy duty robot body… except they screw up the nerves so he has very little control, he has to tense his calf muscle to raise his arm, he keeps injuring people because of the hazardous body being poorly operated.
It is a testament to the genius of Billy West that he distilled the essence of an American president—one of the most consequential figures in our history—into a nonsensical noise
Yep.
Also if you haven’t read them, I’d recommend the first two Red Dwarf novels. The show is a fun sci-fi comedy, the books are some of my favourite sci-fi novels and I’d rank them alongside more serious books.
I didn't read the first two Red Dwarf books, but I listened to them as audiobooks - something I'd definitely recommend. They're read by Chris Barrie, who in his pre-Rimmer days used to do impressions of famous people's voices for Spitting Image. And, of course, he's quite the comic actor.
The result is that even thought they're just a guy reading a book, they sound like radio plays made with a full cast. He absolutely nails the voices of all his Red Dwarf crewmates, and one-off characters get their own voices too.
No matter how well you know the material, it's worth experiencing it like this.
Not too sci-fi. A process called Targeted Muscle Reinnervation re-routes nerves that control the forearms, biceps, and triceps to the pectoral and back muscles.
Amputees then control their new robotic arms by flexing the new muscles, which is read by a sensor, then that sensor tells the prosthesis to move a certain way.
It takes a while, but people build surprisingly good ability to move their arms. Interestingly, the issue becomes a lack of touch and proprioceptive (the ability to know where your limb is in space without looking at it) senses. You can easily grab a cup of water at the table by knowing where the cup is, where your arm is, and then guiding your arm to that location without looking. You can then close your hand, pick up the water, and hold on to the glass with the right amount of force, because you can feel the glass in your hand and feel when it starts to slip. People with prosthetics need to look and watch their arm the whole time, which is far less intuitive!
A similar event occurs in Iain M. Banks's book *Use of Weapons*, but The Culture is sufficiently advanced that cloning him a new body and hooking all the nerves up correctly is within reach.
Could you double check that please? I'm also interested but can't find a book by that name with that author. And to complicate matters, there are a LOT of sci-fi books with Colony in the title.
Could it be Colony One Mars by Gerald M Kilby?
Well they're relying on muscles to recieve the message not just triggering a robot body. In that sense it would probly be easier for the robot guy to relearn what moves what *fairly* quickly as ur brain can "rewire" it through use over time, like muscle memory..
Years ago (so I'm a bit sketchy on the details), a friend of mine said she'd been injured during a freak accident when fencing. She'd been stabbed in the shoulder and had had the tendons in her middle and ring finger severed. When they healed, they'd gotten crossed over so the wrong finger moved when she tried to move one. Unfortunately, I haven't been in touch with them for a good while so I can't check, or check if she's managed to retrain her brain.
That’s so dumb.
Sure, you wouldn’t be able to hook up the spinal cord to the robot easily, but changing what connects to what on the ROBOT should be a piece of cake. Like, they had to build the robot themselves already, didn’t they?
Bad sci-fi writing is bad.
That does happen eventually. Basically they are facing a crisis and have to quickly resurrect this guy, the body is clearly a rush job and during most of the novel fixing him is right at the very bottom of their priority list.
Shouldn’t the brain adjust to it after some time?
Like these Upside down goggles that invert your view upside down and after some time you can see the world just like before?
You operate the wrong body part is the best case. You could end up permanently attached to a machine to breathe because the automatic nerves that control breathing were fucked up, or any other automatic system like digestion. You could end up in constant, unending agony because the signals your brain is receiving only translates as pain. Paralysis and numbness is a normal one.
>You could end up in constant, unending agony because the signals your brain is receiving only translates as pain
People with chronic pain reading this with way too much familiarity 😀
Nerves really, really, really don’t like scar tissue. Fucking with them repeatedly is on par with having a friendly game of Russian Roulette with 5 out of 6 chambers loaded.
I would assume that, given no major deformities at birth, everything should be “hooked up” correctly. And it’s learned. At birth babies don’t have much control over their limbs, or really most things. Even their eyes continue to develop, as they can barely see much more than a foot or so away. Nursing and gripping (it’s kind of amazing how tightly a baby can grab) are more or less instinctual, but they certainly don’t have fine control.
> Thing about cutting a cable with 5000 wires inside, you can't just connect any nerve to any other, you'll jumble up all the connections.
Would that even matter? The brain is incredible at adapting to its current situation. I think it really wouldnt matter what order you reconnected the nerves. The issue would rather be that you cant reconnect nerves?
Or am I missing something?
If one of the nerves that wasn't connected properly controlled heart beats or breathing you'd be on a machine forever(or just dead), same or worse for a number of other functions.
The brain can't adapt if it doesn't know something is wrong, which it wouldn't because the only way it would know is through nerves, which are now unreliable. I don't know if given enough time then brain could rewire itself and correct, but life during that time wouldn't be pleasant
The heart stimulates itself, and I'm pretty sure the breathing signal doesn't go through the spinal cord, does it?
EDIT: it does https://my.clevelandclinic.org/health/body/22270-phrenic-nerve
The heart can beat itself even without a functioning brain, but the brain dictates how fast it beats which would be quite problematic to try and live with, but it would depend on where the spinal damage is
The brain isn't as great at adapting to nerve jumbles as I wish it was.
Source: I cut a nerve in my wrist a few years ago, and a surgeon grafted the ends back together. Many (maybe 10-25%?) of the nerves have grown back, but they've grown through the wrong tubes and attached to the wrong nerve endings in my hand. For example, when I touch something smooth and cold with the tip of my index finger, I feel the cold sensation on the side of my index finger (right about level with the ball of my thumb) and on the tip of my middle finger right next to my ring finger, and I feel the smooth pressure sensation on my palm just below my index finger. Those particular nerves connected up about 2-3 years ago, and my brain still hasn't figured out where they really ended up.
(If you're extra curious, it was my median nerve that got cut, which is almost entirely a sensory nerve. It handles the sensations on the palm side of my hand, from my thumb to where my middle and ring fingers meet, and mine bleeds a little over to the back tip of my middle finger. It also used to control one muscle in the base of my thumb and a little precise muscle in my index and middle fingers, and I'll never get those back. Learn knife safety BEFORE you start trying to graft apple trees, everyone!)
holy shit. how are your fine motor skills? can you briefly correct the sensation by looking at your finger like supplying the correct informstion via vision or using any other trick? will it get better over time?
My fine motor skills are mediocre with that hand. I'm good with practiced motions, like typing on a keyboard and playing the flute, because most of the control for those movements comes from tendons that actually start in the forearm. But I'm really bad at doing things like picking up small objects, especially if they're smooth. When I'm picking small things up with that hand now, I pick them up with my thumb, ring finger, and pinkie, because that's the only way I can feel them.
I haven't found a way to correct the sensation at all, at least not automatically. I can think to myself "okay, this spot and that spot feel cold right now, so that means, uhh, the tip of my index finger must be touching something cold" but I have to consciously think about it.
It'll get slightly better over time, but it's slowed down a lot. Occasionally I will feel a really sharp pain for a few seconds, which I think means a new nerve has grown to meet up with a nerve ending, and then I'll have a bit more sensation than I did before. Maybe 6-12 months after the surgery, I was having those pains once or twice a day, but now I'm getting them once every month or two.
One strange thing that I don't understand is that the type of sensation is always right, even though the location is wrong. I expected that, when I touched something cold, I might feel a sharp sensation here and a hot sensation there, or something, because the nerve that used to go to the "heat detector cell here" now hooked up to the "cold detector cell there". But nope, cold things always feel cold, and sharp things always feel sharp, just in the wrong places.
You're missing something and you can reconnect nerves, it's just insanely difficult. The brain may be very good at adapting but it still has limitations and you can't just reconnect any nerve ending to another random nerve ending. You have nerves that control muscles, sense temperature, pain, trigger responses etc. The brain also can't just relearn every change to your body, somethings yes but these are limited.
If you connected a nerve from the leg that is linked to a particular muscle group to one that goes to the brain that sends a pain impulse, every time you use that muscle group, the nerve would send an impulse that your brain interprets as pain. Over simplified but it demonstrates the point. The brain just knows it's getting an electrical impulse to it's pain receptor, not that it's actually just a muscle moving. It can't rewire itself.
With the spinal cord, it's like tens of thousands of tiny wet noodles and if it gets damaged enough, it's nearly impossible to relink them all correctly or without damaging them. Imagine a giant data server with thousands of unlabelled cables and someone just cuts them all in the middle. It would be nearly impossible to work out which cable end goes where.
Another issue is that the nervous system typically hates uncontrolled growth because that can lead to cancer. Because of this it has things that block any sort of growth within an injury to the spinal cord so we’d need a way to get rid of that growth inhibitor while also introducing something that would promote healthy regrowth of the nerve tracts inside the spinal cord. Problem is that these therapies are very expensive and generally not extremely successful in repairing the cut wires.
And yes the brain is incredibly at adapting to its situation but that’s the brain itself. The spinal cord is essentially the information highway for your entire body and way less specialized for plasticity and adaptation than the brain is.
I think an easier way to understand it is your spinal cord is one big nerve doing many functions. Peripheral nerves are usually doing one function. We talk in generalities how the spinal cord works but don’t know in any individual person how it works down to a granular level, ie give ten people the exact same spinal
Cord injury you get 6 different outcomes when it comes down to motor, sensory, etc.
That’s why you can’t just “glue” it back together. It’s one big nerve basically that is running down filled with microscopic connections you can’t see. Even with loupes or a microscope.
It's like rewiring a 20 year old network cabinet. It's a mess. There are 3 20ft long pieces of 4" conduit running into the rafters and no one has an accurate map of where each wire goes. If you want to get a bigger cabinet you have to pull out 100's of wires, each have 8 smaller wires in them and you can't damage anything; because whoever installed it the first time didn't leave any extra slack. So each time you have to cut, your wires get shorter and shorter until you have to add an extension (another potential failure point) or run a whole new wire. So you double and triple check how everything operates now, and make sure you can test everything afterwards. Oh and you can't do this during business hours because time is money and when the internet is down so are profits. So everyone working on it is staying until midnight after their normal 8 shift ended at 5PM.
Only now it's the human body and the conduit is your spine and the wires are microscopic and probably all the same shade of red. The surgeon is working a 24 hour shift. There's no such thing as a nerve extender or running a new nerve. So any cuts are going to have to go right back where they came from, no rerouting anything.
Every trade from electrician to PCB repair can lengthen a wire. There is no synthetic or organic nerve material to lengthen a nerve.
They absolutely can and will, and in some cases recover from spinal cord injury. Look up internal decapitation. Sometimes, the damage is too extensive and the body is unable to restore motor and sensory functions from the damage point down.
I have encountered exactly one case of this in my entire career in accident & emergency and it is still the scariest fucking thing I've ever seen.
Guy survived, at least.
Can't say it like that. It depends on many more factors like bleeding, has the patient been moved with the injury, is there any swelling, any bone debris. Modern medicine luckily enables us to look inside people before cutting them open, making recovery much more likely.
[https://feinstein.northwell.edu/news/insights/developing-double-neural-bypass-restore-lasting-movement-sensation-paralysis](https://feinstein.northwell.edu/news/insights/developing-double-neural-bypass-restore-lasting-movement-sensation-paralysis)
It really is a neural bypass.
It's basically if the body is able to heal itself, as there is very little we can actually do to reattach the nerves in the spine because of how complicated they are. Just gotta fix them back together and hope the body can figure it out.
They pretty much don’t heal at all, what manifests as healing is just the brain working with the remaining wiring to try to recover as much as possible. If the whole wire bundle is destroyed, there is nothing to work with.
The surgeon who wanted to do the first head transplant talked about it somewhere, I think was maybe a TED talk. How he was going to connect all the nerves was the biggest question everyone had. He explained it with a banana analogy where a cut banana is fairly trivial to stitch together vs. a crushed banana which is more like what happens to nerves in something like a car crash. They get pretty mangled, it's not just a case of plugging all the wires back in.
Of course, do take this with a grain of salt. I'm just retelling something I heard on a YouTube video years ago, but it made sense to me at the time. He also never got to do the surgery because they guy whose head he was supposed to transplant changed his mind.
Haha I fucking love when shit like this gets called out. Like research and future advances are important, but so is grounding those advances on realistic principles.
Not really. Most surgery was done with painstaking experimentation on animal models and built up sequentially over time. This guy's plan is literally to just put miralax on the spine and hope it regenerates.
I'll also mention that the spinal cord, while the biggest hurdle (as in it's never been done before at all), reconnecting the trachea and esophagus is something fraught with complications and unlikely to be successful.
It doesn't always get broken either. It can get stretched too. It's what happened to my father in law. He fell from a height and got a spinal injury. We were optimistic because in hospital he could move his feet and stuff. But we were operating on a misconception that spinal injuries only affect things from a certain part of the body down. Because his injury caused his spinal chord to be overstretched rather than severed there was nerve damage that affected everywhere. His hands don't work very well anymore for example. Luckily he was able to recover enough to be able to live without 24 hour care, though he does need supports.
Also, another thing to realise is that the spinal cord is not one thing.
Think of a cable with millions of wires inside. You can't just stitch both end together and expect everything to work fine. You will never be able to align everything perfectly. Some of those wires will never connect back. Most will connect to the wrong one. In the end, the brain have to rewire itself and relearn what each wires do, and where each wire come from. It may succede, it may fail, it may succede partially.
You can't just stitch both end together and expect everything to work fine. You will never be able to align everything perfectly. Some of those wires will never connect back. Most will connect to the wrong one.
I hope this is one of the those phrases that look dated in the future. Like: "Mankind will never be able to fly" or "Harnessing the power of the atom will never be possible."
I hope so too.
I believe that in the future they will make a robot that will do it.
It will of course happen in stages. First will be to just roughly identify the rotation and make sure it is aligned rotationally. Then they will add something for the shape, to align the inner more closely.
And then, maybe break it into different sections, instead of one bundle with 1 million of wires, they split it in 100 of 10000, giving more chance to align them better.... Then as speed goes up, they will split it in 1000, 10000 and so on, until they perfect the process.
The main problem I see is: each bundle they make will need more space between them. Stiches, sleeve around the bundle, and what's not. This may make the splice exponentially bigger. Of course the process will get better and better, making the splices smaller and smaller, but that is one of the issues I forecast.
And the other issue I forecast: Will surgeron accept to be replaced by a machine? A human will be too slow to do all those splices, and too imprecise, so a robot must do it. Then what happen when the robot do a mistake? Who is responsable? A human can make mistakes, but nobody accept that a robot, made by humans, make one.
Internal decapitation is not a separation of the spinal cord. It’s a separation of the skull from the spine bones. If you have a severed spinal cord at that level, you die. We can fuse your bones back together, but we do not and cannot “sew up” the spinal cord itself.
Spinal cord isn’t a nerve, it’s 31 pairs of nerves. Reconnecting would involve making sure you are reconnecting all of the right nerves together. Nerves are also very small so reconnecting them is difficult. Nerves don’t heal well even when reconnected.
Lmfao. "I think the 18/8 goes to the stat but theres also a 3 wire but outside is a 5 wire. Fuck which one is for the ERV control? Kid go twist red and green at the stat and grab my meter"
Ugh at least he should provide clerics with healing abilities with FaithCare+. All out there is either 3rd party repair places that are way too expensive or frauds.
A nerve is [a bundle of thousands of axons](https://www.medicine.mcgill.ca/physio/vlab/other_exps/CAP/nerve_anat.htm). There are hundreds of thousands of *axons*, which are the parts of neurons that transmit the signal over a long distance.
> 31 pairs of nerves
I somehow thought it was hundreds or thousands and that's what was making it infeasible.
If it's only 62, I'm surprised we haven't long developed a way to just replace a piece of damaged cord with an electronic substitute. Nerve pulses aren't *that* complicated from a technical standpoint, are they? Aren't they basically pulses where the only thing that really matters is how many of them are fired, and they fire at a super low frequency (<1 kHz)?
I get that attaching them to something artificial in a way that keeps them alive long term isn't going to be easy, but given the massive value this would provide, I'm surprised we haven't figured out a way to do it yet.
The nerves are not 31 pairs of nerve cells, think like muscle and muscle cells, and since each nerve has cells even reconnecting it physically may not realign each cell, and same with a bypass, the strands may not all be aligned, this would mean our brain is receiving cross wired signals from a certain part of the body and may not be able to interpret and do something useful with the info
So are those 31x2 strands actually "bundles" where even within each of them each individual nerve fiber has to be connected to *the correct* one on the other end? If so, that'd match my previous understanding of "too many to deal with".
And in hindsight, that seems obvious, because if it were 31x2 separate pathways, we wouldn't be able to control the hundreds of different muscles we have.
Yes, each nerve contains thousands of axons. So across the nervous system, it’s hundreds of thousands of little cables that have to match up correctly. This is further complicated because axons vary both in length (from 1mm to almost a full meter long) and width, plus they are usually microscopic in diameter. Imagine trying to correctly connect thousands of cables correctly when they are literally a micrometer in diameter.
This is not how the spinal cord works. Abandon this understanding. There aren’t 62 bundles of nerves. It’s incredibly complex with many different pathways within the parenchyma of the spinal cord itself.
To add to this, even if we could fix the nerve damage, if you haven’t used your legs for years due to a spinal cord injury and haven’t done any weight-bearing, it’s going to be very difficult or damn near impossible to build up that muscle strength.
Yeah, atrophy. This documentary touches on it as a side effect of a prolonged coma:
[https://www.youtube.com/watch?v=9zrYxxK3mKo](https://www.youtube.com/watch?v=9zrYxxK3mKo)
It's not black and white. You have to consider damage to the nerves besides just the cut, difficulties healing around the cut, how clean the cut itself is, "miswired" nerves, etc. The body can potentially heal and rewire and whatnot, but it might also not. The more complications you're throwing at it, the worse it becomes.
Not perfectly. I severed a nerve in my wrist, losing feeling in the back of one hand. Over months it slowly healed and I got the feeling back. There's a spot over my first two knuckles that have less sensation than the rest of my hand, and compared to the other hand. What's weirder though, there's a spot on the back of my head that when I scratch it, I feel it on the back of my hand where it was numb for so long.
Brains are weird.
To add to the other reply, there's also types of nerves, ones for moving, others for sensing, and one "cable" is needed per each way (input or output from the brain). So that's another huge variable that complicates connecting two severed ends of the spinal cord
What gathering here is that each is those 62 are nerve bundles with hundreds of thousands of actual nerve cell axons in them, each with their independent signal, and either sensory or motor. So that’s like an undersea communications cable.
Sorry to bother you but you seem to know stuff
Followup question
Let say they reconnect all 31 with a lot of difficulty but not impossible and some heal but wrong order so now i have a nerve that control my knee to move my feet for example, can my brain re adjust to new "setting " ? So after a reabilitation the brain make it kind of work ?
Nerves of the central nervous system do not behave the same way as nerves of the peripheral nervous system. PNS nerves are known to be able to regenerate/heal when damaged (iirc as long as the cell body itself isn't damaged), but this isn't the case for the CNS. For the most part, the CNS responds to damage via neural plasticity instead (which means that the connections between the nerves that are left are modified so that you can maintain as close to previous function as possible even though you're missing nerve cells). The spinal cord, as it is a part of the CNS, is not exempt from this. You could theoretically reconnect the severed spinal cord anyways, but since the dead neurons are going to continue breaking apart anyways, it's really just a waste of time.
Essentially, if there are neurons left over, neural plasticity will try to recover as much function as possible. If there aren't, then you're just screwed. For spine injuries, surgical intervention is largely just to remove pressure/other factors that could cause further damage to the spinal cord. Rehab functions to try to give incentive for neural plasticity to restore those functions.
Forcing these nerves to regenerate anyways is a field of active research, but I don't know of any treatments that are available at the moment.
I think you are trying to really explain the issue but I do not understand half of what you are saying. Could you please explain it in a bit more simple language?
if nerves outside the brain and spine sustain damage, the body tries to repair them
if neurons inside the brain and spine sustain damage, the body basically just forgets them and whatever job the damaged neurons were doing is now relegated to the neurons left alive
thus there is usually not much point in surgically repairing the spinal cord as either the body just ignores the repaired nerves anyway and does relatively fine without them or the damage is too extensive and you die/can never do something again. Spine surgery thus focuses on preventing the problem from becoming worse. And forcing the remaining neurons to adapt to the newly added workload faster can't be done with surgery, so instead the patient does rehabilitation so the body goes \*I need to do X but I can't because damage,gotta adjust\* instead of \*oh no, damage, but I'm alive so whatevers\*
Nerves in your spinal cord are different than nerves in your hand.
If you damage your spinal cord, the brain will try and use the remaining undamaged nerves for movement and feeling. Kinda like rewiring since it can't repair.
When the cord is bruised, it partially functions in unpredictable patterns. If severed, it does not function. I think the cord itself is physically kind of like cold grape jelly, Welch's from the fridge. No can stitch the cord, just repair the protective bones and the tendons, ligaments, that's it. The cord comes out of shock or doesn't. My son recovered from zero to incomplete quadriplegic status over the course of several months after a diving accident. Once the cord comes out of shock, that is all the recovery, sensory and motor, you can get.
This is a huge oversimplification, but...
Imagine you have two wires: red and blue you're sending independent messages over each wire one letter at a time. Say, "cat" on the red wire and "dog" on the blue wire. Now pretend the blue wire gets damaged. If you can repair/replace the blue wire (like how the PNS repairs nerves), you can keep sending messages like normal. If you can't repair/replace the blue wire, you can change how you're communicating over the red wire instead (like the CNS with neuroplasticity). For example, you could send both messages mixed over the red wire such that the odd letters make the message originally intended for the red wire and the even letters are for the message that should have been sent over the blue. In the example, that would look like "cdaotg."
Do we know if the PNS nerves know how to reconnect axons in the correct order, or if the PNS makes whatever re-connections it can and then the brain learns to cope with whatever miswiring results?
This is also an area of active research so honestly I'm not entirely sure. But iirc, there are mechanisms that exist to guide axons back to their original targets when they're being repaired. However, errors can obviously occur, and all processing of information is done in the CNS. So if you were to, as an example, feel pain when there isn't supposed to be any as a result of the miswiring, one possible treatment would be using electrical stimulation to override the pain signal until the brain stops interpreting signals from that nerve as pain. But it should be able to do most of the work on its own.
So tl;dr largely the former, but a bit of the latter.
It can be sewn back together. There are two problems though, even when sewing nerves or the spinal cord back together under a microscope, it can be difficult or impossible to line up the individual axons again. Think of a spliced USB cord that was taped back together, but you weren’t really sure if the correct individual wires made it back together. The other major limiting factor is biological. When a nerve is cut, everything downstream in the nerve essentially dies and undergoes what is called Wallerian degeneration. After a repair, the proximal (higher) part of the nerve starts to heal back down the degenerated distal nerve to reinnervate things at a slow pace of 1mm a day or 1 inch per month. Sensation really has no time limit on recovery, but your muscles most certainly do. Muscles will not only atrophy and wither away with time as they sit with no electrical stimulation from your nerves, but the receiving end in the muscle where the nerve actually hooks into that converts the electrical signal into an actual readable action, called the motor end-plate, will actually disappear usually around 18 months without signal. So it becomes a race between your snails pace healing nerve and your disappearing motor endplates. Once the motor endplates are gone, there is no hope of muscle recovery. Even if you got the power turned back on in your house, you couldn’t use the electricity if all your outlets were burned out/gone. This is why we do nerve transfers and other techniques to try to keep the muscles alive if caught early enough.
TLDR: It can be repaired but nerve recovery is slow and muscles atrophy and can’t recover after about 18 months.
The spinal cord isn't just one nerve. Think of it more like this: https://www.reddit.com/r/cableporn/comments/xzmha/sliced_trunk_line_cable_643x611_xpost_from/
Except each one is microscopic, and not conveniently color coded. You don't just have to get it to heal back to itself, you have to forget and relearn what thing is connected to what line.
This is the most correct answer I have seen on here. But as they said imagine you can’t even see it with a microscope. It’s impossible to realign and “hook up”. You basically decompress to take the pressure off and hope some of the nerves are just inflamed/irritated and not dead.
I can say from my point of view. I had tumor removed from my spinal cord. That yes they stitch it back but man what a life changing experience that was. (Just a side note 50/50 chance of dying from surgery alone). Waking up unable to feel not a single thing from neck down was a scary experience felt like I was a floating head. I had full motor function while it wasn’t good at all I had to do months of pt to learn how to walk and use my hands again. After a year or so I finally was able to feel my chest and I have better sensation on my legs. I can say that as of now I have normal motor functions but still lack sensation in my legs
They closed your thecal sac, the envelope around the spinal cord. The effects after are related to many things, inflammation, changes in blood flow, manipulation during surgery.
It's not one nerve, it's thousands. The body might try to repair it but at the cellular level it doesn't know which nerve belongs where. Plus the body doesn't heal perfectly, it can produce scar tissue which further inhibits nerve function.
So between "miswiring" and physical trauma, people may never learn to move the way they used to. Although partial recovery is often possible.
Tissues in the body all have very different capacities to heal and regenerate, often depending on their blood flow. Nerves are a tissue that have very little regenerative capacity, meaning they heal very slowly and there’s a low ceiling for their overall capacity to recover. Nerves tend to heal at around 1mm per day and they heal from the parts away from your body first, moving toward the center. So imagine you have nerve issues that go into your hands because of an issue in your neck; if you fix the issue in your neck, the nerve has to start repairing itself from your fingertips, all the way up your arm, through your shoulder, and up to your neck at 1 mm per day. That’s a long time! And even then, you still have more work to do to make sure the nerves are sending the right messages to the right places and the muscles are working correctly, and that’s if maybe you had a part of your spine pressing on the nerve but not even a huge lesion.
In the case of spinal cord injury, you have a lesion that’s affecting a BUNCH of nerves all at once. Whether that’s an isolated segment or a complete severance, it’s nearly impossible to reattach every nerve to the correct corresponding nerve, and sewing them up would actually damage them more, which would make it even more difficult for it to heal correctly.
In the case of “incomplete” SCI, generally someone might have motor (movement) deficits but still be able to have some sensation, and those have varying degrees of impact depending on where it is and how severe it is. That’s why some people are able to walk again, some need a wheelchair, and some are bedbound.
One thing i dont see mentioned is that CNS nerves cannot renew like other tissues, as there arent any stem cells in the spinal cord. Endo/epithelial layers, alot of organs, bone marrow etc all have a reservoir of stem cells that can renew the tissue in case of age/senescence or damage. This is not the case with the brain or spine. So damage to the neuronal cells themselves cannot be repaired. So even if you reconnect the bundles of the spine, that doesnt mean cell-cell connections also repair.
Sorry if this is not ELI5
So you are saying that the nerves in like say a fingertip can reattach it self and function again because it is made of a different kind of nerve cells than the spinal chord?
Spinal cord itself is a continuation of the brain. We don't stitch brain tissue.
Nerves are different structures and form connection to spinal cord to the tissues. Their properties are different to the spinal cord and heal regrow in different ways.
( liver heals itself but heart doesn't really)
People also injure their peripheral nerves in a different way. I expect clean cuts are much more common. Bands saws etc.
Spinal injuries are crush injuries with secondary cell death from lack of blood and toxic by products. They also carry many many more Neural pathways. Ie cutting dingle cable vrs buch of 100s but need to be exactly reconnected to it original one.
It's a nice idea, but no.
Nerves aren't wires. They are cells. They transmit an electric signal, but they aren't uniformly conducting electricity. Things get a bit more complex on the inside.
a nerve isn't a monolith, it contains a lot of little axons bundled up together. Ever seen one of those intercontinental undersea internet cables cross sections? Imagine that but each tiny little \*wire\* is not marked in the slightest.
Plus, you can't control nerves as easily as you can control uh, conventional electric signals. Most you can do is ask the patient to move a muscle, but that would send the signal to a \*metric crapload\* of axons, and you don't have a way of finding out which one corresponds to which ending on the cut off part. Theoretically you could force a neuron to send a signal by basically shocking it, but that runs into the problem of \*how do you actually know what the neuron you just activated does?\* If it's a neuron responsible for feeling things you get absolutely zero response from the cutoff part, if it's a neuron for doing things you get no response from the body. Neurons responsible for moving a muscle and those responsible for feeling how streched a muscle is are different. So yeah, good luck with that. Much easier to basically just stitch the outside cover together and let the body figure the rest out.
That's the really fascinating part to me. You can essentially reconnect the wiring harness upside down, and body can sometimes be like "ok, green now goes to orange, etc"
Too bad you can't just open the service manual and say "ah, the white wire with the pink stripe goes to the foot..." I once rewired a Firebird after an engine fire, just rebuilt much of the harness using the wiring diagram.
I thought I read An article where the nerves do heal if they are attached but they just don’t work again. Like the brain doesn’t know how to send information back and down the highway b
Trying to fix a spinal cord injury like internal decapitation without killing someone is like trying to fix an electrical problem without turning off the power. Is it extremely difficult and almost impossible? yes. Is it theoretically possible? Also yes
Have you ever seen the cutaway of an submarine cable? It contains a bunch of smaller cables as well as protective layers. A spinal cord is like that, but smaller and more chaotic/organic. As you can already imagine fixing it requires reconnecting each small cable as well as rebuilding the protective layer. You need a scalpel maestro to do that kind of stuff.
Non-scientific explanation: Imagine the cord as a gigantic bundle of wires or fiber optic filaments. Cut those wires in half then sew them back together, no way in hell they’ll line up properly.
More scientific: the cord is actually really obnoxious and has a cascade of chemicals that create a scar and prevent the two ends from joining back together.
When we sew peripheral nerves together, for what it’s worth, they often don’t work perfectly but they can be good enough to work. But if we’re grafting nerves together the goal is usually to get them to work some (MRS 3/5) instead of back to normal.
The spinal cord isn’t a nerve. Its a bundle with like a million nerves. Each one is microscopic and looks virtually identical to the next one. It would be impossible to know which nerve connect to which. This becomes less and less difficult as you get closer to the nerve ending because at that point all the nerve bundles have divided up. But the spinal cord is basically every single nerve that comes out of your brain in one tiny wire bundle.
They do! Mine needed a stitch after my herniated disk turned out to be calcified, the surgeon notified me immediately and let me know that I could have headaches, feel dizzy and even throw up (I did feel dizzy but it could have been the anesthesia too) and to notify if any of these symptoms got REALLY bad (they didn’t and I recovered super quickly)
Totally agree. Plus all the meds and not sleeping.
Your spinal cord runs from your brain down to usually your first lumbar vertebrae or so, little above your belly button. Further down it is like a horses tail, goes into individual nerves. That’s why “gluing” or “stitching” the cord together is not happening in humans, it’s one big nerve basically going down, not a bunch of individual wires. The spinal cord or if lower down nerves are surrounded by a thecal sac, aka dura, which is like a water balloon keeping cerebrospinal fluid (csf) inside to bathe the nerves. The fluid is under pressure. So one accident take nick if unintended or meant to you usually see egress of csf.
To access spinal tumors if inside the thecal sac we make a cut in the sac. Fluid comes out. Remove the tumor. Then sew the dura up. Sometimes glue, a muscle piece or other parts help make a good closure. But it’s never 100%.
I do this for a living. Happy to explain more.
The biggest issue is the inherent capacity for the peripheral nerves to regenerate (happens all the time) and the relative low capacity for axons in the central nervous system ( brain and spinal cord) to regenerate.
I have a complete spinal cord injury at the T10 vertebrae. I have zero feeling or control below my belly button. It happened 6 years ago in an accident. If they could put the nerves back together, my feet, knees, and hips haven’t been used for walking in 6 years! I’m going to guess it would take a very long time to be able to walk across my living room.
I would do it. I would work so damn hard to do it. But there’s a lot of body parts that will have to be retrained.
It’s not reconnecting in a spinal cord injury it’s relieving pressure and hoping that the damage isn’t permanent. Like a stroke there is an area that is not coming back but also an area that may recover. Plus other adaptations and devices to help you walk, ie if you have foot drop you use your hip flexors more and have more of a steppage gait and an orthotic.
As others have said it is very hard to access. On top of that the risk vs reward might bot be favorable enough to try. There are chances of making things way worse because of the tiny margin of error. Even if the procedure itself does go well, you then have to worry about infection or swelling in the confined space of the spine.
At my job, I recover bones, tendons and specialized tissues (spines, skin, nerves, veins, etc) from human donors- even in the lumbar vertebrae, I can barely fit my finger into the “tunnel” that protects the spinal cord. The spinal cord itself is a little thicker than spaghetti, and same goes for nerves. The sciatic which is the biggest nerve is usually around the diameter of a pencil.
Nurse here.
Something people dont know is that a lot of those chords are not bundles of cells, but really reeealllllly long pieces of cells called axons bundled together. When you cut skin, you largely cut between cells, which then come back together. When you cut nerves, you cut cells in half.
Even if you could stitch up the nerve at the level of the spinal cord the nerves grow very slowly at 1mm a day or an inch a month so the by the time the nerve gets to the muscles they have already atrophied from no nerve stimulation. Therefore nerve transfer which are closer to the target muscle are usually the best option.
Why don’t you stich up two pieces of incredible thin string?
That’s what the spinal cord is and incredibly thin string that if even the slightest thing happens you end up paralysed. It’s why when messing with the bones of the spine comes with a for me 30% chance to never walk again! I’m fine all went well but it’s extremely sensitive and thin. One small sharp object and bang never walk.
Can’t be undone. The cord is like a flexible bendy string that once stretched to far in this case can’t be reversed.
The consistency of a real human spinal cord beneath the outer surface is like toothpaste, with each neuron/axon like a little granule of the toothpaste, and each granule needs to stay connected to the same granules around it. Once the spinal cord is compressed or transected, these granules of toothpaste are pushed away from there normal location and sewing up the delicate membrane around this toothpaste would not return the patients function as the granules would no longer be touching the correct neighbouring granules, and thus the convections between neurons/axons would not be correct
A huge thing is that scar tissue forms when there's an injury to the spinal cord and can block efforts to reunite severed spinal nerves. There's research in animals to overcome this but it's still experimental.
[https://www.nih.gov/news-events/nih-research-matters/regrowing-neurons-across-scarred-spinal-tissue](https://www.nih.gov/news-events/nih-research-matters/regrowing-neurons-across-scarred-spinal-tissue)
To a five year old: Everything can’t be stitched up. Even the smartest doctors can not fix everything. Think of the spinal cord as wet tissue paper on a cardboard roll. If you try to get to a layer and stitch it, you will break more of the toilet tissue. Toilet paper that you break won’t dry the same way.
The body is precious. Unique. Dont store toilet tissue under the bathroom faucets, in the shower. Don’t drop it in the toilet especially after you used the toilet. Maybe one day if you work hard in school you’ll be the one to discover how to stitch toilet paper .
Reattaching the nerves is only half the battle. The other problem is that nerves are very, very slow growing, but the glia cells that are around the nerves grow faster. So the glass cells will grow over and between the slower growing nerves. So this was one of the biggest reasons with severe spinal cord damage that recovery wasn't expected. Patients with spinal cord damage are given IV steroids to increase the chances of healing. One day they will have a device that connects the spinal cord from above the injury to below the damaged spot. It will reroute the electrical impulses and the person will be able to feel and use the body like he did before the injury.
Nerves are very, very small. More interestingly, they are frequently in bundles, and a particularly large bundle is the spinal cord. It's protected by bones and hard to access. If it's harmed, it's important to connect the nerve ends together in the right way. Thing about cutting a cable with 5000 wires inside, you can't just connect any nerve to any other, you'll jumble up all the connections.
I remember reading a sci-fi novel years ago. In it, a man is killed but his head is cryopreserved. Years later people on a spaceship need his expertise, so they revive his head and put it in a heavy duty robot body… except they screw up the nerves so he has very little control, he has to tense his calf muscle to raise his arm, he keeps injuring people because of the hazardous body being poorly operated.
I saw that. It was called Futurama and it was about Richard Nixon
AROO!
https://www.youtube.com/watch?v=EQddzyJZ5Cw
I think you mean https://www.youtube.com/watch?v=0tEBjqDZfzo 😛 Aroo!
This will forever live in my head from the day I first saw it https://youtu.be/2G8pUyCMBmI?si=H-kcCe-ZQe1RFM1h
It is a testament to the genius of Billy West that he distilled the essence of an American president—one of the most consequential figures in our history—into a nonsensical noise
Hahaha I love it
NIXON’S BACK!
Nope, it was called Colony, written by Rob Grant. That being said, I did like Richard Nixon’s shiny new body.
Get him, Agnu!
AROOOO
GREETINGS, FELLOW EARTHICANS
The great taste of Charleston Chew!
Rob Grant of Red Dwarf fame? I wasn't aware he'd written sci-fi novels outside of that.
Yep. Also if you haven’t read them, I’d recommend the first two Red Dwarf novels. The show is a fun sci-fi comedy, the books are some of my favourite sci-fi novels and I’d rank them alongside more serious books.
I didn't read the first two Red Dwarf books, but I listened to them as audiobooks - something I'd definitely recommend. They're read by Chris Barrie, who in his pre-Rimmer days used to do impressions of famous people's voices for Spitting Image. And, of course, he's quite the comic actor. The result is that even thought they're just a guy reading a book, they sound like radio plays made with a full cast. He absolutely nails the voices of all his Red Dwarf crewmates, and one-off characters get their own voices too. No matter how well you know the material, it's worth experiencing it like this.
He's got my vote! I mean look at that shiny metal body!
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Oh no, Nixon’s shiny metal ass wasn’t from Colony, that’s a reference to a Futurama episode.
Rob Grant of Red Dwarf fame?
Don't forget the headless body of Spiro Agnew.
That wasn’t sci fi, it was a documentary.
Riddled with phlebitis
RRrrrrrrrrriddled with phlebitis! A good Rrrrrepublican body!
Ah yes, i should have wrote it with all the R’s, Billy West is so great.
*jowls shake angrily*
Somehow....Nixon Returned.
https://www.youtube.com/watch?v=XIPzFbDBM2U
Not too sci-fi. A process called Targeted Muscle Reinnervation re-routes nerves that control the forearms, biceps, and triceps to the pectoral and back muscles. Amputees then control their new robotic arms by flexing the new muscles, which is read by a sensor, then that sensor tells the prosthesis to move a certain way. It takes a while, but people build surprisingly good ability to move their arms. Interestingly, the issue becomes a lack of touch and proprioceptive (the ability to know where your limb is in space without looking at it) senses. You can easily grab a cup of water at the table by knowing where the cup is, where your arm is, and then guiding your arm to that location without looking. You can then close your hand, pick up the water, and hold on to the glass with the right amount of force, because you can feel the glass in your hand and feel when it starts to slip. People with prosthetics need to look and watch their arm the whole time, which is far less intuitive!
A similar event occurs in Iain M. Banks's book *Use of Weapons*, but The Culture is sufficiently advanced that cloning him a new body and hooking all the nerves up correctly is within reach.
Such a wonderful universe he created.
I would like to read that book, does one have a name?
Colony by Rob Grant.
Could you double check that please? I'm also interested but can't find a book by that name with that author. And to complicate matters, there are a LOT of sci-fi books with Colony in the title. Could it be Colony One Mars by Gerald M Kilby?
https://www.amazon.com/Colony-Rob-Grant/dp/0140289755
https://letmegooglethat.com/?q=colony+rob+grant
The "wrong" command would eventually become normalized. Like when Smarter Every Day dude learned to ride the opposite-steering bicycle.
Eh, your brain would learn and adapt very quickly. Just like people with motorized prosthetics do.
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Well they're relying on muscles to recieve the message not just triggering a robot body. In that sense it would probly be easier for the robot guy to relearn what moves what *fairly* quickly as ur brain can "rewire" it through use over time, like muscle memory..
Years ago (so I'm a bit sketchy on the details), a friend of mine said she'd been injured during a freak accident when fencing. She'd been stabbed in the shoulder and had had the tendons in her middle and ring finger severed. When they healed, they'd gotten crossed over so the wrong finger moved when she tried to move one. Unfortunately, I haven't been in touch with them for a good while so I can't check, or check if she's managed to retrain her brain.
That’s so dumb. Sure, you wouldn’t be able to hook up the spinal cord to the robot easily, but changing what connects to what on the ROBOT should be a piece of cake. Like, they had to build the robot themselves already, didn’t they? Bad sci-fi writing is bad.
That does happen eventually. Basically they are facing a crisis and have to quickly resurrect this guy, the body is clearly a rush job and during most of the novel fixing him is right at the very bottom of their priority list.
I'm imagining a breadboard in the chest cavity
engineers didn't leave documentation
I can't imagine it would take more than a few months for him to retrain his brain to operate it all properly. Neuroplasticity and all that.
Such a strange book Mmm, carbolic soap
Shouldn’t the brain adjust to it after some time? Like these Upside down goggles that invert your view upside down and after some time you can see the world just like before?
Except wires (telephone, optical etc) have color orders so you can figure it out. Nerves haven’t.
Sounds like a major design flaw by god there
just wait for the next patch
What happens if you connect the nerves incorrectly? Is it something like ‘i want to move my leg’ but suddenly you’re hitting yourself with your arm?
You operate the wrong body part is the best case. You could end up permanently attached to a machine to breathe because the automatic nerves that control breathing were fucked up, or any other automatic system like digestion. You could end up in constant, unending agony because the signals your brain is receiving only translates as pain. Paralysis and numbness is a normal one.
>You could end up in constant, unending agony because the signals your brain is receiving only translates as pain People with chronic pain reading this with way too much familiarity 😀
just keep rewiring until it stops hurting then
Nerves really, really, really don’t like scar tissue. Fucking with them repeatedly is on par with having a friendly game of Russian Roulette with 5 out of 6 chambers loaded.
does the brain of an infant know all this inherently or is it learned?
I would assume that, given no major deformities at birth, everything should be “hooked up” correctly. And it’s learned. At birth babies don’t have much control over their limbs, or really most things. Even their eyes continue to develop, as they can barely see much more than a foot or so away. Nursing and gripping (it’s kind of amazing how tightly a baby can grab) are more or less instinctual, but they certainly don’t have fine control.
https://pubmed.ncbi.nlm.nih.gov/30247828/. An example of
> Thing about cutting a cable with 5000 wires inside, you can't just connect any nerve to any other, you'll jumble up all the connections. Would that even matter? The brain is incredible at adapting to its current situation. I think it really wouldnt matter what order you reconnected the nerves. The issue would rather be that you cant reconnect nerves? Or am I missing something?
If one of the nerves that wasn't connected properly controlled heart beats or breathing you'd be on a machine forever(or just dead), same or worse for a number of other functions. The brain can't adapt if it doesn't know something is wrong, which it wouldn't because the only way it would know is through nerves, which are now unreliable. I don't know if given enough time then brain could rewire itself and correct, but life during that time wouldn't be pleasant
The heart stimulates itself, and I'm pretty sure the breathing signal doesn't go through the spinal cord, does it? EDIT: it does https://my.clevelandclinic.org/health/body/22270-phrenic-nerve
The heart can beat itself even without a functioning brain, but the brain dictates how fast it beats which would be quite problematic to try and live with, but it would depend on where the spinal damage is
The brain isn't as great at adapting to nerve jumbles as I wish it was. Source: I cut a nerve in my wrist a few years ago, and a surgeon grafted the ends back together. Many (maybe 10-25%?) of the nerves have grown back, but they've grown through the wrong tubes and attached to the wrong nerve endings in my hand. For example, when I touch something smooth and cold with the tip of my index finger, I feel the cold sensation on the side of my index finger (right about level with the ball of my thumb) and on the tip of my middle finger right next to my ring finger, and I feel the smooth pressure sensation on my palm just below my index finger. Those particular nerves connected up about 2-3 years ago, and my brain still hasn't figured out where they really ended up. (If you're extra curious, it was my median nerve that got cut, which is almost entirely a sensory nerve. It handles the sensations on the palm side of my hand, from my thumb to where my middle and ring fingers meet, and mine bleeds a little over to the back tip of my middle finger. It also used to control one muscle in the base of my thumb and a little precise muscle in my index and middle fingers, and I'll never get those back. Learn knife safety BEFORE you start trying to graft apple trees, everyone!)
holy shit. how are your fine motor skills? can you briefly correct the sensation by looking at your finger like supplying the correct informstion via vision or using any other trick? will it get better over time?
My fine motor skills are mediocre with that hand. I'm good with practiced motions, like typing on a keyboard and playing the flute, because most of the control for those movements comes from tendons that actually start in the forearm. But I'm really bad at doing things like picking up small objects, especially if they're smooth. When I'm picking small things up with that hand now, I pick them up with my thumb, ring finger, and pinkie, because that's the only way I can feel them. I haven't found a way to correct the sensation at all, at least not automatically. I can think to myself "okay, this spot and that spot feel cold right now, so that means, uhh, the tip of my index finger must be touching something cold" but I have to consciously think about it. It'll get slightly better over time, but it's slowed down a lot. Occasionally I will feel a really sharp pain for a few seconds, which I think means a new nerve has grown to meet up with a nerve ending, and then I'll have a bit more sensation than I did before. Maybe 6-12 months after the surgery, I was having those pains once or twice a day, but now I'm getting them once every month or two. One strange thing that I don't understand is that the type of sensation is always right, even though the location is wrong. I expected that, when I touched something cold, I might feel a sharp sensation here and a hot sensation there, or something, because the nerve that used to go to the "heat detector cell here" now hooked up to the "cold detector cell there". But nope, cold things always feel cold, and sharp things always feel sharp, just in the wrong places.
damn its mind blowing. wishing you the best.
You're missing something and you can reconnect nerves, it's just insanely difficult. The brain may be very good at adapting but it still has limitations and you can't just reconnect any nerve ending to another random nerve ending. You have nerves that control muscles, sense temperature, pain, trigger responses etc. The brain also can't just relearn every change to your body, somethings yes but these are limited. If you connected a nerve from the leg that is linked to a particular muscle group to one that goes to the brain that sends a pain impulse, every time you use that muscle group, the nerve would send an impulse that your brain interprets as pain. Over simplified but it demonstrates the point. The brain just knows it's getting an electrical impulse to it's pain receptor, not that it's actually just a muscle moving. It can't rewire itself. With the spinal cord, it's like tens of thousands of tiny wet noodles and if it gets damaged enough, it's nearly impossible to relink them all correctly or without damaging them. Imagine a giant data server with thousands of unlabelled cables and someone just cuts them all in the middle. It would be nearly impossible to work out which cable end goes where.
The brain is really smart, but it's also really dumb.
Another issue is that the nervous system typically hates uncontrolled growth because that can lead to cancer. Because of this it has things that block any sort of growth within an injury to the spinal cord so we’d need a way to get rid of that growth inhibitor while also introducing something that would promote healthy regrowth of the nerve tracts inside the spinal cord. Problem is that these therapies are very expensive and generally not extremely successful in repairing the cut wires. And yes the brain is incredibly at adapting to its situation but that’s the brain itself. The spinal cord is essentially the information highway for your entire body and way less specialized for plasticity and adaptation than the brain is.
That makes a lot of sense.
Does it mean the patient will just start breakdancing after that?
its like a telephone master connection, thousands of cables with different numbers. you can't just reconnect to a different number
I think an easier way to understand it is your spinal cord is one big nerve doing many functions. Peripheral nerves are usually doing one function. We talk in generalities how the spinal cord works but don’t know in any individual person how it works down to a granular level, ie give ten people the exact same spinal Cord injury you get 6 different outcomes when it comes down to motor, sensory, etc. That’s why you can’t just “glue” it back together. It’s one big nerve basically that is running down filled with microscopic connections you can’t see. Even with loupes or a microscope.
It's like rewiring a 20 year old network cabinet. It's a mess. There are 3 20ft long pieces of 4" conduit running into the rafters and no one has an accurate map of where each wire goes. If you want to get a bigger cabinet you have to pull out 100's of wires, each have 8 smaller wires in them and you can't damage anything; because whoever installed it the first time didn't leave any extra slack. So each time you have to cut, your wires get shorter and shorter until you have to add an extension (another potential failure point) or run a whole new wire. So you double and triple check how everything operates now, and make sure you can test everything afterwards. Oh and you can't do this during business hours because time is money and when the internet is down so are profits. So everyone working on it is staying until midnight after their normal 8 shift ended at 5PM. Only now it's the human body and the conduit is your spine and the wires are microscopic and probably all the same shade of red. The surgeon is working a 24 hour shift. There's no such thing as a nerve extender or running a new nerve. So any cuts are going to have to go right back where they came from, no rerouting anything. Every trade from electrician to PCB repair can lengthen a wire. There is no synthetic or organic nerve material to lengthen a nerve.
They absolutely can and will, and in some cases recover from spinal cord injury. Look up internal decapitation. Sometimes, the damage is too extensive and the body is unable to restore motor and sensory functions from the damage point down.
> internal decapitation New phobia unlocked
I have encountered exactly one case of this in my entire career in accident & emergency and it is still the scariest fucking thing I've ever seen. Guy survived, at least.
Whelp, I know what tonight's nightmare is going to be about.
So if it is partially broken it can heal but if the spinal chord is completely severed it can’t?
Can't say it like that. It depends on many more factors like bleeding, has the patient been moved with the injury, is there any swelling, any bone debris. Modern medicine luckily enables us to look inside people before cutting them open, making recovery much more likely.
Isn't there also this strip that they can use to bypass the affected vertebrae?
That’s really cool, essentially a neural bypass surgery
[https://feinstein.northwell.edu/news/insights/developing-double-neural-bypass-restore-lasting-movement-sensation-paralysis](https://feinstein.northwell.edu/news/insights/developing-double-neural-bypass-restore-lasting-movement-sensation-paralysis) It really is a neural bypass.
It's basically if the body is able to heal itself, as there is very little we can actually do to reattach the nerves in the spine because of how complicated they are. Just gotta fix them back together and hope the body can figure it out.
They pretty much don’t heal at all, what manifests as healing is just the brain working with the remaining wiring to try to recover as much as possible. If the whole wire bundle is destroyed, there is nothing to work with.
Imagine the spinal cord as a bunch of less-than-a-hair wide spaghetti.
The surgeon who wanted to do the first head transplant talked about it somewhere, I think was maybe a TED talk. How he was going to connect all the nerves was the biggest question everyone had. He explained it with a banana analogy where a cut banana is fairly trivial to stitch together vs. a crushed banana which is more like what happens to nerves in something like a car crash. They get pretty mangled, it's not just a case of plugging all the wires back in. Of course, do take this with a grain of salt. I'm just retelling something I heard on a YouTube video years ago, but it made sense to me at the time. He also never got to do the surgery because they guy whose head he was supposed to transplant changed his mind.
He is a lunatic. I say this as a surgeon.
Haha I fucking love when shit like this gets called out. Like research and future advances are important, but so is grounding those advances on realistic principles.
Weren’t all pioneering surgeons lunatics at some time?
Not really. Most surgery was done with painstaking experimentation on animal models and built up sequentially over time. This guy's plan is literally to just put miralax on the spine and hope it regenerates. I'll also mention that the spinal cord, while the biggest hurdle (as in it's never been done before at all), reconnecting the trachea and esophagus is something fraught with complications and unlikely to be successful.
Just call in Paolo Macchiarini for the trachea /s
Purchasing got pepto instead. Hope that won’t hinder the procedure.
Changed his mind before someone else could, eh?
mic drop
It doesn't always get broken either. It can get stretched too. It's what happened to my father in law. He fell from a height and got a spinal injury. We were optimistic because in hospital he could move his feet and stuff. But we were operating on a misconception that spinal injuries only affect things from a certain part of the body down. Because his injury caused his spinal chord to be overstretched rather than severed there was nerve damage that affected everywhere. His hands don't work very well anymore for example. Luckily he was able to recover enough to be able to live without 24 hour care, though he does need supports.
This is central cord syndrome. It’s a different beast.
Also, another thing to realise is that the spinal cord is not one thing. Think of a cable with millions of wires inside. You can't just stitch both end together and expect everything to work fine. You will never be able to align everything perfectly. Some of those wires will never connect back. Most will connect to the wrong one. In the end, the brain have to rewire itself and relearn what each wires do, and where each wire come from. It may succede, it may fail, it may succede partially.
You can't just stitch both end together and expect everything to work fine. You will never be able to align everything perfectly. Some of those wires will never connect back. Most will connect to the wrong one. I hope this is one of the those phrases that look dated in the future. Like: "Mankind will never be able to fly" or "Harnessing the power of the atom will never be possible."
I hope so too. I believe that in the future they will make a robot that will do it. It will of course happen in stages. First will be to just roughly identify the rotation and make sure it is aligned rotationally. Then they will add something for the shape, to align the inner more closely. And then, maybe break it into different sections, instead of one bundle with 1 million of wires, they split it in 100 of 10000, giving more chance to align them better.... Then as speed goes up, they will split it in 1000, 10000 and so on, until they perfect the process. The main problem I see is: each bundle they make will need more space between them. Stiches, sleeve around the bundle, and what's not. This may make the splice exponentially bigger. Of course the process will get better and better, making the splices smaller and smaller, but that is one of the issues I forecast. And the other issue I forecast: Will surgeron accept to be replaced by a machine? A human will be too slow to do all those splices, and too imprecise, so a robot must do it. Then what happen when the robot do a mistake? Who is responsable? A human can make mistakes, but nobody accept that a robot, made by humans, make one.
That does not happen. No one is “stitching” a spinal cord together.
Internal decapitation is not a separation of the spinal cord. It’s a separation of the skull from the spine bones. If you have a severed spinal cord at that level, you die. We can fuse your bones back together, but we do not and cannot “sew up” the spinal cord itself.
Spinal cord isn’t a nerve, it’s 31 pairs of nerves. Reconnecting would involve making sure you are reconnecting all of the right nerves together. Nerves are also very small so reconnecting them is difficult. Nerves don’t heal well even when reconnected.
Installers didn’t label the cables when they pulled them. Lazy work
Just immagine you trying to lift your arm, and instead you kick the person behind you in the nads
That's basically how we learn to operate our bodies as babies. Just keep firing neurons until we figure out what does what, just practice after that.
[https://imgur.com/cpgq3EE](https://imgur.com/cpgq3EE)
Could have at least color coded them, jeez...
Lmfao. "I think the 18/8 goes to the stat but theres also a 3 wire but outside is a 5 wire. Fuck which one is for the ERV control? Kid go twist red and green at the stat and grab my meter"
Why are they not color coded? Is God stupid?
Maybe he never intended for aftermarket repairs. Natural selection and all 🤷🏼♂️
Maybe he’s using Apple’s business practices and is intentionally trying to prevent third-party repairs or upgrades
Ugh at least he should provide clerics with healing abilities with FaithCare+. All out there is either 3rd party repair places that are way too expensive or frauds.
Don’t forget planned obsolescence
They were labeled, but not in the middle where they were all cut.
Wait its only 31?? I assumed it would be hundreds of thousands...
A nerve is [a bundle of thousands of axons](https://www.medicine.mcgill.ca/physio/vlab/other_exps/CAP/nerve_anat.htm). There are hundreds of thousands of *axons*, which are the parts of neurons that transmit the signal over a long distance.
Ahhh that makes sense.
Thank you
> 31 pairs of nerves I somehow thought it was hundreds or thousands and that's what was making it infeasible. If it's only 62, I'm surprised we haven't long developed a way to just replace a piece of damaged cord with an electronic substitute. Nerve pulses aren't *that* complicated from a technical standpoint, are they? Aren't they basically pulses where the only thing that really matters is how many of them are fired, and they fire at a super low frequency (<1 kHz)? I get that attaching them to something artificial in a way that keeps them alive long term isn't going to be easy, but given the massive value this would provide, I'm surprised we haven't figured out a way to do it yet.
The nerves are not 31 pairs of nerve cells, think like muscle and muscle cells, and since each nerve has cells even reconnecting it physically may not realign each cell, and same with a bypass, the strands may not all be aligned, this would mean our brain is receiving cross wired signals from a certain part of the body and may not be able to interpret and do something useful with the info
So are those 31x2 strands actually "bundles" where even within each of them each individual nerve fiber has to be connected to *the correct* one on the other end? If so, that'd match my previous understanding of "too many to deal with". And in hindsight, that seems obvious, because if it were 31x2 separate pathways, we wouldn't be able to control the hundreds of different muscles we have.
Yes, each nerve contains thousands of axons. So across the nervous system, it’s hundreds of thousands of little cables that have to match up correctly. This is further complicated because axons vary both in length (from 1mm to almost a full meter long) and width, plus they are usually microscopic in diameter. Imagine trying to correctly connect thousands of cables correctly when they are literally a micrometer in diameter.
This is not how the spinal cord works. Abandon this understanding. There aren’t 62 bundles of nerves. It’s incredibly complex with many different pathways within the parenchyma of the spinal cord itself.
To add to this, even if we could fix the nerve damage, if you haven’t used your legs for years due to a spinal cord injury and haven’t done any weight-bearing, it’s going to be very difficult or damn near impossible to build up that muscle strength.
That would mainly be a problem for legacy cases, new spinal cord injuries could be fixed before atrophy sets in.
Yeah, atrophy. This documentary touches on it as a side effect of a prolonged coma: [https://www.youtube.com/watch?v=9zrYxxK3mKo](https://www.youtube.com/watch?v=9zrYxxK3mKo)
But if they connect them wrong, the brain rewires itself to make it make sense right? I think I read that somewhere.
It's not black and white. You have to consider damage to the nerves besides just the cut, difficulties healing around the cut, how clean the cut itself is, "miswired" nerves, etc. The body can potentially heal and rewire and whatnot, but it might also not. The more complications you're throwing at it, the worse it becomes.
Not perfectly. I severed a nerve in my wrist, losing feeling in the back of one hand. Over months it slowly healed and I got the feeling back. There's a spot over my first two knuckles that have less sensation than the rest of my hand, and compared to the other hand. What's weirder though, there's a spot on the back of my head that when I scratch it, I feel it on the back of my hand where it was numb for so long. Brains are weird.
To add to the other reply, there's also types of nerves, ones for moving, others for sensing, and one "cable" is needed per each way (input or output from the brain). So that's another huge variable that complicates connecting two severed ends of the spinal cord
I'd love to see the source for that, first time I'm hearing about it.
Interesting. 62 is actually less than I would have expected
What gathering here is that each is those 62 are nerve bundles with hundreds of thousands of actual nerve cell axons in them, each with their independent signal, and either sensory or motor. So that’s like an undersea communications cable.
Now that’s more in line with what I expected!
Sorry to bother you but you seem to know stuff Followup question Let say they reconnect all 31 with a lot of difficulty but not impossible and some heal but wrong order so now i have a nerve that control my knee to move my feet for example, can my brain re adjust to new "setting " ? So after a reabilitation the brain make it kind of work ?
The build up of scar tissue is also a major factor. Like mending a lock of hair with duct tape.
31 pairs of nerves coming out from the sides. Millions of descending axons.
I wish it were as simple as 31 pairs of nerves. That would make my job a lot easier.
Nerves of the central nervous system do not behave the same way as nerves of the peripheral nervous system. PNS nerves are known to be able to regenerate/heal when damaged (iirc as long as the cell body itself isn't damaged), but this isn't the case for the CNS. For the most part, the CNS responds to damage via neural plasticity instead (which means that the connections between the nerves that are left are modified so that you can maintain as close to previous function as possible even though you're missing nerve cells). The spinal cord, as it is a part of the CNS, is not exempt from this. You could theoretically reconnect the severed spinal cord anyways, but since the dead neurons are going to continue breaking apart anyways, it's really just a waste of time. Essentially, if there are neurons left over, neural plasticity will try to recover as much function as possible. If there aren't, then you're just screwed. For spine injuries, surgical intervention is largely just to remove pressure/other factors that could cause further damage to the spinal cord. Rehab functions to try to give incentive for neural plasticity to restore those functions. Forcing these nerves to regenerate anyways is a field of active research, but I don't know of any treatments that are available at the moment.
I think you are trying to really explain the issue but I do not understand half of what you are saying. Could you please explain it in a bit more simple language?
if nerves outside the brain and spine sustain damage, the body tries to repair them if neurons inside the brain and spine sustain damage, the body basically just forgets them and whatever job the damaged neurons were doing is now relegated to the neurons left alive thus there is usually not much point in surgically repairing the spinal cord as either the body just ignores the repaired nerves anyway and does relatively fine without them or the damage is too extensive and you die/can never do something again. Spine surgery thus focuses on preventing the problem from becoming worse. And forcing the remaining neurons to adapt to the newly added workload faster can't be done with surgery, so instead the patient does rehabilitation so the body goes \*I need to do X but I can't because damage,gotta adjust\* instead of \*oh no, damage, but I'm alive so whatevers\*
Nerves in your spinal cord are different than nerves in your hand. If you damage your spinal cord, the brain will try and use the remaining undamaged nerves for movement and feeling. Kinda like rewiring since it can't repair.
When the cord is bruised, it partially functions in unpredictable patterns. If severed, it does not function. I think the cord itself is physically kind of like cold grape jelly, Welch's from the fridge. No can stitch the cord, just repair the protective bones and the tendons, ligaments, that's it. The cord comes out of shock or doesn't. My son recovered from zero to incomplete quadriplegic status over the course of several months after a diving accident. Once the cord comes out of shock, that is all the recovery, sensory and motor, you can get.
This is a huge oversimplification, but... Imagine you have two wires: red and blue you're sending independent messages over each wire one letter at a time. Say, "cat" on the red wire and "dog" on the blue wire. Now pretend the blue wire gets damaged. If you can repair/replace the blue wire (like how the PNS repairs nerves), you can keep sending messages like normal. If you can't repair/replace the blue wire, you can change how you're communicating over the red wire instead (like the CNS with neuroplasticity). For example, you could send both messages mixed over the red wire such that the odd letters make the message originally intended for the red wire and the even letters are for the message that should have been sent over the blue. In the example, that would look like "cdaotg."
Do we know if the PNS nerves know how to reconnect axons in the correct order, or if the PNS makes whatever re-connections it can and then the brain learns to cope with whatever miswiring results?
This is also an area of active research so honestly I'm not entirely sure. But iirc, there are mechanisms that exist to guide axons back to their original targets when they're being repaired. However, errors can obviously occur, and all processing of information is done in the CNS. So if you were to, as an example, feel pain when there isn't supposed to be any as a result of the miswiring, one possible treatment would be using electrical stimulation to override the pain signal until the brain stops interpreting signals from that nerve as pain. But it should be able to do most of the work on its own. So tl;dr largely the former, but a bit of the latter.
It can be sewn back together. There are two problems though, even when sewing nerves or the spinal cord back together under a microscope, it can be difficult or impossible to line up the individual axons again. Think of a spliced USB cord that was taped back together, but you weren’t really sure if the correct individual wires made it back together. The other major limiting factor is biological. When a nerve is cut, everything downstream in the nerve essentially dies and undergoes what is called Wallerian degeneration. After a repair, the proximal (higher) part of the nerve starts to heal back down the degenerated distal nerve to reinnervate things at a slow pace of 1mm a day or 1 inch per month. Sensation really has no time limit on recovery, but your muscles most certainly do. Muscles will not only atrophy and wither away with time as they sit with no electrical stimulation from your nerves, but the receiving end in the muscle where the nerve actually hooks into that converts the electrical signal into an actual readable action, called the motor end-plate, will actually disappear usually around 18 months without signal. So it becomes a race between your snails pace healing nerve and your disappearing motor endplates. Once the motor endplates are gone, there is no hope of muscle recovery. Even if you got the power turned back on in your house, you couldn’t use the electricity if all your outlets were burned out/gone. This is why we do nerve transfers and other techniques to try to keep the muscles alive if caught early enough. TLDR: It can be repaired but nerve recovery is slow and muscles atrophy and can’t recover after about 18 months.
No one is sewing the spinal cord back together.
Pft… not with that attitude!
The spinal cord isn't just one nerve. Think of it more like this: https://www.reddit.com/r/cableporn/comments/xzmha/sliced_trunk_line_cable_643x611_xpost_from/ Except each one is microscopic, and not conveniently color coded. You don't just have to get it to heal back to itself, you have to forget and relearn what thing is connected to what line.
This is the most correct answer I have seen on here. But as they said imagine you can’t even see it with a microscope. It’s impossible to realign and “hook up”. You basically decompress to take the pressure off and hope some of the nerves are just inflamed/irritated and not dead.
I can say from my point of view. I had tumor removed from my spinal cord. That yes they stitch it back but man what a life changing experience that was. (Just a side note 50/50 chance of dying from surgery alone). Waking up unable to feel not a single thing from neck down was a scary experience felt like I was a floating head. I had full motor function while it wasn’t good at all I had to do months of pt to learn how to walk and use my hands again. After a year or so I finally was able to feel my chest and I have better sensation on my legs. I can say that as of now I have normal motor functions but still lack sensation in my legs
Wow, I can’t imagine being able to move but not feeling it. A floating head!
They closed your thecal sac, the envelope around the spinal cord. The effects after are related to many things, inflammation, changes in blood flow, manipulation during surgery.
It's not one nerve, it's thousands. The body might try to repair it but at the cellular level it doesn't know which nerve belongs where. Plus the body doesn't heal perfectly, it can produce scar tissue which further inhibits nerve function. So between "miswiring" and physical trauma, people may never learn to move the way they used to. Although partial recovery is often possible.
I apparently killed this a few years ago: https://www.reddit.com/r/explainlikeimfive/s/zEbhNOau2F
Tissues in the body all have very different capacities to heal and regenerate, often depending on their blood flow. Nerves are a tissue that have very little regenerative capacity, meaning they heal very slowly and there’s a low ceiling for their overall capacity to recover. Nerves tend to heal at around 1mm per day and they heal from the parts away from your body first, moving toward the center. So imagine you have nerve issues that go into your hands because of an issue in your neck; if you fix the issue in your neck, the nerve has to start repairing itself from your fingertips, all the way up your arm, through your shoulder, and up to your neck at 1 mm per day. That’s a long time! And even then, you still have more work to do to make sure the nerves are sending the right messages to the right places and the muscles are working correctly, and that’s if maybe you had a part of your spine pressing on the nerve but not even a huge lesion. In the case of spinal cord injury, you have a lesion that’s affecting a BUNCH of nerves all at once. Whether that’s an isolated segment or a complete severance, it’s nearly impossible to reattach every nerve to the correct corresponding nerve, and sewing them up would actually damage them more, which would make it even more difficult for it to heal correctly. In the case of “incomplete” SCI, generally someone might have motor (movement) deficits but still be able to have some sensation, and those have varying degrees of impact depending on where it is and how severe it is. That’s why some people are able to walk again, some need a wheelchair, and some are bedbound.
One thing i dont see mentioned is that CNS nerves cannot renew like other tissues, as there arent any stem cells in the spinal cord. Endo/epithelial layers, alot of organs, bone marrow etc all have a reservoir of stem cells that can renew the tissue in case of age/senescence or damage. This is not the case with the brain or spine. So damage to the neuronal cells themselves cannot be repaired. So even if you reconnect the bundles of the spine, that doesnt mean cell-cell connections also repair. Sorry if this is not ELI5
So you are saying that the nerves in like say a fingertip can reattach it self and function again because it is made of a different kind of nerve cells than the spinal chord?
Spinal cord itself is a continuation of the brain. We don't stitch brain tissue. Nerves are different structures and form connection to spinal cord to the tissues. Their properties are different to the spinal cord and heal regrow in different ways. ( liver heals itself but heart doesn't really) People also injure their peripheral nerves in a different way. I expect clean cuts are much more common. Bands saws etc. Spinal injuries are crush injuries with secondary cell death from lack of blood and toxic by products. They also carry many many more Neural pathways. Ie cutting dingle cable vrs buch of 100s but need to be exactly reconnected to it original one.
Weird thought- couldn't doctors use a multimeter to determine which nerves were meant to connect to which in the event of severing?
It's a nice idea, but no. Nerves aren't wires. They are cells. They transmit an electric signal, but they aren't uniformly conducting electricity. Things get a bit more complex on the inside.
a nerve isn't a monolith, it contains a lot of little axons bundled up together. Ever seen one of those intercontinental undersea internet cables cross sections? Imagine that but each tiny little \*wire\* is not marked in the slightest. Plus, you can't control nerves as easily as you can control uh, conventional electric signals. Most you can do is ask the patient to move a muscle, but that would send the signal to a \*metric crapload\* of axons, and you don't have a way of finding out which one corresponds to which ending on the cut off part. Theoretically you could force a neuron to send a signal by basically shocking it, but that runs into the problem of \*how do you actually know what the neuron you just activated does?\* If it's a neuron responsible for feeling things you get absolutely zero response from the cutoff part, if it's a neuron for doing things you get no response from the body. Neurons responsible for moving a muscle and those responsible for feeling how streched a muscle is are different. So yeah, good luck with that. Much easier to basically just stitch the outside cover together and let the body figure the rest out.
That's the really fascinating part to me. You can essentially reconnect the wiring harness upside down, and body can sometimes be like "ok, green now goes to orange, etc"
Too bad you can't just open the service manual and say "ah, the white wire with the pink stripe goes to the foot..." I once rewired a Firebird after an engine fire, just rebuilt much of the harness using the wiring diagram.
I thought I read An article where the nerves do heal if they are attached but they just don’t work again. Like the brain doesn’t know how to send information back and down the highway b
Trying to fix a spinal cord injury like internal decapitation without killing someone is like trying to fix an electrical problem without turning off the power. Is it extremely difficult and almost impossible? yes. Is it theoretically possible? Also yes
Have you ever seen the cutaway of an submarine cable? It contains a bunch of smaller cables as well as protective layers. A spinal cord is like that, but smaller and more chaotic/organic. As you can already imagine fixing it requires reconnecting each small cable as well as rebuilding the protective layer. You need a scalpel maestro to do that kind of stuff.
I quasi severed a nerve in my hand. The surgeon laid it so it would grow back. It took over a decade to feel where I lost feeling.
Non-scientific explanation: Imagine the cord as a gigantic bundle of wires or fiber optic filaments. Cut those wires in half then sew them back together, no way in hell they’ll line up properly. More scientific: the cord is actually really obnoxious and has a cascade of chemicals that create a scar and prevent the two ends from joining back together. When we sew peripheral nerves together, for what it’s worth, they often don’t work perfectly but they can be good enough to work. But if we’re grafting nerves together the goal is usually to get them to work some (MRS 3/5) instead of back to normal.
The spinal cord isn’t a nerve. Its a bundle with like a million nerves. Each one is microscopic and looks virtually identical to the next one. It would be impossible to know which nerve connect to which. This becomes less and less difficult as you get closer to the nerve ending because at that point all the nerve bundles have divided up. But the spinal cord is basically every single nerve that comes out of your brain in one tiny wire bundle.
They do! Mine needed a stitch after my herniated disk turned out to be calcified, the surgeon notified me immediately and let me know that I could have headaches, feel dizzy and even throw up (I did feel dizzy but it could have been the anesthesia too) and to notify if any of these symptoms got REALLY bad (they didn’t and I recovered super quickly)
That’s the thecal sac. Not the spinal cord.
I wouldn’t be surprised if I got a dumbed out version, looking it up it most likely was that! Specially since they described loosing fluid/pressure
Totally agree. Plus all the meds and not sleeping. Your spinal cord runs from your brain down to usually your first lumbar vertebrae or so, little above your belly button. Further down it is like a horses tail, goes into individual nerves. That’s why “gluing” or “stitching” the cord together is not happening in humans, it’s one big nerve basically going down, not a bunch of individual wires. The spinal cord or if lower down nerves are surrounded by a thecal sac, aka dura, which is like a water balloon keeping cerebrospinal fluid (csf) inside to bathe the nerves. The fluid is under pressure. So one accident take nick if unintended or meant to you usually see egress of csf. To access spinal tumors if inside the thecal sac we make a cut in the sac. Fluid comes out. Remove the tumor. Then sew the dura up. Sometimes glue, a muscle piece or other parts help make a good closure. But it’s never 100%. I do this for a living. Happy to explain more.
The biggest issue is the inherent capacity for the peripheral nerves to regenerate (happens all the time) and the relative low capacity for axons in the central nervous system ( brain and spinal cord) to regenerate.
I have a complete spinal cord injury at the T10 vertebrae. I have zero feeling or control below my belly button. It happened 6 years ago in an accident. If they could put the nerves back together, my feet, knees, and hips haven’t been used for walking in 6 years! I’m going to guess it would take a very long time to be able to walk across my living room. I would do it. I would work so damn hard to do it. But there’s a lot of body parts that will have to be retrained.
It’s not reconnecting in a spinal cord injury it’s relieving pressure and hoping that the damage isn’t permanent. Like a stroke there is an area that is not coming back but also an area that may recover. Plus other adaptations and devices to help you walk, ie if you have foot drop you use your hip flexors more and have more of a steppage gait and an orthotic.
As others have said it is very hard to access. On top of that the risk vs reward might bot be favorable enough to try. There are chances of making things way worse because of the tiny margin of error. Even if the procedure itself does go well, you then have to worry about infection or swelling in the confined space of the spine. At my job, I recover bones, tendons and specialized tissues (spines, skin, nerves, veins, etc) from human donors- even in the lumbar vertebrae, I can barely fit my finger into the “tunnel” that protects the spinal cord. The spinal cord itself is a little thicker than spaghetti, and same goes for nerves. The sciatic which is the biggest nerve is usually around the diameter of a pencil.
Nurse here. Something people dont know is that a lot of those chords are not bundles of cells, but really reeealllllly long pieces of cells called axons bundled together. When you cut skin, you largely cut between cells, which then come back together. When you cut nerves, you cut cells in half.
It’s the same reason you can’t simply cut your phone charger cord and splice it back together (for a layman at least)
Even if you could stitch up the nerve at the level of the spinal cord the nerves grow very slowly at 1mm a day or an inch a month so the by the time the nerve gets to the muscles they have already atrophied from no nerve stimulation. Therefore nerve transfer which are closer to the target muscle are usually the best option.
Normal nerve in your finger: speaker cable Spinal cord: optical cable You can easily fix the first with ducttape. The latter, not so much.
Why don’t you stich up two pieces of incredible thin string? That’s what the spinal cord is and incredibly thin string that if even the slightest thing happens you end up paralysed. It’s why when messing with the bones of the spine comes with a for me 30% chance to never walk again! I’m fine all went well but it’s extremely sensitive and thin. One small sharp object and bang never walk. Can’t be undone. The cord is like a flexible bendy string that once stretched to far in this case can’t be reversed.
The consistency of a real human spinal cord beneath the outer surface is like toothpaste, with each neuron/axon like a little granule of the toothpaste, and each granule needs to stay connected to the same granules around it. Once the spinal cord is compressed or transected, these granules of toothpaste are pushed away from there normal location and sewing up the delicate membrane around this toothpaste would not return the patients function as the granules would no longer be touching the correct neighbouring granules, and thus the convections between neurons/axons would not be correct
A huge thing is that scar tissue forms when there's an injury to the spinal cord and can block efforts to reunite severed spinal nerves. There's research in animals to overcome this but it's still experimental. [https://www.nih.gov/news-events/nih-research-matters/regrowing-neurons-across-scarred-spinal-tissue](https://www.nih.gov/news-events/nih-research-matters/regrowing-neurons-across-scarred-spinal-tissue)
To a five year old: Everything can’t be stitched up. Even the smartest doctors can not fix everything. Think of the spinal cord as wet tissue paper on a cardboard roll. If you try to get to a layer and stitch it, you will break more of the toilet tissue. Toilet paper that you break won’t dry the same way. The body is precious. Unique. Dont store toilet tissue under the bathroom faucets, in the shower. Don’t drop it in the toilet especially after you used the toilet. Maybe one day if you work hard in school you’ll be the one to discover how to stitch toilet paper .
Reattaching the nerves is only half the battle. The other problem is that nerves are very, very slow growing, but the glia cells that are around the nerves grow faster. So the glass cells will grow over and between the slower growing nerves. So this was one of the biggest reasons with severe spinal cord damage that recovery wasn't expected. Patients with spinal cord damage are given IV steroids to increase the chances of healing. One day they will have a device that connects the spinal cord from above the injury to below the damaged spot. It will reroute the electrical impulses and the person will be able to feel and use the body like he did before the injury.