Paralyzed limbs

Hey so I had a thought during one of my overnight (happens a lot) about paralysis. We are currently able to implant electrodes into ourselves to connect to robotics such as arms and hands. Those are interpreting the signals from out nerves.

Now here's my thought. If we are able to transfer those signals into a robotic body part then why could we not use the same electrodes to transfer the signal from the good nerves, for say our legs, across the broken/disturbed section back to the same nerve line? Correct me if I'm wrong but if you are paralyzed you did not destroy the entire nerve for your lower body but damaged it at a specific point along that route. Why could we not put a "jumper" in to go around that section to get to the still functioning nerves? They would still work only the signal is broken so you don't receive it or can send it.

I don't believe it would be the "hey I'm 100% back to how I was before" but you would, in my opinion, be capable of at least moving the limbs if not being able to walk again to an extent. I feel like this is only something that can be accomplished on a recently crippled person.

My second question would have to be do nerves full on die if they are not used or is the wiring still good to use after an extended period of time?

Again it's a thought but aside from it being out of the reach of most if not all of us could this be accomplished in a medical facility like a hospital?


  • edited June 2016
    afaik its very hard to connect the right ones (and prevent them from coming unplugged), also they tend to atrophy if connected to electrodes if not supplied with the correct stimulus and some more problems with the chemical part of the connection i cant recall...

    I'd go for stem cells & such to see if the nerve cells reconnect on their own. 
    (they do connect to correct stimuli on their own.)

    Whats the US problem with stem cell research btw? (not directed at you, but a general thing)
  • Most paralytic injuries occur in the spinal cord, so it is most likely a large nerve bundle that is damaged and not a singular nerve fiber. 

    There are a number of projects that are currently being carried out that are similar to what you've just described.


  • @wyldstorm that's just it. The US does hate stem cells which is why I thought about that. stem would most certainly be the better route just its not accepted here.

    @posthuman at least the idea I had isn't completely mad. Some one else is equally out there ;)

    So inorder to mostly fix the damage you would have to jumper every nerve I. The bundle....that sounds very hard being the size and likely space there is in there.

    I could see the nerves atrophied if not supplied (the word i couldn't think of) with stimulus but wouldn't that be provided by the electrode? I would understand the chemical part but that too is to an extent still happening since its in the body right?
  • Hello All, 
           A few thoughts on this question that may explain problems with repairing the central nervous system (CNS): The damage is usually to multiple neurons and so rewiring the damaged nerve bundle would have to occur, as has been mentioned previously. To make matters more tricky, the spinal cord is difficult to operate on due to severe damage that can be caused to other nerves and the possibility of losing cerebro-spinal fluid into the body cavity.
          Another potential issue is the connectivity between the neurons themselves and their biological composition. Neurons generally take two forms (a blanket statement, but bear with me), they tend to be excitatory or inhibitory. Different chemicals and connections account for this variance and when multiple nerves of these separate types are linked together the network can become very complex very quickly.For instance, an inhibitory neuron may "shut off" another inhibitory neuron thereby allowing an excitatory neuron to function (it otherwise would have been inhibited by the middle or interneuron in our scenario).
          Then there's an issue that to my knowledge is still in question, yet there are clues suggesting an answer. You may have heard of cases in which severed fingers that are reattached within a short period of time and can retain function. Why does this only occur in the peripheral, and not the central, nervous system? One idea is that the peripheral nervous system (PNS) acts differently because it has a different set of support cells than the CNS. In the PNS Schwann cells provide a fatty coating to nerve fibers called myelin, which provides insulation to neurons. In the CNS the job of myelination is done by oligodendrocytes. Schwann cells provide myelin in a one-to-one ratio to neurons, they only insulate one neuron. Whereas oligodendrocytes can myelinate (turning our jargon into verbs, apologies if there's confusion) multiple neurons. The upshot of all of this is: damage to a PNS nerve resulting in nerve death also kills all the associated Schwann cells, leaving a large gap of area for new connections to form. Meanwhile, nerve damage in the CNS may kill many nerves without taking out many oligodendrocytes, so there is literally material in the way that blocks cellular regrowth. 
           I'm sure there are even more keen complexity to the system and I can conjecture some more on it if there's interest, especially one the Schwann vs. oligodendrocyte difference and ramifications..

    The CNS due to it higher functional complexity is characterized by greater structural complexity, and so repairs are often difficult due to a lack of biological knowledge and limited technologies to repair problems over long time scales.

    Hope that helps!
  • Yes that did help a lot more. Thank you for that bit of information ;)

    @helixfox it would seem then that the only way the bypass could work then would be on the PnS where there is no spine to really make it more difficult/complex. Am I correct in that statement?

  • That does get back to your original 'jumper' idea very nicely. So currently to ameliorate nerve damage to the CNS (brain and spinal cord) that restricts electrical signals from getting to the PNS (all other nerves) and the muscles themselves, recent advances seek to either a) regrow the damaged nerves, or b) outsource the job to a robotic limb.

            Regrowth is attempted through stimulation by an implanted electrode. The theory behind this is that neural growth is increased by the usage of that area of the neural network (i.e. the more often a cluster of nerves is activated the more resources and resultant growth within that cluster). 

            The use of robot limbs relies on an implanted microelectrode array that is surgically placed in a brain region known to be associated with a particular function such as left arm movement for example. This array picks up the frequency and firing patterns of neurons in its immediate vicinity, encodes the data and sends it to a computer. Currently this is reminiscent of Frankenstein as it requires a cable from the array through the skull to a device that sits on the head which is itself wired to a computer. 

           Here come the real crazy part, by having a patient with an implanted array think about the desired movement task enough, the signals from the array can be analyzed with some truly amazing algorithms, and then paired to have the robot arm perform the desired task whenever the particular firing pattern is sensed by the microelectrodes (insane, right?!?!). After time and lots of practice the number of movements that can be performed by the robot limb increases as the delineation between specific tasks becomes 'learned.'

           Linking back to the jumper idea, it would be incredible if the signals from the array once defined could then  link to a robot frame around, or connected to, the patients damaged limb. It is possible that pairing the limb with the signals sent to the robotic limb could retrain the organic limb into moving to commands from the patients brain. This would require a ton of research on the technology side of things, but if it worked the neural firing info could maybe be concurrently timed with electrode stimulation to the damaged spinal cord and over time the body could heal some of the damage. We are definitely approaching ( or have long past :) ) my concrete knowledge on the subject so I'll taper off here.

           Thanks for the awesome questions!

    If you really want to deep dive into the stuff here is a link to a review paper on neural interfaces with microelectrodes and the applications of such devices:

    Title: Assistive technology and robotic control using motor cortex ensemble-based neural interface systems in humans with tetraplegia

  • My original thought came from Kevin Warwick and his array for the robotic arm. The ability to retrain would definitely be an amazing thing. I know people with missing and damaged limbs often talk about ghost sensations of either having it or using it when it's not actually doing anything (I think that's the worst sentence I've ever wrote hahaha).

    I know about the implants into the skull but that seems just way to invasive and also not overly realistic for some on to have and use out side of a chair. I agree the robotic arm is definitely something that is severely needed expecially for a reasonable price.

    I'm sure I could come up with more questions but I'm out of them for now.
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