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Thread: Severed Spinal Cord Recovery

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  1. #1
    Senior Member melikeconan's Avatar
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    Severed Spinal Cord Recovery

    I have a question about reconnecting a severed spinal cord. If a cure for SCI is found how would they go about reconnecting the correct "lines" together. I dont know much about how the actual spinal cord components but i assume there isnt one "line" that runs all the electric impulses to certain parts of the body. So if there are multiple "lines" that carry the impulses how would they reconnect them to the right "line"? If you dont understand what i am trying to say i will try to explain it better. If you do understand what i am saying then let me know if this is an actual issue as far as a cure is concerned.

  2. #2
    melike,

    Wow, we have a lot of ground to cover. Let me get rid of several misconceptions first. The connections in the spinal cord are not like wires. Please bear with me:

    1. Axons (nerve fibers) in the spinal cord are living parts of neurons (nerve cells). So motor axons (that are responsible for controlling movement) go from the brain to the lower spinal cord where they connect with motoneurons (neurons that control the muscle). Sensory axons (that are responsible for bring sensory information go from neurons present in the periphery (outside of the spinal cord) or in lower spinal cord to the brain. When axons are damaged, the part of the axon that is still connected to the neuron generally survive but the part that has been disconnected from the neuron dies. In order to reconnect, the still living part axon must grow across the injury site and then all the way down to their original connection sites.

    2. Yes, indeed, there are multiple "lines" or axons that transmit information up and down the spinal cord. The normal human spinal cord probably has as many as 20 million axons. Probably less than 10% of these axons are necessary and sufficient to support substantial motor and sensory return. This is probably the reason why many people with so-called "incomplete" spinal cord injuries will recover walking.

    3. A majority of people probably still have axons that cross the injury site. This is even true of people who have so-called "complete" spinal cord injury. So, for example, if somebody has 8% of their axons remaining at the injury site, regeneration only needs to restore 2-3% of the axons in order to get functional recover. By the way, these percentage numbers are estimated from animal studies and nobody really knows what the true percentages are for human. But, this gives you an idea of the number os regenerated axons that may be necessary to restore function.

    4. The connections do not have to be absolutely specific. As it turns out, the spinal cord is quite "plastic", i.e. use different connections for different purposes. In addition, many motor programs (such as walking, sexual function, bladder function, etc.) reside in the spinal cord and not many axons are needs to initiate the program. More axons are needed for control of the programs but these also vary depending on the function.

    I hope that I am not confusing you further. Please ask more questions and I will try my best to explain better.

    Wise.

  3. #3
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    i know I've beaten this subject like a dead horse but...
    If someone suffered infarction from T12 down, that is, not a specific injury site per se, but infarcted tissue all throughout the Conus, is current research not this far yet? If someone has suffered this but has some leg movement and patches of sensation, what does this mean?

    sherman brayton

  4. #4
    Sherman, spinal cord infarcts usually produce complex lesions that involve loss of neurons and some axons. Depending on the distribution and severity of ischemia, it may produce complex combinations of symptoms without a specific level of injury.

    In general, axons tend to resist ischemia longer than neurons. Proprioceptive and light touch sensations are mostly carried by neurons that are situated on the outside of the spinal cord. Presumably, most of these should still be present. Do you know, for example, when your legs or toes are moved and their positions?

    The spinal cord responds to injury by sprouting of surviving axons. These sprouts may connect with surviving neurons. There is likewise sprouting of motoneuronal axons (to muscles).

    For many years, the dogma was that no new neurons are created in the adult spinal cord. To my knowledge, due to this dogma, nobody has really looked in injured or infarcted spinal cord for the possibility of new neurons being produced. I have been thinking we should start looking. If new neurons are produced in the spinal cord after injury (from stem cells that are known to be present), this really changes things.

    There is some evidence to suggest that stem cells transplants will result in new neurons being produced in the spinal cord. A recent study from Johns Hopkins, for example, suggested that embryonic stem cells transplanted to mice with ALS will produce new neurons in the spinal cord.

    Wise.

  5. #5
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    So, unlike a SCI, anterior spinal artery infarction destroys the matter which is the spinal cord. I have proprioception and light touch intact, with a few weakly moving lower limbs, but my complete numbness with my bowel and bladder is a result of a destroyed Conus, not a more straightforward lesion. So treadmill therapy and Miami Project's current research would be uselss to someone with severe spinal cord destruction. Right? What happens when growing axons have no neurons to connect with? I would think that this type of injury would be ideal for research, since there is no clear injury site, but a mass of dead spinal tissue.

    sherman brayton

  6. #6
    sherman, the fact that you have some movement tells me that you have some gray matter in your lower spinal cord. I don't think that you should be assuming that you have a "destroyed conus". You certainly have not convinced me from your description so far. I don't think that you have any basis for concluding that treadmill therapy and Miami Project's current research would be useless to you. And, there is research going on right now that is addressing the issue of replacing neurons in the spinal cord. While it is true that neuronal replacement therapies are not as far along as regenerative research, this situation will change. There are many people who need neuronal replacement including all the people with polio, amyotrophic lateral sclerosis, muscular dystrophy, and other neurodegenerative diseases. There will be treatments for them. It is one of the reasons why I strongly support stem cell research because I think stem cells provide an important source of cells for treating neuronal loss. Wise.

  7. #7
    and a lot of traumatic sci need neuron replacement not just axonal regrowth as I understand it

  8. #8
    melikeconan,

    I forgot to say that "severed" spinal cords in humans are extremely rare. To me, that word means that the spinal cord has been cut through so that there are two ends. This is so rare that in over 25 years in the field, I have witnessed or heard of only several cases. The reason they are so rare is because the dura (the membrane that covers the spinal cord) is quite tough (indeed, the membrane was given the latin word "dura" because it is tough) and difficult to cut except with a bullet or sharp knife.

    The few cases that I believe may have had severed spinal cords involve a gunshot wound where the bullet ended up in the spinal canal, destroying a stretch of the spinal cord. These so-called "bullet-in-canal" injuries are rare and even then usually do not cause severance of the spinal cord. I have heard of cases where the spinal cord was surgically severed but have never myself seen one.

    Some doctors use the word "severed" quite cavalierly and without evidence for a severance of the spinal cord. Even when the spinal cord injury has been very severe where one segment was completely dislocated, crushing the spinal cord, there may still be some axons that remain. Even when spinal cord compression is severe and allowed to remain, there may still be some axons remaining.

    The big difference between a severed spinal cord and a crushed, contused (rapidly and transiently compressed), or compressed spinal cord is the presence of a gap. A vast majority of people with spinal cord injury do not have gap at their injurys site. The spinal cord may be narrowed (atrophied) even to the point of being ribbon-like and there may still be room for enough axons to pass through.

    I have witnessed spinal tumor removal surgeries where the tumor has grown in the spinal cord to the point that only a very thin rim of spinal cord remains. During surgery, after the tumor is removed, the remaining spinal cord can be so thin as to be translucent. Yet, some of these patients walk out of the hospital. Many studies in animals have shown that you can cut as much as 90% of the spinal cord and the rat or cat can recover walking.

    For many years, scientists have been trying the regenerate the severed spinal cords. In fact, this practice became mandatory in the early 1980's when several laboratories discovered that rats could still walk when over 90% of their spinal cords were cut and a thin strand of cord is left. So, the "string criterion" for spinal cord injury was proposed. To show that the spinal cord has been cut completely, the investigator has to pass a string underneath the cord and pull the string up through the cut site.

    Unfortunately, most of the investigators who use this approach to cutting the spinal cord in rats do not repair the dura after they cut the spinal cord. When the dura is not repaired, fibroblasts (cells that form scar tissues) invade into the spinal cord and produce fibrous scars. If the dura is repaired, fibroblasts do not invade into the cord.

    In the vast majority of human spinal cord injury, the dura is not cut open. Of course, in gunshot or knife wounds where the bullet or knife penetrates into the spinal cord, the dura is open. In most human surgeries, the dura is tightly closed to prevent cerebrospinal fluid leakage.

    So, Scientists have been struggling to regenerate cut spinal cords, trying to solve difficult problems that may not be prevalent in human spinal cord injury. At the same time, contusion injuries present different problems that have scientists are only now beginning to address. For example, a contusion injury causes widespread dieback of axons and gray matter. Since the early 1990's, a small group of scientists have been trying to convince the field that contusion injuries is more like human spinal cord injury and that they should start developing therapies for chronic contusion models. It has taken a while for this idea to take hold. But it is finally happening.

    Wise.

  9. #9
    Quote Originally Posted by Wise Young View Post
    melikeconan,

    I forgot to say that "severed" spinal cords in humans are extremely rare. To me, that word means that the spinal cord has been cut through so that there are two ends. This is so rare that in over 25 years in the field, I have witnessed or heard of only several cases. The reason they are so rare is because the dura (the membrane that covers the spinal cord) is quite tough (indeed, the membrane was given the latin word "dura" because it is tough) and difficult to cut except with a bullet or sharp knife.
    Just the same, can people with completely transected spinal cords still benefit from stem cell treatment? thank you

  10. #10
    Quote Originally Posted by clementine View Post
    Just the same, can people with completely transected spinal cords still benefit from stem cell treatment? thank you
    Clementine, there is a doctor (Henreich Cheng in Taiwan... You can search for more information about him in this forum) who specializes in the treatment of severed spinal cords, using peripheral nerve bridges and a cocktail of growth factors. Stem cell therapies alone are not likely to rebuild and reconnect a severed spinal cord, in my opinion. You have to do something to get the two ends of the spinal cord together. However, as I have said, I am skeptical about claims of severed spinal cords. They are very rare. Eisenhower.

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