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Thread: American Spinal Injury Association (ASIA) Impairment Scale

  1. #11
    seneca, I am not sure. There is one paper in 1984 which describes the electrophysiological characteristics of cells that are backfired from the lateral reticular nucleus, and that these cells are responsive to deep pressure (noxious) stimulation of the limbs. Backfired means antidromic or backward activation by stimulating axons in the lateral reticular nucleus, a brainstem nucleus. So, there is a distinct possibility that the spinoreticular tract may carry such information.

    Note that the spinoreticular tract is ascending counterpart of the reticulospinal tract. I was unable to find a picture of the former but the following is a picture of the reticulospinal tract

    The spinoreticular tract which is the sensory tract that goes back to the brainstem is part of the anterior lateral tracts of the spinal cord, i.e. located in the front and side white matter column. The reticular formation neurons that receive the information then relays the signals to the parafascilar nucleus and intralaminar nuclei in the contralateral thalamus. It is believed to be selectively involved in the perception of deep pain.

    • Menetrey D, de Pommery J and Besson JM (1984). Electrophysiological characteristics of lumbar spinal cord neurons backfired from lateral reticular nucleus in the rat. J Neurophysiol 52:595-611. Summary: Spinal neurons antidromically activated from either the lateral reticular nucleus (LRN) or immediately adjacent areas were identified in the rat lumbar spinal cord. In agreement with previous anatomical work (60), these neurons were widely distributed in both the dorsal and ventral horns of the spinal cord and could be subdivided into three main groups according to their location: a) deep ventromedial (DVM) cells, which project more substantially to the LRN than to other supraspinal targets; b) cells of the median portion of the neck of the dorsal horn (mNDH), which project exclusively to the LRN; c) cells lying in other parts of the dorsal horn (superficial layers, nucleus proprius, reticular extension of the neck), by their location, they are indistinguishable from cells projecting to other supraspinal targets. The probability is high that the DVM and mNDH cells contribute exclusively, or at least preferentially, to the lateral component of the spinoreticular tract (lSRT), defined as the direct spinal pathway to the LRN. Although electrophysiological properties of cells were clearly related to their spinal location, several subpopulations could be recognized in each of the three main groups. The majority of DVM neurons were in lamina VII, with some in laminae VI, VIII, and X. With the exception of a few lamina X cells, the DVM neurons had high conduction velocities. Four subpopulations of these neurons were recognized. a) Innocuous proprioceptive cells responded to small changes in joint position, some showing convergence of nonnoxious cutaneous inputs. b) High-threshold cells (approximately 50% of DVM cells). Seventy-five percent of these cells were excited from bilateral receptive fields (mostly symmetric) with noxious cutaneous pinching that extended to subcutaneous tissues. Their evoked responses had long-lasting postdischarges that continued up to several minutes after cessation of the stimulus. c) Inhibited cells had no demonstrable excitatory receptive fields and a high ongoing activity that was tonically depressed by pressure or pinch; poststimulus effects of long duration were observed. d) Cells with no resting discharge and demonstrable excitatory peripheral receptive fields. mNDH cells had recording sites at the medial border of the internal portion of the reticular area of the neck of the dorsal horn.(ABSTRACT TRUNCATED AT 400 WORDS).

  2. #12
    Senior Member jb's Avatar
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    i'm an asia a but i can feel my hemorrhoids. why isn't that considered sensation of s4/s5? it's in the anal/rectal area.

  3. #13
    jb,

    Are you sure that you can feel your hemorrhoid? I assume that you are feeling pain in your rectum when you say that you are "feeling your hemorrhoid". I am not questioning the fact that you are feeling something in your rectum but it may not be sensation.

    On the other hand, if you can feel a suppository being placed in your rectum, or pinprick around the edges of your anal sphincter, that is definitely feeling and I would say that you are not ASIA A but probably ASIA B or C, depending on whether you have any voluntary motor function below your neurological level.

    Apparent sensation can come from a place in the body without being stimulated. In such a case, it may not be sensation, but neuropathic sensation or pain. It is sometimes called phantom feeling.

    Wise.

  4. #14
    seneca, I assumed that you would understand but did not state explicitly that we should be careful extrapolating finding concerning spinal tracts in rat to humans. While humans and rats have many similarities, they also differ in several important respects. First, the corticospinal tract in the rat is located in the dorsal column while it is located in the lateral column in humans. Second, animals have some prominent reflexes and are absent or suppressed in humans; they, for example, have a motor reflex called the cutaneous trunci reflex which contracts the skin that is stimulated, i.e. shaking a fly off when it lands on the skin. Third, most animals are of course quadripedal with tigher forelimb-hindlimb coordination than bipedal humans, as well as differences in locomotor reflexes.

    Note that the differences are not as great as some people think. For many years, clinicians dismissed work being done in rats as being predictive of human motor recovery. I shared this belief and consequently did experiments on cats. However, after now nearly 15 years of observing how they walk, I am becoming more and more convinced that the mechanisms of sensation and walking are not that different in rats. The main problem, of course, is that there is a dearth of detailed neurophysiological data from human that tells us which spinal tract does what.

    Wise.

  5. #15
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    Dr.Young,

    You are so patient to take the time to answer questions.

    I am very confused about where I am on the ASIA scale. I am a T-12/L-1 with no bowel/bladder control. I have never been tested by a doctor for sensory/motor function. I do walk with leg braces and crutches. Yesterday I did an hour on the treadmill.

    Because I can walk am I considered incomplete or does the lack of B/B make me complete?

  6. #16
    I am a C6 class D per Spinal cord unit Augusta Ga VA Hospital. You definately will need to go to someone who does spinal cord injury assessments not just any doctor. Sorry but the average doctors are good in their respective fields but not with spinal cord injuries. I can walk with a cane, but it did and does not come easy. If a mosquito lands on the hair on my leg I know something it there, however if it bites me it may not itch, depending on location. If it is on my left ankle it will itch on my thighs it will just make a whelp. My right leg is the best for movement but my left has the best feeling for hot cold etc. Its a crazy body we live in.

  7. #17
    Redford,

    Your injury level is the most difficult level to diagnose and classify. The following may be a little confusing so let me first define some of the terms. When I say T12 or L1 bony segmental level, I am referring to the T12 or L1 vertebrae and not the spinal cord. As you may know, most of the lumbosacral spinal spinal cord segments are located at T12-L1 bony segmental level. The conus or tip of the spinal cord (S4/5) is just below the L1 bony vertebrae. Below the conus, you have the cauda equina which includes many of the lumbar and sacral spinal roots heading downward and out the appropriate openings between the vertebral segments.

    An injury to the L1 and T12 vertebral level is likely to damage the sacral gray matter of the spinal cord. Depending on the extent of damage, the injury may have spared the lumbar spinal cord (located at T9-T11 vertebral levels) but may have damaged the S1-5 spinal cord which contains much of the circuitry that controls the bladder. The circuitry that controls the anal sphincter is at S4/5. Note that neurons that control the toes are situated at spinal cord level S1. Can you wiggle your toes? Also the S2 dermatomes are located on the back of your thighs, S3 around your buttocks, and S4/5 around the anus.


    So, based on your description, you may have a sacral neurological level, perhaps S1. You should have little or reduced sensation in the back of your leg and buttock. If you have no sensation around or voluntary contraction of your anal sphincter, you would be an ASIA A with a neurological level of perhaps S1. If you have sensation around your anus, you would be an ASIA B with a neurological level at S1. If you have any voluntary contraction of your sphincter, you would be considered an ASIA D (since there are no key muscles below S1 that can be used to distiguish between ASIA C or D).

    Actually, I would love to have some experienced physiatrist on board here to discuss and debate these issues because I suspect that there may be disagreements amongst clinicians concerning how to classify a patient with your symptoms.

    Wise.

  8. #18
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    Dr. Young,

    Thank you for your response to my questions regarding the ASIA scale. I do have sensation on the back of my thigh and outer buttocks.
    My toes do move but I cannot control movement.
    It seems like the response is in slow motion, other times my toes curl - very difficult to describe.

    Is my neurological level then S-3?

    Thanks for all you do.



    Never, never, never quit. - Winston Churchill

  9. #19
    Dr. Young, do you have any explanation, in regard to axons, as to how I can have sensory function in half of a level? I printed off the classification test and we were testing with pinprick and light touch. My bicep on both arms are sensitive to both pinprick and light touch but only halfway down the bicep. Does this mean there are still some existing sensory connections at C5? And approximately how many axons are at each level? I believe I remember you saying there were on average approximately 12-15 million axons total? If only a certain percentage work, does that explain why some patches are more sensitive than others? If so, does your 10 percent rule apply to sensory function as to number of axons needed?

  10. #20
    Redford, according to the ASIA classification, the neurological level is the lowest level with normal motor and sensory function. As you describe, you can move but not control your toes, therefore your motor function at S1 is not normal. How is your ankle movement. Even though you can feel at S1, S2, and S3, this suggests that your neurological level is above S1. It may be L3, L4, or L5, depending on your motor function at those levels. Look in the classification booklet for the description of the key muscles for each of those levels.

    Carl, there may be dermatome expansion after spinal cord injury, i.e. a spinal root may receive information from an area larger than its original dermatome. Also, sensory testing at the edges of the dermatome may not be reliable. That is why the ASIA classification specifies a particular point where the pin sensation should be tested.

    Regarding the number of axons, I don't know what the minimum and necessary number of axons is required for normal sensation. However, I suspect that the number of axons varies depending on the dermatome. Some dermatomes may have more axonal innervation than others.

    Wise.

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