|12-15-2001, 11:56 AM||#1|
Join Date: Oct 2001
Spinal Cord Imagery
This may be a dumb question but does the technology exist to safely insert a dye into the spinal cord to view the actual damage? I would think that this would be necessary for researches not only to determine the best type of treatment but to also check to see if the treatment was successful. It would also let us (the patients) know our actual damage and what is needed for recovery i.e.
1. Remyelination of axons
2. Regrowth of axons
3. Regrowth of peripheral nerves, etc.
Given that some healing does take place in the cord wouldn't this be useful to know. If all that is needed is time for the cord to heal instead of medical intervention it sure would get rid of some desparate measures by people who are still in the early stages of recovery. It would also let chronic SCIs better pick the therapy to be looking for. Am I making any sense?
|12-15-2001, 02:57 PM||#2|
Join Date: Jul 2001
Location: New Brunswick, NJ, USA
Becky, I wish that there were such dyes and high resolution imaging approaches that would allow us to see at the cellular level.
The resolution of MRI depends on the magnet fields that are used. The magnets polarize molecules and these molecules (mostly molecules containing hydrogen for standard MRI machines) emit signals that then provide images of tissues. Since hydrogen is most abundant in water, the MRI signals reflect the water content in the tissue. There are small differences in water content between cells and mylinated tissues (which contain a lot of fat).
MRI is indeed able to detect areas of demyelination in people who have multiple sclerosis. They are able to show the presence of tissues. They can even show blood flow (using a technique called fMRI) but their resolution is not so great, probably no better than ±1 mm with the best scanners available. Axons and myelin probably are no thicker than 0.01 mm and therefore MRI is far from being able to image individual cells, axons, or myelin although they can tell us quite a lot about the quality of myelin in the tissue.
I want to point out that a thin layer of spinal cord that is no thicker than 1-2 mm in thickness would be able to carry enough axons to support some function. Also, just because there is continuous tissue at the injury site does not mean that there are sufficeint functioning axons crossing the injury site. To illustrate the inadequacy of MRI, if you ask a neuroradiologist to predict whether a patient is "complete" or "incomplete" based on MRI imaging alone, I suspect that the best would not be able to have a prediction rate of better than 80% or less. Let me see if i can find some information on this.