Ren, I can't explain it, and I don't think neuros can either. I think it just shows the limits of MRIs, and why they shouldn't reign supreme in the MS world. Grey matter changes are something we know little about, but are extremely suspect. I hope technology catches up with this before long.
My understanding from the Neuro-Rads and Rad Physics people that I used to work with is that the fluid tissue density in brain grey matter is pretty close, so it is very difficult to image with standard MRI. There are some experimental high field density MRIs that have shown promise in Grey Matter imaging (Oxford's 9.4 Tesla High Field.) There are also some Tc-99 SPECT and PET studies that can provide some information related to Grey Matter. There are also some new MRI Tensor Sequences that seem to provide better imaging of grey matter.
I think our resident Doc calls these technical steps "miracles." Mostly lots of math inside the computer. But it is really based on Radio Direction Finding techniques from
World War 2. The physics of the MRI magnet are a different case. Consider that the Earth's magnetic field is about 0.5 Gauss. A 3 Tesla MRI is about 60,000 gauss in the center of the bore. So the Oxford Research MRI is about 188,000 Gauss (or about 376,000 times the Earth's magnetic field.) And they can start imaging grey matter.
On of the things to keep in mind is that X-rays (including CAT) are real images. Things are where they appear. MRI is a "derived image." Things may not be where the MRI says they are. The magnet makes the H2O molecules line up and vibrate (fancy term is Molecular Precession.) The MRI knows the Z axis from the table and measures the signal strength for the various X and Y axis pairs with antennas in the bore of the MRI. Then the computer makes a XY map of the signal strength for each Z slice. The computer can then cut any plane through the 3D model. There are various excitation and relaxation times that are used and we hear these referred to as T1 and T2 sequences. There are also ways to get the dipole water molecules to "spin" in the field. These are the "PSE or Proton Spin Echo sequences" There are also setting on the "receiver" that listens to "attenuate" or filter some of the signals. And we can do more "tweaking" of the receiver data to clear things up in the computer using Fourier Transforms (differential calculus,) etc.
Bob (ex-BioMed Engineering Tech. and current IT Systems Engineering Professional)
They have proven that there are gray matter changes, although they're not visible on a normal MRI, mainly because gray matter has no or very little myelin - therefore no water to excite, so no picture.
However, they have done MRIs that look at the iron deposition in gray matter, and they've found that brains of people with MS have much more iron deposited than normal brains. It stands to reason that the gray matter would function less well as a result.
But all that aside, the brain itself is constantly losing axons with MS. This happens even without lesion formation. In a normal healthy brain, axons are being regrown all the time - in MS, more axons are breaking than we're regrowing. So eventually a person with very few lesions will show brain atrophy, as the brain shrinks.
Rendean, have they looked at the size of your ventricles compared to a normal brain?
My neuro has told me the same thing about not having the technology yet to image gray matter, at least access to that technology outside academic/research entities.
So, Ren, in a nutshell from what the others have soe eloquently explained, it is possible that there is damage going on in the gray matter and that damage, resulting in symptons, is not showing up on the MRI.
Why not bring this up with your neuro next time and see what he thinks. He seems to be a forward thinking doctor.
Bob = This is what is really happening. Thanks, Bob. Now I feel really smart. :))
A large portion of the neurology field needs to believe and does believe that the MRIs are the "end all" and that they show the real story and the whole story of what is happening in the brain. Thus, if there is not a spinal lesion, they will discard the finding of hyperreflexia. Now I do not understand how they can see that each advance in MRI strength and software sophistication shows more info than before, yet they insist that the MRI is a perfect diagnostic machine. No thinking needed.
But, there is also a large thinking group that realizes that the MRIs are a tool, and indirect tool and that they are still flawed. My neuro has said that MRIs don't even begin to show all that is damaged in the brain. He reads the "clinical picture" (the history and exam) still.
Even though our knowledge of gray matter lesions is growing, we still cannot image it easily or cheaply. Thus, the import of gray matter lesions, of axonal death and of the microscopic changes in Normal Appearing White Matter - NAWM - is mostly overlooked by the majority of our docs.
Thanks to all for your answers. COBOB your answer was great...guess I still have a little grey matter left!! Jen, your health Page is just as good explaining T1 T2.
So, the bottom line is my brain is losing axons and function even though my MRI is "stable" on 3T. This is the explanation for my down hill slide?
I only briefly talked with my neuro about my MRI done on Monday with a 3T. I will go into more depth with him on my regular appt in a couple of weeks.
Quick change of subject : Did my 3rd sphenopalatine block yesterday. If anyone here is given the opportunity to have this basically non-invasive techniquue should do it if 'atypical face pain" is in their list of symptoms. Great results for moderate discomfort lasting 20 minutes.
Hey, you went to med school and did a residency....Not me. I just hung out with smart folks that did interesting stuff. I did some of the early work with digitally reconstructed radiographs where we took CT data sets and turned them into what looked like xray films. I also did some work with layering CT with MRI and MRA images (for IMRT planning.) That's why I'm aware of the MR images not really mapping to actual anatomy. We were using fiduciary landmarks (copper nipple makers) stuck to 3 places on the skull to "reference" the different image sets.
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