Hi Martin,
for the MS study we were *very* careful to make sure that the white
matter in the regions of detected effect was normal appearing, so I don't
think it explains the thinning we saw. As for the effect you are seeing,
you'll need to look through your individual subjects to see if this is the
case. Do you have any T2 or PD data for the same subjects? You could look
at those for the suspicious ones to distinguish damaged wm from gray
matter. David Salat has thought about this much more than I have, and may
have more to add.
cheers,
Bruce
On Mon, 12 Jan 2009, Martin Kavec wrote:
Hi,
I have been running quite a few clinical subjects (close to 300) through FS
pipeline and comparing cortical thickness from parcellated cortex for each
individual subject to its agematched controls. The subject clinical symptoms
are not specific, ranging from amnesia, reduced ability to generate words,
confusion, ...
Every now and that I see that the cortical thickness is suspiciously higher
than STD of the controls even if there are no leftovers after brain
extraction (I specifically verify it, and if necessary do the corrections).
In the vast majority of these cases I also find lower total white matter
volume.
I am speculating, if possible subcortical WM disease (as detected by reduced
total volume of the WM) may come into the play. If subcortical WM gets
darker, near the intensity of the GM, the cortical thickness may be
overestimated. Could anybody comment on this idea?
I suppose there is no way of correcting this. At the same time I wonder,
whether cortical atrophy in MS assessed by the FS is accurate. The cortical
atrophy reported in MS by FS methods (Sailer2003) was highly focal, and I am
wondering if such atrophy can reflect the wide range of disables and clinical
symptoms.
I would appreciate any comments to my thought.
Best,
Martin
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