Dear FSL experts,

 

I am puzzled about some findings in TBSS. I am comparing a group of patients (n=30) with a group of healthy controls (n=40), using TBSS according to the user guidelines (i.e. randomise, tfce, ...).I obtain widespread group differences (HC > patients) on FA values in corpus callosum, corona radiata and corticopinal tracts, in both left and right hemispheres, However, there are no differences, not even below threshold, on MD, AD, and RD. I don't trust the results on FA, but I also don't know what the problem might be.

 

I checked single subject data for a few regions that are significant in FA, and the results look okay (i.e. normal distribution of FA values, no outliers).

I know that the controls have larger brains overall than the patients (all adults though), therefore I included ICV in the analysis as covariate, but this did not change the outcome..

 

Does anyone have an idea how else to check whether the results are valid, or could give me a hint how those findings could be interpreted?

 

Thanks in advance,

Mark