Shamseldeen Younes Mahmoud MD, Presenter: Nothing to Disclose

Ken E Sakaie DPHIL, Abstract Co-Author: Nothing to Disclose

Jian Lin, Abstract Co-Author: Nothing to Disclose

Mark J Lowe, Abstract Co-Author: Nothing to Disclose

Micheal D. Phillips MD, Abstract Co-Author: Stockholder, Prism Clinical Imaging

To study the correlation between white matter diffusion tensor imaging parameters and age.

16 healthy subjects (12 female / 4 male) were included. Age ranged from 28 to 60 years (34.9 ± 10.5 mean ± SD). Measurements were performed on a Siemens TIM Trio (Erlangen, Germany) with a standard 12-channel head coil. HARDI data were acquired with a twice-refocused spin echo [Reese 2003] (TE/TR=102/7700msec, 128x128x48 matrix, FOV=256x256x96mm), 71 b=1000 sec/mm2 acquisitions with gradient directions selected by a coulomb repulsion algorithm [Jones 1999], and 8 b=0 acquisitions at equally spaced intervals. Motion correction was performed using FSL [Smith 2004]. Tensors were calculated using log-linear regression [Basser 1994]. 9 ROIs were drawn with in-house software in bilateral frontal, bilateral temporal, bilateral parietal, genu, splenium and body of the corpus callosum. Tensor values (Transverse diffusivity, longitudinal diffusivity, mean diffusivity, and fraction anisotropy) were averaged over each ROI for each individual.

Transverse Diffusivity (TD) in the frontal white matter was lowest during the fourth decade (defined as middle age/mid life). Mean Diffusivity (MD) showed a similar trend and Fractional Anisotropy (FA) was highest in the mid life period.

Transverse diffusivity has been implicated as a measure of white matter integrity [Herrera 2008]. We report lowest TD during the fourth decade, reflecting highest structural organization and stable myelination of the frontal white matter tracts, agrees with general evidence of adult intellectual developmental course, intellectual stability and psychological competence noted in the middle age [Schaie 1994]. Although our finding suggests that white matter TD is lowest in the fourth decade of life, the principal observation is that onset of gradual white matter decline begins at this stage of life. This finding is consistent with previous findings that suggest that the frontal white matter regions are early biomarkers of age-related decline in white matter integrity [Madden 2007, Salat 2005].

Oligodendrocytes expression of myelin synthesis/repair may slow or cease in the fourth decade after full brain maturation may explain conversion of Relapsing Remitting to Secondary Progressive MS

Mahmoud, S, Sakaie, K, Lin, J, Lowe, M, Phillips, M, Observed Onset of Frontal White Matter Decline in the Fourth Decade: A Diffusion Tensor Imaging Study.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8001821.html