Assessment of normal-appearing white and gray matter in patients with primary progressive multiple sclerosis: a diffusion-tensor magnetic resonance imaging study.
BACKGROUND
Diffusion-tensor magnetic resonance imaging is sensitive to the more destructive aspects of multiple sclerosis (MS) evolution occurring outside and within T2-visible lesions and, as a consequence, holds promise for providing a more complete picture of primary progressive (PP) MS-related tissue damage than conventional magnetic resonance imaging.


OBJECTIVE
To improve our understanding of PPMS by assessing the extent of occult pathological features in the normal-appearing white and gray matter of the brain using diffusion-tensor magnetic resonance imaging.


METHODS
Ninety-six patients with PPMS, 47 patients with secondary progressive (SP) MS, and 44 healthy control subjects were studied. T2-hyperintense and T1-hypointense lesion volumes were calculated, and the volume of the whole brain tissue was measured. Diffusion-tensor magnetic resonance imaging scans were postprocessed and analyzed to obtain the mean diffusivity and fractional anisotropy histograms from the brain and from the normal-appearing white and gray matter in isolation.


RESULTS
The mean T2-hyperintense and T1-hypointense lesion volumes were lower in patients with PPMS than in patients with SPMS, while the mean absolute brain volumes were similar in the 2 groups. The average lesion diffusivity was significantly higher in patients with SPMS than in patients with PPMS (P<.001). Histogram-derived metrics of the brain tissue and normal-appearing white and gray matter were significantly different between patients with PPMS and healthy subjects (range, P =.004 to <.001). Average diffusivity values were significantly higher in patients with SPMS than in patients with PPMS for all the tissues studied (range, P =.001 to <.001). Fractional anisotropy histogram-derived quantities did not significantly differ between the 2 patient groups (range, P =.94 to.03).


CONCLUSIONS
This study confirms that, in patients with PPMS, normal-appearing white and gray matter are not spared by disease-related pathological processes, although they are affected to a lesser degree than in patients with SPMS.
Rovaris
Marco
M
Neuroimaging Research Unit, Department of Neuroscience, Scientific Institute and University Ospedale San Raffaele, Via Olgettina 60, 20132 Milan, Italy.
Bozzali
Marco
M
Iannucci
Giuseppe
G
Ghezzi
Angelo
A
Caputo
Domenico
D
Montanari
Enrico
E
Bertolotto
Antonio
A
Bergamaschi
Roberto
R
Capra
Ruggero
R
Mancardi
Giovanni Luigi
GL
Martinelli
Vittorio
V
Comi
Giancarlo
G
Filippi
Massimo
M
D000328:Adult; D000368:Aged; D001921:Brain / Q000473:pathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012595:Scleroderma, Systemic / Q000473:pathology*