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Vascular Description of Perivenular Lesions in Multiple Sclerosis


2011 Exceptional Summer Student Award Winner Manori De Alwis Manori De Alwis

Background and objective:
Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) that affects the white matter of the brain and spinal cord. Most MS lesions develop around small, inflamed veins. However, whether these veins are different from those that do not develop lesions or from similar veins in healthy subjects is unknown.

Methods:
We studied 19 MS patients and 2 healthy volunteers. Using a newly designed segmented echo-planar imaging protocol, we acquired sagittal whole-brain T2*-weighted images in a 3 tesla Philips scanner after gadolinium administration (TR=51ms; TE=28ms; 0.55mm isotropic voxels; acquisition time 6min). We identified focal white matter lesions and classified them into two groups, depending on whether their cross-sectional diameter was smaller or greater than 3.5 mm. Specialized image analysis software (Carestream PACS Ver. 11.1) allowed us to identify and reconstruct the courses of intraparenchymal veins both within and outside these lesions. We measured the diameters of the veins both inside and just outside lesions and compared the results to the diameters of healthy veins in MS cases and normal veins in non-MS cases. We also recorded lesion location (juxtacortical, subcortical, or periventricular), lesion size, and the length of the vein inside each lesion.

Results:
We analyzed a total of 150 veins: 45 veins surrounded by small perivenular lesions, 41 veins centering large lesions, and 64 veins without lesions. The mean diameter of the veins inside MS lesions (0.76±0.14mm) was smaller than the mean diameter of veins just outside the lesion area (1.18±0.13mm) in both larger and smaller lesions (p <0.001). Extralesional veins in MS cases were larger than those in healthy volunteers (1.18±0.14mm vs. 0.99±0.09mm; p < 0.001). Of small lesions, 58% were in the periventricular white matter, 33% in the subcortical white matter, and 9% in the juxtacortical white matter. There was a slight positive linear correlation between vein and lesion diameter in small perivenular lesions. There was also a positive correlation between vein length and lesion diameter in larger lesions.

Discussion:
Veins inside lesions are significantly smaller in comparison to similar veins in the same brains that are located outside lesions. This finding gives new insight into the vascular component of MS lesions, perhaps corresponding to a compressive effect of the perivascular inflammatory cuff within lesions. The finding that healthy veins of MS patients are significantly larger than those of healthy volunteers may reflect a pre-lesional vascular change in MS Brains or potentially an effect of diffuse brain volume loss.

Last updated December 23, 2013