Abnormal diffusivity of normal appearing brain tissue in multiple sclerosis: a diffusion-weighted MR imaging study.

OBJECTIVE: To assess whether water diffusivity in normal appearing brain tissue including white and gray matter of multiple sclerosis (MS) patients shown by diffusion-weighted imaging (DWI) differs from normal individuals. MATERIAL AND METHOD: Conventional MRI and DWI were performed in 37 multiple sclerosis patients and 31 control subjects, matched for age and sex. Quantitative diffusivity values were obtained from variable locations of normal appearing white and gray matter from both hemispheres by using a standardized region of interest template. +/- 2. 9 x 10(-5) mm2/s and 85.90 x 10(-5) +/- 2.45 x 10(-5) mm2/s) than normal control subjects (NAWM: 73.46 x 10(-5) +/- 1.77 x 10(-5) mm2/s and NAGM: 82.90 x 10(-5) +/- 0.91 x 10(-5) mm2/s) with p-value < 0.0001. CONCLUSION: Water diffusivity was higher in all NAWM regions, deep gray matter regions, and some cortical gray matter region of MS patients than normal controls. DWI can quantify the presence and extent of MRI-undetectable pathology in the normal appearing brain tissue that were the disease burden.

ADC measurements in various patterns of multiple sclerosis lesions.

OBJECTIVE: To determine the difference of mean apparent diffusion coefficients (ADC) among different patterns of focal multiple sclerosis (MS) lesions, to compare mean lesion ADC between 2 clinical subgroups and to correlate mean lesion ADC with disability. MATERIAL AND METHOD: Thirty seven patients (26 with relapsing-remitting multiple sclerosis (MS) and 11 with secondary-progressive MS) underwent both conventional and diffusion-weighted MR imaging of the brain. After creating ADC maps, region identification was done by using b = 0 images and T2-weighted images. ADC values were measured for MS lesions and (NAWM). RESULTS: A total of 288 lesions were identified on the images. The mean ADC for the lesions was significantly higher than that of NAWM Hypointense T1 lesions (n = 221) had a significantly higher mean ADC than isointense T1 lesions (n = 67) in both nonenhancing lesions (n = 250) and enhancing lesions (n = 38). The enhanced rim of ring-enhancing lesions (n = 18) had lower ADC than the central nonenhanced portions. Confluent lesions (n = 62) had a substantially higher mean ADC than discrete lesion (n = 226). Mean lesion ADC of secondary progressive MS was significantly higher than relapsing remitting MS. No correlation between mean lesion ADC and (EDSS) score was found CONCLUSION: Quantitative diffusion-weighted imaging is useful to elucidate the heterogeneous pathological substrate of MS in different patterns of MS lesions, to differentiate 2 major clinical subgroups.