DIFFUSION TENSOR IMAGING OF OPTIC RADIATION IN MULTIPLE SCLEROSIS: CORRELATION WITH VEP

Purpose: To test the significance of FA and MD of diffusion tensor imaging in differentiating MS patients with normal and delayed VEP Material and Methods: This study was conducted upon 70 patients (aged 18-46 years: mean 32years) with multiple sclerosis that underwent diffusion tensor imaging and VEP. The average fractional anisotropy (FA) and mean diffusivity (MD) value of the right and left optic radiation in patients with normal (n=39) and delayed (n=28) were calculated and correlated with VEP of both sides. The receiver operating characteristic curve was drawn to detect the cutoff point of FA and MD of optic radiation used to differentiate patients with normal and delayed VEP. Correlation between FA, MD of OR with VEP, disease duration and EDSS were tested by person correlation coefficient. Also inter-observer agreement was done by comparing the FA and MD obtained by the two observers. A P value less than 0.05 was considered statistically significant.Results: The mean FA of optic radiation in patient with delayed VEP (0.36?0.03 and 0.36?0.08 X103mm2/s first and second observer respectively) was significantly lower than the mean FA of optic radiation in patient with normal VEP (00.39?0.03 and 0.39?0.04 X10-3mm2/s first and second observer respectively). The mean MD of optic radiation in patient with delayed VEP (0.96?0.06 and 0.98?0.07 X10-3mm2/s first and second observer respectively) was significantly higher than the mean MD of optic radiation in patient with normal VEP (0.88?0.05 and 0.89?0.05 X10-3mm2/s first and second observer respectively). Selection of FA of ≤0.38 and ≤0.395 X10-3mm2/s (first and second observer respectively) to differentiate patient with delayed and normal VEP has an area under the curve of 0.804 and 0.734, , a sensitivity of 75% and 82.1% , a specificity of 82.1% and 56.4 % , and accuracy of 79.1 % and 67.16 %, respectively. Selection of MD of ≥0.885 and ≥0.90 X10-3mm2/s (first and second observer respectively) to differentiate patient with delayed and normal VEP has an area under the curve of 0.901 and 0.893, a sensitivity of 96.4 % and 92.9 %, a specificity of 76.9 % and 71.8 %, and accuracy of 85.07 % and 80.6 % respectively