Diffusion tensor imaging evaluations of visual pathways with acute and chronic optic neuritis and assessments of superiority and correlations with the other evaluation techniques

Introduction And Purpose Assessment of the afferent visual pathway using clinical, imaging and electrophysiological methods provides insights into the pathophysiology of MS. In the present study we aim to investigate diffusion tensor imaging(DTI) evaluatıons of visual pathways in patients wıth acute and chronic optic neuritis and assessıng to superiority to other evaluation techniques Subjects and Methods In the present study, we performed DTI in total 26 patients and 12 healthy control subjects. The patients have acute episode of ON in 17 eyes, chronic ON in 20 eyes and 15 unaffected eyes ,based on clinical features. In addition,visual afferent system was evaluated with neuro-opthalmological examinations, OCT, VEP, orbital and cranial MRI in all participants in the study . Moreover in the study we investigated the correlation between applied methods. Results The mean of the measured values of fractional anisotropy (FA) in optic nerve was found to be significantly lower in the patients with acute optic neuritis (p<0.05) and cronic optic neuritis(p<0,05) The average values of mean diffusivity(MD) in patients with acute and chronic optic neuritis were significantly increased compared to unaffected eyes of patients and healthy controls (p<0.05). Peripapillary retinal nerve fiber layer thickness(RNLFT), P100 amplitude and latency measurements and visual acuity was significantly different between groups(P <0.01). The eyes with abnormal orbita MRI findings have statisticaly significant decrease in FA (p< 0.05), increase in MD (p <0.01), prolongation of P100 latency (p <0.01) and decrease P100 amplitude (p<0.05), decrease in RNLFT (p < 0.05) and visual acuity (p <0.01) compared to normal eyes. Mean values of FA measured in optic tract was significantly decreased (p<0,05) and MD significantly was increased (p<0.05) between groups. The mean of the measured values of fractional anisotropy (FA) in optic nerves was correlated with prolongation of P100 latency and decrease in RNLFT.(p<0.05) in the patients with acute optic neuritis. Furthermore mean MD value was correlated with RNLFT, visual acuity(p<0.05) and P100 latency,RNLFT was correlated with visual acuity in the patients with acute optic neuritis. The mean of the measured values of FA was correlated with mean MD value and visual acuity(p<0.05), the mean MD value was correlated with mean P100 amplitude and visual acuity in the patients with cronic optic neuritis.(p<0.05) The mean FA and MD values was found to be correlated in the normal controls.(p<0.05) Conclusion Briefly, the most severe abnormalities for MD and FA in DTI have been seen in the optic nerve compared to chiasm and optic tract abnormalities. Furthermore, the eyes of chronic optic neuritis having more demyelination,gliosis and axonal loss have shown more increase MD values and decrease FA values than the others. MD and FA values of DTI, P100 latencies of VEP, RNLFT in OCT, visual acuity and colour vision all of them were very significantly different between the groups. Our results have suggested that DTI derived measurements correlate with visual disability and tissue injury and then it is important from a clinical point of view and understanding of pathological processes.