Diffusion tensor imaging of the optic nerve in subacute anterior ischemic optic neuropathy at 3T.

BACKGROUND AND PURPOSE: DTI can provide in vivo information about the pathology of optic nerve disease, but there is no study of DTI in the setting of ION, the most frequent acute optic neuropathies in patients over 50 years of age. Our aim was to investigate the potential of DTI in the diagnosis of subacute AION at 3T. MATERIALS AND METHODS: Twenty-six patients with unilateral AION and 15 healthy controls were enrolled in this study. DTI and pattern VEP were performed on the ONs of all subjects. The mean ADC, FA, and eigenvalue maps were obtained for quantitative analysis. Quantitative electrophysiology was also performed on all subjects. RESULTS: The mean ADC and orthogonal eigenvalue λ(⊥) in affected nerves increased, and the mean FA was reduced compared with clinically unaffected contralateral nerves (P < .001) and control nerves (P < .001). However, no significant changes of the mean principal eigenvalue λ(‖) in affected nerves compared with unaffected contralateral nerves (P = .13) and control nerves (P = .14) were seen. There was a significant correlation of whole-field VEP amplitude with ADC (r = -0.63, P = .001) and λ(⊥) (r = -0.47, P = .015) but no correlation with FA (P = .06) and λ(‖) (P = .06). CONCLUSIONS: DTI measurement of ischemic ONs provides in vivo information about pathology and may serve as a biomarker of axonal and myelin damage in AION.