Diffusion weighted imaging-based differentiation of arteritic and non-arteritic anterior ischemic optic neuropathy.

Purpose: To assess the utility of DWI-MRI to differentiate arteritic (A-AION) from non-arteritic (NA-AION) ischemic optic neuropathy.

Methods: This bicentric cohort-study evaluated 3T DWI-MRI scans performed within 10 days after onset of AION in patients treated between 2014 and 2024 at two tertiary care centers. DWI was first assessed for the presence of restricted diffusion within the optic nerve. Quantitative apparent diffusion coefficient (ADC) evaluation was performed by placing a region of interest (ROI) within the affected optic nerve. Qualitative and quantitative DWI assessments were compared between A-AION and NA-AION patients.

Results: Twenty A-AION patients (75.7 ± 6.8 years; 16 [80.0%] female) and 59 NA-AION patients (64.6 ± 10.7 years; 22 [37.3%] female) with a total of 82 (A-AION: 23; NA-AION: 59) DWI-MRI scans were included in the study. Restricted diffusion on ADC was significantly more frequent in A-AION, when compared to NA-AION (82.6% vs. 42.4%; p = 0.001). Corresponding sensitivity, specificity, positive and negative predictive value of qualitative ADC assessment for the identification of A-AION were 0.83, 0.58, 0.43 and 0.89. Quantitative ADC analysis revealed significantly lower values in optic nerves affected by A-AION (ADC: 448.0 ± 256.2 × 10 mm/s vs. 671.5 ± 174.9 × 10 mm/s, p = 0.002).

Conclusion: Restricted diffusion of the optic nerve is more frequent in A-AION and associated with lower optic nerve ADC values, when compared to NA-AION. Prospective studies are required to further explore the potential of DWI in discerning arteritic from non-arteritic AION.