Structure-function relationship between magnetic resonance imaging lesion areas and visual field defects in initial optic neuritis with altitudinal hemianopsia

Purpose To study the spatial association of magnetic resonance imaging (MRI) contrast enhancement (CE) areas with visual field defect (VFD) asymmetry in initial cases of optic neuritis (ON) with altitudinal hemianopsia (AH) with reference to nonarteritic anterior ischemic optic neuropathy (NAION) with AH. Study design Multicenter, cross-sectional study. Methods The present study comprised 19 ON patients and 20 NAION patients with AH who underwent orbital contrast fat-suppressed MRI. The signal-to-intensity ratio (SIR) was calculated by dividing the maximum CE of the optic nerve by the mean CE of the cerebral white matter in 11 coronal sections at 3-mm intervals from immediately posterior to the eyeball to the optic chiasm. Sections in ON patients with an SIR exceeding the mean plus 2 standard deviations of the SIR at the corresponding section in the NAION group were considered abnormal. The correlation between upper-to-lower CE asymmetry in the maximum SIR section and VFD counterpart was determined. Results The ON group had significantly higher maximum SIR than that of the NAION group (1.77 ± 0.88 vs. 1.25 ± 0.32; P < .01). Seven of the 19 patients had sections with abnormally high CE extending posteriorly beyond the orbital apex. Significant spatial correspondence was observed between CE and VFD asymmetry (r s = 0.563; P = .015) in the ON group but not in the NAION group (r s = − 0. 048; P = .850). Conclusions ON patients with AH frequently show CE even in the intracerebral optic nerve, maintaining a moderate structure-function correspondence.