Abstract
Purpose: :
To evaluate in patients with Leber’s hereditary optic neuropathy (LHON) the integrity of white matter (WM) microstructure and the regional distribution of WM damage of the whole brain using diffusion tensor imaging (DTI). To correlate DTI data with neuro-ophthalmological parameters, including optical coherence tomography (OCT) measurements of Peripapillary Retinal Nerve Fiber Layer (PRNFL).
Methods: :
Dual-echo and DTI scans with diffusion gradients applied in 35 non-collinear directions were acquired, using a 3.0 Tesla scanner, from 13 LHON patients and 25 matched controls. Tract-Based Spatial Statistics (TBSS) analysis, a fully automated technique applied on DTI data, was performed using FMRIB's Diffusion Toolbox (FDT). The neuro-ophthalmological parameters considered for statistical comparisons were: best-corrected LogMAR visual acuity, mean deviation (MD) of automated standardized perimetry (Humphrey Zeiss, 30-2 SITA standard), average and temporal quadrant PRNFL thickness obtained using OCT (Stratus OCT, Carl Zeiss Ophthalmic Systems Inc, fast RNFL thickness 3.4).
Results: :
In LHON patients, compared to controls, TBSS analysis revealed: 1) statistically significantly decreased fractional anisotropy and increased mean and radial diffusivity localized in the optic tracts and optic radiations 2) no statistically significant differences in other brain WM tracts. Statistically significant correlations were found comparing TBSS data with visual acuity, not with mean average or temporal PRNFL thicknesses nor with visual field parameters.
Conclusions: :
Our data suggest a microstructural disruption of the WM tracts along the posterior optic pathways in LHON patients. This evidence of axonal damage, presumably due to postsynaptic degeneration or primary disease localization, seems exclusively localized along the visual pathway, with sparing of the remaning WM tracts.
Keywords: optic nerve • imaging/image analysis: clinical • nerve fiber layer