Optic nerve and optic radiation neurodegeneration in patients with glaucoma: in vivo analysis with 3-T diffusion-tensor MR imaging.
OBJECTIVE
To evaluate, with high-field-strength diffusion-tensor (DT) magnetic resonance (MR) imaging, the axonal architecture of the optic nerves and optic radiations in patients with glaucoma and determine whether DT MR imaging-derived parameters correlate with disease severity.


METHODS
The study was approved by the institutional review board. All participants provided written informed consent. Sixteen patients with primary open-angle glaucoma were examined. Glaucoma severity was clinically assessed with use of a six-stage system based on static threshold visual field parameters. Ten healthy individuals served as control subjects. DT MR imaging was performed with a 3-T MR unit. Mean diffusivity (MD) and fractional anisotropy (FA) maps were automatically created. Regions of interest were positioned on the MD and FA maps, and mean MD and mean FA values were calculated for each optic nerve and each optic radiation.


RESULTS
The optic radiations and optic nerves of patients with glaucoma, as compared with control subjects, had significantly higher MD and significantly lower FA. The mean MD values for the optic nerves and the glaucoma stages varied consistently (r = 0.8087, P < .0001). A negative correlation between mean FA for the optic nerves and glaucoma stage (r = -0.7464, P < .0001) was observed.


CONCLUSIONS
Glaucoma is a complex neurologic disease that affects optic nerves and optic radiations. The finding that DT MR imaging-derived MD and FA in the optic nerves correlate with glaucoma severity suggests that these parameters could serve as complementary indicators of disease severity.
Garaci
Francesco G
FG
Department of Diagnostic Imaging, Molecular Imaging, Interventional Radiology and Radiotherapy, University Hospital Tor Vergata, Viale Oxford 81, 00133 Rome, Italy. garaci@gmail.com
Bolacchi
Francesca
F
Cerulli
Angelica
A
Melis
Milena
M
Spanò
Arnoldo
A
Cedrone
Claudio
C
Floris
Roberto
R
Simonetti
Giovanni
G
Nucci
Carlo
C
D000344:Afferent Pathways / Q000473:pathology*; D000368:Aged; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D005901:Glaucoma / Q000150:complications* / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009900:Optic Nerve / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000150:complications* / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity