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Simone Waerntges, Tobias Engelhorn, Ahmed El-Rafei, Joachim Hornegger, Arnd Doerfler, Georg Michelson; Axonal Integrity and Myelin Damage in the Optic Radiation Depend on Age in Healthy Subjects - A DT-MRI Analysis. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2981.
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To investigate the extent of age-related impairment of the 4th neuron of the visual pathway and the influence of sex differences in healthy subjects. High-field-strength diffusion-tensor (DT) magnetic resonance imaging (MRI) was applied to quantify the axonal integrity (measured by the fractional anisotropy, FA, and mean diffusivity, MD) and the demyelination/ glia cell impairment (measured by the radial diffusivity, RD) of the optic radiation.
Twenty-nine subjects (mean age 53.3±15.8 years, thereof 19 women) with eye diseases without neuronal participation (i.e. pterygium, nasolacrimal duct obstruction, corneal dystrophy, eye lid tumor) and without a history of systemic neurological diseases underwent DT-MRI examination of the optic radiation. Magnetic resonance images did not show cerebral space occupying lesions along the visual pathway. The optic radiations in the DT-MRI were outlined semi-automatically and the mean values of FA, MD, and RD of the two optic radiations were calculated. Their impairment by age and gender was averaged by univariate analysis of variance (ANOVA). The best-adjusted reasonable regression curves were determined by curve fitting.
Age influenced FA, MD, and RD in the optic radiations by 17.0% (p=0.029), 24.6% (p=0.007), and 30.4% (p=0.002), respectively. Quadratic equations with r2=0.200 (p=0.055), r2=0.364 (p=0.003), and r2=0.392 (p=0.002), respectively, provided the best-adjusted reasonable regression curves. Gender had no significant effect on any parameter measured.
DT-MRI-derived parameters of axonal integrity and demyelination or glia cell impairment of the optic radiations are suggested to be influenced significantly by age but not by gender.
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