In vivo assessments of ocular dynamics, axonal transport and microstructural integrity in the visual system upon neonatal hypoxic-ischemic injury

Abstract

This study employed dynamic gadolinium-enhanced MRI, manganese-enhanced MRI and diffusion tensor imaging to evaluate the ocular dynamics, axonal transport and microstructural integrity in the visual system of adult rats that underwent neonatal unilateral hypoxic-ischemic injury. Dynamic Gd-enhanced MRI showed leakage of the Gd contrast into the vitreous humor from the anterior chamber in the ipsilesional eye but not the contralesional eye after systemic administration of Gd. Manganese-enhanced MRI showed reduced anterograde axonal transport of Mn2+ ions along the visual pathway projected from the ipsilesional eye compared to contralesional eye upon bilateral Mn2+ intravitreal injection. In addition, the superior colliculus ipsilateral to the injured hemisphere appeared to be displaced across the midline to the contralateral hemisphere. Diffusion tensor imaging showed disorganization of the ipsilesional optic nerve compared to the contralesional optic nerve. The results of this study provided important evidence for understanding the chronic pathophysiological changes in the visual system after neonatal unilateral hypoxic-ischemic injury. (Abstract by ISMRM)