Long-term effects of neonatal hypoxia-ischemia on structural and physiological integrity of the eye and visual pathway by multimodal MRI
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Updated: Apr 19, 2026
Early Pathological and Magnetic Resonance Detection of Cerebral Injury Using a Rat Model of Neonatal Hypoxic Ischemic Encephalopathy
Published on: October 28, 2022
Kevin C Chan1, Swarupa Kancherla1, Shu-Juan Fan2
1UPMC Eye Center, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States.
Insights
Neonatal hypoxia-ischemia causes long-term eye and brain damage. Multimodal MRI revealed structural and physiological deficits in visual pathways, highlighting vulnerability to eye injury.
Area of Science:
- Neuroscience
- Ophthalmology
- Developmental Biology
Background:
- Neonatal hypoxia-ischemia (HI) is a leading cause of infant brain injury, often resulting in visual impairments.
- The precise long-term effects of HI on the visual system and its underlying mechanisms remain incompletely understood.
- Advancements in perinatal care improve survival but do not fully elucidate the pathogenesis of HI-induced visual deficits.
Purpose of the Study:
- To investigate the chronic structural and physiological consequences of neonatal HI on the eye and brain's visual pathways.
- To test the hypothesis that HI induces MRI-detectable alterations in the visual system.
- To utilize advanced MRI techniques for in vivo assessment of visual system integrity post-HI.
Main Methods:
- Neonatal Sprague-Dawley rats (postnatal day 7) underwent unilateral common carotid artery ligation followed by 2 hours of hypoxia.
- One year later, multimodal MRI, including T2-weighted, gadolinium-enhanced, chromium-enhanced, manganese-enhanced, and diffusion tensor imaging (DTI), was performed on the visual system.
- A 7-Tesla scanner was used to evaluate and compare structural and physiological parameters between the affected (ipsilesional) and unaffected (contralesional) hemispheres.
Main Results:
- Systemic gadolinium revealed blood-ocular barrier leakage in the ipsilesional eye, indicating chronic ocular damage.
- Intravitreal chromium confirmed compromised retinal integrity in the ipsilesional eye.
- Despite visual cortex loss, retinocollicular and retinogeniculate pathways showed enhanced manganese transport and better structural integrity (DTI) in the ipsilesional hemisphere compared to controls, suggesting compensatory mechanisms or differential vulnerability.
Conclusions:
- High-field, multimodal MRI effectively demonstrated in vivo long-term structural and physiological deficits in the visual system following neonatal HI.
- The study identified significant ocular and neural pathway damage persisting one year after the initial injury.
- Retinocollicular and retinogeniculate pathways are more susceptible to anterograde degeneration originating from ocular injury than retrograde degeneration from cortical damage.
Purpose:
Neonatal hypoxia-ischemia is a major cause of brain damage in infants and may frequently present visual impairments. Although advancements in perinatal care have increased survival, the pathogenesis of hypoxic-ischemic injury and the long-term consequences to the visual system remain unclear. We hypothesized that neonatal hypoxia-ischemia can lead to chronic, MRI-detectable structural and physiological alterations in both the eye and the brain's visual pathways.
Methods:
Eight Sprague-Dawley rats underwent ligation of the left common carotid artery followed by hypoxia for 2 hours at postnatal day 7. One year later, T2-weighted MRI, gadolinium-enhanced MRI, chromium-enhanced MRI, manganese-enhanced MRI, and diffusion tensor MRI (DTI) of the visual system were evaluated and compared between opposite hemispheres using a 7-Tesla scanner.
Results:
Within the eyeball, systemic gadolinium administration revealed aqueous-vitreous or blood-ocular barrier leakage only in the ipsilesional left eye despite comparable aqueous humor dynamics in the anterior chamber of both eyes. Binocular intravitreal chromium injection showed compromised retinal integrity in the ipsilesional eye. Despite total loss of the ipsilesional visual cortex, both retinocollicular and retinogeniculate pathways projected from the contralesional eye toward ipsilesional visual cortex possessed stronger anterograde manganese transport and less disrupted structural integrity in DTI compared with the opposite hemispheres.
Conclusions:
High-field, multimodal MRI demonstrated in vivo the long-term structural and physiological deficits in the eye and brain's visual pathways after unilateral neonatal hypoxic-ischemic injury. The remaining retinocollicular and retinogeniculate pathways appeared to be more vulnerable to anterograde degeneration from eye injury than retrograde, transsynaptic degeneration from visual cortex injury.
