Patterns of excitotoxin-induced brain lesions in the newborn rabbit: a neuropathological and MRI correlation

There is pressing need to employ new advances in structural MR brain imaging to better diagnose brain damage in newborn infants. Timely application of such technology will enable improved therapeutic interventions. Diffusion-weighted sequences are a sensitive marker of very early neuronal injury, the spatial pattern of which provides critical information regarding the underlying pathophysiology. We have modified our murine model of excitotoxic neonatal brain injury to the rabbit, an animal whose brain is larger and where the neuroanatomic organization of the subcortical white matter more closely resembles that of the human. Utilizing this rabbit model, we undertook an MRI/histopathologic correlation. We found that as with the mouse, there is a spatiotemporal selectivity to the pattern of brain injury, and that the period from postnatal day (P) 7 to P9 in rabbits corresponds to the time of maximum vulnerability of the brain to excitotoxic white matter damage, which neuropathologically simulates periventricular leukomalacia (PVL). We additionally noted that diffusion-weighted imaging provided the most sensitive means of detecting such lesions and that this method was sensitive to structural maturational changes accompanying the normal cortical ontogeny. Taken together, our findings suggest that this rabbit model of perinatal excitotoxic brain injury will be a valuable addition to experimental approaches to further our understanding of perinatal brain damage, that diffusion-weighted imaging will be an invaluable adjunct to the diagnosis of such injury, and that therapeutic strategies aimed at interrupting the evolution of PVL should include targeting the pathophysiologic cascade induced by excitotoxic neonatal brain injury.