Abstract
We investigated whether the changes detectable with magnetic resonance imaging techniques during and after an episode of cerebral hypoxia-ischemia differ in immature and older brain. Diffusion weighted (DW) and T2-weighted (T2W) images were repeatedly acquired before, during, and after an episode of cerebral hypoxia-ischemia (unilateral carotid artery occlusion plus hypoxia) in 2- and 4-wk-old rats lightly anesthetized with isoflurane. Areas of increased brightness were detected in DW images from both 2- and 4-wk-old rats by 10-20 min after the start of hypoxia. These hyperintense areas increased during hypoxia, comprising 60.8 ± 4.9% and 30.5 ± 2.7% of the brain image at the level of the thalamus in 2-wk-old and 4-wk-old animals, respectively (p < 0.003). Hyperintense areas (e.g. 27.0 ± 8.3%) also appeared in T2W images during hypoxia-ischemia in 2-wk-old animals, but these did not occur in 4-wk-old animals (p < 0.02). This observation was reflected in T2, which increased during hypoxia-ischemia in the 2-wk-old but not the 4-wk-old group. By 60 min after the termination of hypoxia-ischemia in either age group, areas of hyperintensity resolved and then reappeared 24 h later on both DW and T2W images. Thus, irrespective of age, magnetic resonance imaging changes during transient hypoxia-ischemia generally recover with a delayed or secondary increase in DW and T2W hyperintensity hours later. Immature brain differs from older brain primarily with respect to some combination of hypoxic/ischemic cellular or biochemical changes, that are detectable as increases in T2 within 2-wk-old but not 4-wk-old animals.
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Abbreviations
- DW:
-
diffusion-weighted
- T2W:
-
T2-weighted
- MR:
-
magnetic resonance
- TR:
-
repetition time
- TE:
-
echo time
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Acknowledgements
The authors thank R. Summers and T. Foniok for assistance with the statistical calculations and MR image acquisition, respectively.
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Supported in part by a grant from the Heart and Stroke Foundation of Manitoba.
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Ning, G., Malisza, K., Del Bigio, M. et al. Magnetic Resonance Imaging during Cerebral Hypoxia-Ischemia: T2 Increases in 2-Week-Old But Not 4-Week-Old Rats. Pediatr Res 45, 173–179 (1999). https://doi.org/10.1203/00006450-199902000-00003
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DOI: https://doi.org/10.1203/00006450-199902000-00003
