MRI identification of early white matter injury in anoxic-ischemic encephalopathy

Background: Anoxic-ischemic encephalopathy (AIE) affects the gray matter mo re than the white matter. Recent animal experiments suggest that the white matter is more sensitive to ischemia than previously thought. The authors d escribe the MRI findings in seven patients with AIE who demonstrate early p referential involvement of the white matter. Materials and methods: A retro spective case series study was performed, including seven patients with AIE who underwent MRI of the brain within 7 days of insult. Demographic inform ation, type of insult, clinical. examination findings, EEG findings, and cl inical outcome were obtained. MRI studies were reviewed with specific atten tion to the cortex, deep gray matter, and the white matter structures. Mean apparent diffusion coefficient (ADC) was calculated in regions of interest placed in the cerebellar hemispheres, putamen, thalamus, splenium of corpu s callosum, centrum semiovale, and medial frontal cortex. Results: The caus es of AIE were cardiac arrhythmias in two patients, myocardial infarction i n one, drug overdose in two, carbon monoxide poisoning in one, and respirat ory failure and sepsis in one. The median time to MRT was 2.5 days. Symmetr ic areas of restricted diffusion were found in the periventricular white ma tter tracts (7/7 patients), the corpus callosum (6/7 patients), internal ca psule (5/7 patients), and the subcortical association fibers (3/7 patients) . ADC maps confirmed the restricted diffusion. Gray matter involvement was seen in three patients, and was more prominent on conventional imaging sequ ences compared with diffusion-weighted imaging. A subtle decrease in mean A DC was seen in cortex. Conclusions: Prominent, symmetric restricted diffusi on can occur early after AIE in white matter, whereas gray matter involveme nt may be less prominent. Further studies involving a larger sample and ser ial imaging are required to confirm these preliminary findings.