Objective: The aim of this study was to establish a more objective method for confirming tissue injury in term neonates who present with early seizures that are believed to be hypoxic-ischemic in origin.
Methods: We studied the relationship between contemporaneous diffusion-weighted magnetic resonance imaging and conventional magnetic resonance imaging in 63 symptomatic term-born neonates and 15 control term infants performed in the neonatal period. Apparent diffusion coefficients (ADC) were obtained for multiple regions of the brain.
Results: ADC values in the 15 control infants were 1 (1-1.15) (median [range]) x 10(-3)/mm2/second in the thalami and 1.1 (1-1.3) x 10(-3)/mm2/second in the lentiform nuclei, 1.5 (1.3-1.7) x 10(-3)/mm2/second in the centrum semiovale, 1.6 (1.46-1.7) x 10(-3)/mm2/second in the anterior white matter (WM), and 1.55 (1.35-1.85) x 10(-3)/mm2/second in the posterior WM with little variation over time. ADC values were significantly reduced in the first week after severe injury to either WM or basal ganglia and thalami (BGT), but values normalized at the end of the first week and then increased during week 2. ADC values were either normal or increased in moderate BGT and WM lesions when compared with controls. ADC values < 1.1 x 10(-3)/mm2/second were always associated with WM infarction and values <0.8 x 10(-3)/mm2/second with thalamic infarction.
Conclusion: A reduced ADC soon after delivery allows the presence of tissue infarction to be confirmed at a time when conventional imaging changes may be subtle. However, as both moderate WM and BGT lesions may have normal or increased ADC values, a normal ADC value during the first week does not signify normal tissue. ADC values should always be measured in combination with visual analysis of both conventional and diffusion-weighed images for maximum detection of pathologic tissue, and the timing of the scan needs to be taken into account when interpreting the results.