Neonatal hypoxic-ischemic encephalopathy: detection with diffusion-weighted MR imaging

Abstract

Background and purpose: Although diffusion-weighted imaging has been shown to be highly sensitive in detecting acute cerebral infarction in adults, its use in detecting neonatal hypoxic-ischemic encephalopathy (HIE) has not been fully assessed. We examined the ability of this technique to detect cerebral changes of acute neonatal HIE in different brain locations.

Methods: Fifteen MR examinations were performed in 14 neonates with HIE (median age, 6.5 days; range, 2-11 days). Imaging comprised conventional T1-weighted, proton density-weighted, and T2-weighted sequences and echo-planar diffusion-weighted sequences. The location, extent, and image timing of ischemic damage on conventional and diffusion-weighted sequences and apparent diffusion coefficient (ADC) maps were compared.

Results: Although conventional sequences showed cerebral changes consistent with ischemia on all examinations, diffusion-weighted imaging showed signal hyperintensity associated with decreased ADC values in only seven subjects (47%). All subjects with isolated cortical infarction on conventional sequences had corresponding hyperintensity on diffusion-weighted images and decreased ADC values, as compared with 14% of subjects with deep gray matter/perirolandic cortical damage. The timing of imaging did not significantly alter diffusion-weighted imaging findings.

Conclusion: Diffusion-weighted imaging, performed with the technical parameters in this study, may have a lower correlation with clinical evidence of HIE than does conventional MR imaging. The sensitivity of diffusion-weighted imaging in detecting neonatal HIE appears to be affected by the pattern of ischemic damage, with a lower sensitivity if the deep gray matter is affected as compared with isolated cerebral cortex involvement.

fig 1.

Subject 4: watershed ischemia. A, T1-weighted image shows hypointensity bilaterally in the anterior and posterior watershed areas. B, T2-weighted image shows hyperintensity in the same areas, suggesting edema. C, Anisotropic diffusion-weighted image (z gradient) shows corresponding signal hyperintensity. D, Isotropic ADC map confirms a decrease in water diffusion with hypointensity in all watershed regions, most prominently seen in left posterior watershed area.

fig 2.

Subject 10: deep gray matter ischemia. A and B, T1-weighted (A) and T2-weighted (B) images show hyperintensity in the thalami and lentiform nuclei. C and D, Anisotropic diffusion-weighted image (z gradient) (C) and isotropic ADC map (D) confirm normal water diffusion.

fig 3.

Cortical injuries: correlation between image timing and ADC changes. The age of each subject with cortical ischemic damage is shown. ADC changes within the ischemic region were calculated using normal published values , with error bars shown (SD). All subjects except case 12 (day 11) had a significant decrease in ADC values

fig 4.

Thalamic injuries: correlation between image timing and ADC changes. The age of each subject with thalamic ischemic damage is shown. Four imaging studies show a significant decrease in ADC: subjects 5 (day 2); 12 (days 4 and 11), and 13 (day 9)