Ultra-early study of edema formation in cerebral contusion using diffusion MRI and ADC mapping

Our previous studies have reported that heterogeneous mechanisms exist in early edema formation in cerebral contusion, and cytotoxic edema plays an important role within 48 hours post-trauma. It is remains unclear, when edema begins to develop following injury. In order to determine the time course of edema development, diffusion imaging and ADC (apparent diffusion co-efficient) mapping was performed in 10 patients within 24 hours post-trauma with cerebral contusion.

Diffusion imaging and ADC mapping were performed employing 1.0 T echo planar MRI. ADC values were indicated as a ration relative to the values of intact brain areas.

Within 3 hours post-trauma, diffusion MRI showed no remarkable changes, and the ADC values were within normal limit (ADC ratio (=contused/normal brain) = 1.00 +/- 0.21, (mean +/- SD)). At 6 hours post-trauma, diffusion images demonstrated a low intensity core in the contusion proper and a high intensity rim in the peripheral area of contusion. The ADC value increased in the contusion proper (ADC ratio = 1.26 +/- 0.13) and decreased in the peripheral area (ADC ratio = 0.58 +/- 0.19).

These findings indicated that early cellular swelling in the peripheral area of contusion begins within 6 hours following injury. This delayed occurrence of contusion-induced cellular swelling suggests that the CBF does not decrease to ischemic level immediately following injury.