Mechanisms of the mass effect of cerebral contusion: ICP monitoring and diffusion MRI study.

Abstract

Cerebral contusion is sometimes associated with a non-hemorrhagic mass effect which progresses rapidly within 12-48 hours post-trauma. In order to determine the mechanisms underlying such a mass effect, we analyzed data obtained from ICP monitoring and diffusion MRI in a total of 38 patients with cerebral contusion. Diffusion imaging and ADC mapping were performed employing 1.5 T echo planar MRI. ADC values were expressed as a ratio relative to the values of intact brain areas. In 6 patients, ICP became uncontrollable medically and surgical resection of the contused brain tissue was eventually performed. Within 24 hours post-trauma, diffusion images revealed a low intensity core and a high intensity rim in the contusion. The ADC ratio increased in the central area (1.13 +/- 0.21) and decreased in the peripheral area (0.67 +/- 0.14). A crescent-shaped zone of very high ADC ratio (1.45 +/- 0.14) was observed at the border between these two areas during the period of 24-48 hours. It appears that the capacitance of edema fluid accumulation is elevated by cellular disintegration in the central area, whereas the resistance to edema fluid propagation is elevated by cellular swelling in the peripheral area. We suggest that such events facilitate extracellular edema fluid accumulation within contused brain tissue and contribute, together with cellular swelling itself, to the non-hemorrhagic mass effect of cerebral contusion.