Serial diffusion and perfusion MRI analysis of the perihemorrhagic zone in a rat ICH model.

OBJECTIVES: Cerebral ischemia has been proposed as a contributing mechanism to secondary neuronal injury after intracranial hemorrhage (ICH). We aimed to examine perihemorrhagic changes with an animal experimental MRI study using a stroke-MRI protocol. In a subset of animals the feasibility and effects of stereotactic hematoma evacuation was investigated.

METHODS: An MRI compatible setup for rats was established using a double injection model. ICH was stereotactically placed into the right basal ganglia of 49 Wistar rats. Coronal T2-WI, T2*-WI, DWI and PWI were generated with a 2.35T animal MRI scanner at 3 time points. Clot volumes, normalized ADC and relative MTT values were analysed in 3 hematoma regions (periphery, outer rim, healthy ipsilateral tissue) in all sequences.

RESULTS: There were no perihemorrhagic ADC decreases consistent with ischemic cytotoxic edema but a mild vasogenic edema surrounding the ICH could be observed. This improved partially with evacuation. Reduced perfusion was seen in the periphery and outer rim. This disappeared with lysis and evacuation of the clot.

CONCLUSION: No evidence for the existence of a perihemorrhagic ischemic area was found. But, reversible perfusion reduction in this model indicates that early evacuation may help reducing secondary neuronal changes.