Relative cerebral blood flow during the secondary expansion of a cortical lesion in rats.

The size of a cerebral contusion is not finite at the moment of trauma, but liable to secondary increase during the following hours and days. In the present study we investigated whether this phenomenon may be related to changes in cortical blood flow (cCBF). In rats a cortical lesion grew to 140% of its initial volume during the first 24 h after injury. During the time of most rapid lesion expansion (<6 h after the insult) marked hypoperfusion (approximately 30% of baseline) was found in the ipsilateral hemisphere by laser Doppler scanning fluxmetry. In the peri-contusional area cCBF slowly recovered to approximately 80% of baseline, while in the distant brain not affected by delayed cell death, significant hyperperfusion (approximately 160% of baseline) was observed. Thus, early hypoperfusion might be an important mechanism for secondary lesion expansion.