Application of 2,3,5-triphenyltetrazolium chloride staining to evaluate injury volume after controlled cortical impact brain injury: role of brain edema in evolution of injury volume.

A reliable method for measuring injury volume after traumatic brain injury (TBI) is of great importance when studying pharmacological protective agents in the field of head trauma research. Utilization of 2,3,5-triphenyltetrazolium chloride (TTC) has gained extensive acceptance in stroke research and has recently been applied to injury volume measurement in the lateral fluid percussion model. The present study was undertaken to apply this method to the controlled cortical impact (CCI) model and to study the role of brain edema. Male Sprague-Dawley rats were subjected to CCI brain injury at a velocity of 3 m/sec and 1 mm (mild), 2 mm (moderate), and 3 mm (severe injury) deformation, while rats in the control group were subjected to the same surgical procedure but received no injury. Absolute and corrected injury volumes with TTC staining and brain edema measurements with the wet-dry method were evaluated at 1, 2, 3, 4, and 7 days after TBI. The most prominent injury volume in the moderate injury group (2 mm deformation) was seen at postinjury day 1 and 2 (day 1, absolute: 49.1+/-5.6, corrected: 40.5+/-7.9; day 2, absolute: 46+/-6.9, corrected: 40.2+/-10.5), whereas the smallest injury volume was found at postinjury day 7 (absolute: 24.9+/-7, corrected: 27.4+/-7.4). The time course of brain edema studies demonstrates that brain edema formation peaks at postinjury day 1. A statistically significant reduction of injury volume was observed after postinjury day 4. We also observed that due to the presence of brain edema absolute injury volume is more than corrected injury volume in the first 3 days after injury as opposed to injury volume at postinjury day 7. These results suggest that the measurement of injury volume with TTC staining should be corrected for brain edema in the CCI brain injury model.