Figure 14.

Intracranial strain and strain rate fields are important in understanding the response of brain tissue to mechanical trauma, but injury mechanisms are complicated. Although strain fields are clearly related to apoptotic cell death in a closed-head model of traumatic brain injury in the juvenile rat, cell death is not directly colocalized with strain, and much injury occurs downstream of regions of high strain. (a, b) Schematic depictions of coronal (a) and sagittal (b) sections of the juvenile (P7) rat brain, illustrating the pattern of (dimensionless) strain magnitude during parasagittal indentation of the flexible skull. The location of the impactor tip is shown by the solid horizontal line. (c,d,e) Activated caspase-3-stained sections from a P8 rat brain 24 h postimpact; caspase-3 is a sensitive indicator of apoptosis. Arrows in panels c and e indicate the direction of impact and the center of the impact site. Panels c and d are coronal sections cut in a rostrocaudal plane slightly caudal to the impact site (c), or at a much more caudal level (d). These sections show that the delayed pathological reaction at the cerebrocortical level is primarily concentrated medial to the point of impact. Panel e is a sagittal section revealing that this cerebrocortical delayed pathological reaction extends in a caudal (but not rostral) direction. Reproduced from Reference 45.