Maturation-dependent response of the piglet brain to scaled cortical impact

Object. The goal of this study was to investigate the relationship between maturational stage and the brain's response to mechanical trauma in a gyren cephalic model of focal brain injury. Age-dependent differences in injury r esponse might explain certain unique clinical syndromes seen in infants and young children and would determine whether specific therapies might be par ticularly effective or even counterproductive at different ages. Methods. To deliver proportionally identical injury inputs to animals of di fferent ages, the authors have developed a piglet model of focal contusion injury by using specific volumes of rapid cortical displacement that are pr ecisely scaled to changes in size and dimensions of the growing brain. Usin g this model, the histological response to a scaled focal cortical impact w as compared at 7 days after injury in piglets that were 5 days, 1 month, an d 4 months of age at the time of trauma. Despite comparable injury inputs a nd stable physiological parameters, the percentage of hemisphere injured di ffered significantly among ages, with the youngest animals sustaining the s mallest lesions (0.8%, 8.4%, and 21.5%, for 5-day-, 1-month-, and 4-month-o ld animals, respectively, p = 0.0018). Conclusions. These results demonstrate that, for this particular focal inju ry type and severity, vulnerability to mechanical trauma increases progress ively during maturation. Because of its developmental and morphological sim ilarity to the human brain, the piglet brain provides distinct advantages i n modeling age-specific responses to mechanical trauma. Differences in path ways leading to cell death or repair may be relevant to designing therapies appropriate for patients of different ages.