Basic science; maturation-dependent response of the immature brain to experimental subdural hematoma

In children less than 2 years of age, the radiographic finding of a subdural hematoma (SDH) in the absence of trauma is highly suggestive of inflicted head injury. Little is understood about the unique pathophysiologic response of the immature brain to a SDH. The goal of the current study was to develop an experimental SDH model to determine whether there is a maturation-dependent response of the immature brain to SDH. Fifteen domestic Yorkshire piglets of three different age groups (five each of 5-days, 1-month, and 4-months old) were selected for study. A volume of blood equal to 10% of the intracranial volume (4.5 cc in the 5-day old, 5.4 cc in the 1-month old, and 9.4 cc in the 4-month old) was injected through a right frontal burr hole. Histologic analysis, including hematoxylin and eosin staining and TUNEL staining, was performed at 7 days survival. A significant difference in percentage of injured hemisphere was noted between the 5-day old group and the 1- and 4-month old animals (p = 0.0382). The number of TUNEL-positive cells/HPF increased significantly with increasing animal age (p = 0.0450). The current study demonstrates a significant maturation-dependent response of the immature brain to SDH, with the youngest animals being quite resistant to a SDH alone. This model will allow further study of additional cerebral insults, such as the addition of apnea or seizures, which may act synergistically along with a SDH to overwhelm the innate neuroprotective capacity of the immature brain to traumatic injury.