as background to this report, the committee acknowledges the importance of developing good animal models and identifying biomarkers of the disease progression and outcomes, and therefore recommendations are made for improving these areas of research.

Much of our understanding of the pathobiology of TBI has arisen from animal models that mimic features of human TBI. There are a number of detailed reviews of models of TBI (Artinian et al., 2006; Morales et al., 2005; O’Connor et al., 2005). Some examples of in vivo models are presented in Figure 3-1. The general objective of these models is to repli­cate certain aspects of human brain injury. It is important to note that there is currently no single model that can accurately reflect the heterogeneity of human TBI, and in each of these models, pathologic and neurologic outcomes vary according to the severity and location of the insult and heterogeneity of the vasculature. Also, there are no good animal models for mild or repetitive TBI.

Here the committee briefly reviews several of the most commonly used animal models of TBI (Morales et al., 2005): the weight-drop model, the controlled cortical impact model, the fluid percussion model, and the impact acceleration model (Figure 3-2). Each of these models produces motor/sensory and cognitive impairments. The weight-drop, midline fluid percussion, and controlled cortical impact models produce focal contusions and, depending on injury severity, may be associated with subarachnoid and intraparenchymal hemorrhages,

FIGURE 3-1 Classification of in vivo models of TBI.

SOURCE: Cernak, 2005.