Impact Acceleration Model

To overcome the risk of experimentally induced skull fracture, which is a rare finding in human TBI, a model of impact acceleration was developed that uses a stainless steel protection helmet to avoid fracture when animals are subjected to TBI of higher magnitude. This protective shield is glued to the vertex of the skull after opening the scalp and distributes the load widely over the skull, thereby minimizing the likelihood of fracture. When combined with a large blunt weight that causes acceleration of the head and minor contact phenomena, this impact predominantly leads to shear forces. To perform the trauma, the head of the anesthetized animal is placed unrestrained and in prone position on the platform, adjusted to the end of the device, and the impact is delivered via a free-falling weight. The platform has to be covered by a foam of known spring constant to allow defined movement of the head after the impact, which has been shown to profoundly determine the injury-induced changes. Because the mass and height of the weight can be varied, the posttraumatic response has been characterized over a broad range of severity.

This model was characterized to produce mainly diffuse brain injury. Massive diffuse axonal swelling with its severity related to the level of trauma was observed after injury (e.g., in cerebral peduncles, rubrospinal or corticospinal tracts, medulla oblonga-ta, corpus callosum, and internal capsule). Moreover, structural changes in dendrites and mild subarachnoid hemorrhage without focal contusions or lesions have been reported with mild impact, whereas increasing the impact energy leads to more extensive subarachnoid and petechial hemorrhage in the acute posttraumatic period. However, neuronal damage in the supraven-tricular cortex directly beneath the impact site that is correlated with injury severity and cell death in the hippocampus have been described.

Evaluation of the animal's posttraumatic behavioral function showed cognitive deficits and impairments in neurologic motor function. Although in one study the more severely injured animals did not show full recovery from behavioral impairments during the investigation period, no long-term studies have been performed to test for persisting impairments in neurologic motor and cognitive function in the more chronic period of months after TBI.

Sleeping Sanctuary

Sleeping Sanctuary

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