Single severe traumatic brain injury produces progressive pathology with ongoing contralateral white matter damage one year after injury.

There is increasing recognition that traumatic brain injury (TBI) may initiate long-term neurodegenerative processes, particularly chronic traumatic encephalopathy. However, insight into the mechanisms transforming an initial biomechanical injury into a neurodegenerative process remain elusive, partly as a consequence of the paucity of informative pre-clinical models. This study shows the functional, whole brain imaging and neuropathological consequences at up to one year survival from single severe TBI by controlled cortical impact in mice. TBI mice displayed persistent sensorimotor and cognitive deficits. Longitudinal T2 weighted magnetic resonance imaging (MRI) showed progressive ipsilateral (il) cortical, hippocampal and striatal volume loss, with diffusion tensor imaging demonstrating decreased fractional anisotropy (FA) at up to one year in the il-corpus callosum (CC: -30%) and external capsule (EC: -21%). Parallel neuropathological studies indicated reduction in neuronal density, with evidence of microgliosis and astrogliosis in the il-cortex, with further evidence of microgliosis and astrogliosis in the il-thalamus. One year after TBI there was also a decrease in FA in the contralateral (cl) CC (-17%) and EC (-13%), corresponding to histopathological evidence of white matter loss (cl-CC: -68%; cl-EC: -30%) associated with ongoing microgliosis and astrogliosis. These findings indicate that a single severe TBI induces bilateral, long-term and progressive neuropathology at up to one year after injury. These observations support this model as a suitable platform for exploring the mechanistic link between acute brain injury and late and persistent neurodegeneration.

Blood-Brain Barrier Disruption Is an Early Event That May Persist for Many Years After Traumatic Brain Injury in Humans.

Traumatic brain injury (TBI) is a risk factor for dementia. Mixed neurodegenerative pathologies have been described in late survivors of TBI, but the mechanisms driving post-TBI neurodegeneration remain elusive. Increasingly, blood-brain barrier (BBB) disruption has been recognized in a range of neurologic disorders including dementias, but little is known of the consequences of TBI on the BBB. Autopsy cases of single moderate or severe TBI from the Glasgow TBI Archive (n = 70) were selected to include a range from acute (10 hours-13 days) to long-term (1-47 years) survival, together with age-matched uninjured controls (n = 21). Multiple brain regions were examined using immunohistochemistry for the BBB integrity markers fibrinogen and immunoglobulin G. After TBI, 40% of patients dying in the acute phase and 47% of those surviving a year or more from injury showed multifocal, abnormal, perivascular, and parenchymal fibrinogen and immunoglobulin G immunostaining localized to the gray matter, with preferential distribution toward the crests of gyri and deep neocortical layers. In contrast, when present, controls showed only limited localized immunostaining. These preliminary data demonstrate evidence of widespread BBB disruption in a proportion of TBI patients emerging in the acute phase and, intriguingly, persisting in a high proportion of late survivors.