Traumatic brain injury (TBI) results in a number of impairments, often including visual symptoms. In some cases, visual impairments after head trauma are mediated by traumatic injury to the optic nerve, termed traumatic optic neuropathy (TON), which has few effective options for treatment. Using a murine closed-head weight-drop model of head trauma, we previously reported in adult mice that there is relatively selective injury to the optic tract and thalamic/brainstem projections of the visual system. In the current study, we performed blunt head trauma on adolescent C57BL/6 mice and investigated visual impairment in the primary visual system, now including the retina and using behavioral and histologic methods at new time points. After injury, mice displayed evidence of decreased optomotor responses illustrated by decreased optokinetic nystagmus. There did not appear to be a significant change in circadian locomotor behavior patterns, although there was an overall decrease in locomotor behavior in mice with head injury. There was evidence of axonal degeneration of optic nerve fibers with associated retinal ganglion cell death. There was also evidence of astrogliosis and microgliosis in major central targets of optic nerve projections. Further, there was elevated expression of endoplasmic reticulum (ER) stress markers in retinas of injured mice. Visual impairment, histologic markers of gliosis and neurodegeneration, and elevated ER stress marker expression persisted for at least 30 days after injury. The current results extend our previous findings in adult mice into adolescent mice, provide direct evidence of retinal ganglion cell injury after head trauma and suggest that axonal degeneration is associated with elevated ER stress in this model of TON.

Traumatic brain injury (TBI) results in a number of impairments, often including visual symptoms. In some cases, visual symptoms after head trauma are mediated by traumatic injury to the optic nerve, termed traumatic optic neuropathy (TON), which has few options for treatment. Using a murine closed head model of head trauma, we have previously reported in adult mice that there is relatively selective injury to the optic system of the brain. In the current study, we performed blunt head trauma on adolescent C57BL/6 mice, and investigated visual impairment and retinal and optic system injury, using behavioral and histologic methods. After injury, mice display evidence of decreased optomotor responses, as evidence by decreased optokinetic nystagmus responses. There does not appear to be a significant change in circadian locomotor behavior patterns, although there is an overall decrease in locomotor behavior in mice with head injury. There is evidence of axonal degeneration of optic nerve fibers, with associated retinal ganglion cell death. There is also evidence of astrogliosis and microgliosis in major central targets of optic nerve projections. Further, there is elevated expression of markers of endoplasmic reticulum (ER) stress in retinas of injured mice. The current results extend our previous findings in adult mice into adolescent mice, provide direct evidence of retinal ganglion cell injury after head trauma, and suggest that axonal degeneration is associated with elevated ER stress in this model of TON. Visual impairment, histologic markers of gliosis and neurodegeneration, and elevated ER stress marker expression persist for at least 30 days after injury.