Cognitive impairment after traumatic brain injury: The role of MRI and possible pathological basis

Traumatic brain injury (TBI) is closely related to increased incidence of cognitive impairment from the acute phase to chronic phase. At present, the pathological mechanism leading to cognitive impairment after TBI is still not fully understood. We hypothesize that neuron loss, diffuse axonal injury, microbleed, and blood-brain barrier (BBB) disruption altogether contribute to the development of cognitive impairment. Furthermore, the disruption of structural and functional neural network related to the cognitive function might bring about the final step in the occurrence of cognitive impairment after TBI. In this review, we summarize the role of different MRI techniques in the assessment of the pathological changes related to cognitive impairment after TBI. These MRI techniques include T1-MPRAGE sequence reflecting neuron loss, diffusion tensor imaging reflecting diffuse axonal injury, diffusion kurtosis imaging reflecting diffuse axonal injury and reactive gliosis, susceptibility weighted imaging showing microbleed, arterial spin labeling showing blood flow and dynamic contrast enhanced MRI showing BBB disruption. In the future, correlational study of multi-MRI sequences scan, pathological examination, and cognitive tests will provide valuable information for understanding the mechanism of cognitive impairment after TBI and manage TBI patients.