Traumatic cerebral vascular injury (TCVI) is a very frequent, if not universal, feature after traumatic brain injury (TBI). It is likely responsible, at least in part, for functional deficits and TBI-related chronic disability. Because there are multiple pharmacologic and non-pharmacologic therapies that promote vascular health, TCVI is an attractive target for therapeutic intervention after TBI. The cerebral microvasculature is a component of the neurovascular unit (NVU) coupling neuronal metabolism with local cerebral blood flow. The NVU participates in the pathogenesis of TBI, either directly from physical trauma or as part of the cascade of secondary injury that occurs after TBI. Pathologically, there is extensive cerebral microvascular injury in humans and experimental animal, identified with either conventional light microscopy or ultrastructural examination. It is seen in acute and chronic TBI, and even described in chronic traumatic encephalopathy (CTE). Non-invasive, physiologic measures of cerebral microvascular function show dysfunction after TBI in humans and experimental animal models of TBI. These include imaging sequences (MRI-ASL), Transcranial Doppler (TCD), and Near InfraRed Spectroscopy (NIRS). Understanding the pathophysiology of TCVI, a relatively under-studied component of TBI, has promise for the development of novel therapies for TBI.

The incidence of traumatic brain injury (TBI) in the United States was 3.5 million cases in 2009, according to the Centers for Disease Control and Prevention. It is a contributing factor in 30.5% of injury-related deaths among civilians. Additionally, since 2000, more than 260,000 service members were diagnosed with TBI, with the vast majority classified as mild or concussive (76%). The objective assessment of TBI via imaging is a critical research gap, both in the military and civilian communities. In 2011, the Department of Defense (DoD) prepared a congressional report summarizing the effectiveness of seven neuroimaging modalities (computed tomography [CT], magnetic resonance imaging [MRI], transcranial Doppler [TCD], positron emission tomography, single photon emission computed tomography, electrophysiologic techniques [magnetoencephalography and electroencephalography], and functional near-infrared spectroscopy) to assess the spectrum of TBI from concussion to coma. For this report, neuroimaging experts identified the most relevant peer-reviewed publications and assessed the quality of the literature for each of these imaging technique in the clinical and research settings. Although CT, MRI, and TCD were determined to be the most useful modalities in the clinical setting, no single imaging modality proved sufficient for all patients due to the heterogeneity of TBI. All imaging modalities reviewed demonstrated the potential to emerge as part of future clinical care. This paper describes and updates the results of the DoD report and also expands on the use of angiography in patients with TBI.