Imaging of Cerebrovascular Function in Chronic Traumatic Brain Injury

Abstract

Traumatic cerebrovascular injury (TCVI) is a common pathologic mechanism of traumatic brain injury (TBI) and presents an attractive target for intervention. The aims of this study were to assess cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) using magnetic resonance imaging (MRI) to assess their value as biomarkers of TCVI in chronic TBI, characterize the spatial distribution of TCVI, and assess the relationships between each biomarker and neuropsychological and clinical assessments. Forty-two subjects (27 chronic TBI, 15 age- and gender-matched healthy volunteers) were studied cross-sectionally. CBF was measured by arterial spin labeling and CVR by assessing the MRI-blood oxygen level-dependent signal with hypercapnia challenge. A focused neuropsychological battery adapted from the TBI Common Data Elements and neurobehavioral symptom questionnaires were administered at the time of the imaging session. Chronic TBI subjects showed a significant reduction in mean global, gray matter (GM), and white matter (WM) CVR, compared with healthy volunteers (p < 0.001). Mean GM CVR had the greatest effect size (Cohen's d = 0.9). CVR maps in chronic TBI subjects showed patchy, multifocal CVR deficits. CBF discriminated poorly between TBI subjects and healthy volunteers and did not correlate with CVR. Mean global CVR correlated best with chronic neurobehavioral symptoms among TBI subjects. Global, GM, and WM CVR are reliable and potentially useful biomarkers of TCVI in the chronic stage after moderate-to-severe TBI. CBF is less useful as biomarker of TCVI. CVR correlates best with chronic TBI symptoms. CVR has potential as a predictive and pharmacodynamic biomarker for interventions targeting TCVI.

Systematic review on the characterization of chronic traumatic encephalopathy by MRI and MRS

“…Furthermore, a significant group difference in dorsal anterior cingulate was found. Amyot et al found significant reductions in mean global, GM, and WM cerebrovascular reactivity in chronic TBI individuals by BOLD analysis . However, no significant group difference for CBF was found by ASL analysis.…”

“…The age range of all studies was from school level to retirement age (13.5–74 years). Of all included in vivo studies, 22 used an age‐matched control group . All articles were published between 1994 and 2018.…”

“…Thirteen studies used diffusion MRI, specifically diffusion tensor imaging (DTI), generalized q‐sampling imaging (GQI), diffusion kurtosis imaging (DKI), and diffusion weighted imaging (DWI) . Six studies acquired functional MRI (fMRI) with either blood oxygenation level‐dependent (BOLD) or arterial spin labeling (ASL) sequences . One study applied MRS .…”

“…Of the 25 selected articles, 21 applied structural MRI, whereas all of them were based on in vivo data. Of those, seven applied solely structural MRI sequences, whereas all others additionally either applied diffusion MRI, functional MRI, MRS or a combination thereof . T 1 ‐w, T 2 ‐w, FLAIR, SWI, and PD‐w were utilized in these studies.…”

“…Of the 25 included studies, six focused on fMRI . Chronic TBI patients in the study by Wiese et al were divided into left and right hemispheric lesions .…”