MRI Study Offers Insights on Traumatic Brain Injury and Cerebral Microbleeds

Emerging magnetic resonance imaging (MRI) research may provide new insights on vascular brain imaging in patients with traumatic brain injury (TBI).

In a new study, recently published in JAMA Network Open, researchers reviewed MRI findings and clinical data from 617 healthy adults (median age of 52), including 223 participants who had a history of TBI. Of those participants with TBI, 27.4 percent had two TBI events and more than two TBI events occurred in 16.6 percent of the study participants, according to the study.

While MRI markers of small vessel disease (SVD), including lacunes, peripheral vascular space (PVC) and white matter hyperintensity (WMN) were associated with higher cardiovascular disease (CVD) risk, the researchers found that cerebral microbleed (CMB) was the only MRI SVD marker to be significantly associated with TBI or mild TBI (mTBI).

“The lack of association between CMB and vascular risk factors in the TBI group suggests that CMB in these individuals may be less likely driven by chronic vascular pathology, and more likely to be acquired from TBI (what may be described as traumatic CMB). In support of this, results were regionally restricted to lobar CMB but not deep CMB. This is consistent with the observation that while wider chronic vascular disease more typically relates to the development of subcortical CMB, lobar CMB often stem from origins other than underlying vascular disease, including TBI,” wrote Audrey Low, Ph.D., who is affiliated with Departments of Psychiatry and Clinical Neurosciences at the University of Cambridge in Cambridge, United Kingdom, and colleagues.

The study authors pointed out that a higher CMB count was associated with increased TBI events and one in six study participants was diagnosed with CMB on MRI. Out of the 109 cases involving CMB detection, the researchers noted that 86 participants had lobar CMB and nine participants had a combination of lobar and deep CMB.

“While further research on the regional distribution of traumatic CMB is required, findings suggest that CMB detected in lobar regions warrant greater consideration of nonvascular causes, especially when detected in younger individuals,” emphasized Low and colleagues.

The researchers added that participants with a previous TBI were 2.5 times more likely to be current smokers. Traumatic brain injuries were also over 20 percent more common in men than in women (48.9 percent vs. 28.2 percent).

While multivariable analysis from previous research (including TBI and other modifiable risk factors for dementia) found no significant differences between men and women with respect to TBI history, differences in SVD burden may be a key factor, according to the study authors.

“The cumulative evidence underscores the importance of considering sex differences to elucidate the pathophysiology and etiology of CMB, and perhaps SVD by extension,” posited Low and colleagues.

(Editor’s note: For related content, see “MRI Brain Scans Show Similarities Between TBI and Alzheimer’s,” “New MRI Study Examines Impact of Disparities with Childhood Adversity Exposure on Brain Development” and “Study Links PTSD to Higher Carotid Atherosclerosis and White Matter Hyperintensity in Midlife Women.”)

In regard to study limitations, the authors cautioned about extrapolation of the study findings to broader populations in light of the cohort being predominantly comprised of White participants and those with higher education levels. They also noted potential accuracy issues with the use of self-reported measures from study participants.