December 1, 2021 -- MRI elucidates the long-term effects mild traumatic brain injury (TBI) can have on patients, according to two studies highlighted on Tuesday at the RSNA meeting.
In one talk, presenter Alexander Asturias of Touro University of Nevada in Henderson shared results from research that found that MRI diffusion tensor imaging (DTI) of the corpus callosum can help clinicians predict outcomes in mild TBI patients.
The study addresses a knowledge gap, Asturias told session attendees.
"Prior studies have demonstrated associations between fractional anisotrophy [FA] values of the corpus callosum [CC] with clinical outcomes in mild traumatic brain injury patients," he said. "But these were often small studies focused on targeted symptoms and specific populations, such as [children or veterans]. The goal of this study was to identify statistical association between FA of the CC and mild TBI patient symptomatology in a large and diverse group of civilian subjects."
Asturias and colleagues included clinical data from 446 people with mild traumatic brain injury, assessing incidence and longevity of eight common symptoms: cognitive deficits, headache, fatigue, loss of consciousness, depression, anxiety, problems with balance, and mood swings. Of these symptoms, headache was the most common (94%), with balance (70%) and cognitive (73%) taking second and third place, respectively. The most common cause of injury was car accidents, Asturias noted.
Patients were scanned with MRI DTI on one of eight 3-tesla MRI systems (GE Healthcare, Philips Healthcare, and Siemens Healthineers), and median time between scanning and the injury was 100 days.
Asturias' group found that postinjury cognitive deficits were associated with reduced FA values in the whole, anterior, and medial corpus callosum. The team also found that reduced FA values in the posterior corpus callosum were associated with longer duration of postinjury depression and rapid mood changes.
"Lower fractional anisotrophy values of the anterior/mid-body/total corpus callosum associated significantly with prolonged cognitive deficiency post mild TBI," he said. "To our knowledge, we are the first to describe relationship between mild TBI-related neurophychological symptoms and reduced corpus callosum fractional anisotrophy."
TBI impairs the glymphatic system
In a study also included in the session roster, researchers led by Jianfeng Bao, PhD, of Zhengzhou University in Zhengzhou, China, found that the glymphatic system in the brain -- which is responsible for clearing waste in the body -- is impaired in people who have sustained even mild traumatic brain injuries (TBI).
How traumatic brain injury results in neurodegeneration and dementia is unclear, according to Bao's group. Recent animal studies have shown that the glymphatic system, the brain's waste clearance system, is damaged after TBI. In what Bao and colleagues believe to be the first human study, the team compared the TBI sufferers' glymphatic system to healthy controls' using MRI.
Twenty-three study participants (16 TBI patients and seven healthy controls) underwent gadolinium-enhanced T1-weighted (T1W) MRI scans. The group used brain atlas templates to identify regions of interest on the cerebrospinal fluid pathway; it also assessed signal intensity on the images at four time points for each region of interest.
Bao and colleagues found that the percentage changes in T1W signal intensity were higher in those study participants who had suffered traumatic brain injury than in their healthy counterparts for cerebrospinal fluid and gray matter, but not for white matter in all the regions of interest. The investigators attributed the higher signal in TBI patients to the reduced efficiency of the brain to clear the contrast agent -- an important function of the glymphatic system.
Impaired glymphatic system function offers a new way to understand how traumatic brain injury may affect patients in the long term, the group noted. And the study confirms that gadolinium-enhanced T1W MRI is an effective way to assess glymphatic system function in people.
"[After TBI], the glymphatic system ... is impaired," the team wrote in its abstract. "[This happens prior to other dementia symptoms and may be useful in predicting future cognitive decline and risk of dementia in TBI people."