Radiology: MRI shows disrupted brain connectivity in post-concussive patients
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| Images show group thalamic RSNs in 3D views obtained by using the one-sample t test ( P , .001, k . 100) in patients with MTBI. Source: Radiology. |
By finding abnormal thalamic resting-state networks (RSNs) in patients with MTBI, the study bolsters support for presumed subtle thalamic injury and demonstrates that fMRI can be used as an additional imaging modality to detect thalamocortical connectivity abnormalities and understand complex persistent post-concussive syndrome.
“Using resting-state functional MRI [fMRI], we found increased functional connectivity of thalamocortical networks in patients following MTBI, due to the subtle injury of the thalamus,” said study co-author Yulin Ge, MD, associate professor in the department of radiology at New York University Langone Medical Center in New York City. “These findings hold promise for better elucidating the underlying cause of a variety of post-traumatic symptoms that are difficult to spot and characterize using conventional imaging methods.”
According to the Centers for Disease Control and Prevention, each year in the U.S. 1.5 million people sustain traumatic brain injuries, resulting from sudden trauma to the brain. MTBI, or concussion, accounts for at least 75 percent of all traumatic brain injuries. Typically in patients with MTBI, there is an absence of obvious structural lesions, which has made it difficult to understand the pathophysiology of MTBI, offered Ge and colleagues.
Mounting evidence has suggested that thalamic injury may be an important factor in MTBI. However, imaging markers for thalamic injury are lacking.
“The RSNs have great potential for studying thalamic dysfunction in several clinical disorders including traumatic brain injury,” Ge continued.
Resting-state functional MRI (RS-fMRI) has rapidly emerged as a novel informative tool for investigating brain connectivity between regions that are functionally linked. The technique may be able to provide objective measurements in patients with MTBI and post-traumatic symptoms that are difficult to explain via conventional MRI findings, wrote the researchers.
Ge and colleagues sought to determine whether thalamic RSNs are disrupted in patients with TBI. They used RS-fMRI to study the brain activity of 24 patients with MTBI and 17 healthy control patients from March 2008 to December 2009, and also compared performance on neuropsychologic and neurobehavorial tests in these patients.
A normal pattern of thalamic RSNs with relatively symmetric and restrictive connectivity was demonstrated in the healthy control group. In patients with MTBI, this pattern was disrupted, with significantly increased thalamic RSNs and decreased symmetry. These findings correlated with clinical symptoms and diminished neurocognitive functions in the patients with MTBI, as evaluated by a psychologist blinded to fMRI results and patient cohort.
“It is vital to develop a sensitive and objective imaging tool that allows researchers to better detect thalamic injury, which is considered to be subtle and largely underestimated in MTBI,” the researchers stated.
Ge and colleagues identified several imitations to the study, noting that although it focused on the thalamic functional network, other RSNs also may be abnormal in patients with MTBI. In addition, the possibility of structural changes in the thalamus remains open. “Future studies exploring the relationship between structural and functional network deficits and between these abnormalities and clinical posttraumatic symptoms in a longitudinal design will be valuable,” the researchers concluded.
Ge indicated that the results of the study have implications for a new therapeutic strategy, based on sound understanding of the underlying mechanisms of thalamocortical disruption and post-concussive syndrome.