Default-Mode Network Disruption in Mild Traumatic Brain Injury

Abstract

Purpose:To investigate the integrity of the default-mode network (DMN) by using independent component analysis (ICA) methods in patients shortly after mild traumatic brain injury (MTBI) and healthy control subjects, and to correlate DMN connectivity changes with neurocognitive tests and clinical symptoms. Materials and Methods:This study was approved by the institutional review board and complied with HIPAA regulations. Twenty-three patients with MTBI who had posttraumatic symptoms shortly after injury (,2 months) and 18 age-matched healthy control subjects were included in this study.Resting-state functional magnetic resonance imaging was performed at 3 T to characterize the DMN by using ICA methods, including a single-participant ICA on the basis of a comprehensive template from core seeds in the posterior cingulate cortex (PCC) and medial prefrontal cortex (MPFC) nodes. ICA z images of DMN components were compared between the two groups and correlated with neurocognitive tests and clinical performance in patients by using Pearson and Spearman rank correlation. Results:When compared with the control subjects, there was significantly reduced connectivity in the PCC and parietal regions and increased frontal connectivity around the MPFC in patients with MTBI (P , .01). These frontoposterior opposing changes within the DMN were significantly correlated (r = 20.44, P = .03). The reduced posterior connectivity correlated positively with neurocognitive dysfunction (eg, cognitive flexibility), while the increased frontal connectivity correlated negatively with posttraumatic symptoms (ie, depression, anxiety, fatigue, and postconcussion syndrome). Conclusion:These results showed abnormal DMN connectivity patterns in patients with MTBI, which may provide insight into how neuronal communication and information integration are disrupted among DMN key structures after mild head injury. Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights. (25) showed decreased connectivity within DMN nodes and increased headache, dizziness, fatigue, irritability, insomnia, poor concentration, memory difficulty, or an intolerance of stress, emotion, or alcohol) that have lasted at least 3 months (6), as well as evidence of deficits in attention and memory (7). PCS is frequently overlooked at the time of initial injury and can develop and persist for variable periods of time. However, the underlying pathophysiology of PCS is still poorly understood.In recent years, resting-state functional magnetic resonance (MR) imaging has enabled evaluation of critical brain networks on the basis of baseline energy expenditure in awake and resting states of the brain. Resting-state networks are composed of brain regions with highly correlated time courses of robust low-frequency (,0.1 Hz) blood oxygen level-dependent signal fluctuations (8), which are believed to represent the maintenance of baseline human cognition and metab...

Mild Traumatic Brain Injury: Longitudinal Regional Brain Volume Changes

“…The precuneal region is important because of its large number of reciprocal connections with frontal systems and its involvement in executive function, working memory, and conscious information processing (59). The cingulate gyrus isthmus and the precuneus region are of considerable interest given their vulnerability to traumatic injury (20,60).…”

“…In chronic traumatic encephalopathy, a neurodegenerative disease resulting from repetitive traumatic head injuries, brain atrophy involves both cerebral gray matter (GM) and white matter (WM) and is associated with tau neurofibrillary degeneration (15,16). Although there is typically no evidence of structural brain abnormality at conventional neuroimaging after MTBI, recent data (17)(18)(19)(20) obtained by using a variety of newer techniques, including proton spectroscopy, advanced diffusion techniques, and functional magnetic resonance (MR) imaging, demonstrate postconcussive microstructural, metabolic, and functional changes in the brain. Whether a single concussive episode and the resultant microstructural, metabolic, and functional changes that have been associated with such an injury culminate in longterm brain atrophy is not known.…”

MR Imaging Applications in Mild Traumatic Brain Injury: An Imaging Update

“…Limited physical stress has been shown to further alter the integrity of the DMN in mTBI patients (121,122). Interestingly, unlike activation changes in task-mediated functional MR imaging, changes in DMN have been linked to neurocognitive dysfunction and posttraumatic symptoms (119). Although the DMN is not activated during functional tasks, this finding suggests that its integrity is intimately connected with cognition and cognitive function.…”

Detection of Mild Traumatic Brain Injury by Machine Learning Classification Using Resting State Functional Network Connectivity and Fractional Anisotropy

“…15,16 Using functional MRI (fMRI) to explore functional changes related to gray matter, reduced resting state functional connectivity in the default mode network (DMN) along with increased connectivity within the ventromedial prefrontal cortex has been found in patients with mTBI. [17][18][19] Weaker functional connectivity between important networks has been found in relation to mTBI including DMN-basal ganglia, attention-sensorimotor, attentionfrontal, and within the sensorimotor networks. 20 Increased resting state functional connectivity in the thalamus has been reported including thalamo-thalamo, thalamo-frontal, and thalamo-temporal circuits.…”