Diffusion tensor MR imaging in diffuse axonal injury. AJNR Am J Neuroradiol

Department of Medical Physics, University of Wisconsin, Madison 53706-1532, USA.
American Journal of Neuroradiology (Impact Factor: 3.59). 06/2002; 23(5):794-802.
Source: PubMed


Disruption of the cytoskeletal network and axonal membranes characterizes diffuse axonal injury (DAI) in the first few hours after traumatic brain injury. Histologic abnormalities seen in DAI hypothetically decrease the diffusion along axons and increase the diffusion in directions perpendicular to them. DAI therefore is hypothetically associated in the short term with decreased diffusion anisotropy. We tested this hypothesis by measuring the diffusion characteristics of traumatized brain tissue with use of diffusion tensor MR imaging.
Five patients with mild traumatic brain injuries and 10 control subjects were studied with CT, conventional MR imaging, and diffusion tensor imaging. All patients were examined within 24 hours of injury. In each participant, diffusion tensor indices from homologous normal-appearing white matter regions of both hemispheres were compared. These indices were also compared between homologous regions of each patient and the control group. In two patients, diffusion tensor images from the immediate post-trauma period were compared with those at 1 month follow-up.
Patients displayed significant reduction of diffusion anisotropy in several regions compared with the homologous ones in the contralateral hemisphere. Such differences were not observed in the control subjects. Significant reduction of diffusion anisotropy was also detected when diffusion tensor results from the patients were compared with those of the controls. This reduction was often less evident 1 month after injury.
White matter regions with reduced anisotropy are detected in the first 24 hours after traumatic brain injury. Therefore, diffusion tensor imaging may be a powerful technique for in vivo detection of DAI.

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    • "n and radial diffu - sivity ) but new abnormalities in others ( axial diffusivity ) , suggesting that cellular edema and inflammation normalize , but axonal injury may persist . Other studies have provided evidence that DTI metrics reflecting axonal injury may par - tially normalize , suggesting a process of recovery that is incomplete ( e . g . , Arfanakis et al . , 2002 ; Grossman et al . , 2013 ; Mayer et al . , 2010 ; but see Ling et al . , 2012 ) . Taken together , these studies leave open the possibility of continued axonal recovery over more extended time periods , although it is notable that persistent white matter changes have been observed even years after mTBI ( e . g . , Inglese et al . , 200"
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    ABSTRACT: Recent advances in neuroimaging methodologies sensitive to axonal injury have made it possible to assess in vivo the extent of traumatic brain injury (TBI) -related disruption in neural structures and their connections. The objective of this paper is to review studies examining connectivity in TBI with an emphasis on structural and functional MRI methods that have proven to be valuable in uncovering neural abnormalities associated with this condition. We review studies that have examined white matter integrity in TBI of varying etiology and levels of severity, and consider how findings at different times post-injury may inform underlying mechanisms of post-injury progression and recovery. Moreover, in light of recent advances in neuroimaging methods to study the functional connectivity among brain regions that form integrated networks, we review TBI studies that use resting-state functional connectivity MRI methodology to examine neural networks disrupted by putative axonal injury. The findings suggest that TBI is associated with altered structural and functional connectivity, characterized by decreased integrity of white matter pathways and imbalance and inefficiency of functional networks. These structural and functional alterations are often associated with neurocognitive dysfunction and poor functional outcomes. TBI has a negative impact on distributed brain networks that lead to behavioral disturbance.
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    • "We therefore decided to use diffusion tensor magnetic resonance imaging (DTI) as an independent non-invasive method to assess axonal pathology in human TBI patients. DTI is a sensitive and robust method to assess white matter structural integrity following TBI (Arfanakis et al., 2002; Inglese et al., 2005; Nakayama et al., 2006; Salmond et al., 2006; Kraus et al., 2007; Newcombe et al., 2007; Niogi et al., 2008; Sidaros et al., 2008; Perlbarg et al., 2009; Niogi and Mukherjee, 2010; Kinnunen et al., 2011; Galanaud et al., 2012; Hulkower et al., 2013). DTI measures the directional diffusion of water, which in normal white matter is restricted by the orientation of axon bundles. "
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    • "Another study (Fernández-Espejo et al., 2012) used probabilistic tractography on patients with different DOC states (VS, MCS, exit-MCS) and controls to explain differences in the structural connectivity of the default mode network that correlate with clinical diagnosis and CRS-R. The prospective setup is rarely performed on such patients (Arfanakis et al., 2002; Dinkel et al., 2014). A follow-up study of up to 5 years post-injury, has recently been published regarding 13 severe TBI patients (Dinkel et al., 2014). "
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