Objective: Functional connectivity in the default mode network (DMN) is known to be reduced in patients with disorders of consciousness, to a different extent depending on their clinical severity. Nevertheless, the integrity of the structural architecture supporting this network and its relation with the exhibited functional disconnections are very poorly understood. We investigated the structural connectivity and white matter integrity of the DMN in patients with disorders of consciousness of varying clinical severity. Methods: Fifty-two patients-19 in a vegetative state (VS), 27 in a minimally conscious state (MCS), and 6 emerging from a minimally conscious state (EMCS)-and 23 healthy volunteers participated in the study. Structural connectivity was assessed by means of probabilistic tractography, and the integrity of the resulting fibers was characterized by their mean fractional anisotropy values. Results: Patients showed significant impairments in all of the pathways connecting cortical regions within this network, as well as the pathway connecting the posterior cingulate cortex/precuneus with the thalamus, relative to the healthy volunteers. Moreover, the structural integrity of this pathway, as well as that of those connecting the posterior areas of the network, was correlated with the patients' behavioral signs for awareness, being higher in EMCS patients than those in the upper and lower ranges of the MCS patients, and lowest in VS patients. Interpretation: These results provide a possible neural substrate for the functional disconnection previously described in these patients, and reinforce the importance of the DMN in the genesis of awareness and the neural bases of its disorders. ANN NEUROL 2012;72:335-343 P atients with disorders of consciousness (DOC) show metabolic impairments and functional disconnections within corticocortical and thalamic-cortical areas of the default mode network (DMN) [1][2][3][4] to an extent that appears to correspond to clinical severity. 5 Thus, poorer functional connectivity is observed in vegetative state (VS) patients (who show no behavioral signs of awareness) 6 than in minimally conscious state (MCS) patients (who show intermittent behavioral signs of awareness). 7It is generally assumed that functional connectivity within intrinsic networks reflects structural connectivity. A plausible hypothesis, then, is that the reduced functional connectivity observed in the DMN of DOC patients reflects structural disconnections within this network, providing anatomical support for the description of these patients as suffering from ''disconnection syndromes.'' 8 However, the relationship between structure and function in the DMN is not straightforward. 9 It has View this article online at wileyonlinelibrary.com.

IMPORTANCE Traumatic brain injury (TBI) has been associated with adverse mental health outcomes, such as posttraumatic stress disorder (PTSD) and major depressive disorder (MDD), but little is known about factors that modify risk for these psychiatric sequelae, particularly in the civilian sector.OBJECTIVE To ascertain prevalence of and risk factors for PTSD and MDD among patients evaluated in the emergency department for mild TBI (mTBI). DESIGN, SETTING, AND PARTICIPANTS Prospective longitudinal cohort study (February 2014 to May 2018). Posttraumatic stress disorder and MDD symptoms were assessed using the PTSD Checklist for DSM-5 and the Patient Health Questionnaire-9 Item. Risk factors evaluated included preinjury and injury characteristics. Propensity score weights-adjusted multivariable logistic regression models were performed to assess associations with PTSD and MDD. A total of 1155 patients with mTBI (Glasgow Coma Scale score, 13-15) and 230 patients with nonhead orthopedic trauma injuries 17 years and older seen in 11 US hospitals with level 1 trauma centers were included in this study. MAIN OUTCOMES AND MEASURES Probable PTSD (PTSD Checklist for DSM-5 score, Ն33) and MDD (Patient Health Questionnaire-9 Item score, Ն15) at 3, 6, and 12 months postinjury. RESULTS Participants were 1155 patients (752 men [65.1%]; mean [SD] age, 40.5 [17.2] years) with mTBI and 230 patients (155 men [67.4%]; mean [SD] age, 40.4 [15.6] years) with nonhead orthopedic trauma injuries. Weights-adjusted prevalence of PTSD and/or MDD in the mTBI vs orthopedic trauma comparison groups at 3 months was 20.0% (SE, 1.4%) vs 8.7% (SE, 2.2%) (P < .001) and at 6 months was 21.2% (SE, 1.5%) vs 12.1% (SE, 3.2%) (P = .03). Risk factors for probable PTSD at 6 months after mTBI included less education (adjusted odds ratio, 0.89; 95% CI, 0.82-0.97 per year), being black (adjusted odds ratio, 5.11; 95% CI, 2.89-9.05), self-reported psychiatric history (adjusted odds ratio, 3.57; 95% CI, 2.09-6.09), and injury resulting from assault or other violence (adjusted odds ratio, 3.43; 95% CI, 1.56-7.54). Risk factors for probable MDD after mTBI were similar with the exception that cause of injury was not associated with increased risk. CONCLUSIONS AND RELEVANCEAfter mTBI, some individuals, on the basis of education, race/ethnicity, history of mental health problems, and cause of injury were at substantially increased risk of PTSD and/or MDD. These findings should influence recognition of at-risk individuals and inform efforts at surveillance, follow-up, and intervention.

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BACKGROUND & PURPOSE Precision Medicine is an approach to disease diagnosis, treatment and prevention which relies on quantitative biomarkers that minimize the variability of individual patient measurements. The aim of this study is to assess the inter-site variability after harmonization of a high angular resolution 3T diffusion tensor imaging protocol across 13 scanners at the 11 academic medical centers participating in the Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) multisite study. MATERIALS AND METHODS Diffusion MRI was acquired from a novel isotropic diffusion phantom developed at the National Institute of Standards and Technology (NIST) and from the brain of a traveling volunteer on thirteen 3T MR scanners representing three major vendors (General Electric, Philips and Siemens). Means of the DTI parameters and their coefficients of variation (CoVs) across scanners were calculated for each DTI metric and white matter tract. RESULTS For the NIST diffusion phantom, the CoV of apparent diffusion coefficient (ADC) across the 13 scanners was < 3.8% for a range of diffusivities from 0.4 to1.1×10−6 mm2/s. For the volunteer, the CoVs across scanners of the 4 primary DTI metrics, each averaged over the entire white matter skeleton, were all < 5%. In individual white matter tracts, large central pathways showed good reproducibility with the CoV consistently below 5%. However, smaller tracts showed more variability with the CoV of some DTI metrics reaching 10%. CONCLUSION The results suggest the feasibility of standardizing DTI across 3T scanners from different MR vendors in a large-scale neuroimaging research study.