White Matter Hyperintensities and Mild TBI in Post-9/11 Veterans and Service Members.

INTRODUCTION: The neurobehavioral significance of white matter hyperintensities (WMHs) seen on magnetic resonance imaging after traumatic brain injury (TBI) remains unclear, especially in Veterans and Service Members with a history of mild TBI (mTBI). In this study, we investigate the relation between WMH, mTBI, age, and cognitive performance in a large multisite cohort from the Long-term Impact of Military-relevant Brain Injury Consortium-Chronic Effects of Neurotrauma Consortium. MATERIALS AND METHODS: The neuroimaging and neurobehavioral assessments for 1,011 combat-exposed, post-9/11 Veterans and Service Members (age range 22-69 years), including those with a history of at least 1 mTBI (n = 813; median postinjury interval of 8 years) or negative mTBI history (n = 198), were examined. RESULTS: White matter hyperintensities were present in both mTBI and comparison groups at similar rates (39% and 37%, respectively). There was an age-by-diagnostic group interaction, such that older Veterans and Service Members with a history of mTBI demonstrated a significant increase in the number of WMHs present compared to those without a history of mTBI. Additional associations between an increase in the number of WMHs and service-connected disability, insulin-like growth factor-1 levels, and worse performance on tests of episodic memory and executive functioning-processing speed were found. CONCLUSIONS: Subtle but important clinical relationships are identified when larger samples of mTBI participants are used to examine the relationship between history of head injury and radiological findings. Future studies should use follow-up magnetic resonance imaging and longitudinal neurobehavioral assessments to evaluate the long-term implications of WMHs following mTBI.

-----Comparison of T1-Post and FLAIR-Post MRI for identification of traumatic meningeal enhancement in traumatic brain injury patients.

Traumatic meningeal enhancement (TME) is a novel biomarker observed on post-contrast fluid-attenuated inversion recovery (FLAIR) in patients who undergo contrast-enhanced magnetic resonance imaging (MRI) after suspected traumatic brain injury (TBI). TME may be seen on acute MRI despite the absence of other trauma-related intracranial findings. In this study we compare conspicuity of TME on FLAIR post-contrast and T1 weighted imaging (T1WI) post-contrast, and investigate if TME is best detected by FLAIR post-contrast or T1WI post-contrast sequences. Subjects selected for analysis enrolled in the parent study (NCT01132937) in 2016 and underwent contrast-enhanced MRI within 48 hours of suspected TBI. Two blinded readers reviewed pairs of pre- and post-contrast T1WI and FLAIR images for presence or absence of TME. Discordant pairs between the two blinded readers were reviewed by a third reader. Cohen's kappa coefficient was used to calculate agreement. Twenty-five subjects (15 males, 10 females; median age 48 (Q1:35-Q3:62; IQR: 27)) were included. The blinded readers had high agreement for presence of TME on FLAIR (Kappa of 0.90), but had no agreement for presence of TME on T1WI (Kappa of -0.24). The FLAIR and T1WI scans were compared among all three readers and 62% of the cases positive on FLAIR could be seen on T1WI. However, 38% of the cases who were read positive on FLAIR for TME were read negative for TME on T1WI. Conspicuity of TME is higher on post-contrast FLAIR MRI than on post-contrast T1WI. TME as seen on post-contrast FLAIR MRI can aid in the identification of patients with TBI.

MR imaging of hypoxic-ischemic injury in term neonates: pearls and pitfalls.

Hypoxic-ischemic injury (HII) continues to be an important cause of neonatal mortality and morbidity. In recent years, the role of magnetic resonance (MR) imaging has increased by providing early detection to initiate preventive measures and assess the severity of tissue injury, and it often serves as a prognostic indicator. However, because of the subtle findings and temporal variability of signal abnormalities, the imaging diagnosis often remains troublesome, particularly for trainees and general radiologists who do not often encounter these findings. The imaging manifestations between term and preterm infants differ significantly; the imaging findings in term neonates are discussed. Two main patterns of HII have been described in term neonates: peripheral and basal ganglia-thalamus, with the predominant pattern in an affected infant dependent on the duration and severity of the insult. The peripheral pattern occurs in the setting of mild hypoxia or ischemia of prolonged duration, with predominant findings in the cerebral cortex and subcortical white matter along the intervascular boundary zones. The basal ganglia-thalamus pattern is most often secondary to a more severe hypoxic or ischemic event of short duration and manifests with abnormal hyperintensity on T1-weighted images and hypointensity on T2-weighted images in the posterolateral putamen and ventrolateral thalamus. Associated loss of normal hyperintensity on T1-weighted images and hypointensity on T2-weighted images in the posterior limb of the internal capsule may be present. Restricted diffusion and evolution of imaging findings may be seen in each of these regions, depending on when images are obtained. Advanced imaging techniques, including MR spectroscopy, may add valuable information and specificity, with an abnormal lactate peak often serving as an indicator of HII in term neonates.