Susceptibility-Weighted Imaging and Proton Magnetic Resonance Spectroscopy in Assessment of Outcome After Pediatric Traumatic Brain Injury

Prognostic value of computed tomography and magnetic resonance imaging findings in acute traumatic brain injury in prediction of poor neurological outcome and mortality: a systematic review and meta-analysis

Traumatic brain injury (TBI) is a major cause of morbidity and mortality, impacting healthcare systems and economies. Early identification of poor outcomes is crucial for effective treatment. This systematic review assesses the prognostic value of computed tomography (CT) and magnetic resonance imaging (MRI) findings in predicting poor neurological outcomes and mortality in the acute phase of TBI. A comprehensive search of Scopus, MEDLINE, and Web of science databases was performed to identify studies examining CT and MR-based imaging findings and their association with poor outcomes as assessed by Glasgow outcome score as well as mortality within the early acute phase of TBI following injury/admission. Qualitative evaluation of included studies revealed several imaging sequences that modify the outcome of the patients, including extra-axial and intra-axial hemorrhage, swirl sign, contrast extravasation, midline shift, closed and open cranial cisterns, signs of edema, presence of cranial fractures, intracranial hemorrhage, cerebral microbleeds, diffuse axonal injury, apparent diffusion coefficient and fractional anisotropy in diffusion tensor imaging, as well as, concentrations of brain metabolites(N-acetyl aspartate, Creatinine, Choline, Myo-inositol, glutamate, and glutamine) in magnetic resonance spectroscopy. Among these markers, subarachnoid hemorrhage (SAH) and subdural hematoma (SDH) emerged as the most predictive of poor outcomes based on meta-analysis findings. SAH was significantly associated with an increased risk of mortality (OR: 3.35, 95% CI: 2.41-4.65, I²=51.3%) and poor outcomes (OR: 2.69, 95% CI: 2.44-2.96, I²=0%). Similarly, SDH correlated with higher mortality risk (OR: 2.44, 95% CI: 2.14-2.78, I²=0%) and worse outcomes (OR: 2.00, 95% CI: 1.12-3.59, I²=60.9%). In contrast, epidural hematoma (EDH) was linked to better outcomes (OR: 0.60, 95% CI: 0.52-0.68, I²=0%) but not significantly associated with mortality (OR: 0.38, 95% CI: 0.09-1.65, I²=73.7%). The results of this systematic review and meta-analysis provide an overview of clinically feasible imaging markers of prognostic value and may inform clinical decision-making in the future.

Traumatic axonal injury: Clinic, forensic and biomechanics perspectives

Identification of Traumatic axonal injury (TAI) is critical in clinical practice, particularly in terms of long-term prognosis, but also for medico-legal issues, to verify whether the death or the after-effects were attributable to trauma. Multidisciplinary approaches are an undeniable asset when it comes to solving these problems. The aim of this work is therefore to list the different techniques needed to identify axonal lesions and to understand the lesion mechanisms involved in their formation. Imaging can be used to assess the consequences of trauma, to identify indirect signs of TAI, to explain the patient's initial symptoms and even to assess the patient's prognosis. Three-dimensional reconstructions of the skull can highlight fractures suggestive of trauma. Microscopic and immunohistochemical techniques are currently considered as the most reliable tools for the early identification of TAI following trauma. Finite element models use mechanical equations to predict biomechanical parameters, such as tissue stresses and strains in the brain, when subjected to external forces, such as violent impacts to the head. These parameters, which are difficult to measure experimentally, are then used to predict the risk of injury. The integration of imaging data with finite element models allows researchers to create realistic and personalized computational models by incorporating actual geometry and properties obtained from imaging techniques. The personalization of these models makes their forensic approach particularly interesting.

White Matter Metabolite Ratios Predict Cognitive Outcome in Pediatric Traumatic Brain Injury

The prognostic ability of global white matter and gray matter metabolite ratios following pediatric traumatic brain injury (TBI) and their relationship to 12-month neuropsychological assessments of intelligence quotient (IQ), attention, and memory is presented. Three-dimensional proton magnetic resonance spectroscopic imaging (MRSI) in pediatric subjects with complicated mild (cMild), moderate, and severe TBI was acquired acutely (6-18 days) and 12 months post-injury and compared to age-matched typically developing adolescents. A global linear regression model, co-registering MRSI metabolite maps with 3D high-resolution magnetic resonance images, was used to identify longitudinal white matter and gray matter metabolite ratio changes. Acutely, gray matter NAA/Cr, white matter NAA/Cr, and white matter NAA/Cho ratios were significantly lower in TBI groups compared to controls. Gray matter NAA/Cho was reduced only in the severe TBI group. At 12 months, all metabolite ratios normalized to control levels in each of the TBI groups. Acute gray matter and white matter NAA ratios were significantly correlated to 12-month assessments of IQ, attention, and memory. These findings suggest that whole brain gray matter and white matter metabolite ratios reflect longitudinal changes in neuronal metabolism following TBI, which can be used to predict neuropsychological outcomes in pediatric subjects.

The Current State of Susceptibility-Weighted Imaging and Quantitative Susceptibility Mapping in Head Trauma

Susceptibility-weighted imaging (SWI) is a MR imaging technique suited to detect structural and microstructural abnormalities in traumatic brain injury (TBI). This review article provide an insight in to the physics principles of SWI and its clinical application in unraveling the complex interaction of the biophysical mechanisms of head injury. Literature evidences support SWI as the most ideal sequence in detection of microbleeds, which is the "tip of the iceberg" biomarker of microvascular injuries. The review also detailed the emerging advance techniques of Quantitative susceptibility mapping (QSM) and artificial intelligence offer the ability to detect and follow the evolution of microbleeds in patient with chronic TBI. These new techniques offers a unique insight into the acute and chronic state of TBI.

The diagnostic potential of fluid and imaging biomarkers in chronic traumatic encephalopathy (CTE)

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease characterized by cognitive, affective, and motor dysfunction. The main pathophysiological mechanisms are chronic neuroinflammation, hyper-phosphorylated tau (p-tau) accumulation and neurodegeneration. CTE is mostly caused by exposure to multiple mild traumatic brain injuries, placing people participating in, for example, high contact sports at increased risk. Currently, CTE can solely be diagnosed post mortem based on the spatial pattern of tau-accumulation. Herein, we review candidate imaging and molecular biomarkers for their sensitivity and specificity and we look whether these are sufficient for reliable ante mortem diagnosis. Of the imaging biomarkers, PET appears to have the best potential. Candidate fluid biomarkers consist of genes and proteins found in brain derived extracellular vesicles, as well as cerebrospinal fluid (CSF) p-tau levels. However, neither these biomarkers nor the imaging biomarkers have the discriminatory power to differentiate between CTE and other tauopathies, highlighting the need for further validation. Future research could incorporate machine learning methodologies to differentiate between the tau accumulation patterns detected by PET/fMRI in Alzheimer's and CTE patients. Additionally, proteomic and metabolomic profiling of CSF and plasma associated with chronic mild traumatic brain injuries could highlight potential biomarkers for identifying at risk patients.

Potential role of susceptibility-weighted imaging in the diagnosis of non-neoplastic pediatric neurological diseases

Background

This study aimed to assess the added value and current applications of SWI in the diagnosis of pediatric non-neoplastic neurological diseases, including its ability to characterize hemorrhage in various brain lesions and its important role in the evaluation of both arterial as well as venous ischemic brain lesions.

Results

Forty pediatric patients with a median age of 9 years were included in our prospective study; 23 were males and 17 females. SWI had a significantly higher detection rate than conventional MRI for traumatic brain injury (TBI) lesions, hemorrhagic lesions in acute necrotizing encephalopathy (ANEC), and cavernoma lesions (p = 0.005, p = 0.038, and p = 0.046, respectively). The sensitivity, specificity and accuracy of SWI for the detection of venous ischemic insult was 88.9%, 50%, and 76.9% respectively. SWI was significantly better than the conventional MRI (p = 0.046) for the detection of chronic ischemic brain insults and ischemic lesions with added hemorrhagic components.

Conclusion

SWI is a technique with reasonable acquisition time that could improve the diagnostic performance of MRI for the evaluation of various pediatric non-neoplastic neurological diseases.

Diffuse axonal injury: a case report and MRI findings

Diffuse axonal injury (DAI) is one of the most severe types of primary traumatic brain injury. In recent years, MR imaging has been gaining popularity as an adjunctive imaging method in patients with DAI. In this case report, we describe MRI findings of an 11-year-old male patient diagnosed with DAI and discuss the role of different sequences in the evaluation of DAI.

Magnetic Resonance Imaging Findings Are Associated with Long-Term Global Neurological Function or Death after Traumatic Brain Injury in Critically Ill Children

The identification of children with traumatic brain injury (TBI) who are at risk of death or poor global neurological functional outcome remains a challenge. Magnetic resonance imaging (MRI) can detect several brain pathologies that are a result of TBI; however, the types and locations of pathology that are the most predictive remain to be determined. Forty-two critically ill children with TBI were recruited prospectively from pediatric intensive care units at five Canadian children's hospitals. Pathologies detected on subacute phase MRIs included cerebral hematoma, herniation, cerebral laceration, cerebral edema, midline shift, and the presence and location of cerebral contusion or diffuse axonal injury (DAI) in 28 regions of interest were assessed. Global functional outcome or death more than 12 months post-injury was assessed using the Pediatric Cerebral Performance Category score. Linear modeling was employed to evaluate the utility of an MRI composite score for predicting long-term global neurological function or death after injury, and nonlinear Random Forest modeling was used to identify which MRI features have the most predictive utility. A linear predictive model of favorable versus unfavorable long-term outcomes was significantly improved when an MRI composite score was added to clinical variables. Nonlinear Random Forest modeling identified five MRI variables as stable predictors of poor outcomes: presence of herniation, DAI in the parietal lobe, DAI in the subcortical white matter, DAI in the posterior corpus callosum, and cerebral contusion in the anterior temporal lobe. Clinical MRI has prognostic value to identify children with TBI at risk of long-term unfavorable outcomes.

Simultaneous feedback control for joint field and motion correction in brain MRI

T2*-weighted gradient-echo sequences count among the most widely used techniques in neuroimaging and offer rich magnitude and phase contrast. The susceptibility effects underlying this contrast scale with B₀, making T2*-weighted imaging particularly interesting at high field. High field also benefits baseline sensitivity and thus facilitates high-resolution studies. However, enhanced susceptibility effects and high target resolution come with inherent challenges. Relying on long echo times, T2*-weighted imaging not only benefits from enhanced local susceptibility effects but also suffers from increased field fluctuations due to moving body parts and breathing. High resolution, in turn, renders neuroimaging particularly vulnerable to motion of the head. This work reports the implementation and characterization of a system that aims to jointly address these issues. It is based on the simultaneous operation of two control loops, one for field stabilization and one for motion correction. The key challenge with this approach is that the two loops both operate on the magnetic field in the imaging volume and are thus prone to mutual interference and potential instability. This issue is addressed at the levels of sensing, timing, and control parameters. Performance assessment shows the resulting system to be stable and exhibit adequate loop decoupling, precision, and bandwidth. Simultaneous field and motion control is then demonstrated in examples of T2*-weighted in vivo imaging at 7T.

Cutting to the Pathophysiology Chase: Translating Cutting-Edge Neuroscience to Rehabilitation Practice in Sports-Related Concussion Management

Mild traumatic brain injury, or concussion, is a common sports injury. Concussion involves physical injury to brain tissue and vascular and axonal damage that manifests as transient and often nonspecific clinical symptoms. Concussion diagnosis is challenging, and the relationship between brain injury and clinical symptoms is unclear. The purpose of this commentary was to translate cutting-edge neuroscience to rehabilitation practice. We (1) highlight potential biomarkers that may improve our understanding of concussion and its recovery, (2) explain why researchers must address the paucity of concussion research in female athletes, and (3) present female-specific factors that should be accounted for in future studies. Integrating objective, quantitative measures of concussion pathophysiology with concussion history, genetics, and genomics will help caregivers identify concussed athletes, tailor recovery protocols, and protect athletes from potential long-term effects of cumulative head impact. J Orthop Sports Phys Ther 2019;49(11):811-818. Epub 1 Jun 2019. doi:10.2519/jospt.2019.8884.

Magnetic resonance spectroscopy of fiber tracts in children with traumatic brain injury: A combined MRS - Diffusion MRI study

Traumatic brain injury can cause extensive damage to the white matter (WM) of the brain. These disruptions can be especially damaging in children, whose brains are still maturing. Diffusion magnetic resonance imaging (dMRI) is the most commonly used method to assess WM organization, but it has limited resolution to differentiate causes of WM disruption. Magnetic resonance spectroscopy (MRS) yields spectra showing the levels of neurometabolites that can indicate neuronal/axonal health, inflammation, membrane proliferation/turnover, and other cellular processes that are on-going post-injury. Previous analyses on this dataset revealed a significant division within the msTBI patient group, based on interhemispheric transfer time (IHTT); one subgroup of patients (TBI-normal) showed evidence of recovery over time, while the other showed continuing degeneration (TBI-slow). We combined dMRI with MRS to better understand WM disruptions in children with moderate-severe traumatic brain injury (msTBI). Tracts with poorer WM organization, as shown by lower FA and higher MD and RD, also showed lower N-acetylaspartate (NAA), a marker of neuronal and axonal health and myelination. We did not find lower NAA in tracts with normal WM organization. Choline, a marker of inflammation, membrane turnover, or gliosis, did not show such associations. We further show that multi-modal imaging can improve outcome prediction over a single modality, as well as over earlier cognitive function measures. Our results suggest that demyelination plays an important role in WM disruption post-injury in a subgroup of msTBI children and indicate the utility of multi-modal imaging.

Neuroimaging of the Injured Pediatric Brain: Methods and New Lessons

Traumatic brain injury (TBI) is a significant public health problem in the United States, especially for children and adolescents. Current epidemiological data estimate over 600,000 patients younger than 20 years are treated for TBI in emergency rooms annually. While many patients experience a full recovery, for others there can be long-lasting cognitive, neurological, psychological, and behavioral disruptions. TBI in youth can disrupt ongoing brain development and create added family stress during a formative period. The neuroimaging methods used to assess brain injury improve each year, providing researchers a more detailed characterization of the injury and recovery process. In this review, we cover current imaging methods used to quantify brain disruption post-injury, including structural magnetic resonance imaging (MRI), diffusion MRI, functional MRI, resting state fMRI, and magnetic resonance spectroscopy (MRS), with brief coverage of other methods, including electroencephalography (EEG), single-photon emission computed tomography (SPECT), and positron emission tomography (PET). We include studies focusing on pediatric moderate-severe TBI from 2 months post-injury and beyond. While the morbidity of pediatric TBI is considerable, continuing advances in imaging methods have the potential to identify new treatment targets that can lead to significant improvements in outcome.

Both hemorrhagic and non-hemorrhagic traumatic MRI lesions are associated with the microstructural damage of the normal appearing white matter

Traumatic microbleeds (TMBs) and non-hemorrhagic lesions (NHLs) on MRI are regarded as surrogate markers of diffuse axonal injury. However, the actual relation between lesional and diffuse pathology remained unclear, since lesions were related to clinical parameters, largely influenced by extracranial factors. The aim of this study is to directly compare TMBs, NHLs and their regional features with the co-existing diffuse injury of the normal appearing white matter (NAWM) as measured by diffusion tensor imaging (DTI). Thirty-eight adults with a closed traumatic brain injury (12 mild, 4 moderate and 22 severe) who underwent susceptibility weighted imaging (SWI), T1-, T2 weighted and FLAIR MRI and routine CT were included in the study. TMB (on SWI) and NHL (on T1-, T2 weighted and FLAIR images) features and Rotterdam scores were evaluated. DTI metrics such as fractional anisotropy (FA) and mean diffusivity (MD) were measured over different NAWM regions. Clinical parameters including age; Glasgow Coma Scale; Rotterdam score; TMB and NHL features were correlated to regional NAWM diffusivity using multiple regression. Overall NHL presence and basal ganglia area TMB load were significantly, negatively correlated with the subcortical NAWM FA values (partial r=-0.37 and -0.36; p=0.006 and 0.025, respectively). The presence of any NHL, or TMBs located in the basal ganglia area indicates diffuse NAWM damage even after adjusting for clinical and CT parameters. To estimate DAI, a conventional lesional MRI pathology evaluation might at least in part substitute the use of quantitative DTI, which is yet not widely feasible in a clinical setting.

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

Mild traumatic brain injury (mTBI), also commonly referred to as concussion, affects millions of Americans annually. Although computed tomography is the first-line imaging technique for all traumatic brain injury, it is incapable of providing long-term prognostic information in mTBI. In the past decade, the amount of research related to magnetic resonance (MR) imaging of mTBI has grown exponentially, partly due to development of novel analytical methods, which are applied to a variety of MR techniques. Here, evidence of subtle brain changes in mTBI as revealed by these techniques, which are not demonstrable by conventional imaging, will be reviewed. These changes can be considered in three main categories of brain structure, function, and metabolism. Macrostructural and microstructural changes have been revealed with three-dimensional MR imaging, susceptibility-weighted imaging, diffusion-weighted imaging, and higher order diffusion imaging. Functional abnormalities have been described with both task-mediated and resting-state blood oxygen level-dependent functional MR imaging. Metabolic changes suggesting neuronal injury have been demonstrated with MR spectroscopy. These findings improve understanding of the true impact of mTBI and its pathogenesis. Further investigation may eventually lead to improved diagnosis, prognosis, and management of this common and costly condition. (©) RSNA, 2016.

Advanced neuroimaging applied to veterans and service personnel with traumatic brain injury: state of the art and potential benefits

Traumatic brain injury (TBI) remains one of the most prevalent forms of morbidity among Veterans and Service Members, particularly for those engaged in the conflicts in Iraq and Afghanistan. Neuroimaging has been considered a potentially useful diagnostic and prognostic tool across the spectrum of TBI generally, but may have particular importance in military populations where the diagnosis of mild TBI is particularly challenging, given the frequent lack of documentation on the nature of the injuries and mixed etiologies, and highly comorbid with other disorders such as post-traumatic stress disorder, depression, and substance misuse. Imaging has also been employed in attempts to understand better the potential late effects of trauma and to evaluate the effects of promising therapeutic interventions. This review surveys the use of structural and functional neuroimaging techniques utilized in military studies published to date, including the utilization of quantitative fluid attenuated inversion recovery (FLAIR), susceptibility weighted imaging (SWI), volumetric analysis, diffusion tensor imaging (DTI), magnetization transfer imaging (MTI), positron emission tomography (PET), magnetoencephalography (MEG), task-based and resting state functional MRI (fMRI), arterial spin labeling (ASL), and magnetic resonance spectroscopy (MRS). The importance of quality assurance testing in current and future research is also highlighted. Current challenges and limitations of each technique are outlined, and future directions are discussed.

Neuroimaging Assessment of Cerebrovascular Reactivity in Concussion: Current Concepts, Methodological Considerations, and Review of the Literature

Concussion is a form of traumatic brain injury (TBI) that presents with a wide spectrum of subjective symptoms and few objective clinical findings. Emerging research suggests that one of the processes that may contribute to concussion pathophysiology is dysregulation of cerebral blood flow (CBF) leading to a mismatch between CBF delivery and the metabolic needs of the injured brain. Cerebrovascular reactivity (CVR) is defined as the change in CBF in response to a measured vasoactive stimulus. Several magnetic resonance imaging (MRI) techniques can be used as a surrogate measure of CBF in clinical and laboratory studies. In order to provide an accurate assessment of CVR, these sequences must be combined with a reliable, reproducible vasoactive stimulus that can manipulate CBF. Although CVR imaging currently plays a crucial role in the diagnosis and management of many cerebrovascular diseases, only recently have studies begun to apply this assessment tool in patients with concussion. In order to evaluate the quality, reliability, and relevance of CVR studies in concussion, it is important that clinicians and researchers have a strong foundational understanding of the role of CBF regulation in health, concussion, and more severe forms of TBI, and an awareness of the advantages and limitations of currently available CVR measurement techniques. Accordingly, in this review, we (1) discuss the role of CVR in TBI and concussion, (2) examine methodological considerations for MRI-based measurement of CVR, and (3) provide an overview of published CVR studies in concussion patients.

Improved sensitivity of 3.0 Tesla susceptibility-weighted imaging in detecting traumatic bleeds and its use in predicting outcomes in patients with mild traumatic brain injury

BACKGROUND

The efficacy of susceptibility-weighted imaging (SWI) for detecting intracranial bleeds (ICBs) in patients with mild traumatic brain injury (MTBI) has not been directly compared to that of T2*-weighted gradient-recalled-echo imaging (T2*WI). Further, its prognostic value for MTBI patients remains unproven.

PURPOSE

To compare the sensitivity of ICB identification between SWI and T2*WI and examine the prognostic value of SWI for MTBI patients.

MATERIAL AND METHODS

T2*WI, SWI, and clinical information of 63 MTBI patients were collected. Sensitivity was compared between T2*WI and SWI for ICB identification, and statistical analysis was conducted to understand the correlations between SWI and clinical characteristics.

RESULTS

ICBs were detected in more patients (47 vs. 35, P < 0.001) and more ICBs were detected (276 vs. 147, P < 0.001) on SWI than T2*WI. On SWI, patients with conscious disturbance showed higher ICBs prevalence (84.6% vs. 58.3%, P = 0.020), and more patients from the post-concussive syndrome (PCS)(+) group than the PCS(-)group were ICBs positive (86.1% vs. 59.3%, P = 0.015). The numbers of ICBs were significantly higher in the PCS(+) group than the PCS(-) group (P < 0.001). Significant correlation was found between PCS and ICBs number (r = 0.510, P < 0.001). Multiple logistic regression analysis showed that ICB number was an independent variable predicting occurrence of PCS.

CONCLUSION

SWI is more sensitive than T2*WI in detecting hemorrhagic foci in MTBI patients and may offer valuable prognostic information regarding these patients, for example, information on PCS. Further, cerebral parenchymal hemorrhage may affect long-term outcomes in MTBI patients.

Neuroimaging findings in pediatric sports-related concussion

OBJECT

The goal in this review was to summarize the results of clinical neuroimaging studies performed in patients with sports-related concussion (SRC) who were referred to a multidisciplinar ypediatric concussion program.

METHODS

The authors conducted a retrospective review of medical records and neuroimaging findings for all patients referred to a multidisciplinary pediatric concussion program between September 2013 and July 2014. Inclusion criteria were as follows: 1) age ≤ 19 years; and 2) physician-diagnosed SRC. All patients underwent evaluation and follow-up by the same neurosurgeon. The 2 outcomes examined in this review were the frequency of neuroimaging studies performed in this population (including CT and MRI) and the findings of those studies. Clinical indications for neuroimaging and the impact of neuroimaging findings on clinical decision making were summarized where available. This investigation was approved by the local institutional ethics review board.

RESULTS

A total of 151 patients (mean age 14 years, 59% female) were included this study. Overall, 36 patients (24%) underwent neuroimaging studies, the results of which were normal in 78% of cases. Sixteen percent of patients underwent CT imaging; results were normal in 79% of cases. Abnormal CT findings included the following: arachnoid cyst (1 patient), skull fracture (2 patients), suspected intracranial hemorrhage (1 patient), and suspected hemorrhage into an arachnoid cyst (1 patient). Eleven percent of patients underwent MRI; results were normal in 75% of cases. Abnormal MRI findings included the following: intraparenchymal hemorrhage and sylvian fissure arachnoid cyst (1 patient); nonhemorrhagic contusion (1 patient); demyelinating disease (1 patient); and posterior fossa arachnoid cyst, cerebellar volume loss, and nonspecific white matter changes (1 patient).

CONCLUSIONS

Results of clinical neuroimaging studies are normal in the majority of pediatric patients with SRC. However, in selected cases neuroimaging can provide information that impacts decision making about return to play and retirement from the sport.

Use of multisequence 3.0-T MRI to detect severe traumatic brain injury and predict the outcome

OBJECTIVE

The aim of this study was to evaluate multisequence 3.0-T MRI in the detection of severe traumatic brain injury (sTBI) and in predicting the outcome.

METHODS

32 patients with sTBI were prospectively enrolled, and multisequence 3.0-T MRI was performed 4-8 weeks post injury. Quantitative data were recorded on each sequence. The ability to display the parenchymal lesions was compared with that of 64-slice spiral CT. The clinical and radiological results were correlated with the Glasgow Outcome Scale Extended scores 6 months after injury.

RESULTS

3.0-T MRI could display more lesions than CT, especially when the lesion was deeply located. The lesion volumes and diffuse axonal injury (DAI) scores were different between good and poor outcome groups on fluid attenuated inversion recovery (p < 0.05). The apparent diffusion coefficient (ADC) values of the splenium of the corpus callosum and brain stem were also different (p < 0.05). Patients with unfavourable outcome showed a significantly higher volume of haemorrhage on susceptibility-weighted imaging than those with favourable outcomes and had haemorrhages generally located more deeply. Logistic regression analysis revealed that the location of haemorrhage and the ADC values of the splenium of the corpus callosum were independent risk factors for poor outcome, with an overall predictive accuracy of 91.4%.

CONCLUSION

The joint use of conventional and advanced sequences of 3.0-T MRI can comprehensively detect the pathological changes occurring after sTBI. Haemorrhagic and non-haemorrhagic DAIs in deep structures strongly suggest poor outcome.

ADVANCES IN KNOWLEDGE

This article improves the understanding of advanced MRI sequences in the detection of patients with sTBI and prediction of prognosis.

A review of neuroimaging findings in repetitive brain trauma

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease confirmed at postmortem. Those at highest risk are professional athletes who participate in contact sports and military personnel who are exposed to repetitive blast events. All neuropathologically confirmed CTE cases, to date, have had a history of repetitive head impacts. This suggests that repetitive head impacts may be necessary for the initiation of the pathogenetic cascade that, in some cases, leads to CTE. Importantly, while all CTE appears to result from repetitive brain trauma, not all repetitive brain trauma results in CTE. Magnetic resonance imaging has great potential for understanding better the underlying mechanisms of repetitive brain trauma. In this review, we provide an overview of advanced imaging techniques currently used to investigate brain anomalies. We also provide an overview of neuroimaging findings in those exposed to repetitive head impacts in the acute/subacute and chronic phase of injury and in more neurodegenerative phases of injury, as well as in military personnel exposed to repetitive head impacts. Finally, we discuss future directions for research that will likely lead to a better understanding of the underlying mechanisms separating those who recover from repetitive brain trauma vs. those who go on to develop CTE.

ACR Appropriateness Criteria head trauma--child

Head trauma is a frequent indication for cranial imaging in children. CT is considered the first line of study for suspected intracranial injury because of its wide availability and rapid detection of acute hemorrhage. However, the majority of childhood head injuries occur without neurologic complications, and particular consideration should be given to the greater risks of ionizing radiation in young patients in the decision to use CT for those with mild head trauma. MRI can detect traumatic complications without radiation, but often requires sedation in children, owing to the examination length and motion sensitivity, which limits rapid assessment and exposes the patient to potential anesthesia risks. MRI may be helpful in patients with suspected nonaccidental trauma, with which axonal shear injury and ischemia are more common and documentation is critical, as well as in those whose clinical status is discordant with CT findings. Advanced techniques, such as diffusion tensor imaging, may identify changes occult by standard imaging, but data are currently insufficient to support routine clinical use. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 3 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Characterization of microstructural injury: a novel approach in infant abusive head trauma-initial experience

Abusive head trauma (AHT) is the leading cause of morbidity and mortality among abused children, yet the neuroanatomical underpinnings of AHT outcome is incompletely understood. The aim of this study was to characterize white matter (WM) abnormalities in infants with AHT using diffusion tensor imaging (DTI) and determine which microstructural abnormalities are associated with poor outcome. Retrospective DTI data from 17 infants (>3 months) with a diagnosis of AHT and a comparison cohort of 34 term infants of similar post-conceptual age (PCA) were compared using a voxel-based DTI analysis of cerebral WM. AHT cases were dichotomously classified into mild/moderate versus severe outcome. Clinical variables and conventional imaging findings were also analyzed in relation to outcome. Outcomes were classified in accordance with the Pediatric Cerebral Performance Category Score (PCPCS). Reduced axial diffusivity (AD) was shown in widespread WM regions in the AHT infants compared with controls as well as in the AHT severe outcome group compared with the AHT mild/moderate outcome group. Reduced mean diffusivity (MD) was also associated with severe outcome. Radial diffusivity (RD), conventional magnetic resonance findings, brain metric measurements, and clinical/laboratory variables (with the exception of Glascow Coma Scale) did not differ among AHT outcome groups. Findings support the unique role of DTI techniques, beyond conventional imaging, in the evaluation of microstructural WM injury of AHT. Reduced AD (likely reflecting axonal damage) and MD were associated with poor clinical outcome. DTI abnormalities may uniquely reflect AHT patterns of axonal injury that are not characterized by conventional imaging, which may have both therapeutic and prognostic implications.

Comparison of subgroups based on hemorrhagic lesions between SWI and FLAIR in pediatric traumatic brain injury

PURPOSE

The purpose of this study was to investigate efficient ways to diagnose and predict clinical outcomes for childhood traumatic brain injury.

METHODS

Hemorrhagic signal intensities in nine brain regions were observed using axial fluid-attenuated inversion recovery (FLAIR) and susceptibility-weighted imaging (SWI). After having divided the subjects into mild presentation (GCS 14-15) and moderate-to-severe presentation groups (GCS ≤13), we divided the patients into three subgroups: Subgroup I, hemorrhagic foci observed only on SWI and not on FLAIR; Subgroup II, hemorrhagic foci observed on both SWI and FLAIR in the same brain regions; and Subgroup III, any cases with additional foci on SWI in other brain regions. We investigated the clinical course and compared lesion numbers and distributions of hemorrhagic lesions on SWI among the subgroups.

RESULTS

Three clinical variables (hospitalization period in intensive care unit, total days of hospitalization, and outcome based on Pediatric Cerebral Performance Category Scale score) showed significant relevance to the three subgroups. Subgroup I showed the fewest lesions followed by Subgroups II and III, respectively. In all three subgroups, lesions were most abundant in cortical regions. Lesion in the thalamus, basal ganglia, corpus callosum, and brainstem was least in Subgroup I and gradually increased in Subgroups II and III. Such distinction was more significant in the moderate-to-severe group when compared with the mild group.

CONCLUSIONS

In cases of pediatric traumatic brain injury, categorizing patients into one of the above three subgroups based on hemorrhagic lesions on SWI and FLAIR is a promising method for predicting patient's clinical outcome.

Quantitative T2 changes and susceptibility-weighted magnetic resonance imaging in murine pregnancy

OBJECTIVE

To evaluate gestational age-dependent changes in the T2 relaxation time in normal murine placentas in vivo. The role of susceptibility-weighted imaging (SWI) in visualization of the murine fetal anatomy was also elucidated.

METHODS

Timed-pregnant CD-1 mice at gestational day (GD) 12 and GD17 underwent magnetic resonance imaging. Multi-echo spin echo and SWI data were acquired. The placental T2 values on GD12 and GD17 were quantified. To account for the influence of systemic maternal physiological factors on placental perfusion, maternal muscle was used as a reference for T2 normalization. A linear mixed-effects model was used to fit the normalized T2 values, and the significance of the coefficients was tested. Fetal SWI images were processed and reviewed for venous vasculature and skeletal structures.

RESULTS

The average placental T2 value decreased significantly on GD17 (40.17 ± 4.10 ms) compared to the value on GD12 (55.78 ± 8.13 ms). The difference in normalized T2 values also remained significant (p = 0.001). Using SWI, major fetal venous structures like the cardinal vein, the subcardinal vein, and the portal vein were visualized on GD12. In addition, fetal skeletal structures could also be discerned on GD17.

CONCLUSION

The T2 value of a normal murine placenta decreases with advancing gestation. SWI provided clear visualization of the fetal venous vasculature and bony structures. © 2014 S. Karger AG, Basel.

Neuroimaging in repetitive brain trauma

Sports-related concussions are one of the major causes of mild traumatic brain injury. Although most patients recover completely within days to weeks, those who experience repetitive brain trauma (RBT) may be at risk for developing a condition known as chronic traumatic encephalopathy (CTE). While this condition is most commonly observed in athletes who experience repetitive concussive and/or subconcussive blows to the head, such as boxers, football players, or hockey players, CTE may also affect soldiers on active duty. Currently, the only means by which to diagnose CTE is by the presence of phosphorylated tau aggregations post-mortem. Non-invasive neuroimaging, however, may allow early diagnosis as well as improve our understanding of the underlying pathophysiology of RBT. The purpose of this article is to review advanced neuroimaging methods used to investigate RBT, including diffusion tensor imaging, magnetic resonance spectroscopy, functional magnetic resonance imaging, susceptibility weighted imaging, and positron emission tomography. While there is a considerable literature using these methods in brain injury in general, the focus of this review is on RBT and those subject populations currently known to be susceptible to RBT, namely athletes and soldiers. Further, while direct detection of CTE in vivo has not yet been achieved, all of the methods described in this review provide insight into RBT and will likely lead to a better characterization (diagnosis), in vivo, of CTE than measures of self-report.

Imaging dopamine neurotransmission in live human brain

Dopamine is an important regulator of cognition and behavior, but its precise influence on human brain processing remains unclear because of the lack of a reliable technique to study dopamine in the live human brain. In the recent years, a number of techniques have been developed to detect, map, and measure dopamine released during task performance. Most of these techniques are based on molecular imaging methods and have varying degrees of sensitivity. We developed a single-scan dynamic molecular imaging technique for the detection of dopamine released during task performance in the live human brain. This technique is extremely sensitive and has test-retest reliability. Using this technique, we detected dopamine released during the processing of a number of cognitive, behavioral, and emotional tasks. Since this technique acquires data that cannot be obtained using any other techniques, it extends the scope of neuroimaging research.

Cerebral glucose metabolism in an immature rat model of pediatric traumatic brain injury

Altered cerebral metabolism and mitochondrial function have been identified in experimental and clinical studies of pediatric traumatic brain injury (TBI). Metabolic changes detected using (1)H (proton) magnetic resonance spectroscopy correlate with long-term outcomes in children after severe TBI. We previously identified early (4-h) and sustained (24-h and 7-day) abnormalities in brain metabolites after controlled cortical impact (CCI) in immature rats. The current study aimed to identify specific alterations of cerebral glucose metabolism at 24 h after TBI in immature rats. Rats (postnatal days 16-18) underwent CCI to the left parietal cortex. Sham rats underwent craniotomy only. Twenty-four hours after CCI, rats were injected (intraperitoneally) with [1,6-(13)C]glucose. Brains were removed, separated into hemispheres, and frozen. Metabolites were extracted with perchloric acid and analyzed using (1)H and (13)C-nuclear magnetic resonance spectroscopy. TBI resulted in decreases in N-acetylaspartate in both hemispheres, compared to sham contralateral. At 24 h after TBI, there was significant decrease in the incorporation of (13)C label into [3-(13)C]glutamate and [2-(13)C]glutamate in the injured brain. There were no differences in percent enrichment of [3-(13)C]glutamate, [4-(13)C]glutamate, [3-(13)C]glutamine, or [4-(13)C]glutamine. There was significantly lower percent enrichment of [2-(13)C]glutamate in both TBI sides and the sham craniotomy side, compared to sham contralateral. No differences were detected in enrichment of (13)C glucose label in [2-(13)C]glutamine, [2-(13)C]GABA (gamma-aminobutyric acid), [3-(13)C]GABA, or [4-(13)C]GABA, [3-(13)C]lactate, or [3-(13)C]alanine between groups. Results suggest that overall oxidative glucose metabolism in the immature brain recovers at 24 h after TBI. Specific reductions in [2-(13)C]glutamate could be the result of impairments in either neuronal or astrocytic metabolism. Future studies should aim to identify pathways leading to decreased metabolism and develop cell-selective "metabolic rescue."

MR venography of the fetal brain using susceptibility weighted imaging

PURPOSE

To evaluate the feasibility of performing fetal brain magnetic resonance venography using susceptibility weighted imaging (SWI).

MATERIALS AND METHODS

After obtaining informed consent, pregnant women in the second and third trimester were imaged using a modified SWI sequence. Fetal SWI acquisition was repeated when fetal or maternal motion was encountered. The median and maximum number of times an SWI sequence was repeated was four and six respectively. All SWI image data were systematically evaluated by a pediatric neuroradiologist for image quality using an ordinal scoring scheme: 1. diagnostic; 2. diagnostic with artifacts; and 3. nondiagnostic. The best score in an individual fetus was used for further statistical analysis. Visibility of venous vasculature was also scored using a dichotomous variable. A subset of SWI data was re-evaluated by the first and independently by a second pediatric neuroradiologist. Kappa coefficients were computed to assess intra-rater and inter-rater reliability.

RESULTS

SWI image data from a total of 22 fetuses were analyzed. Median gestational age and interquartile range of the fetuses imaged were 32 (29.9-34.9) weeks. In 68.2% of the cases (n = 15), there was no artifact; 22.7% (n = 5) had minor artifacts and 9.1% (n = 2) of the data was of nondiagnostic quality. Cerebral venous vasculature was visible in 86.4% (n = 19) of the cases. Substantial agreement (Kappa = 0.73; 95% confidence interval 0.44-1.00)) was observed for intra-rater reliability and moderate agreement (Kappa = 0.48; 95% confidence interval 0.19-0.77) was observed for inter-rater reliability.

CONCLUSION

It is feasible to perform fetal brain venography in humans using SWI.

Repetitive traumatic brain injury and development of chronic traumatic encephalopathy: a potential role for biomarkers in diagnosis, prognosis, and treatment?

The diagnosis of chronic traumatic encephalopathy (CTE) upon autopsy in a growing number of athletes and soldiers alike has resulted in increased awareness, by both the scientific/medical and lay communities, of the potential for lasting effects of repetitive traumatic brain injury. While the scientific community has come to better understand the clinical presentation and underlying pathophysiology of CTE, the diagnosis of CTE remains autopsy-based, which prevents adequate monitoring and tracking of the disease. The lack of established biomarkers or imaging modalities for diagnostic and prognostic purposes also prevents the development and implementation of therapeutic protocols. In this work the clinical history and pathologic findings associated with CTE are reviewed, as well as imaging modalities that have demonstrated some promise for future use in the diagnosis and/or tracking of CTE or repetitive brain injury. Biomarkers under investigation are also discussed with particular attention to the timing of release and potential utility in situations of repetitive traumatic brain injury. Further investigation into imaging modalities and biomarker elucidation for the diagnosis of CTE is clearly both needed and warranted.

Imaging brain trauma

PURPOSE OF REVIEW

Traumatic brain injury (TBI) is a leading cause of death and long-term cognitive and behavioral dysfunction in children and young adults, yet effective treatments are lacking, in part because critical aspects of TBI neurobiology and natural history are not understood. We review recent advances in neuroimaging and discuss how they are helping to address these fundamental gaps.

RECENT FINDINGS

Novel imaging methods provide detailed information on how TBI affects anatomical integrity (diffusion tensor imaging; voxel-based morphometry; susceptibility-weighted imaging, magnetization transfer imaging), metabolic activity (magnetic resonance spectroscopy), perfusion (positron emission tomography, perfusion computed tomography, perfusion magnetic resonance), and patterns of functional activation (functional magnetic resonance imaging). Individually and collectively, these methods can significantly enhance TBI diagnosis and outcome prediction.

SUMMARY

Refinements in neuroimaging offer a window into the complex neuroanatomical and neurophysiological disturbances induced by TBI. Research is needed to understand how these alterations evolve with time and in response to therapeutic interventions.

Decreased fractional anisotropy evaluated using tract-based spatial statistics and correlated with cognitive dysfunction in patients with mild traumatic brain injury in the chronic stage

BACKGROUND AND PURPOSE

The relationship between white matter disruption and cognitive dysfunction of patients with mTBI in the chronic stage remains unclear. The aim of this study was to identify white matter integrity by using DTI in patients with mTBI without morphologic traumatic abnormalities seen with conventional imaging and to evaluate the association of such regions with cognitive function.

MATERIALS AND METHODS

Diffusion tensor images from 51 consecutive patients with mTBI without morphologic traumatic abnormalities on conventional MRI were processed, and FA maps were generated as a measure of white matter integrity. All subjects underwent cognitive examinations (MMSE and WAIS-R FIQ). Correlations between the skeletonized FA values in the white matter and the cognitive function were analyzed by using regression analysis.

RESULTS

In patients with mTBI, significantly decreased FA value clusters in the white matter compared with the healthy controls were found in the superior longitudinal fasciculus, superior frontal gyrus, insula, and fornix. Cognitive examination scores positively correlated with FA values in a number of regions in deep brain structures, which were anatomically close or physiologically intimate to the regions with significant FA value reduction, in patients with mTBI.

CONCLUSIONS

The present study shows that patients with mTBI in the chronic stage have certain regions with abnormally reduced white matter integrity in the brain. Although the clinical and pathologic-anatomic correlation of these findings remains to be elucidated, these brain regions are strongly suggested to be related to chronic persistent cognitive impairments in these patients.

Chronic traumatic encephalopathy: neurodegeneration following repetitive concussive and subconcussive brain trauma

Chronic Traumatic Encephalopathy (CTE) is a neurodegenerative disease thought to be caused, at least in part, by repetitive brain trauma, including concussive and subconcussive injuries. It is thought to result in executive dysfunction, memory impairment, depression and suicidality, apathy, poor impulse control, and eventually dementia. Beyond repetitive brain trauma, the risk factors for CTE remain unknown. CTE is neuropathologically characterized by aggregation and accumulation of hyperphosphorylated tau and TDP-43. Recent postmortem findings indicate that CTE may affect a broader population than was initially conceptualized, particularly contact sport athletes and those with a history of military combat. Given the large population that could potentially be affected, CTE may represent an important issue in public health. Although there has been greater public awareness brought to the condition in recent years, there are still many research questions that remain. Thus far, CTE can only be diagnosed post-mortem. Current research efforts are focused on the creation of clinical diagnostic criteria, finding objective biomarkers for CTE, and understanding the additional risk factors and underlying mechanism that causes the disease. This review examines research to date and suggests future directions worthy of exploration.

Susceptibility weighted imaging and its relationship to outcome after pediatric traumatic brain injury

INTRODUCTION

Traumatic brain injury (TBI) sustained during childhood can cause difficulties in a wide range of physical, neurological, cognitive, social and functional domains. However, the ability of health professionals and researchers to accurately predict the outcome of pediatric TBI remains limited. The advent of advanced neuroimaging techniques shows some promise in improving outcome prediction, as they contribute to greater sensitivity in characterizing intracranial lesions underlying many cognitive and functional deficits. In this study, the relationship between lesions identified on susceptibility weighted imaging (SWI) and cognitive and functional outcomes was investigated following childhood TBI.

METHOD

Participants between 5 and 14 years of age with varying levels of TBI severity (mild, mild complicated, moderate, severe, n = 106) underwent susceptibility weighted scanning on average 1-month post-injury and completed an assessment of intellectual functioning, processing speed, and behavioral and adaptive skills 6-month post-injury.

RESULTS

More severe TBI was generally associated with poorer intellectual functioning, greater behavioral problems and lower adaptive functioning. Number and volume of SWI lesions were significantly correlated with clinical outcome variables including Glasgow Coma Score (GCS), surgical intervention, length of hospital stay and length of intubation, as well as with intellectual functioning. Together, SWI and GCS accounted for a significant, though small, proportion of the variance in intellectual quotient (IQ).

CONCLUSIONS

SWI is a sensitive technique for detecting brain lesions at all TBI severity levels and shows promise in contributing to prediction of cognitive outcomes in the initial stages post-injury.

Emerging imaging tools for use with traumatic brain injury research

This article identifies emerging neuroimaging measures considered by the inter-agency Pediatric Traumatic Brain Injury (TBI) Neuroimaging Workgroup. This article attempts to address some of the potential uses of more advanced forms of imaging in TBI as well as highlight some of the current considerations and unresolved challenges of using them. We summarize emerging elements likely to gain more widespread use in the coming years, because of 1) their utility in diagnosis, prognosis, and understanding the natural course of degeneration or recovery following TBI, and potential for evaluating treatment strategies; 2) the ability of many centers to acquire these data with scanners and equipment that are readily available in existing clinical and research settings; and 3) advances in software that provide more automated, readily available, and cost-effective analysis methods for large scale data image analysis. These include multi-slice CT, volumetric MRI analysis, susceptibility-weighted imaging (SWI), diffusion tensor imaging (DTI), magnetization transfer imaging (MTI), arterial spin tag labeling (ASL), functional MRI (fMRI), including resting state and connectivity MRI, MR spectroscopy (MRS), and hyperpolarization scanning. However, we also include brief introductions to other specialized forms of advanced imaging that currently do require specialized equipment, for example, single photon emission computed tomography (SPECT), positron emission tomography (PET), encephalography (EEG), and magnetoencephalography (MEG)/magnetic source imaging (MSI). Finally, we identify some of the challenges that users of the emerging imaging CDEs may wish to consider, including quality control, performing multi-site and longitudinal imaging studies, and MR scanning in infants and children.

Abusive head trauma Part II: radiological aspects

Abusive head trauma (AHT) is a relatively common cause of neurotrauma in young children. Radiology plays an important role in establishing a diagnosis and assessing a prognosis. Computed tomography (CT), followed by magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI), is the best tool for neuroimaging. There is no evidence-based approach for the follow-up of AHT; both repeat CT and MRI are currently used but literature is not conclusive. A full skeletal survey according to international guidelines should always be performed to obtain information on possible underlying bone diseases or injuries suspicious for child abuse. Cranial ultrasonography is not indicated as a diagnostic modality for the evaluation of AHT. If there is a suspicion of AHT, this should be communicated with the clinicians immediately in order to arrange protective measures as long as AHT is part of the differential diagnosis.

CONCLUSION

The final diagnosis of AHT can never be based on radiological findings only; this should always be made in a multidisciplinary team assessment where all clinical and psychosocial information is combined and judged by a group of experts in the field.

Quantification of brain edema and hemorrhage by MRI after experimental traumatic brain injury in rabbits predicts subsequent functional outcome

We use multiple MRI modalities to measure cerebral edema and intracerebral hemorrhage quantitatively after TBI in rabbits and to acquire the early prognostic MRI information. Multiple MRI modalities (DCE-MRI, DWI and SWI) were used to assess cerebral edema and intracerebral hemorrhage quantitatively at different time points within a month after TBI in 15 rabbits. The functional outcomes were evaluated at 1 and 30 days after TBI. The relationships between the quantitative MRI information at different time points and functional outcome at 30 days were analyzed. The volume transfer coefficient (K (trans)) in the focal lesion area and the perifocal lesion area at the acute phase correlated with the functional outcome at 30 days (p < 0.05). The apparent diffusion coefficient (ADC) value at 7 days in the focal lesion area correlated with the functional outcome at 30 days (p < 0.01) and had a trend to correlate at 3 days (p = 0.08). In the perifocal lesion area, the ADC values at both acute and subacute phase correlated with the functional outcome at 30 days (p < 0.05). The volume of hemorrhage correlated with functional outcome at 30 days (p < 0.05). The cerebral edema assessed by DCE-MRI (K (trans)) and DWI (ADC) and intracerebral hemorrhage assessed by SWI may have predictive values.

Ketogenic diet prevents alterations in brain metabolism in young but not adult rats after traumatic brain injury

Previous studies have shown that the change of cerebral metabolic rate of glucose (CMRglc) in response to traumatic brain injury (TBI) is different in young (PND35) and adult rats (PND70), and that prolonged ketogenic diet treatment results in histological and behavioral neuroprotection only in younger rat brains. However, the mechanism(s) through which ketones act in the injured brain and the biochemical markers of their action remain unknown. Therefore, the current study was initiated to: 1) determine the effect of injury on the neurochemical profile in PND35 compared to PND70 rats; and 2) test the effect of early post-injury administration of ketogenic diet on brain metabolism in PND35 versus PND70 rats. The data show that alterations in energy metabolites, amino acid, and membrane metabolites were not evident in PND35 rats on standard diet until 24  h after injury, when the concentration of most metabolites was reduced from sham-injured values. In contrast, acute, but transient deficits in energy metabolism were measured at 6  h in PND70 rats, together with deficits in N-acetylaspartate that endured until 24  h. Administration of a ketogenic diet resulted in significant increases in plasma β-hydroxybutyrate (βOHB) levels. Similarly, brain βOHB levels were significantly elevated in all injured rats, but were elevated by 43% more in PND35 rats compared to PND70 rats. As a result, ATP, creatine, and phosphocreatine levels at 24  h after injury were significantly improved in the ketogenic PND35 rats, but not in the PND70 group. The improvement in energy metabolism in the PND35 brains was accompanied by the recovery of NAA and reduction of lactate levels, as well as amelioration of the deficits of other amino acids and membrane metabolites. These results indicate that the PND35 brains are more resistant to the injury, indicated by a delayed deficit in energy metabolism. Moreover, the younger brains revert to ketones metabolism more quickly than do the adult brains, resulting in better neurochemical and cerebral metabolic recovery after injury.

Susceptibility weighted imaging: a pictorial review

Susceptibility weighted imaging (SWI) is a valuable technique in the evaluation of a wide variety of intracranial pathologies. SWI is a gradient echo sequence utilising both phase and magnitude data to achieve exquisite sensitivity to tissue magnetic susceptibility effects. Normal SWI appearances and common artefacts are illustrated. Examples of SWI in common intracranial pathologies such as subarachnoid, intraventricular and intraparenchymal haemorrhage, intra-axial and extra-axial tumours, pyogenic and non-pyogenic infections, trauma, neurodegenerative diseases and vascular disease including aneurysms, vascular malformations are illustrated and discussed. This pictorial essay will enable radiologists to recognise the normal, artefactual and common intracranial pathological appearances of SWI.

Advanced neuroimaging in children with nonaccidental trauma

Physical abuse associated with nonaccidental trauma (NAT) affects approximately 144,000 children per year in the USA and, frequently, these injuries affect the developing brain. Most infants with suspected NAT are initially evaluated by skull X-rays and computed tomography to determine whether fractures are present, the severity of the acute injury and the need for urgent neurosurgical intervention. Increasingly, magnetic resonance imaging (MRI) is conducted as it provides additional diagnostic and prognostic information about the extent and nature of the injury. In this review, we examine 4 MRI techniques as they apply to children who present acutely after NAT. Susceptibility-weighted imaging is a 3-D high-resolution MRI technique that is more sensitive than conventional imaging in detecting hemorrhagic lesions that are often associated with diffuse axonal injury (DAI). Magnetic resonance spectroscopy acquires metabolite information reflecting neuronal integrity and function from multiple brain regions and provides a sensitive, noninvasive assessment of neurochemical alterations that offers early prognostic information regarding outcome. Diffusion-weighted imaging (DWI) is based on differences in the diffusion of water molecules within the brain and has been shown to be very sensitive in the early detection of ischemic injury. It is now being used to study the direct effects of traumatic injury as well as those due to secondary ischemia. Diffusion tensor imaging is a form of DWI and allows better evaluation of white matter fiber tracts by taking advantage of the intrinsic directionality (anisotropy) of water diffusion in the human brain. It has been shown to be useful in identifying white matter abnormalities after DAI when conventional imaging appears normal. Although these imaging methods have been studied primarily in adults and children with accidental traumatic brain injury, it is clear that they have the potential to provide additional value in the imaging and clinical evaluation of children with NAT.