Detecting Lesions after Traumatic Brain Injury Using Susceptibility Weighted Imaging: A Comparison with Fluid-Attenuated Inversion Recovery and Correlation with Clinical Outcome

Appropriate incorporation of susceptibility-weighted magnetic resonance imaging into routine imaging protocols for accurate diagnosis of traumatic brain injuries: a systematic review

Traumatic brain injury (TBI) results from physical or traumatic injuries to the brain's surrounding bony structures and associated tissues, which can lead to various sequelae, including simple concussion, acute epidural hematoma, parenchymal contusions, subarachnoid hemorrhage, diffuse axonal injury, and chronic traumatic encephalopathy. Susceptibility-weighted imaging (SWI) has enhanced the accuracy of neuroimaging for these injuries. SWI is based on 3D gradient echo magnetic resonance imaging (MRI) with long echo times and flow compensation. Owing to its sensitivity to deoxyhemoglobin, hemosiderin, iron, and calcium, SWI is extremely informative and superior to conventional MRI for the diagnosis and follow-up of patients with acute, subacute, and prolonged hemorrhage. This systematic review aimed to evaluate and summarize the published articles that report SWI results for the evaluation of TBI and to determine correlations between clinical status and SWI results. Consequently, our analysis also aimed to identify the appropriate MRI sequences to use in the assessment of patients with TBI. We searched the Medline and Embase online electronic databases for relevant papers published from 2012 onwards. We found that SWI had higher sensitivity than gradient echo MRI in detecting and characterizing microbleeds in TBIs and was able to differentiate diamagnetic calcifications from paramagnetic microhemorrhages. However, it is important that future research not only continues to evaluate the utility of SWI in TBIs but also attempts to overcome the limitations of the studies described in this review, which should help validate the conclusions and recommendations from our analysis.

Computational Fractal-Based Analysis of MR Susceptibility-Weighted Imaging (SWI) in Neuro-Oncology and Neurotraumatology

Susceptibility-weighted imaging (SWI) is a magnetic resonance imaging (MRI) technique able to depict the magnetic susceptibility produced by different substances, such as deoxyhemoglobin, calcium, and iron. The main application of SWI in clinical neuroimaging is detecting microbleedings and venous vasculature. Quantitative analyses of SWI have been developed over the last few years, aimed to offer new parameters, which could be used as neuroimaging biomarkers. Each technique has shown pros and cons, but no gold standard exists yet. The fractal dimension (FD) has been investigated as a novel potential objective parameter for monitoring intratumoral space-filling properties of SWI patterns. We showed that SWI patterns found in different tumors or different glioma grades can be represented by a gradient in the fractal dimension, thereby enabling each tumor to be assigned a specific SWI fingerprint. Such results were especially relevant in the differentiation of low-grade versus high-grade gliomas, as well as from high-grade gliomas versus lymphomas.Therefore, FD has been suggested as a potential image biomarker to analyze intrinsic neoplastic architecture in order to improve the differential diagnosis within clinical neuroimaging, determine appropriate therapy, and improve outcome in patients.These promising preliminary findings could be extended into the field of neurotraumatology, by means of the application of computational fractal-based analysis for the qualitative and quantitative imaging of microbleedings in traumatic brain injury patients. In consideration of some evidences showing that SWI signals are correlated with trauma clinical severity, FD might offer some objective prognostic biomarkers.In conclusion, fractal-based morphometrics of SWI could be further investigated to be used in a complementary way with other techniques, in order to form a holistic understanding of the temporal evolution of brain tumors and follow-up response to treatment, with several further applications in other fields, such as neurotraumatology and cerebrovascular neurosurgery as well.

Military-related mild traumatic brain injury: clinical characteristics, advanced neuroimaging, and molecular mechanisms

Mild traumatic brain injury (mTBI) is a significant health burden among military service members. Although mTBI was once considered relatively benign compared to more severe TBIs, a growing body of evidence has demonstrated the devastating neurological consequences of mTBI, including chronic post-concussion symptoms and deficits in cognition, memory, sleep, vision, and hearing. The discovery of reliable biomarkers for mTBI has been challenging due to under-reporting and heterogeneity of military-related mTBI, unpredictability of pathological changes, and delay of post-injury clinical evaluations. Moreover, compared to more severe TBI, mTBI is especially difficult to diagnose due to the lack of overt clinical neuroimaging findings. Yet, advanced neuroimaging techniques using magnetic resonance imaging (MRI) hold promise in detecting microstructural aberrations following mTBI. Using different pulse sequences, MRI enables the evaluation of different tissue characteristics without risks associated with ionizing radiation inherent to other imaging modalities, such as X-ray-based studies or computerized tomography (CT). Accordingly, considering the high morbidity of mTBI in military populations, debilitating post-injury symptoms, and lack of robust neuroimaging biomarkers, this review (1) summarizes the nature and mechanisms of mTBI in military settings, (2) describes clinical characteristics of military-related mTBI and associated comorbidities, such as post-traumatic stress disorder (PTSD), (3) highlights advanced neuroimaging techniques used to study mTBI and the molecular mechanisms that can be inferred, and (4) discusses emerging frontiers in advanced neuroimaging for mTBI. We encourage multi-modal approaches combining neuropsychiatric, blood-based, and genetic data as well as the discovery and employment of new imaging techniques with big data analytics that enable accurate detection of post-injury pathologic aberrations related to tissue microstructure, glymphatic function, and neurodegeneration. Ultimately, this review provides a foundational overview of military-related mTBI and advanced neuroimaging techniques that merit further study for mTBI diagnosis, prognosis, and treatment monitoring.

MRI factors associated with cognitive functioning after acute onset brain injury: Systematic review and meta-analysis

Impairments of memory, attention, and executive functioning are frequently reported after acute onset brain injury. MRI markers hold potential to contribute to identification of patients at risk for cognitive impairments and clarification of mechanisms. The aim of this systematic review was to summarize and value the evidence on MRI markers of memory, attention, and executive functioning after acute onset brain injury. We included ninety-eight studies, on six classes of MRI factors (location and severity of damage (n = 15), volume/atrophy (n = 36), signs of small vessel disease (n = 15), diffusion-weighted imaging measures (n = 36), resting-state functional MRI measures (n = 13), and arterial spin labeling measures (n = 1)). Three measures showed consistent results regarding their association with cognition. Smaller hippocampal volume was associated with worse memory in fourteen studies (pooled correlation 0.58 [95% CI: 0.46-0.68] for whole, 0.11 [95% CI: 0.04-0.19] for left, and 0.34 [95% CI: 0.17-0.49] for right hippocampus). Lower fractional anisotropy in cingulum and fornix was associated with worse memory in six and five studies (pooled correlation 0.20 [95% CI: 0.08-0.32] and 0.29 [95% CI: 0.20-0.37], respectively). Lower functional connectivity within the default-mode network was associated with worse cognition in four studies. In conclusion, hippocampal volume, fractional anisotropy in cingulum and fornix, and functional connectivity within the default-mode network showed consistent associations with cognitive performance in all types of acute onset brain injury. External validation and cut off values for predicting cognitive impairments are needed for clinical implementation.

History of traumatic brain injury in relation to cognitive functioning, memory complaints and brain structure in mid-life

In this study, we investigated history of traumatic brain injury with loss of consciousness in relation to cognitive functioning, subjective memory complaints and brain structure in mid-life. This study included 2,005 participants (mean age: 47.6 years, standard deviation: 5.0, women: 65%) from the ORACLE study between 2017-2020. History of traumatic brain injury was defined as at least one life-time self-reported head injury with loss of consciousness. Associations of history of traumatic brain injury with (1) cognitive functioning (measured with the 15-Word learning test, Stroop task, Letter-digit substitution test, Word fluency test, Purdue pegboard test, and Design organization test) (2) current subjective memory complaints (present/absent, measured with a survey), and (3) brain structure (total brain volume, frontal and temporal lobes volume, gray matter volume, white matter volume, white matter hyperintensities volume, infarcts, and microbleeds, measured with brain-MRI) were assessed using linear or logistic regression models and adjusted for relevant confounders. In total, 250 of 2,005 (12%) participants reported a history of traumatic brain injury. Of those who reported the time post-injury (n=173), most participants (n=151, 87%) reported that it occurred more than 10 years ago. We found no associations between history of traumatic brain injury and any of the cognitive tests. We did find that a history of traumatic brain injury was associated with having mid-life subjective memory complaints (odds ratio (OR): 1.87, 95% confidence interval (CI): 1.35; 2.58). This association was also present when investigating only those who reported an injury more than 10 years ago (OR:1.69, 95% CI: 1.15; 2.50). Additionally, the association was stronger in those with more than 30 minutes loss of consciousness (OR: 3.57, 95%CI: 1.48; 8.59) than in those with less than 30 minutes loss of consciousness (OR: 1.85, 95%CI: 1.25; 2.74), when compared to those without history of traumatic brain injury. Lastly, we found no associations between history of traumatic brain injury and any of the structural brain-MRI outcomes. In conclusion, our study suggests that at least one life-time traumatic brain injury with loss of consciousness in mid-life is associated with long-term subjective memory complaints, but not with cognitive functioning or brain structure.

Cerebral Microbleeds and Structural White Matter Integrity in Patients With Traumatic Brain Injury-A Diffusion Tensor Imaging Study

Diffuse axonal injury (DAI) is a common neuropathological manifestation of traumatic brain injury (TBI), presenting as traumatic alterations in the cerebral white matter (WM) microstructure and often leading to long-term neurocognitive impairment. These WM alterations can be assessed using diffusion tensor imaging (DTI). Cerebral microbleeds (CMBs) are a common finding on head imaging in TBI and are often considered a visible sign of DAI, although they represent diffuse vascular injury. It is poorly known how they associate with long-term white matter integrity. This study included 20 patients with TBI and CMBs, 34 patients with TBI without CMBs, and 11 controls with orthopedic injuries. DTI was used to assess microstructural WM alterations. CMBs were detected using susceptibility-weighted imaging (SWI) and graded according to their location in the WM and total lesion load was counted. Patients underwent SWI within 2 months after injury. DTI and clinical outcome assessment were performed at an average of eight months after injury. Outcome was assessed using the extended Glasgow Outcome Scale (GOSe). The Glasgow Coma Scale (GCS) and length of post-traumatic amnesia (PTA) were used to assess clinical severity of the injury. We found that CMB grading and total lesion load were negatively associated with fractional anisotropy (FA) and positively associated with mean diffusivity (MD). Patients with TBI and CMBs had decreased FA and increased MD compared with patients with TBI without CMBs. CMBs were also associated with worse clinical outcome. When adjusting for the clinical severity of the injury, none of the mentioned associations were found. Thus, the difference in FA and MD is explained by patients with TBI and CMBs having more severe injuries. Our results suggest that CMBs are not associated with greater WM alterations when adjusting for the clinical severity of TBI. Thus, CMBs and WM alterations may not be strongly associated pathologies in TBI.

Postoperative magnetic resonance imaging may predict poor outcome in children with severe traumatic brain injuries who undergo cranial surgery

OBJECTIVE

Multiple studies have evaluated the use of MRI for prognostication in pediatric patients with severe traumatic brain injury (TBI) and have found a correlation between diffuse axonal injury (DAI)-type lesions and outcome. However, there remains a limited understanding about the use of MRI for prognostication after severe TBI in children who have undergone cranial surgery.

METHODS

Children with severe TBI who underwent craniectomy or craniotomy at Primary Children's Hospital in Salt Lake City, Utah, between 2010 and 2019 were identified retrospectively. Of these 92 patients, 43 underwent postoperative brain MRI within 4 months of surgery. Susceptibility-weighted imaging (SWI) and FLAIR sequences were used to designate areas of hemorrhagic and nonhemorrhagic cerebral lesions related to DAI. Patients were then stratified based on the location of the DAI as read by a neuroradiologist as superficial, deep, or brainstem. The location of the DAI and other variables associated with poor outcome, including Glasgow Coma Scale (GCS) score, pediatric trauma score, mechanism of injury, and time to surgery, were analyzed for correlation with poor outcome. Outcomes were reported using the King's Outcome Scale for Childhood Head Injury (KOSCHI).

RESULTS

In the 43 children with severe TBI who underwent postoperative brain MRI, the median GCS score on arrival was 4. The most common cause of injury was falls (14 patients, 33%). The most common primary intracranial pathology was subdural hematoma in 26 patients (60%), followed by epidural hematoma in 9 (21%). Fifteen patients (35%) had cerebral herniation and 31 (72%) had evidence of contusion. Variables associated with poor outcome included cerebral herniation (r = 0.338, p = 0.027) and location of DAI (r = 0.319, p = 0.037). In a separate analysis, brainstem DAI was shown to predict poor outcome, whereas location (no, superficial, or deep DAI) did not. Logistic regression showed that brainstem DAI (OR 22.3, p = 0.020) had a higher odds ratio than cerebral herniation (OR 10.5, p = 0.044) for poor outcome. Thirty-six children (84%) had a satisfactory outcome at last follow-up; 3 (7%) children died.

CONCLUSIONS

The majority of children in this series who presented with a severe TBI and underwent craniectomy or craniotomy made a satisfactory recovery. In patients in whom there is a concern for poor outcome, the location of DAI-type lesions with SWI and FLAIR may assist in prognostication. The authors' results revealed that DAI-type lesions in the brainstem and evidence of cerebral herniation may indicate a poorer prognosis; however, more studies with larger cohorts are needed to make definitive conclusions.

Incidence and Predictors of Aspiration Pneumonia Among Traumatic Brain Injury in Northwest Ethiopia

Background

A significantly greater proportion of patients who die due to aspiration pneumonia were diagnosed with in-hospital aspiration pneumonia (19%). The incidence and major predictors are not known clearly, especially in Ethiopia.

Objective

To determine the incidence and predictors of aspiration pneumonia among adult traumatic brain injury patients at Felege Hiwot comprehensive specialized hospital, Bahir Dar, North west Ethiopia, in 2021.

Methods

An institution-based retrospective study was conducted from all admitted adult traumatic brain injury patients at Felege Hiwot comprehensive specialized hospital from January 1, 2015 to December 31, 2020 for 51 days of survival. Descriptive statistics, Kaplan–Meier survival curve log rank test, and the Cox proportional hazard regression model were used.

Results

A total of 396 adult patients diagnosed and admitted with traumatic brain injury in the past 5 years were included. Seventy patients (17.67%) developed aspiration pneumonia, providing an incidence rate of 32.39 (95% CI=25-62–40.94) per 1,000 person days of observation. Independent predictors were being referred for AHR (2.43; 95% CI=1.12–5.25), nasogastric tube insertion AHR (3.02; 95% CI=1.43–6.39), and baseline Glasgow coma scale <8 AHR (3.88; 95% CI=1.42–10.062).

Conclusion

Having a nasogastric tube and low baseline Glasgow coma scale were significant predictors. This improves prehospital and hospital care during transportation and admission time.

Susceptibility-Weighted MRI and Microbleeds in Mild Traumatic Brain Injury: Prediction of Posttraumatic Complaints?

BACKGROUND

Only in 7-15% of patients with mild traumatic brain injury (mTBI), traumatic CT-abnormalities are found. Nevertheless, 40% of mTBI patients suffer from posttraumatic complaints not resolving after 6 months. We discuss the ability of susceptibility-weighted imaging (SWI), sensitive for microbleeds, to detect more subtle brain abnormalities.

SUMMARY

After a search on PubMed, we selected 15 studies on SWI in adult mTBI patients; 11 studies on 3T MRI, and 4 studies on 1.5T MRI. All 1.5T studies showed that, compared to T2, gradient echo, diffusion-weighted imaging, or fluid-attenuated inversion recovery sequences, SWI is more sensitive for microbleeds. Only two 1.5T studies described the association between SWI findings and outcome. In 3 of the 4 studies, no control group was present. The mean number of microbleeds varied from 3.2 to 6.4 per patient. In the 3T studies, the percentage of patients with traumatic microbleeds varied from 5.7 to 28.8%, compared to 0-13.3% in normal controls. Microbleeds were particularly located subcortical or juxtacortical. The number of microbleeds in mTBI varied from 1 to 10 per patient. mTBI patients with microbleeds appeared to have higher symptom severity at 12 months and perform worse on tests of psychomotor speed and speed of information processing after 3 and 12 months, compared to mTBI patients without microbleeds. Key Messages: There is some evidence that traumatic microbleeds predict cognitive outcome and persistent posttraumatic complaints in patients with mTBI.

Cerebral Microbleeds May Be Less Detectable by Susceptibility Weighted Imaging MRI From 24 to 72 Hours After Traumatic Brain Injury

Purpose: A former rodent study showed that cerebral traumatic microbleeds (TMBs) may temporarily become invisible shortly after injury when detected by susceptibility weighted imaging (SWI). The present study aims to validate this phenomenon in human SWI.

Methods: In this retrospective study, 46 traumatic brain injury (TBI) patients in various forms of severity were included and willingly complied with our strict selection criteria. Clinical parameters potentially affecting TMB count, Rotterdam and Marshall CT score, Mayo Clinic Classification, contusion number, and total volume were registered. The precise time between trauma and MRI [5 h 19 min to 141 h 54 min, including SWI and fluid-attenuated inversion recovery (FLAIR)] was individually recorded; TMB and FLAIR lesion counts were assessed. Four groups were created based on elapsed time between the trauma and MRI: 0–24, 24–48, 48–72, and >72 h. Kruskal–Wallis, ANOVA, Chi-square, and Fisher’s exact tests were used to reveal differences among the groups within clinical and imaging parameters; statistical power was calculated retrospectively for each comparison.

Results: The Kruskal–Wallis ANOVA with Conover post hoc analysis showed significant (p = 0.01; 1−β > 0.9) median TMB number differences in the subacute period: 0–24 h = 4.00 (n = 11); 24–48 h = 1 (n = 14); 48–72 h = 1 (n = 11); and 72 h ≤ 7.5 (n = 10). Neither clinical parameters nor FLAIR lesions depicted significant differences among the groups.

Conclusion: Our results demonstrate that TMBs on SWI MRI may temporarily become less detectable at 24–72 h following TBI.

White Matter Hyperintensities Are Not Related to Symptomatology or Cognitive Functioning in Service Members with a Remote History of Traumatic Brain Injury

This study aimed to determine whether magnetic resonance imaging (MRI) white matter hyperintensities (WMHs) are associated with symptom reporting and/or cognitive performance in 1202 active-duty service members with prior single or multiple mild traumatic brain injury (mTBI). Patients with mTBI evaluated at the National Intrepid Center of Excellence (NICoE) at Walter Reed National Military Medical Center (WRNMMC) were divided into those with (n = 632) and without (n = 570) WMHs. The groups were compared on several self-report scales including the Neurobehavioral Symptom Inventory (NSI), Post-Traumatic Stress Disorder (PTSD) Checklist-Civilian Version (PCL-C), Satisfaction with Life Scale (SWLS), and Short Form-36 Health Survey (SF-36). They were also compared on several neuropsychological measures, including tests of attention, working memory, learning and memory, executive functioning, and psychomotor functioning. After correction for multiple comparisons, there were no significant differences between the two groups on any self-reported symptom scale or cognitive test. When comparing a subgroup with the highest (20+) WMH burden (n = 60) with those with no WMHs (n = 60; matched on age, education, sex, race, rank, and TBI number), only SF-36 Health Change significantly differed between the subgroups; the multiple WMH subgroup reported worsening health over the past year (t[53] = 3.52, p = 0.001, d = 0.67) compared with the no WMH subgroup. These findings build on prior research suggesting total WMHs are not associated with significant changes in self-reported symptoms or cognitive performance in patients with a remote history of mTBI. As such, clinicians are encouraged to use caution when reporting such imaging findings.

Traumatic microbleeds suggest vascular injury and predict disability in traumatic brain injury

Traumatic microbleeds are small foci of hypointensity seen on T2*-weighted MRI in patients following head trauma that have previously been considered a marker of axonal injury. The linear appearance and location of some traumatic microbleeds suggests a vascular origin. The aims of this study were to: (i) identify and characterize traumatic microbleeds in patients with acute traumatic brain injury; (ii) determine whether appearance of traumatic microbleeds predict clinical outcome; and (iii) describe the pathology underlying traumatic microbleeds in an index patient. Patients presenting to the emergency department following acute head trauma who received a head CT were enrolled within 48 h of injury and received a research MRI. Disability was defined using Glasgow Outcome Scale-Extended ≤6 at follow-up. All magnetic resonance images were interpreted prospectively and were used for subsequent analysis of traumatic microbleeds. Lesions on T2* MRI were stratified based on 'linear' streak-like or 'punctate' petechial-appearing traumatic microbleeds. The brain of an enrolled subject imaged acutely was procured following death for evaluation of traumatic microbleeds using MRI targeted pathology methods. Of the 439 patients enrolled over 78 months, 31% (134/439) had evidence of punctate and/or linear traumatic microbleeds on MRI. Severity of injury, mechanism of injury, and CT findings were associated with traumatic microbleeds on MRI. The presence of traumatic microbleeds was an independent predictor of disability (P < 0.05; odds ratio = 2.5). No differences were found between patients with punctate versus linear appearing microbleeds. Post-mortem imaging and histology revealed traumatic microbleed co-localization with iron-laden macrophages, predominately seen in perivascular space. Evidence of axonal injury was not observed in co-localized histopathological sections. Traumatic microbleeds were prevalent in the population studied and predictive of worse outcome. The source of traumatic microbleed signal on MRI appeared to be iron-laden macrophages in the perivascular space tracking a network of injured vessels. While axonal injury in association with traumatic microbleeds cannot be excluded, recognizing traumatic microbleeds as a form of traumatic vascular injury may aid in identifying patients who could benefit from new therapies targeting the injured vasculature and secondary injury to parenchyma.

Higher sensitivity for traumatic cerebral microbleeds at 7 T ultra-high field MRI: is it clinically significant for the acute state of the patients and later quality of life?

Background

The present study evaluates the possible prognostic benefits of 7 T susceptibility weighted imaging (SWI) of traumatic cerebral microbleeds (TMBs) over 3 T SWI to predict the acute clinical state and subjective impairments, including health-related quality of life (HRQOL), after closed head injury (CHI).

Methods

The study group comprised 10 participants with known TMBs All subjects underwent 3 T magnetic resonance imaging (MRI) and 7 T MRI, respectively. Location and count of TMBs were independently evaluated by two neuroradiologists. The initial Glasgow Coma Scale (GCS), the duration of coma and further clinical data were taken from the patients records. HRQOL was assessed by means of a questionnaire. Memory complaints and neurological symptoms were inquired at the time of the MRI examinations.

Results

SWI revealed a total of 485 TMBs at 3 T, 584 TMBs at 7 T with similar spatial resolution, and 684 TMBs at 7 T with a factor of 10 higher spatial resolution. The TMBs depicted by 7 T high-resolution SWI were correlated with the duration of coma (Spearman's rho of 0.77). The corresponding association with TMBs in 3 T MRI SWI showed a Spearman's rho of 0.71. The initial GCS score and TMBs correlated with a Spearman's rho of -0.35 at 3 T SWI MRI and a rho of -0.33 at 7 T high-resolution SWI, respectively. The physical aspect of HRQOL correlated substantially with the count of TMBs (rho = 0.44 for 3 T SWI and rho = 0.35 for both 7 T SWI sequences, respectively).

Conclusions

The number of TMBs showed a substantial association with indicators of the acute clinical state and chronic neurobehavioral parameters after CHI, but there was no additional advantage of 7 T MRI. These preliminary findings warrant a larger prospective study for the future.

White matter hyperintensities increases with traumatic brain injury severity: associations to neuropsychological performance and fatigue

Objective: To examine the prevalence of white matter hyperintensities (WMHs) in patients with traumatic brain injury (TBI) as compared to healthy controls, and to investigate whether there is an association between WMH lesion burden and performance on neuropsychological tests in patients with TBI.Methods: A total of 59 patients with TBI and 27 age- and gender-matched healthy controls underwent thorough neuropsychological testing and magnetic resonance imaging. The quantification of WMH lesions was performed using the fully automated Lesion Segmentation Tool.Results: WMH lesions were more common in patients with TBI than in healthy controls (p = .032), and increased with higher TBI severity (p = .025). Linear regressions showed that WMH lesions in patients with TBI were not related to performance on any neuropsychological tests (p > .05 for all). However, a negative relationship between number of WMH lesions in patients with TBI and self-assessed fatigue was found (r = - 0.33, p = .026).Conclusion: WMH lesions are more common in patients with TBI than in healthy controls, and WMH lesions burden increases with TBI severity. These lesions could not explain decreased cognitive functioning in patients with TBI but did relate to decreased self-assessment of fatigue after TBI.

MRI in 30 cats with traumatic brain injury

OBJECTIVES

The aim of this study was to evaluate the MRI findings in cats following traumatic brain injury (TBI), and establish which features identified might correlate with prognosis.

METHODS

The magnetic resonance images of 30 cats with clinical signs attributed to the brain following TBI were retrospectively reviewed to assess the imaging features seen and their correlation with outcome.

RESULTS

Twenty-one of 30 cats had a good outcome (full recovery or minor ongoing neurological deficits); the other nine either died or had ongoing neurological deficits that significantly affected quality of life. There was evidence of parenchymal injury in only 20/30 cats, including 8/9 that had a poor outcome. The frequency of bilateral or multifocal parenchymal lesions on T2-weighted imaging, and mass effect, particularly caudal transtentorial herniation, was statistically significantly higher in patients with a poorer outcome. Extra-axial haemorrhage was not identified. Concurrent soft tissue injury was noted in all cats, with a poorer prognosis statistically associated with a peripharyngeal pattern of injury and orbital trauma.

CONCLUSIONS AND RELEVANCE

The number of cases with MRI-identified brain pathology, the patterns of injuries identified and the specific imaging features that appear to have effects on prognosis differ in this series of cats from those published in similar case series of dogs. Further work is needed to establish if cat-specific guidelines are needed to assess brain MRI following trauma.

Limited Colocalization of Microbleeds and Microstructural Changes after Severe Traumatic Brain Injury

Severe traumatic brain injury (TBI) produces shearing forces on long-range axons and brain vessels, causing axonal and vascular injury. To examine whether microbleeds and axonal injury colocalize after TBI, we performed whole-brain susceptibility-weighted imaging (SWI) and diffusion tensor imaging (DTI) in 14 patients during the subacute phase after severe TBI. SWI was used to determine the number and volumes of microbleeds in five brain regions: the frontotemporal lobe; parieto-occipital lobe; midsagittal region (cingular cortex, parasagittal white matter, and corpus callosum); deep nuclei (basal ganglia and thalamus); and brainstem. Averaged fractional anisotropy (FA) and mean diffusivity (MD) were measured to assess microstructural changes in the normal appearing white matter attributed to axonal injury in the same five regions. Regional expressions of microbleeds and microstructure were used in a partial least-squares model to predict the impairment of consciousness in the subacute stage after TBI as measured with the Coma Recovery Scale-Revised (CRS-R). Only in the midsagittal region, the expression of microbleeds was correlated with regional changes in microstructure as revealed by DTI. Microbleeds and microstructural DTI-based metrics of deep, but not superficial, brain regions were able to predict individual CRS-R. Our results suggest that microbleeds are not strictly related to axonal pathology in other than the midsagittal region. While each measure alone was predictive, the combination of both metrics scaled best with individual CRS-R. Structural alterations in deep brain structures are relevant in terms of determining the severity of impaired consciousness in the acute stage after TBI.

Patients with Mild Traumatic Brain Injury Recruited from Both Hospital and Primary Care Settings: A Controlled Longitudinal Magnetic Resonance Imaging Study

With an emphasis on traumatic axonal injury (TAI), frequency and evolution of traumatic intracranial lesions on 3T clinical magnetic resonance imaging (MRI) were assessed in a combined hospital and community-based study of patients with mild traumatic brain injury (mTBI). The findings were related to post-concussion symptoms (PCS) at 3 and 12 months. Prospectively, 194 patients (16–60 years of age) were recruited from the emergency departments at a level 1 trauma center and a municipal outpatient clinic into the Trondheim mTBI follow-up study. MRI was acquired within 72 h (n = 194) and at 3 (n = 165) and 12 months (n = 152) in patients and community controls (n = 78). The protocol included T2, diffusion weighted imaging, fluid attenuated inversion recovery (FLAIR), and susceptibility weighted imaging (SWI). PCS was assessed with British Columbia Post Concussion Symptom Inventory in patients and controls. Traumatic lesions were present in 12% on very early MRI, and in 5% when computed tomography (CT) was negative. TAI was found in 6% and persisted for 12 months on SWI, whereas TAI lesions on FLAIR disappeared or became less conspicuous on follow-up. PCS occurred in 33% of patients with lesions on MRI and in 19% in patients without lesions at 3 months (p = 0.12) and in 21% with lesions and 14% without lesions at 12 months (p = 0.49). Very early MRI depicted cases of TAI in patients with mTBI with microbleeds persisting for 12 months. Patients with traumatic lesions may have a more protracted recovery, but the study was underpowered to detect significant differences for PCS because of the low frequency of trauma-related MRI lesions.

Cerebral Microbleeds Temporarily Become Less Visible or Invisible in Acute Susceptibility Weighted Magnetic Resonance Imaging: A Rat Study

Previously, we reported human traumatic brain injury cases demonstrating acute to subacute microbleed appearance changes in susceptibility-weighted imaging (SWI—magnetic resonance imaging [MRI]). This study aims to confirm and characterize such temporal microbleed appearance alterations in an experimental model. To elicit microbleed formation, brains of male Sprague Dawley rats were pierced in a depth of 4 mm, in a parasagittal position bilaterally using 159 μm and 474 μm needles, without the injection of autologous blood or any agent. Rats underwent 4.7 T MRI immediately, then at multiple time points until 125 h. Volumes of hypointensities consistent with microbleeds in SWI were measured using an intensity threshold-based approach. Microbleed volumes across time points were compared using repeated measures analysis of variance. Microbleeds were assessed by Prussian blue histology at different time points. Hypointensity volumes referring to microbleeds were significantly decreased (corrected p < 0.05) at 24 h compared with the immediate or the 125 h time points. By visual inspection, microbleeds were similarly detectable at the immediate and 125 h imaging but were decreased in extent or completely absent at 24 h or 48 h. Histology confirmed the presence of microbleeds at all time points and in all animals. This study confirmed a general temporary reduction in visibility of microbleeds in the acute phase in SWI. Such short-term appearance dynamics of microbleeds should be considered when using SWI as a diagnostic tool for microbleeds in traumatic brain injury and various diseases.

Corticostriatal Hyperactivation to Reward Presentation in Individuals With TBI With High Depressive Symptomatology: A Pilot Study

OBJECTIVE

To examine the impact of depression on neural mechanisms associated with outcome processing (rewarding and punishing outcomes) in persons with traumatic brain injury (TBI).

SETTING

Kessler Foundation's Rocco Ortenzio Neuroimaging Center.

PARTICIPANTS

A total of 16 adults with moderate to severe TBI.

MAIN MEASURES

Chicago Multiscale Depression Inventory (CMDI); Behavioral Inhibition/Behavioral Activation Scale (BIS/BAS); functional MRI of the head while performing a gambling task, with a reward (+$1.00) and punishment (-$0.50).

RESULTS

Individuals with TBI reporting high depressive symptomatology exhibited increased activation in the ventromedial prefrontal cortex (VMPFC) and striatum during presentation of rewarding outcomes compared with individuals with TBI reporting low depressive symptomatology. Punishing outcome presentation was not associated with any change in brain activation. No differences in volume of the striatum and VMPFC were observed between groups.

CONCLUSIONS

Current findings provide the first evidence of differences in neural mechanisms underlying outcome processing between individuals with TBI with and without depression. The results suggest that depressive symptomatology might have a different effect on individuals with TBI than what is typically observed in individuals without TBI reporting with depression, with the possibility of rewards becoming more reinforcing as depressive symptomatology increases. Future studies should explore the potential implications of behavioral responses to rewards and punishments in TBI and how they can affect rehabilitation approaches and activities of daily living.

Sleep and fatigue after TBI

BACKGROUND

Whilst post traumatic brain injury fatigue (PTBIF) and sleep disturbance are common sequelae following brain injury, underlying mechanisms, and the potential for targeted interventions remain unclear.

OBJECTIVE

To present a review of recent studies exploring the epidemiology of PTBIF and sleep disturbance, the relationship and neuropsychological correlates of these issues, potential approaches to intervention, and implications for neurorehabilitation.

METHODS

A review of relevant literature was undertaken, with a focus on PTBIF relating to sleep disturbance, the neuropsychological correlates of these issues and implications for neurorehabilitation. This paper does not set out to provide a systematic review.

RESULTS

Multidimensional approaches to assessment and treatment of sleep disturbance and PTBIF are required.

CONCLUSIONS

There is a need for more robust findings in determining the complex nature of relationships between PTBIF, sleep disturbance, and correlates. Longitudinal prospective data is required to increase our understanding of the nature and course of PTBIF and sleep disturbance post TBI. Large scale clinical trials are required in evaluating the potential benefits of interventions.

Age-dependent differences in the impact of paediatric traumatic brain injury on executive functions: A prospective study using susceptibility-weighted imaging

Childhood and adolescence represent sensitive developmental periods for brain networks implicated in a range of complex skills, including executive functions (EF; inhibitory control, working memory, and cognitive flexibility). As a consequence, these skills may be particularly vulnerable to injuries sustained during these sensitive developmental periods. The present study investigated 1) whether age at injury differentially affects EF 6 months and 2 years after TBI in children aged 5-15 years, and 2) whether the association between brain lesions and EF depend on age at injury. Children with TBI (n = 105) were categorized into four age-at-injury groups based on previous studies and proposed timing of cerebral maturational spurts: early childhood (5-6 years, n = 14), middle childhood (7-9 years, n = 24), late childhood (10-12 years, n = 52), and adolescence (13-15 years, n = 15). EF were assessed with performance-based tasks and a parent-report of everyday EF. TBI patients' EF scores 6 months and 2 years post-injury were compared to those of typically developing (TD) controls (n = 42). Brain lesions were identified using susceptibility weighted imaging (SWI). Results indicated that inhibitory control performance 2 years post-injury was differentially affected by the impact of TBI depending on age at injury. Follow-up analyses did not reveal significant differences within the age groups, preventing drawing strong conclusions regarding the contribution of age at injury to EF outcome after TBI. Tentatively, large effect sizes suggest that vulnerability is most apparent in early childhood and adolescence. Everyday inhibitory control behaviour was worse for children with TBI than TD children across childhood and adolescence at the 2-year assessment. There was no evidence for impairment in working memory or cognitive flexibility after TBI at the group level. Given small group sizes, findings from analyses into correlations between EF and SWI lesions should be interpreted with caution. Extent, number and volume of brain lesions correlated with adolescent everyday EF behaviour 6 months post-injury. Taken together, the results emphasize the need for long-term follow-up after paediatric TBI during sensitive developmental periods given negative outcomes 2-year post injury. Inhibitory control seems to be particular vulnerable to the impact of TBI. Findings of associations between EF and SWI lesions need to be replicated with larger samples.

Profiling biomarkers of traumatic axonal injury: From mouse to man

Traumatic brain injury (TBI) poses a major public health problem on a global scale. Its burden results from high mortality and significant morbidity in survivors. This stems, in part, from an ongoing inadequacy in diagnostic and prognostic indicators despite significant technological advances. Traumatic axonal injury (TAI) is a key driver of the ongoing pathological process following TBI, causing chronic neurological deficits and disability. The science underpinning biomarkers of TAI has been a subject of many reviews in recent literature. However, in this review we provide a comprehensive account of biomarkers from animal models to clinical studies, bridging the gap between experimental science and clinical medicine. We have discussed pathogenesis, temporal kinetics, relationships to neuro-imaging, and, most importantly, clinical applicability in order to provide a holistic perspective of how this could improve TBI diagnosis and predict clinical outcome in a real-life setting. We conclude that early and reliable identification of axonal injury post-TBI with the help of body fluid biomarkers could enhance current care of TBI patients by (i) increasing speed and accuracy of diagnosis, (ii) providing invaluable prognostic information, (iii) allow efficient allocation of rehabilitation services, and (iv) provide potential therapeutic targets. The optimal model for assessing TAI is likely to involve multiple components, including several blood biomarkers and neuro-imaging modalities, at different time points.

[Pathophysiology of intracranial injuries]

Traumatic brain injury (TBI) constitutes a heterogeneous condition that affects the most complex organ of the human body. It is commonly classified by its location as focal injury (e.g. epidural hematoma) and diffuse injury (e.g. diffuse axonal shearing injury) as well as by primary and secondary tissue injury. Accordingly, direct mechanical force causes the primary insult. The tissue damage occurring afterwards is subsumed under the term secondary brain damage. Some of these processes are overlapping and include in the early phase local cerebral ischemia resulting in excitotoxicity, which together with the triggered neuroinflammatory cascade causes the formation of cerebral edema and ultimately increased intracranial pressure once the intracranial compliance is exhausted. In survivors the long-term sequelae of the late stage include seizures caused by synaptic reorganization (incidence depending on the severity of TBI), persistent neuroinflammation promoting further neurodegeneration and increased risk for Alzheimer's disease probably because of TBI-related protein misfolding (tauopathy). Acute phase biomarkers of TBI should ideally originate from the injured brain. They should help distinguish disease severity and predict morbidity and mortality; however, the most commonly used biomarkers (S-100β and neurone-specific enolase) show a low specificity. In theory their successors (i. e. GFAP, pNF-H) seem more specific; however, these "new kids on the block" still need to be thoroughly investigated in large scale studies.

The association between microhaemorrhages and post - traumatic functional outcome in the chronic phase after mild traumatic brain injury

PURPOSE

In the chronic phase after mild traumatic brain injury (mTBI), microhaemorrhages are frequently detected on magnetic resonance imaging (MRI). It is however unclear whether microhaemorrhages are associated with functional outcome and which MRI sequence is most appropriate to address this association. We aimed to determine the association between microhaemorrhages and functional outcome in the chronic posttraumatic phase after injury with the most suitable MRI sequence to address this association.

METHODS

One hundred twenty-seven patients classified with mTBI admitted to the outpatient clinic from 2008 to 2015 for persisting posttraumatic complaints were stratified according to the presence of MRI abnormalities (n = 63 (MRI+ group) and n = 64 without abnormalities (MRI- group)). For the detection of microhaemorrhages, susceptibility-weighted imaging (SWI) and T2* gradient recalled echo (T2*GRE) were used. The relation between the functional outcome (dichotomized Glasgow Outcome Scale Extended scores) and the number and localization of microhaemorrhages was analysed using binary logistic regression.

RESULTS

SWI detected twice as many microhaemorrhages compared to T2*GRE: 341 vs. 179. Lesions were predominantly present in the frontal and temporal lobes. Unfavourable outcome was present in 67% of the MRI+ group with a significant association of total number of microhaemorrhages in the temporal cortical area on SWI (OR 0.43 (0.21-0.90) p = 0.02), with an explained variance of 44%. The number of microhaemorrhages was not correlated with the number of posttraumatic complaints.

CONCLUSION

An unfavourable outcome in the chronic posttraumatic phase is associated with the presence and number of microhaemorrhages in the temporal cortical area. SWI is preferably used to detect these microhaemorrhages.

Early detection of cerebral microbleeds following traumatic brain injury using MRI in the hyper-acute phase

•

Traumatic cerebral microbleeds (TCMBS) can be identified using susceptibility weighted imaging in the first few hours after injury.

•

TCMBs are a useful indicator of severity in this time frame.

•

The presence of TCMBs is an early indicator of injury severity following trauma.

•

There is a relationship between decreasing size of TCMBs and recovery.

Background

Traumatic brain injury (TBI) is a leading cause of death and disability in people under 45. Advanced imaging techniques to identify injury and classify severity in the first few hours and days following trauma could improve patient stratification and aid clinical decision making. Traumatic cerebral microbleeds (TCMBs), detectable on magnetic resonance susceptibility weighted imaging (SWI), can be used as markers of long-term clinical outcome. However, the relationship between TCMBs and injury severity in the first few hours after injury, and their natural evolution, is unknown.

Methods

We obtained SWI scans in 10 healthy controls, and 13 patients scanned 3–24 h following TBI and again at 7–15 days. TCMBs were identified and total volume quantified for every lesion in each scan.

Results

TCMBs were present in 6 patients, all with more severe injury classified by GCS. No lesions were identified in patients with an initial GCS of 15. Improvement in GCS in the first 15 days following injury was significantly associated with a reduction in microbleed volume over the same time-period.

Conclusion

MRI is feasible in severely injured patients in the first 24 h after trauma. Detection of TCMBs using SWI provides an objective early marker of injury severity following trauma. TCMBs revealed in this time frame, offer the potential to help determine the degree of injury, improving stratification, in order to identify patients who require admission to hospital, transfer to a specialist center, or an extended period of intubation on intensive care.

Susceptibility-weighted imaging: current status and future directions

Susceptibility-weighted imaging (SWI) is a method that uses the intrinsic nature of local magnetic fields to enhance image contrast in order to improve the visibility of various susceptibility sources and to facilitate diagnostic interpretation. It is also the precursor to the concept of the use of phase for quantitative susceptibility mapping (QSM). Nowadays, SWI has become a widely used clinical tool to image deoxyhemoglobin in veins, iron deposition in the brain, hemorrhages, microbleeds and calcification. In this article, we review the basics of SWI, including data acquisition, data reconstruction and post-processing. In particular, the source of cusp artifacts in phase images is investigated in detail and an improved multi-channel phase data combination algorithm is provided. In addition, we show a few clinical applications of SWI for the imaging of stroke, traumatic brain injury, carotid vessel wall, siderotic nodules in cirrhotic liver, prostate cancer, prostatic calcification, spinal cord injury and intervertebral disc degeneration. As the clinical applications of SWI continue to expand both in and outside the brain, the improvement of SWI in conjunction with QSM is an important future direction of this technology. Copyright © 2016 John Wiley & Sons, Ltd.

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.

Sleep Disturbances in Traumatic Brain Injury: A Meta-Analysis

STUDY OBJECTIVES

Sleep disturbances are frequently reported following traumatic brain injury (TBI); however, the exact disturbances remain unclear. This meta-analysis aimed to characterize sleep disturbance in community dwelling patients with TBI as compared to controls.

METHODS

Two investigators independently conducted a systematic search of multiple electronic databases from inception to May 27, 2015. Studies were selected if they compared sleep in community dwelling individuals with TBI relative to a control population without head injury. Data were pooled in meta-analysis with outcomes expressed as the standard mean difference (SMD) and 95% confidence interval (CI). The primary outcomes were derived from polysomnography and secondary outcomes were derived from subjective sleep measures.

RESULTS

Sixteen studies were included, combining 637 TBI patients and 567 controls, all of whom were community dwelling. Pooled polysomnography data revealed that TBI patients had poorer sleep efficiency (SMD = -0.47, CI: -0.89, -0.06), shorter total sleep duration (SMD = -0.37, CI: -0.59, -0.16), and greater wake after sleep onset time (SMD = 0.60, CI: 0.33, 0.87). Although sleep architecture was similar between the groups, a trend suggested that TBI patients may spend less time in REM sleep (SMD = -0.22, CI: -0.45, 0.01). Consistent with polysomnographic derangement, TBI patients reported greater subjective sleepiness and poorer perceived sleep quality.

CONCLUSIONS

The evidence suggests that TBI is associated with widespread objective and subjective sleep deficits. The present results highlight the need for physicians to monitor and address sleep deficits following TBI.

Uncovering cortico-striatal correlates of cognitive fatigue in pediatric acquired brain disorder: Evidence from traumatic brain injury

Cognitive fatigue is among the most profound and disabling sequelae of pediatric acquired brain disorders, however the neural correlates of these symptoms in children remains unexplored. One hypothesis suggests that cognitive fatigue may arise from dysfunction of cortico-striatal networks (CSNs) implicated in effort output and outcome valuation. Using pediatric traumatic brain injury (TBI) as a model, this study investigated (i) the sub-acute effect of brain injury on CSN volume; and (ii) potential relationships between cognitive fatigue and sub-acute volumetric abnormalities of the CSN. 3D T1 weighted magnetic resonance imaging sequences were acquired sub-acutely in 137 children (TBI: n = 103; typically developing - TD children: n = 34). 67 of the original 137 participants (49%) completed measures of cognitive fatigue and psychological functioning at 24-months post-injury. Results showed that compared to TD controls and children with milder injuries, children with severe TBI showed volumetric reductions in the overall CSN package, as well as regional gray matter volumetric change in cortical and subcortical regions of the CSN. Significantly greater cognitive fatigue in the TBI patients was associated with volumetric reductions in the CSN and its putative hub regions, even after adjusting for injury severity, socioeconomic status (SES) and depression. In the first study to evaluate prospective neuroanatomical correlates of cognitive fatigue in pediatric acquired brain disorder, these findings suggest that post-injury cognitive fatigue is related to structural abnormalities of cortico-striatal brain networks implicated in effort output and outcome valuation. Morphometric magnetic resonance imaging (MRI) may have potential to unlock early prognostic markers that may assist to identify children at elevated risk for cognitive fatigue post-TBI.

Microbleeds may expand acutely after traumatic brain injury

BACKGROUND AND PURPOSE

Susceptibility weighted imaging (SWI) is a very sensitive tool for the detection of microbleeds in traumatic brain injury (TBI). The number and extent of such traumatic microbleeds (TMBs) have been shown to correlate with the severity of the injury and the clinical outcome. However, the acute dynamics of TMBs have not been revealed so far. Since TBI is known to constitute dynamic pathological processes, we hypothesized that TMBs are not constant in their appearance, but may progress acutely after injury.

MATERIALS AND METHODS

We present here five closed moderate/severe (Glasgow coma scale≤13) TBI patients who underwent SWI very early (average=23.4 h), and once again a week (average=185.8 h) after the injury. The TMBs were mapped at both time points by a conventional radiological approach and their numbers and volumes were measured with manual tracing tools by two observers. TMB counts and extents were compared between time points.

RESULTS

TMBs were detected in four patients, three of them displaying an apparent TMB change. In these patients, TMB confluence and apparent growth were detected in the corpus callosum, coronal radiation or subcortical white matter, while unchanged TMBs were also present. These changes caused a decrease in the TMB count associated with an increase in the overall TMB volume over time.

CONCLUSION

We have found a compelling evidence that diffuse axonal injury-related microbleed development is not limited strictly to the moment of injury: the TMBs might expand in the acute phase of TBI. The timing of SWI acquisition may be relevant for optimizing the prognostic utility of this imaging biomarker.

Iron Deposition Is Positively Related to Cognitive Impairment in Patients with Chronic Mild Traumatic Brain Injury: Assessment with Susceptibility Weighted Imaging

Background. This study aimed to evaluate the usability of SWI in assessment of brain iron to detect cognitive dysfunction in patients with chronic mild traumatic brain injury (mTBI). Methods. 39 patients with mTBI and 37 normal controls were given the Mini-Mental State Examination (MMSE) and underwent SWI scanning at least 6 months after injury. Angle radian values were calculated with phase images. The angle radian values were compared between groups using analysis of covariance, and their association with MMSE scores was analyzed using Spearman correlations. Results. Significantly higher angle radian values (p < 0.05) were found in the head of the caudate nucleus, the lenticular nucleus, the hippocampus, the thalamus, the right substantia nigra, the red nucleus, and the splenium of the corpus callosum (SCC) in the mTBI group, compared to the control group. MMSE scores were negatively correlated with angle radian values in the right substantia nigra (r = −0.685, p < 0.001). Conclusions. Patients with chronic mTBI might have abnormally high accumulations of iron, and their MMSE scores are negatively associated with angle radian values in the right substantia nigra, suggesting a role of SWI in the assessment of cognitive impairments of these patients.

Magnetic resonance susceptibility weighted imaging in neurosurgery: current applications and future perspectives

Susceptibility weighted imaging (SWI) is a relatively new imaging technique. Its high sensitivity to hemorrhagic components and ability to depict microvasculature by means of susceptibility effects within the veins allow for the accurate detection, grading, and monitoring of brain tumors. This imaging modality can also detect changes in blood flow to monitor stroke recovery and reveal specific subtypes of vascular malformations. In addition, small punctate lesions can be demonstrated with SWI, suggesting diffuse axonal injury, and the location of these lesions can help predict neurological outcome in patients. This imaging technique is also beneficial for applications in functional neurosurgery given its ability to clearly depict and differentiate deep midbrain nuclei and close submillimeter veins, both of which are necessary for presurgical planning of deep brain stimulation. By exploiting the magnetic susceptibilities of substances within the body, such as deoxyhemoglobin, calcium, and iron, SWI can clearly visualize the vasculature and hemorrhagic components even without the use of contrast agents. The high sensitivity of SWI relative to other imaging techniques in showing tumor vasculature and microhemorrhages suggests that it is an effective imaging modality that provides additional information not shown using conventional MRI. Despite SWI's clinical advantages, its implementation in MRI protocols is still far from consistent in clinical usage. To develop a deeper appreciation for SWI, the authors here review the clinical applications in 4 major fields of neurosurgery: neurooncology, vascular neurosurgery, neurotraumatology, and functional neurosurgery. Finally, they address the limitations of and future perspectives on SWI in neurosurgery.

Predictors of longitudinal outcome and recovery of pragmatic language and its relation to externalizing behaviour after pediatric traumatic brain injury

The purpose of the present investigation was to evaluate the contribution of age-at-insult and brain pathology on longitudinal outcome and recovery of pragmatic language in a sample of children and adolescents with traumatic brain injury (TBI). Children and adolescents with mild to severe TBI (n=112) were categorized according to timing of brain insult: (i) Middle Childhood (5-9 years; n=41); (ii) Late Childhood (10-11 years; n=39); and (iii) Adolescence (12-15 years; n=32) and group-matched for age, gender and socio-economic status (SES) to a typically developing (TD) control group (n=43). Participants underwent magnetic resonance imaging (MRI) including a susceptibility weighted imaging (SWI) sequence 2-8 weeks after injury and were assessed on measures of pragmatic language and behavioural functioning at 6- and 24-months after injury. Children and adolescents with TBI of all severity levels demonstrated impairments in these domains at 6-months injury before returning to age-expected levels at 2-years post-TBI. However, while adolescent TBI was associated with post-acute disruption to skills that preceded recovery to age-expected levels by 2-years post injury, the middle childhood TBI group demonstrated impairments at 6-months post-injury that were maintained at 2-year follow up. Reduced pragmatic communication was associated with frontal, temporal and corpus callosum lesions, as well as more frequent externalizing behaviour at 24-months post injury. Findings show that persisting pragmatic language impairment after pediatric TBI is related to younger age at brain insult, as well as microhemorrhagic pathology in brain regions that contribute to the anatomically distributed social brain network. Relationships between reduced pragmatic communication and more frequent externalizing behavior underscore the need for context-sensitive rehabilitation programs that aim to increase interpersonal effectiveness and reduce risk for maladaptive behavior trajectories into the long-term post injury.

Cellular and molecular mechanisms of injury and spontaneous recovery

Until recently, most have assumed that traumatic brain injury (TBI) was singularly associated with the overt destruction of brain tissue resulting in subsequent morbidity or death. More recently, experimental and clinical studies have shown that the pathobiology of TBI is more complex, involving a host of cellular and subcellular changes that impact on neuronal function and viability while also affecting vascular reactivity and the activation of multiple biological response pathways. Here we review the brain's response to injury, examining both focal and diffuse changes and their implications for post-traumatic brain dysfunction and recovery. TBI-induced neuronal dysfunction and death as well as the diffuse involvement of multiple fiber projections are discussed together with considerations of how local axonal membrane changes or channelopathy translate into local ionic dysregulation and axonal disconnection. Concomitant changes in the cerebral microcirculation are also discussed and their relationship with the parallel changes in the brain's metabolism is considered. These cellular and subcellular events occurring within neurons and their blood supply are correlated with multiple biological response modifiers evoked by generalized post-traumatic inflammation and the parallel activation of oxidative stress processes. The chapter closes with considerations of recovery following focal or diffuse injury. Evidence for dynamic brain reorganization/repair is presented, with considerations of traumatically induced circuit disruption and their progression to either adaptive or in some cases, maladaptive reorganization.

The emergence of age-dependent social cognitive deficits after generalized insult to the developing brain: a longitudinal prospective analysis using susceptibility-weighted imaging

Childhood and adolescence are critical periods for maturation of neurobiological processes that underlie complex social and emotional behavior including Theory of Mind (ToM). While structural correlates of ToM are well described in adults, less is known about the anatomical regions subsuming these skills in the developing brain or the impact of cerebral insult on the acquisition and establishment of high-level social cognitive skills. This study aimed to examine the differential influence of age-at-insult and brain pathology on ToM in a sample of children and adolescents with traumatic brain injury (TBI). Children and adolescents with TBI (n = 112) were categorized according to timing of brain insult: (i) middle childhood (5-9 years; n = 41); (ii) late childhood (10-11 years; n = 39); and (iii) adolescence (12-15 years; n = 32) and group-matched for age, gender, and socioeconomic status to a typically developing (TD) control group (n = 43). Participants underwent magnetic resonance imaging including a susceptibility-weighted imaging (SWI) sequence 2-8 weeks postinjury and were assessed on a battery of ToM tasks at 6- and 24-months after injury. Results showed that for adolescents with TBI, social cognitive dysfunction at 6- and 24-months postinjury was associated with diffuse neuropathology and a greater number of lesions detected using SWI. In the late childhood TBI group, we found a time-dependent emergence of social cognitive impairment, linked to diffuse neuropathology. The middle childhood TBI group demonstrated performance unrelated to SWI pathology and comparable to TD controls. Findings indicate that the full extent of social cognitive deficits may not be realized until the associated skills reach maturity. Evidence for brain structure-function relationships suggests that the integrity of an anatomically distributed network of brain regions and their connections is necessary for the acquisition and establishment of high-level social cognitive skills.

Artifactual microhemorrhage generated by susceptibility weighted image processing

BACKGROUND

To report that artifactual microhemorrhages are introduced by the two-dimensional (2D) homodyne filtering method of generating susceptibility weighted images (SWI) when open-ended fringelines (OEF) are present in phase data.

METHODS

SWI data from 28 traumatic brain injury (TBI) patients was obtained on a 3 tesla clinical Siemens scanner using both the product 3D gradient echo sequence (GRE) with generalized autocalibrating partially parallel acquisition acceleration and an in-house developed segmented echo planar imaging (sEPI) sequence without GRAPPA acceleration. SWI processing included (i) 2D homodyne method implemented on the scanner console and (ii) a 3D Fourier-based phase unwrapping followed by 3D high pass filtering. Original and enhanced magnitude and phase images were carefully reviewed for sites of type III OEFs and microhemorrhages by a neuroradiologist on a PACS workstation.

RESULTS

Nineteen of 28 (68%) phase datasets acquired using GRAPPA-accelerated GRE acquisition demonstrated type III OEFs. In SWI images, artifactual microhemorrhages were found on 17 of 19 (89%) cases generated using 2D homodyne processing. Application of a 3D Fourier-based unwrapping method prior HP filtering minimized the appearance of the phase singularities in the enhanced phase, and did not generate microhemorrhage-like artifacts in magnitude images.

CONCLUSION

The 2D homodyne filtering method may introduce artifacts mimicking intracranial microhemorrhages in SWI images when type III OEFs are present in phase images. Such artifacts could lead to overestimation of pathology, e.g., TBI. This work demonstrates that 3D phase unwrapping methods minimize this artifact. However, methods to properly combine phase across coils are needed to eliminate this artifact.