Imaging brain trauma

Agreement of Magnetic Resonance Imaging With Computed Tomography in the Assessment for Acute Skull Fractures in a Canine and Feline Cadaver Model

Computed tomography (CT) is the imaging modality of choice to evaluate patients with acute head trauma. However, magnetic resonance imaging (MRI) may be chosen in select cases. The objectives of this study were to evaluate the agreement of MRI with CT in the assessment for presence or absence of acute skull fractures in a canine and feline cadaver model, compare seven different MRI sequences (T1-W, T2-W, T2-FLAIR, PD-W, T2^*-W, “SPACE” and “VIBE”), and determine agreement of four different MRI readers with CT data. Pre- and post-trauma CT and MRI studies were performed on 10 canine and 10 feline cadaver heads. Agreement of MRI with CT as to presence or absence of a fracture was determined for 26 individual osseous structures and four anatomic regions (cranium, face, skull base, temporomandibular joint). Overall, there was 93.5% agreement in assessing a fracture as present or absent between MRI and CT, with a significant difference between the pre and post trauma studies (99.4 vs. 87.6%; p < 0.0001; OR 0.042; 95% CI 0.034–0.052). There was no significant difference between dogs and cats. The agreement for the different MRI sequences with CT ranged from 92.6% (T2^*-W) to 94.4% (PD-W). There was higher agreement of MRI with CT in the evaluation for fractures of the face than other anatomic regions. Agreement with CT for individual MRI readers ranged from 92.6 to 94.7%. A PD-W sequence should be added to the MR protocol when evaluating the small animal head trauma patient.

Mapping the Connectome Following Traumatic Brain Injury

There is a paucity of accurate and reliable biomarkers to detect traumatic brain injury, grade its severity, and model post-traumatic brain injury (TBI) recovery. This gap could be addressed via advances in brain mapping which define injury signatures and enable tracking of post-injury trajectories at the individual level. Mapping of molecular and anatomical changes and of modifications in functional activation supports the conceptual paradigm of TBI as a disorder of large-scale neural connectivity. Imaging approaches with particular relevance are magnetic resonance techniques (diffusion weighted imaging, diffusion tensor imaging, susceptibility weighted imaging, magnetic resonance spectroscopy, functional magnetic resonance imaging, and positron emission tomographic methods including molecular neuroimaging). Inferences from mapping represent unique endophenotypes which have the potential to transform classification and treatment of patients with TBI. Limitations of these methods, as well as future research directions, are highlighted.

Brain Oxygenation Monitoring

A mismatch between cerebral oxygen supply and demand can lead to cerebral hypoxia/ischemia and deleterious outcomes. Cerebral oxygenation monitoring is an important aspect of multimodality neuromonitoring. It is increasingly deployed whenever intracranial pressure monitoring is indicated. Although there is a large body of evidence demonstrating an association between cerebral hypoxia/ischemia and poor outcomes, it remains to be determined whether restoring cerebral oxygenation leads to improved outcomes. Randomized prospective studies are required to address uncertainties about cerebral oxygenation monitoring and management. This article describes the different methods of monitoring cerebral oxygenation, their indications, evidence base, limitations, and future perspectives.

Relationship Between Diffusion Tensor Imaging (DTI) Findings and Cognition Following Pediatric TBI: A Meta-Analytic Review

This study meta-analyzed research examining relationships between diffusion tensor imaging and cognition following pediatric traumatic brain injury (TBI). Data from 14 studies that correlated fractional anisotropy (FA) or apparent diffusion coefficient/mean diffusivity with cognition were analyzed. Short-term (<4 weeks post-TBI) findings were inconsistent, but, in the medium to long term, FA values for numerous large white matter tracts and the whole brain were related to cognition. However, the analyses were limited by the diversity of brain regions and cognitive outcomes that have been examined; all in relatively small samples. Moreover, additional data are needed to investigate the impact of age and injury severity on these findings.

Diffusion Tensor Imaging (DTI) findings following pediatric non-penetrating TBI: a meta-analysis

This study meta-analyzed research examining Diffusion Tensor Imaging following pediatric non-penetrating traumatic brain injury to identify the location and extent of white matter changes. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) data from 20 studies were analyzed. FA increased and ADC decreased in most white matter tracts in the short-term (moderate-to-large effects), and FA decreased and ADC increased in the medium- to long-term (moderate-to-very-large effects). Whole brain (short-term), cerebellum and corpus callosum (medium- to long-term) FA values have diagnostic potential, but the impact of age/developmental stage and injury severity on FA/ADC, and the predictive value, is unclear.

Advanced neuroimaging of mild traumatic brain injury

This article focuses on advancements in neuroimaging techniques, compares the advantages of each of the modalities in the evaluation of mild traumatic brain injury, and discusses their contribution to our understanding of the pathophysiology as it relates to prognosis. Advanced neuroimaging techniques discussed include anatomic/structural imaging techniques, such as diffusion tensor imaging and susceptibility-weighted imaging, and functional imaging techniques, such as functional magnetic resonance imaging, perfusion-weighted imaging, magnetic resonance spectroscopy, and positron emission tomography.

Prognosis in severe brain injury

BACKGROUND

The prediction of neurologic outcome is a fundamental concern in the resuscitation of patients with severe brain injury.

OBJECTIVE

To provide an evidence-based update on neurologic prognosis following traumatic brain injury and hypoxic-ischemic encephalopathy after cardiac arrest.

DATA SOURCE

Search of the PubMed database and manual review of bibliographies from selected articles to identify original data relating to prognostic methods and outcome prediction models in patients with neurologic trauma or hypoxic-ischemic encephalopathy.

DATA SYNTHESIS AND CONCLUSION

Articles were scrutinized regarding study design, population evaluated, interventions, outcomes, and limitations. Outcome prediction in severe brain injury is reliant on features of the neurologic examination, anatomical and physiological changes identified with CT and MRI, abnormalities detected with electroencephalography and evoked potentials, and physiological and biochemical derangements at both the brain and systemic levels. Use of such information in univariable association studies generally lacks specificity in classifying neurologic outcome. Furthermore, the accuracy of established prognostic classifiers may be affected by the introduction of outcome-modifying interventions, such as therapeutic hypothermia following cardiac arrest. Although greater specificity may be achieved with scoring systems derived from multivariable models, they generally fail to predict outcome with sufficient accuracy to be meaningful at the single patient level. Discriminative models which integrate knowledge of genetic determinants and biologic processes governing both injury and repair and account for the effects of resuscitative and rehabilitative care are needed.

The reliability of magnetic resonance imaging in traumatic brain injury lesion detection

OBJECTIVE

This study compares inter-rater-reliability, lesion detection and clinical relevance of T2-weighted imaging (T2WI), Fluid Attenuated Inversion Recovery (FLAIR), T2*-gradient recalled echo (T2*-GRE) and Susceptibility Weighted Imaging (SWI) in Traumatic Brain Injury (TBI).

METHODS

Three raters retrospectively scored 56 TBI patients' MR images (12-76 years old, median TBI-MRI interval 7 weeks) on number, volume, location and intensity. Punctate lesions (diameter <10 mm) were scored separately from large lesions (diameter ≥ 10 mm). Injury severity was assessed with the Glasgow Coma Scale (GCS), outcome with the Glasgow Outcome Scale-Extended (GOSE).

RESULTS

Inter-rater-reliability for lesion volume and punctate lesion count was good (ICC = 0.69-0.94) except for punctate lesion count on T2WI (ICC = 0.19) and FLAIR (ICC = 0.15). SWI showed the highest number of lesions (mean = 30.0), followed by T2*-GRE (mean = 15.4), FLAIR (mean = 3.1) and T2WI (mean = 2.2). Sequences did not differ in detected lesion volume. Punctate lesion count on T2*-GRE (r = -0.53) and SWI (r = -0.49) correlated with the GCS (p < 0.001).

CONCLUSIONS

T2*-GRE and SWI are more sensitive than T2WI and FLAIR in detecting (haemorrhagic) traumatic punctate lesions. The correlation between number of punctate lesions on T2*-GRE/SWI and the GCS indicates that haemorrhagic lesions are clinically relevant. The considerable inter-rater-disagreement in this study advocates cautiousness in interpretation of punctate lesions using T2WI and FLAIR.

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.

Neuropsychological and neuroimaging findings in traumatic brain injury and post-traumatic stress disorder

Advances in imaging technology, coupled with military personnel returning home from Iraq and Afghanistan with traumatic brain injury (TBI) and/or post-traumatic stress disorder (PTSD), have increased interest in the neuropsychology and neurobiology of these two conditions. There has been a particular focus on differential diagnosis. This paper provides an overview of findings regarding the neuropsychological and neurobiological underpinnings of TBI and for PTSD. A specific focus is on assessment using neuropsychological measures and imaging techniques. Challenges associated with the assessment of individuals with one or both conditions are also discussed. Although use of neuropsychological and neuroimaging test results may assist with diagnosis and treatment planning, further work is needed to identify objective biomarkers for each condition. Such advances would be expected to facilitate differential diagnosis and implementation of best treatment practices.