Prediction of poor outcome after hypoxic-ischemic brain injury by diffusion-weighted imaging: A systematic review and meta-analysis

Regional Brain Net Water Uptake in Computed Tomography after Cardiac Arrest - A Novel Biomarker for Neuroprognostication

BACKGROUND

Selective water uptake by neurons and glial cells and subsequent brain tissue oedema are key pathophysiological processes of hypoxic-ischemic encephalopathy (HIE) after cardiac arrest (CA). Although brain computed tomography (CT) is widely used to assess the severity of HIE, changes of brain radiodensity over time have not been investigated. These could be used to quantify regional brain net water uptake (NWU), a potential prognostic biomarker.

METHODS

We conducted an observational prognostic accuracy study including a derivation (single center cardiac arrest registry) and a validation (international multicenter TTM2 trial) cohort. Early (<6 h) and follow-up (>24 h) head CTs of CA patients were used to determine regional NWU for grey and white matter regions after co-registration with a brain atlas. Neurological outcome was dichotomized as good versus poor using the Cerebral Performance Category Scale (CPC) in the derivation cohort and Modified Rankin Scale (mRS) in the validation cohort.

RESULTS

We included 115 patients (81 derivation, 34 validation) with out-of-hospital (OHCA) and in-hospital cardiac arrest (IHCA). Regional brain water content remained unchanged in patients with good outcome. In patients with poor neurological outcome, we found considerable regional water uptake with the strongest effect in the basal ganglia. NWU >8% in the putamen and caudate nucleus predicted poor outcome with 100% specificity (95%-CI: 86-100%) and 43% (moderate) sensitivity (95%-CI: 31-56%).

CONCLUSION

This pilot study indicates that NWU derived from serial head CTs is a promising novel biomarker for outcome prediction after CA. NWU >8% in basal ganglia grey matter regions predicted poor outcome while absence of NWU indicated good outcome. NWU and follow-up CTs should be investigated in larger, prospective trials with standardized CT acquisition protocols.

Electroencephalography Prediction of Neurological Outcomes After Hypoxic-Ischemic Brain Injury: A Systematic Review and Meta-Analysis

Background. Predicting neurological outcomes after hypoxic-ischemic brain injury (HIBI) is difficult. Objective. Electroencephalography (EEG) can identify acute and subacute brain abnormalities after hypoxic brain injury and predict HIBI recovery. We examined EEG's ability to predict neurologic outcomes following HIBI. Method. A PRISMA-compliant search was conducted in the Medline, Embase, Cochrane, and Central databases until January 2023. EEG-predicted neurological outcomes in HIBI patients were selected from relevant perspective and retrospective cohort studies. RevMan did meta-analysis, while QDAS2 assessed research quality. Results. Eleven studies with 3761 HIBI patients met the inclusion and exclusion criteria. We aggregated study-level estimates of sensitivity and specificity for EEG patterns determined a priori using random effect bivariate and univariate meta-analysis when appropriate. Positive indicators and anatomical area heterogeneity impacted prognosis accuracy. Funnel plots analyzed publication bias. Significant heterogeneity of greater than 80% was among the included studies with P < 0.001. The area under the curve was 0.94, the threshold effect was P < 0.001, and the sensitivity and specificity, with 95% confidence intervals, were 0.91 (0.84-0.99) and 0.86 (0.75-0.97). EEG detects status epilepticus and burst suppression with good sensitivity, specificity, and little probability of false-negative impairment result attribution. Study quality varied by domain, but patient flow and timing were well conducted in all. Conclusion. EEG can predict the outcome of HIBI with good prognostic accuracy, but more standardized cross-study protocols and descriptions of EEG patterns are needed to better evaluate its prognostic use for patients with HIBI.

BOston Neonatal Brain Injury Dataset for Hypoxic Ischemic Encephalopathy (BONBID-HIE): Part I. MRI and Manual Lesion Annotation

Hypoxic ischemic encephalopathy (HIE) is a brain injury that occurs in 1 ~ 5/1000 term neonates. Accurate identification and segmentation of HIE-related lesions in neonatal brain magnetic resonance images (MRIs) is the first step toward predicting prognosis, identifying high-risk patients, and evaluating treatment effects. It will lead to a more accurate estimation of prognosis, a better understanding of neurological symptoms, and a timely prediction of response to therapy. We release the first public dataset containing neonatal brain diffusion MRI and expert annotation of lesions from 133 patients diagnosed with HIE. HIE-related lesions in brain MRI are often diffuse (i.e., multi-focal), and small (over half the patients in our data having lesions occupying <1% of brain volume). Segmentation for HIE MRI data is remarkably different from, and arguably more challenging than, other segmentation tasks such as brain tumors with focal and relatively large lesions. We hope that this dataset can help fuel the development of MRI lesion segmentation methods for HIE and small diffuse lesions in general.

Differential Glial Chitotriosidase 1 and Chitinase 3-like Protein 1 Expression in the Human Primary Visual Cortex and Cerebellum after Global Hypoxia-Ischemia

Here, we studied the neuroinflammation- and ischemia-related glial markers chitotriosidase 1 (CHIT1) and chitinase-3-like protein 1 (CHI3L1, alias YKL-40) in the human striate cortex and cerebellum at different time points after global hypoxic-ischemic brain injury (HIBI). Both regions differ considerably in their glial cell population but are supplied by the posterior circulation. CHIT1 and CHI3L1 expression was compared to changes in microglial (IBA1, CD68), astrocytic (GFAP, S100β), and neuronal markers (H&E, neurofilament heavy chain, NfH; calretinin, CALR) using immunohistochemistry and multiple-label immunofluorescence. Initial striatal cortical and cerebellar Purkinje cell damage, detectable already 1/2 d after HIBI, led to delayed neuronal death, whereas loss of cerebellar NfH-positive stellate and CALR-positive granule cells was variable. During the first week post-HIBI, a transient reduction of IBA1-positive microglia was observed in both regions, and fragmented/clasmatodendritic cerebellar Bergmann glia appeared. In long-term survivors, both brain regions displayed high densities of activated IBA1-positive cells and CD68-positive macrophages, which showed CHIT1 co-localization in the striate cortex. Furthermore, enlarged GFAP- and S100β-positive astroglia emerged in both regions around 9-10 d post-HIBI, i.e., along with clearance of dead neurons from the neuropil, although GFAP-/S100β-positive gemistocytic astrocytes that co-expressed CHI3L1 were found only in the striate cortex. Thus, only GFAP-/S100β-positive astrocytes in the striate cortex, but not cerebellar Bergmann glia, differentiated into CHI3L1-positive gemistocytes. CHIT1 was co-expressed almost entirely in macrophages in the striate cortex and not cerebellum of long-term survivors, thereby indicating that CHIT1 and CHI3L1 could be valuable biomarkers for monitoring the outcome of global HIBI.

Regional Distribution of Brain Injury After Cardiac Arrest: Clinical and Electrographic Correlates

BACKGROUND AND OBJECTIVES

Disorders of consciousness, EEG background suppression, and epileptic seizures are associated with poor outcome after cardiac arrest. Our objective was to identify the distribution of diffusion MRI-measured anoxic brain injury after cardiac arrest and to define the regional correlates of disorders of consciousness, EEG background suppression, and seizures.

METHODS

We analyzed patients from a single-center database of unresponsive patients who underwent diffusion MRI after cardiac arrest (n = 204). We classified each patient according to recovery of consciousness (command following) before discharge, the most continuous EEG background (burst suppression vs continuous), and the presence or absence of seizures. Anoxic brain injury was measured with the apparent diffusion coefficient (ADC) signal. We identified ADC abnormalities relative to controls without cardiac arrest (n = 48) and used voxel lesion symptom mapping to identify regional associations with disorders of consciousness, EEG background suppression, and seizures. We then used a bootstrapped lasso regression procedure to identify robust, multivariate regional associations with each outcome variable. Last, using area under receiver operating characteristic curves, we then compared the classification ability of the strongest regional associations to that of brain-wide summary measures.

RESULTS

Compared to controls, patients with cardiac arrest demonstrated ADC signal reduction that was most significant in the occipital lobes. Disorders of consciousness were associated with reduced ADC most prominently in the occipital lobes but also in deep structures. Regional injury more accurately classified patients with disorders of consciousness than whole-brain injury. Background suppression mapped to a similar set of brain regions, but regional injury could no better classify patients than whole-brain measures. Seizures were less common in patients with more severe anoxic injury, particularly in those with injury to the lateral temporal white matter.

DISCUSSION

Anoxic brain injury was most prevalent in posterior cerebral regions, and this regional pattern of injury was a better predictor of disorders of consciousness than whole-brain injury measures. EEG background suppression lacked a specific regional association, but patients with injury to the temporal lobe were less likely to have seizures. Regional patterns of anoxic brain injury are relevant to the clinical and electrographic sequelae of cardiac arrest and may hold importance for prognosis.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that disorders of consciousness after cardiac arrest are associated with widely lower ADC values on diffusion MRI and are most strongly associated with reductions in occipital ADC.

18F-fluorodeoxyglucose positron-emitted tomography for predicting neurological outcome in hypoxic-ischemic encephalopathy

Background: ¹⁸F-fluorodeoxyglucose positron-emitted tomography (FDG-PET) is a promising yet unexplored functional neuroimaging tool in the study and prognosis of hypoxic-ischemic encephalopathy (HIE) after cardiac arrest or respiratory failure. The present study aimed to correlate clinical data and FDG-PET scans for both analysis and prognostic use. Methods: 24 patients from an intensive rehabilitation ward were retrospectively evaluated. Data collected included age, gender, cause of anoxic event, length of stay in acute and rehabilitation units, discharge destination, and evaluation at admission and discharge using three clinical scales to assess cognitive function, independence and disability. Subjects were identified as good and bad performers on the basis of quantitative analysis of FDG-PET scans with the Cortex ID software. The relation between glucose uptake reduction and neurological outcome was evaluated. Results: good and bad performers presented no statistically significant difference regarding demographical data and in-hospital length of stay. The two categories significantly differed for impairment and disability levels both at admission and at discharge from the inpatient rehabilitation unit. Conclusions: FDG-PET considerably facilitates the early identification of patients with HIE who will have poor neurological outcome and could inform planning for their rehabilitation and care.