Decreased DNA Methylation of RGMA is Associated with Intracranial Hypertension After Severe Traumatic Brain Injury: An Exploratory Epigenome-Wide Association Study

BACKGROUND

Cerebral edema and intracranial hypertension are major contributors to unfavorable prognosis in traumatic brain injury (TBI). Local epigenetic changes, particularly in DNA methylation, may influence gene expression and thus host response/secondary injury after TBI. It remains unknown whether DNA methylation in the central nervous system is associated with cerebral edema severity or intracranial hypertension post TBI. We sought to identify epigenome-wide DNA methylation patterns associated with these forms of secondary injury after TBI.

METHODS

We obtained genome-wide DNA methylation profiles of DNA extracted from ventricular cerebrospinal fluid samples at three different postinjury time points from a prospective cohort of patients with severe TBI (n = 89 patients, 254 samples). Cerebral edema and intracranial pressure (ICP) measures were clustered to generate composite end points of cerebral edema and ICP severity. We performed an unbiased epigenome-wide association study (EWAS) to test associations between DNA methylation at 419,895 cytosine-phosphate-guanine (CpG) sites and cerebral edema/ICP severity categories. Given inflated p values, we conducted permutation tests for top CpG sites to filter out potential false discoveries.

RESULTS

Our data-driven hierarchical clustering across six cerebral edema and ICP measures identified two groups differing significantly in ICP based on the EWAS-identified CpG site cg22111818 in RGMA (Repulsive guidance molecule A, permutation p = 4.20 × 10-8). At 3-4 days post TBI, patients with severe intracranial hypertension had significantly lower levels of methylation at cg22111818.

CONCLUSIONS

We report a novel potential relationship between intracranial hypertension after TBI and an acute, nonsustained reduction in DNA methylation at cg22111818 in the RGMA gene. To our knowledge, this is the largest EWAS in severe TBI. Our findings are further strengthened by previous findings that RGMA modulates axonal repair in other central nervous system disorders, but a role in intracranial hypertension or TBI has not been previously identified. Additional work is warranted to validate and extend these findings, including assessment of its possible role in risk stratification, identification of novel druggable targets, and ultimately our ability to personalize therapy in TBI.

Choice of Whole Blood versus Lactated Ringer's Resuscitation Modifies the Relationship between Blood Pressure Target and Functional Outcome after Traumatic Brain Injury plus Hemorrhagic Shock in Mice

Civilian traumatic brain injury (TBI) guidelines recommend resuscitation of patients with hypotensive TBI with crystalloids. Increasing evidence, however, suggests that whole blood (WB) resuscitation may improve physiological and survival outcomes at lower resuscitation volumes, and potentially at a lower mean arterial blood pressure (MAP), than crystalloid after TBI and hemorrhagic shock (HS). The objective of this study was to assess whether WB resuscitation with two different MAP targets improved behavioral and histological outcomes compared with lactated Ringer's (LR) in a mouse model of TBI+HS. Anesthetized mice (n = 40) underwent controlled cortical impact (CCI) followed by HS (MAP = 25-27 mm Hg; 25 min) and were randomized to five groups for a 90 min resuscitation: LR with MAP target of 70 mm Hg (LR70), LR60, WB70, WB60, and monitored sham. Mice received a 20 mL/kg bolus of LR or autologous WB followed by LR boluses (10 mL/kg) every 5 min for MAP below target. Shed blood was reinfused after 90 min. Morris Water Maze testing was performed on days 14-20 post-injury. Mice were euthanized (21 d) to assess contusion and total brain volumes. Latency to find the hidden platform was greater versus sham for LR60 (p < 0.002) and WB70 (p < 0.007) but not LR70 or WB60. The WB resuscitation did not reduce contusion volume or brain tissue loss. The WB targeting a MAP of 60 mm Hg did not compromise function versus a 70 mm Hg target after CCI+HS, but further reduced fluid requirements (p < 0.03). Using LR, higher achieved MAP was associated with better behavioral performance (rho = -0.67, p = 0.028). Use of WB may allow lower MAP targets without compromising functional outcome, which could facilitate pre-hospital TBI resuscitation.

Drug repurposing for COVID-19 based on an integrative meta-analysis of SARS-CoV-2 induced gene signature in human airway epithelium

Drug repurposing has the potential to bring existing de-risked drugs for effective intervention in an ongoing pandemic-COVID-19 that has infected over 131 million, with 2.8 million people succumbing to the illness globally (as of April 04, 2021). We have used a novel `gene signature'-based drug repositioning strategy by applying widely accepted gene ranking algorithms to prioritize the FDA approved or under trial drugs. We mined publically available RNA sequencing (RNA-Seq) data using CLC Genomics Workbench 20 (QIAGEN) and identified 283 differentially expressed genes (FDR<0.05, log2FC>1) after a meta-analysis of three independent studies which were based on severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) infection in primary human airway epithelial cells. Ingenuity Pathway Analysis (IPA) revealed that SARS-CoV-2 activated key canonical pathways and gene networks that intricately regulate general anti-viral as well as specific inflammatory pathways. Drug database, extracted from the Metacore and IPA, identified 15 drug targets (with information on COVID-19 pathogenesis) with 46 existing drugs as potential-novel candidates for repurposing for COVID-19 treatment. We found 35 novel drugs that inhibit targets (ALPL, CXCL8, and IL6) already in clinical trials for COVID-19. Also, we found 6 existing drugs against 4 potential anti-COVID-19 targets (CCL20, CSF3, CXCL1, CXCL10) that might have novel anti-COVID-19 indications. Finally, these drug targets were computationally prioritized based on gene ranking algorithms, which revealed CXCL10 as the common and strongest candidate with 2 existing drugs. Furthermore, the list of 283 SARS-CoV-2-associated proteins could be valuable not only as anti-COVID-19 targets but also useful for COVID-19 biomarker development.

Abcc8 (Sulfonylurea Receptor-1) Impact on Brain Atrophy after Traumatic Brain Injury Varies by Sex

Females have been understudied in pre-clinical and clinical traumatic brain injury (TBI), despite distinct biology and worse clinical outcomes versus males. Sulfonylurea receptor 1 (SUR1) inhibition has shown promising results in predominantly male TBI. A phase II trial is ongoing. We investigated whether SUR1 inhibition effects on contusional TBI differ by sex given that this may inform clinical trial design and/or interpretation. We studied the moderating effects of sex on post-injury brain tissue loss in 142 male and female ATP-binding cassette transporter subfamily C member 8 (Abcc8) wild-type, heterozygote, and knockout mice (12-15 weeks). Monkey fibroblast-like cells and mouse brain endothelium-derived cells were used for in vitro studies. Mice were injured with controlled cortical impact and euthanized 21 days post-injury to assess contusion, brain, and hemisphere volumes (vs. genotype- and sex-matched naïves). Abcc8 knockout mice had smaller contusion volumes (p = 0.012) and larger normalized contralateral (right) hemisphere volumes (nRHV; p = 0.03) after injury versus wild type. This was moderated by sex: Contusions were smaller (p = 0.020), nRHV was higher (p = 0.001), and there was less global atrophy (p = 0.003) in male, but not female, knockout versus wild-type mice after TBI. Less atrophy occurred in males for each copy of Abcc8 lost (p = 0.023-0.002, all outcomes). In vitro, sex-determining region Y (SRY) stimulated Abcc8 promoter activity and increased Abcc8 expression. Loss of Abcc8 strongly protected against post-traumatic cerebral atrophy in male, but not female, mice. This may partly be mediated by SRY on the Y-chromosome. Sex differences may have important implications for ongoing and future trials of SUR1 blockade.

Genetic Variants Associated With Intraparenchymal Hemorrhage Progression After Traumatic Brain Injury

IMPORTANCE

Intracerebral hemorrhage progression is associated with unfavorable outcome after traumatic brain injury (TBI). No effective treatments are currently available. This secondary injury process reflects an extreme form of vasogenic edema and blood-brain barrier breakdown. The sulfonylurea receptor 1-transient receptor potential melastatin 4 (SUR1-TRPM4) cation channel is a key underlying mechanism. A phase 2 trial of SUR1-TRPM4 inhibition in contusional TBI is ongoing, and a phase 3 trial is being designed. Targeted identification of patients at increased risk for hemorrhage progression may inform prognostication, trial design (including patient selection), and ultimately treatment response.

OBJECTIVE

To determine whether ABCC8 (SUR1) and TRPM4 genetic variability are associated with intraparenchymal hemorrhage (IPH) progression after severe TBI, based on the putative involvement of the SUR1-TRPM4 channel in this pathophysiology.

DESIGN, SETTING, AND PARTICIPANTS

In this genetic association study, DNA was extracted from 416 patients with severe TBI prospectively enrolled from a level I trauma academic medical center from May 9, 2002, to August 8, 2014. Forty ABCC8 and TRPM4 single-nucleotide variants (SNVs) were genotyped (multiplex, unbiased). Data were analyzed from January 7, 2020, to May 3, 2021.

MAIN OUTCOMES AND MEASURES

Primary analyses addressed IPH progression at 6, 24, and 120 hours in patients without acute craniectomy (n = 321). Multivariable regressions and receiver operating characteristic curves assessed SNV and haplotype associations with progression. Spatial modeling and functional predictions were determined using standard software.

RESULTS

Of the 321 patients included in the analysis (mean [SD] age, 37.0 [16.3] years; 247 [76.9%] male), IPH progression occurred in 102. Four ABCC8 SNVs were associated with markedly increased odds of progression (rs2237982 [odds ratio (OR), 2.60-3.80; 95% CI, 1.14-5.90 to 1.80-8.02; P = .02 to P < .001], rs2283261 [OR, 3.37-4.77; 95% CI, 1.07-10.77 to 1.89-12.07; P = .04 to P = .001], rs3819521 [OR, 2.96-3.92; 95% CI, 1.13-7.75 to 1.42-10.87; P = .03 to P = .009], and rs8192695 [OR, 3.06-4.95; 95% CI, 1.02-9.12 to 1.67-14.68]; P = .03-.004). These are brain-specific expression quantitative trait loci (eQTL) associated with increased ABCC8 messenger RNA levels. Regulatory annotations revealed promoter and enhancer marks and strong and/or active brain-tissue transcription, directionally consistent with increased progression. Three SNVs (rs2283261, rs2237982, and rs3819521) in this cohort have been associated with intracranial hypertension. Four TRPM4 SNVs were associated with decreased IPH progression (rs3760666 [OR, 0.40-0.49; 95% CI, 0.19-0.86 to 0.27-0.89; P = .02 to P = .009], rs1477363 [OR, 0.40-0.43; 95% CI, 0.18-0.88 to 0.23-0.81; P = .02 to P = .006], rs10410857 [OR, 0.36-0.41; 95% CI, 0.20-0.67 to 0.20-0.85; P = .02 to P = .001], and rs909010 [OR, 0.27-0.40; 95% CI, 0.12-0.62 to 0.16-0.58; P = .002 to P < .001]). Significant SNVs in both genes cluster downstream, flanking exons encoding the receptor site and SUR1-TRPM4 binding interface. Adding genetic variation to clinical models improved receiver operating characteristic curve performance from 0.6959 to 0.8030 (P = .003).

CONCLUSIONS AND RELEVANCE

In this genetic association study, 8 ABCC8 and TRPM4 SNVs were associated with IPH progression. Spatial clustering, brain-specific eQTL, and regulatory annotations suggest biological plausibility. These findings may have important implications for neurocritical care risk stratification, patient selection, and precision medicine, including an upcoming phase 3 trial design for SUR1-TRPM4 inhibition in severe TBI.

Pain Trajectories Following Subarachnoid Hemorrhage are Associated with Continued Opioid Use at Outpatient Follow-up

BACKGROUND

Subarachnoid hemorrhage (SAH) is characterized by the worst headache of life and associated with long-term opioid use. Discrete pain trajectories predict chronic opioid use following other etiologies of acute pain, but it is unknown whether they exist following SAH. If discrete pain trajectories following SAH exist, it is uncertain whether they predict long-term opioid use. We sought to characterize pain trajectories after SAH and determine whether they are associated with persistent opioid use.

METHODS

We reviewed pain scores from patients admitted to a single tertiary care center for SAH from November 2015 to September 2019. Group-based trajectory modeling identified discrete pain trajectories during hospitalization. We compared outcomes across trajectory groups using χ² and Kruskal-Wallis tests. Multivariable regression determined whether trajectory group membership was an independent predictor of long-term opioid use, defined as continued use at outpatient follow-up.

RESULTS

We identified five discrete pain trajectories among 305 patients. Group 1 remained pain free. Group 2 reported low scores with intermittent spikes and slight increase over time. Group 3 noted increasing pain severity through day 7 with mild improvement until day 14. Group 4 experienced maximum pain with steady decrement over time. Group 5 reported moderate pain with subtle improvement. In multivariable analysis, trajectory groups 3 (odds ratio [OR] 3.5; 95% confidence interval [CI] 1.5-8.3) and 5 (OR 8.0; 95% CI 3.1-21.1), history of depression (OR 3.6; 95% CI 1.3-10.0) and racial/ethnic minority (OR 2.3; 95% CI 1.3-4.1) were associated with continued opioid use at follow-up (median 62 days following admission, interquartile range 48-96).

CONCLUSIONS

Discrete pain trajectories following SAH exist. Recognition of pain trajectories may help identify those at risk for long-term opioid use.

Cerebrospinal Fluid Sulfonylurea Receptor-1 is Associated with Intracranial Pressure and Outcome after Pediatric TBI: An Exploratory Analysis of the Cool Kids Trial

Sulfonylurea receptor-1 (SUR1) is recognized increasingly as a key contributor to cerebral edema, hemorrhage progression, and possibly neuronal death in multiple forms of acute brain injury. SUR1 inhibition may be protective and is actively undergoing evaluation in Phase-2/3 trials of traumatic brain injury (TBI) and stroke. In adult TBI, SUR1 expression is associated with intracranial hypertension and contusion expansion; its role in pediatric TBI remains unexplored. We tested 61 cerebrospinal fluid (CSF) samples from 16 pediatric patients with severe TBI enrolled in the multicenter Phase-3 randomized controlled "Cool Kids" trial and seven non-brain injured pediatric controls for SUR1 expression by enzyme-linked immunosorbent assay. Linear mixed models evaluated associations between mean SUR1 and intracranial pressure (ICP) over the first seven days and pediatric Glasgow Outcome Scale-Extended (GOS-E Peds) over the initial year after injury. SUR1 was undetectable in control CSF and increased versus control in nine of 16 patients with TBI. Mean SUR1 was not associated with age, sex, or therapeutic hypothermia. Each 1-point increase in initial Glasgow Coma Score was associated with a 1.68 ng/mL decrease in CSF SUR1. The CSF SUR1 was associated with increased ICP over seven days (b = 0.73, p = 0.004) and worse (higher) GOS-E Peds score (b = 0.24, p = 0.004). In this exploratory pediatric study, CSF SUR1 was undetectable in controls and variably elevated in severe TBI. Mean CSF SUR1 concentration was associated with ICP and outcome. These findings are distinct from our previous report in adults with severe TBI, where SUR1 was detected universally. SUR1 may be a viable therapeutic target in a subset of pediatric TBI, and further study is warranted.

B-Cell Lymphoma 2 (Bcl-2) Gene Is Associated with Intracranial Hypertension after Severe Traumatic Brain Injury

Severe traumatic brain injury (TBI) activates the apoptotic cascade in neurons and glia as part of secondary cellular injury. B-cell lymphoma 2 (Bcl-2) gene encodes a pro-survival protein to suppress programmed cell death, and variation in this gene has potential to affect intracranial pressure (ICP). Participants were recruited from a single clinical center using a prospective observational study design. Inclusion criteria were: age 16-80 years; Glasgow Coma Scale (GCS) score 4-8; and at least 24 h of ICP monitoring treated between 2000-2014. Outcomes were mean ICP, spikes >20 and >25 mm Hg, edema, and surgical intervention. Odds ratios (OR), mean increases/decreases (B), and 95% confidence intervals (CIs) were reported. In 264 patients, average age was 39.2 years old and 78% of patients were male. Mean ICPs were 11.4 ± 0.4 mm Hg for patients with homozygous wild-type (AA), 12.8 ± 0.6 mm Hg for heterozygous (AG), and 14.3 ± 1.2 mm Hg for homozygous variant (GG; p = 0.023). Rs17759659 GG genotype was associated with more ICP spikes >20 mm Hg (p = 0.017) and >25 mm Hg (p = 0.048). Multi-variate analysis showed that GG relative to AA genotype had higher ICP (B = 2.7 mm Hg, 95% CI [0.5,4.9], p = 0.015), edema (OR = 2.5 [1.0, 6.0], p = 0.049) and need for decompression (OR = 3.7 [1.5-9.3], p = 0.004). In this prospective severe TBI cohort, Bcl-2 rs17759659 was associated with increased risk of intracranial hypertension, cerebral edema, and need for surgical intervention. The variant allele may impact programmed cell death of injured neurons, resulting in elevated ICP and post-traumatic secondary insults. Further risk stratification and targeted genotype-based therapies could improve outcomes after severe TBI.

B-Cell Lymphoma 2 (Bcl-2) and Regulation of Apoptosis after Traumatic Brain Injury: A Clinical Perspective

Background and Objectives: The injury burden after head trauma is exacerbated by secondary sequelae, which leads to further neuronal loss. B-cell lymphoma 2 (Bcl-2) is an anti-apoptotic protein and a key modulator of the programmed cell death (PCD) pathways. The current study evaluates the clinical evidence on Bcl-2 and neurological recovery in patients after traumatic brain injury (TBI). Materials and Methods: All studies in English were queried from the National Library of Medicine PubMed database using the following search terms: (B-cell lymphoma 2/Bcl-2/Bcl2) AND (brain injury/head injury/head trauma/traumatic brain injury) AND (human/patient/subject). There were 10 investigations conducted on Bcl-2 and apoptosis in TBI patients, of which 5 analyzed the pericontutional brain tissue obtained from surgical decompression, 4 studied Bcl-2 expression as a biomarker in the cerebrospinal fluid (CSF), and 1 was a prospective randomized trial. Results: Immunohistochemistry (IHC) in 94 adults with severe TBI showed upregulation of Bcl-2 in the pericontusional tissue. Bcl-2 was detected in 36-75% of TBI patients, while it was generally absent in the non-TBI controls, with Bcl-2 expression increased 2.9- to 17-fold in TBI patients. Terminal deoxynucleotidyl transferase-mediated biotinylated dUTP nick-end labeling (TUNEL) positivity for cell death was detected in 33-73% of TBI patients. CSF analysis in 113 TBI subjects (90 adults, 23 pediatric patients) showed upregulation of Bcl-2 that peaked on post-injury day 3 and subsequently declined after day 5. Increased Bcl-2 in the peritraumatic tissue, rising CSF Bcl-2 levels, and the variant allele of rs17759659 are associated with improved mortality and better outcomes on the Glasgow Outcome Score (GOS). Conclusions: Bcl-2 is upregulated in the pericontusional brain and CSF in the acute period after TBI. Bcl-2 has a neuroprotective role as a pro-survival protein in experimental models, and increased expression in patients can contribute to improvement in clinical outcomes. Its utility as a biomarker and therapeutic target to block neuronal apoptosis after TBI warrants further evaluation.

Cerebral Edema in Traumatic Brain Injury: a Historical Framework for Current Therapy

PURPOSE OF REVIEW

The purposes of this narrative review are to (1) summarize a contemporary view of cerebral edema pathophysiology, (2) present a synopsis of current management strategies in the context of their historical roots (many of which date back multiple centuries), and (3) discuss contributions of key molecular pathways to overlapping edema endophenotypes. This may facilitate identification of important therapeutic targets.

RECENT FINDINGS

Cerebral edema and resultant intracranial hypertension are major contributors to morbidity and mortality following traumatic brain injury. Although Starling forces are physical drivers of edema based on differences in intravascular vs extracellular hydrostatic and oncotic pressures, the molecular pathophysiology underlying cerebral edema is complex and remains incompletely understood. Current management protocols are guided by intracranial pressure measurements, an imperfect proxy for cerebral edema. These include decompressive craniectomy, external ventricular drainage, hyperosmolar therapy, hypothermia, and sedation. Results of contemporary clinical trials assessing these treatments are summarized, with an emphasis on the gap between intermediate measures of edema and meaningful clinical outcomes. This is followed by a brief statement summarizing the most recent guidelines from the Brain Trauma Foundation (4th edition). While many molecular mechanisms and networks contributing to cerebral edema after TBI are still being elucidated, we highlight some promising molecular mechanism-based targets based on recent research including SUR1-TRPM4, NKCC1, AQP4, and AVP1.

SUMMARY

This review outlines the origins of our understanding of cerebral edema, chronicles the history behind many current treatment approaches, and discusses promising molecular mechanism-based targeted treatments.

Downstream TRPM4 Polymorphisms Are Associated with Intracranial Hypertension and Statistically Interact with ABCC8 Polymorphisms in a Prospective Cohort of Severe Traumatic Brain Injury

Sulfonylurea-receptor-1(SUR1) and its associated transient-receptor-potential cation channel subfamily-M (TRPM4) channel are key contributors to cerebral edema and intracranial hypertension in traumatic brain injury (TBI) and other neurological disorders. Channel inhibition by glyburide is clinically promising. ABCC8 (encoding SUR1) single-nucleotide polymorphisms (SNPs) are reported as predictors of raised intracranial pressure (ICP). This project evaluated whether TRPM4 SNPs predicted ICP and TBI outcome. DNA was extracted from 435 consecutively enrolled severe TBI patients. Without a priori selection, all 11 TRPM4 SNPs available on the multiplex platform (Illumina:Human-Core-Exome v1.0) were genotyped spanning the 25 exon gene. A total of 385 patients were analyzed after quality control. Outcomes included ICP and 6 month Glasgow Outcome Scale (GOS) score. Proxy SNPs, spatial modeling, and functional predictions were determined using established software programs. rs8104571 (intron-20) and rs150391806 (exon-24) were predictors of ICP. rs8104571 heterozygotes predicted higher average ICP (β = 10.3 mm Hg, p = 0.00000029), peak ICP (β = 19.6 mm Hg, p = 0.0007), and proportion ICP >25 mm Hg (β = 0.16 p = 0.004). rs150391806 heterozygotes had higher mean (β = 7.2 mm Hg, p = 0.042) and peak (β = 28.9 mm Hg, p = 0.0015) ICPs. rs8104571, rs150391806, and 34 associated proxy SNPs in linkage-disequilibrium clustered downstream. This region encodes TRPM4's channel pore and a region postulated to juxtapose SUR1 sequences encoded by an ABCC8 DNA segment containing previously identified relevant SNPs. There was an interaction effect on ICP between rs8104571 and a cluster of predictive ABCC8 SNPs (rs2237982, rs2283261, rs11024286). Although not significant in univariable or a basic multivariable model, in an expanded model additionally accounting for injury pattern, computed tomographic (CT) appearance, and intracranial hypertension, heterozygous rs8104571 was associated with favorable 6 month GOS (odds ratio [OR] = 16.7, p = 0.007951). This trend persisted in a survivor-only subcohort (OR = 20.67, p = 0.0168). In this cohort, two TRPM4 SNPs predicted increased ICP with large effect sizes. Both clustered downstream, spanning a region encoding the channel pore and interacting with SUR1. If validated, this may guide risk stratification and eventually inform treatment-responder classification for SUR1-TRPM4 inhibition in TBI. Larger studies are warranted.

Regionally clustered ABCC8 polymorphisms in a prospective cohort predict cerebral oedema and outcome in severe traumatic brain injury

OBJECTIVE

ABCC8 encodes sulfonylurea receptor 1, a key regulatory protein of cerebral oedema in many neurological disorders including traumatic brain injury (TBI). Sulfonylurea-receptor-1 inhibition has been promising in ameliorating cerebral oedema in clinical trials. We evaluated whether ABCC8 tag single-nucleotide polymorphisms predicted oedema and outcome in TBI.

METHODS

DNA was extracted from 485 prospectively enrolled patients with severe TBI. 410 were analysed after quality control. ABCC8 tag single-nucleotide polymorphisms (SNPs) were identified (Hapmap, r²>0.8, minor-allele frequency >0.20) and sequenced (iPlex-Gold, MassArray). Outcomes included radiographic oedema, intracranial pressure (ICP) and 3-month Glasgow Outcome Scale (GOS) score. Proxy SNPs, spatial modelling, amino acid topology and functional predictions were determined using established software programs.

RESULTS

Wild-type rs7105832 and rs2237982 alleles and genotypes were associated with lower average ICP (β=-2.91, p=0.001; β=-2.28, p=0.003) and decreased radiographic oedema (OR 0.42, p=0.012; OR 0.52, p=0.017). Wild-type rs2237982 also increased favourable 3-month GOS (OR 2.45, p=0.006); this was partially mediated by oedema (p=0.03). Different polymorphisms predicted 3-month outcome: variant rs11024286 increased (OR 1.84, p=0.006) and wild-type rs4148622 decreased (OR 0.40, p=0.01) the odds of favourable outcome. Significant tag and concordant proxy SNPs regionally span introns/exons 2-15 of the 39-exon gene.

CONCLUSIONS

This study identifies four ABCC8 tag SNPs associated with cerebral oedema and/or outcome in TBI, tagging a region including 33 polymorphisms. In polymorphisms predictive of oedema, variant alleles/genotypes confer increased risk. Different variant polymorphisms were associated with favourable outcome, potentially suggesting distinct mechanisms. Significant polymorphisms spatially clustered flanking exons encoding the sulfonylurea receptor site and transmembrane domain 0/loop 0 (juxtaposing the channel pore/binding site). This, if validated, may help build a foundation for developing future strategies that may guide individualised care, treatment response, prognosis and patient selection for clinical trials.

Seizures After Intracerebral Hemorrhage: Incidence, Risk Factors, and Impact on Mortality and Morbidity

OBJECTIVE

Spontaneous intracerebral hemorrhage (ICH) is one of the most frequent causes of epilepsy in the United States. However, reported risk factors for seizure after are inconsistent, and their impact on inpatient morbidity and mortality is unclear. We aimed to study the incidence, risk factors, and impact of seizures after ICH in a nationwide patient sample.

METHODS

We queried the Nationwide Inpatient Sample for patients admitted to the hospital with a primary diagnosis of ICH between the years 1999 and 2011. Patients were subsequently dichotomized into groups of those with a diagnosis consistent with seizure and those without. Multivariate logistic regression was used to assess risk factors for seizure in this patient sample, and the association between seizures and mortality and morbidity. Logistic regression was then used for trend analysis of incidence of seizure diagnoses over time.

RESULTS

We identified 220,075 patients admitted with a primary diagnosis of ICH. Of these, 11.87% had a diagnosis consistent with seizure. Factors associated with increased risk of seizure after ICH included higher categorical van Walraven score, encephalopathy, alcohol abuse, solid tumor, and prior stroke. Seizure was independently associated with decreased odds of morbidity (odds ratio [OR], 0.89; 95% confidence interval [CI], 0.86-0.92) and mortality (OR, 0.75; 95% CI, 0.72-0.77) in multivariate models controlling for existing comorbidities.

CONCLUSIONS

Seizures after were associated with decreased mortality and morbidity despite attempts to correct for existing comorbidities. Continuous monitoring of these patients for seizures may not be necessary in all circumstances, despite their frequency.

ABCC8 Single Nucleotide Polymorphisms are Associated with Cerebral Edema in Severe TBI

OBJECTIVE

Cerebral edema (CE) in traumatic brain injury (TBI) is the consequence of multiple underlying mechanisms and is associated with unfavorable outcomes. Genetic variability in these pathways likely explains some of the clinical heterogeneity observed in edema development. A role for sulfonylurea receptor-1 (Sur1) in CE is supported. However, there are no prior studies examining the effect of genetic variability in the Sur1 gene (ABCC8) on the development of CE. We hypothesize that ABCC8 single nucleotide polymorphisms (SNPs) are predictive of CE.

METHODS

DNA was extracted from 385 patients. SNPs in ABCC8 were genotyped using the Human Core Exome v1.2 (Illumina). CE measurements included acute CT edema, mean and peak intracranial pressure (ICP), and need for decompressive craniotomy.

RESULTS

Fourteen SNPs with minor allele frequency >0.2 were identified. Four SNPS rs2283261, rs3819521, rs2283258, and rs1799857 were associated with CE measures. In multiple regression models, homozygote-variant genotypes in rs2283261, rs3819521, and rs2283258 had increased odds of CT edema (OR 2.45, p = 0.007; OR 2.95, p = 0.025; OR 3.00, p = 0.013), had higher mean (β = 3.13, p = 0.000; β = 2.95, p = 0.005; β = 3.20, p = 0.008), and peak ICP (β = 8.00, p = 0.001; β = 7.64, p = 0.007; β = 6.89, p = 0.034). The homozygote wild-type genotype of rs1799857 had decreased odds of decompressive craniotomy (OR 0.47, p = 0.004).

CONCLUSIONS

This is the first report assessing the impact of ABCC8 genetic variability on CE development in TBI. Minor allele ABCC8 SNP genotypes had increased risk of CE, while major SNP alleles were protective-potentially suggesting an evolutionary advantage. These findings could guide risk stratification, treatment responders, and the development of novel targeted or gene-based therapies against CE in TBI and other neurological disorders.

Use of Aspirin and P2Y12 Response Assays in Detecting Reversal of Platelet Inhibition With Platelet Transfusion in Patients With Traumatic Brain Injury on Antiplatelet Therapy

BACKGROUND

At present, guidelines are lacking on platelet transfusion in patients with a traumatic intracranial bleed and history of antiplatelet therapy. The aspirin and P2Y 12 response unit (ARU and PRU, respectively) assays detect the effect of aspirin and P2Y 12 inhibitors in the cardiac population.

OBJECTIVE

To describe the reversal of platelet inhibition after platelet transfusion using the ARU and PRU assays in patients with traumatic brain injury.

METHODS

Between 2010 and 2015, we conducted a prospective comparative cohort study of patients presenting with a positive head computed tomography and a history of antiplatelet therapy. ARU and PRU assays were performed on admission and 6 hours after transfusion, with a primary end point of detection of disinhibition after platelet transfusion.

RESULTS

One hundred seven patients were available for analysis. Seven percent of patients taking aspirin and 27% of patients taking clopidogrel were not therapeutic on admission per the ARU and PRU, respectively. After platelet transfusion, 51% of patients on any aspirin and 67% of patients on any clopidogrel failed to be reversed. ARU increased by 71 ± 76 per unit of apheresis platelets for patients taking any aspirin, and PRU increased by 48 ± 46 per unit of apheresis platelets for patients taking any clopidogrel.

CONCLUSION

A significant percentage of patients taking aspirin or clopidogrel were not therapeutic and thus would be unlikely to benefit from a platelet transfusion. In patients with measured platelet inhibition, a single platelet transfusion was not sufficient to reverse platelet inhibition in almost half.

Sulfonylurea Receptor-1: A Novel Biomarker for Cerebral Edema in Severe Traumatic Brain Injury

OBJECTIVES

Cerebral edema is a key poor prognosticator in traumatic brain injury. There are no biomarkers identifying patients at-risk, or guiding mechanistically-precise therapies. Sulfonylurea receptor-1-transient receptor potential cation channel M4 is upregulated only after brain injury, causing edema in animal studies. We hypothesized that sulfonylurea receptor-1 is measurable in human cerebrospinal fluid after severe traumatic brain injury and is an informative biomarker of edema and outcome.

DESIGN

A total of 119 cerebrospinal fluid samples were collected from 28 severe traumatic brain injury patients. Samples were retrieved at 12, 24, 48, 72 hours and before external ventricular drain removal. Fifteen control samples were obtained from patients with normal pressure hydrocephalus. Sulfonylurea receptor- 1 was quantified by enzyme-linked immunosorbent assay. Outcomes included CT edema, intracranial pressure measurements, therapies targeting edema, and 3-month Glasgow Outcome Scale score.

MAIN RESULTS

Sulfonylurea receptor-1 was present in all severe traumatic brain injury patients (mean = 3.54 ± 3.39 ng/mL, peak = 7.13 ± 6.09 ng/mL) but undetectable in all controls (p < 0.001). Mean and peak sulfonylurea receptor-1 was higher in patients with CT edema (4.96 ± 1.13 ng/mL vs 2.10 ± 0.34 ng/mL; p = 0.023). There was a temporal delay between peak sulfonylurea receptor-1 and peak intracranial pressure in 91.7% of patients with intracranial hypertension. There was no association between mean/peak sulfonylurea receptor-1 and mean/peak intracranial pressure, proportion of intracranial pressure greater than 20 mm Hg, use of edema-directed therapies, decompressive craniotomy, or 3-month Glasgow Outcome Scale. However, decreasing sulfonylurea receptor-1 trajectories between 48 and 72 hours were significantly associated with improved cerebral edema and clinical outcome. Area under the multivariate model receiver operating characteristic curve was 0.881.

CONCLUSIONS

This is the first report quantifying human cerebrospinal fluid sulfonylurea receptor-1. Sulfonylurea receptor-1 was detected in severe traumatic brain injury, absent in controls, correlated with CT-edema and preceded peak intracranial pressure. Sulfonylurea receptor-1 trajectories between 48 and 72 hours were associated with outcome. Because a therapy inhibiting sulfonylurea receptor-1 is available, assessing cerebrospinal fluid sulfonylurea receptor-1 in larger studies is warranted to evaluate our exploratory findings regarding its diagnostic, and monitoring utility, as well as its potential to guide targeted therapies in traumatic brain injury and other diseases involving cerebral edema.