Depolarization time and extracellular glutamate levels aggravate ultraearly brain injury after subarachnoid hemorrhage

From spreading depolarization to blood-brain barrier dysfunction: navigating traumatic brain injury for novel diagnosis and therapy

Considerable strides in medical interventions during the acute phase of traumatic brain injury (TBI) have brought improved overall survival rates. However, following TBI, people often face ongoing, persistent and debilitating long-term complications. Here, we review the recent literature to propose possible mechanisms that lead from TBI to long-term complications, focusing particularly on the involvement of a compromised blood-brain barrier (BBB). We discuss evidence for the role of spreading depolarization as a key pathological mechanism associated with microvascular dysfunction and the transformation of astrocytes to an inflammatory phenotype. Finally, we summarize new predictive and diagnostic biomarkers and explore potential therapeutic targets for treating long-term complications of TBI.

Focal brain cooling suppresses spreading depolarization and reduces endothelial nitric oxide synthase expression in rats

This study aimed to investigate the effects of focal brain cooling (FBC) on spreading depolarization (SD), which is associated with several neurological disorders. Although it has been studied from various aspects, no medication has been developed that can effectively control SD. As FBC can reduce neuronal damage and promote functional recovery in pathological conditions such as epilepsy, cerebral ischemia, and traumatic brain injury, it may also potentially suppress the onset and progression of SD. We created an experimental rat model of SD by administering 1 M potassium chloride (KCl) to the cortical surface. Changes in neuronal and vascular modalities were evaluated using multimodal recording, which simultaneously recorded brain temperature (BrT), wide range electrocorticogram, and two-dimensional cerebral blood flow. The rats were divided into two groups (cooling [CL] and non-cooling [NC]). Warm or cold saline was perfused on the surface of one hemisphere to maintain BrT at 37°C or 15°C in the NC and CL groups, respectively. Western blot analysis was performed to determine the effects of FBC on endothelial nitric oxide synthase (eNOS) expression. In the NC group, KCl administration triggered repetitive SDs (mean frequency = 11.57/h). In the CL group, FBC increased the duration of all KCl-induced events and gradually reduced their frequency. Additionally, eNOS expression decreased in the cooled brain regions compared to the non-cooled contralateral hemisphere. The results obtained by multimodal recording suggest that FBC suppresses SD and decreases eNOS expression. This study may contribute to developing new treatments for SD and related neurological disorders.

Targeted Temperature Management for Poor Grade Aneurysmal Subarachnoid Hemorrhage: A Pilot Study

OBJECTIVE

We assessed the effectiveness and safety of target temperature management (TTM) in treating patients with poor-grade aneurysmal subarachnoid hemorrhage (aSAH). The primary objective was to evaluate the neurological outcome at 3 months. Secondary objectives were to assess mortality, delayed cerebral ischemia, cerebral edema, hydrocephalus, midline shift, and laboratory indicators related to TTM.

METHODS

A single-blind, nonrandomized controlled trial was conducted. After admission, patients with poor-grade aSAH (Hunt-Hess scores IV ∼ V) were assigned to a TTM group or a control group in a 1:1 ratio. TTM with core temperatures ranging from 36°C to 37°C was performed immediately and maintained until microclipping or endovascular embolization. Subsequently, rapid induction to 33°C ∼ 35°C was carried out and maintained for 3 to 5 days. Then, the patients underwent slow rewarming to 36°C ∼ 37°C and maintained at that temperature for a minimum of 48 hours.

RESULTS

Sixty patients (30 treated with TTM and 30 with standard treatment) were included in the study. At 3 months, a favorable prognosis (modified Rankin scale score 0 to 3) was significantly higher in the TTM group than in the control group (n = 14, 46.7% vs. n = 6, 20.0%, P = 0.028). Adjusted multivariate logistics regression analysis indicated that TTM (odds ratio = 0.20, 95% confidence interval: 0.05-0.77, P = 0.019) reduced the number of unfavorable prognoses 3 months after admission.

CONCLUSIONS

This study demonstrated the effectiveness and safety of TTM in patients with poor-grade aSAH, and its implementation improved neurological outcomes. Multicenter randomized controlled studies with a large number of patients are needed to confirm these observations.

Power suppression in EEG after the onset of SAH is a significant marker of early brain injury in rat models

We analyzed the correlation between the duration of electroencephalogram (EEG) recovery and histological outcome in rats in the acute stage of subarachnoid hemorrhage (SAH) to find a new predictor of the subsequent outcome. SAH was induced in eight rats by cisternal blood injection, and the duration of cortical depolarization was measured. EEG power spectrums were given by time frequency analysis, and histology was evaluated. The appropriate frequency band and recovery percentage of EEG (defined as EEG recovery time) to predict the neuronal damage were determined from 25 patterns (5 bands × 5 recovery rates) of receiver operating characteristic (ROC) curves. Probit regression curves were depicted to evaluate the relationships between neuronal injury and duration of depolarization and EEG recovery. The optimal values of the EEG band and the EEG recovery time to predict neuronal damage were 10-15 Hz and 40%, respectively (area under the curve [AUC]: 0.97). There was a close relationship between the percentage of damaged neurons and the duration of depolarization or EEG recovery time. These results suggest that EEG recovery time, under the above frequency band and recovery rate, may be a novel marker to predict the outcome after SAH.

Substantially elevated serum glutamate and CSF GOT-1 levels associated with cerebral ischemia and poor neurological outcomes in subarachnoid hemorrhage patients

Brain injury and cerebral vasospasm during the 14 days after the subarachnoid hemorrhage (SAH) are considered the leading causes of poor outcomes. The primary injury induces a cascade of events, including increased intracranial pressure, cerebral vasospasm and ischemia, glutamate excitotoxicity, and neuronal cell death. The objective of this study was to monitor the time course of glutamate, and associated enzymes, such as glutamate-oxaloacetate transaminase (GOT1), glutamate-pyruvate transaminase (GPT) in cerebrospinal fluid (CSF) and serum, shortly after SAH, and to assess their prognostic value. A total of 74 participants participated in this study: 45 participants with SAH and 29 controls. Serum and CSF were sampled up to 14 days after SAH. SAH participants' clinical and neurological status were assessed at hospitalization, at discharge from the hospital, and 3 months after SAH. Furthermore, a logistic regression analysis was carried out to evaluate the ability of GOT1 and glutamate levels to predict neurological outcomes. Our results demonstrated consistently elevated serum and CSF glutamate levels after SAH. Furthermore, serum glutamate level was significantly higher in patients with cerebral ischemia and poor neurological outcome. CSF GOT1 was significantly higher in patients with uncontrolled intracranial hypertension and cerebral ischemia post-SAH, and independently predicted poor neurological outcomes.