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We have previously shown that normobaric hyperoxia may benefit peri-lesional brain and white matter following traumatic brain injury (TBI). This study examined the impact of brief exposure to hyperoxia using diffusion tensor imaging (DTI) to identify axonal injury distant from contusions. Fourteen patients with acute moderate/severe TBI underwent baseline DTI and following one hour of 80% oxygen. Thirty-two controls underwent DTI, with 6 undergoing imaging following graded exposure to oxygen. Visible lesions were excluded and data compared with controls. We used the 99% prediction interval (PI) for zero change from historical control reproducibility measurements to demonstrate significant change following hyperoxia. Following hyperoxia DTI was unchanged in controls. In patients following hyperoxia, mean diffusivity (MD) was unchanged despite baseline values lower than controls (p < 0.05), and fractional anisotropy (FA) was lower within the left uncinate fasciculus, right caudate and occipital regions (p < 0.05). 16% of white and 14% of mixed cortical and grey matter patient regions showed FA decreases greater than the 99% PI for zero change. The mechanistic basis for some findings are unclear, but suggest that a short period of normobaric hyperoxia is not beneficial in this context. Confirmation following a longer period of hyperoxia is required.

Management of Traumatic Brain Injury (TBI) focuses on controlling intracranial pressure (ICP), while other treatments, such as the use of neuromuscular blocking agents (NMBAs), need scientific evidence. We conducted a systematic review to investigate the usefulness of NMBAs in the context of TBI and/or increased ICP. We searched MEDLINE and EMBASE databases up to January 31st 2014, including both clinical and experimental findings. We found a total of 34 articles, of which 22 were prospective clinical trials. No systematic review/meta-analyses were found. Seven studies evaluated NMBA boluses in preventing stimulation-related ICP surges: paralysis was effective during tracheal suctioning and physiotherapy but not during bronchoscopy. Fourteen small studies (8 to 25 patients) assessed the effect of NMBA boluses on ICP. Two studies showed an ICP increase by succinylcholine and one found a decrease in ICP after atracurium. No ICP changes were observed in the other studies. One prospective study confirmed that discontinuing paralysis increases energy expenditure. Two retrospective studies investigated mortality/morbidity: one found that early paralysis (continued for >12 h) was not beneficial and potentially associated with extra-cranial complications, while the second demonstrated a correlation between continuous infusion of NMBA and time spent with ICP > 20 mmHg. Eight animal studies were also retrieved. In most studies, NMBA bolus was beneficial in controlling ICP, especially when performing stimulating procedures. However, retrospective evidence found potential harm by continuous NMBA infusion. In the context of TBI patients, we discuss the potentially positive effects of paralysis with its negative ones. Well-conducted randomized controlled trials and/or large pharmaco-epidemiologic studies are warranted.

Ischemia and metabolic dysfunction remain important causes of neuronal loss after head injury, and we have shown that normobaric hyperoxia may rescue such metabolic compromise. This study examines the impact of hyperoxia within injured brain using diffusion tensor imaging (DTI). Fourteen patients underwent DTI at baseline and after 1 hour of 80% oxygen. Using the apparent diffusion coefficient (ADC) we assessed the impact of hyperoxia within contusions and a 1 cm border zone of normal appearing pericontusion, and within a rim of perilesional reduced ADC consistent with cytotoxic edema and metabolic compromise. Seven healthy volunteers underwent imaging at 21%, 60%, and 100% oxygen. In volunteers there was no ADC change with hyperoxia, and contusion and pericontusion ADC values were higher than volunteers (P<0.01). There was no ADC change after hyperoxia within contusion, but an increase within pericontusion (P<0.05). We identified a rim of perilesional cytotoxic edema in 13 patients, and hyperoxia resulted in an ADC increase towards normal (P=0.02). We demonstrate that hyperoxia may result in benefit within the perilesional rim of cytotoxic edema. Future studies should address whether a longer period of hyperoxia has a favorable impact on the evolution of tissue injury.

Objectives: To image amyloid deposition in patients with traumatic brain injury (TBI) using carbon 11-labeled Pittsburgh Compound B ([11C]PiB) positron emission tomography (PET) and to validate these findings using tritium-labeled PiB ([3H]PiB) autoradiography and immunocytochemistry in autopsy-acquired tissue., Design, Setting, and Participants: In vivo PET at tertiary neuroscience referral center and ex vivo immunocytochemistry of autopsy-acquired brain tissue from a neuropathology archive. [11C]PiB PET was used to image amyloid deposition in 11 controls (median [range] age, 35 [24-60] years) and in 15 patients (median [range] age, 33 [21-50] years) between 1 and 361 days after a TBI. [3H]PiB autoradiography and immunocytochemistry for β-amyloid (Aβ) and β-amyloid precursor protein in brain tissue were obtained from separate cohorts of 16 patients (median [range] age, 46 [21-70] years) who died between 3 hours and 56 days after a TBI and 7 controls (median [range] age, 61 [29-71] years) who died of other causes., Main Outcomes and Measures: We quantified the [11C]PiB distribution volume ratio and standardized uptake value ratio in PET images. The distribution volume ratio and the standardized uptake value ratio were measured in cortical gray matter, white matter, and multiple cortical and white matter regions of interest, as well as in striatal and thalamic regions of interest. We examined [3H]PiB binding and Aβ and β-amyloid precursor protein immunocytochemistry in autopsy-acquired brain tissue., Results: Compared with the controls, the patients with TBI showed significantly increased [11C]PiB distribution volume ratios in cortical gray matter and the striatum (corrected P < .05 for both), but not in the thalamus or white matter. Increases in [11C]PiB distribution volume ratios in patients with TBI were seen across most cortical subregions, were replicated using comparisons of standardized uptake value ratios, and could not be accounted for by methodological confounders. Autoradiography revealed [3H]PiB binding in neocortical gray matter, in regions where amyloid deposition was demonstrated by immunocytochemistry; white matter showed Aβ and β-amyloid precursor protein by immunocytochemistry, but no [3H]PiB binding. No plaque-associated amyloid immunoreactivity or [3H]PiB binding was seen in cerebellar gray matter in autopsy-acquired tissue from either controls or patients with TBI, although 1 sample of cerebellar tissue from a patient with TBI showed amyloid angiopathy in meningeal vessels., Conclusions and Relevance: [11C]PiB shows increased binding following TBI. The specificity of this binding is supported by neocortical [3H]PiB binding in regions of amyloid deposition in the postmortem tissue of patients with TBI. [11C]PiB PET could be valuable in imaging amyloid deposition following TBI.

Objective: Patients with traumatic brain injury who fail to obey commands after sedation-washout pose one of the most significant challenges for neurological prognostication. Reducing prognostic uncertainty will lead to more appropriate care decisions and ensure provision of limited rehabilitation resources to those most likely to benefit. Bedside markers of covert residual cognition, including speech comprehension, may reduce this uncertainty.Methods: We recruited 28 patients with acute traumatic brain injury who were 2 to 7 days sedation-free and failed to obey commands. Patients heard streams of isochronous monosyllabic words that built meaningful phrases and sentences while their brain activity via electroencephalography (EEG) was recorded. In healthy individuals, EEG activity only synchronizes with the rhythm of phrases and sentences when listeners consciously comprehend the speech. This approach therefore provides a measure of residual speech comprehension in unresponsive patients.Results: Seventeen and 16 patients were available for assessment with the Glasgow Outcome Scale Extended (GOSE) at 3 months and 6 months, respectively. Outcome significantly correlated with the strength of patients' acute cortical tracking of phrases and sentences (r > 0.6, p < 0.007), quantified by inter-trial phase coherence. Linear regressions revealed that the strength of this comprehension response (beta = 0.603, p = 0.006) significantly improved the accuracy of prognoses relative to clinical characteristics alone (eg, Glasgow Coma Scale [GCS], computed tomography [CT] grade).Interpretation: A simple, passive, auditory EEG protocol improves prognostic accuracy in a critical period of clinical decision making. Unlike other approaches to probing covert cognition for prognostication, this approach is entirely passive and therefore less susceptible to cognitive deficits, increasing the number of patients who may benefit. ANN NEUROL 2021;89:646-656. [ABSTRACT FROM AUTHOR]

IntroductionThe UK population is ageing with increasing number of elderly patients suffering traumatic brain injury (TBI). The purpose of this study was to identify national TBI admission demographics, analyse the temporal evolution of TBI mortality in a single centre and conduct a systematic review of the literature to identify whether there is an age bias amongst researchers studying TBI.MethodsNational demographics for TBI were obtained from Health Episode Statistics. TBI patients admitted from 2000 to 2011 to Cambridge University Hospitals Neurocritical Care Unit (NCCU) were divided into age groups (<60, 60–74, ≥75 years). Temporal evolution of mortality was analysed using a logistic regression method. A systematic literature review was conducted to identify primary TBI research studies. Patient’s ages were extracted and an average mean age was calculated and compared over time.ResultsFrom 1998, national TBI admissions have increased with the greatest rise in >60-year age group (p < 0.0001). In a tertiary referral critical care unit (n = 1145), the 60–74 year age group (compared to <60) had a significantly lower improvement in mortality over time (OR: 1.15, 95% CI: 1.02–1.31). A literature review revealed a mean age of 32.73 years (SD ± 12.85) for patients recruited to primary TBI studies.ConclusionDespite increased admissions of elderly patients following TBI and static mortality (single centre, 60–74 year age group) there is little or no evidence of a corresponding increase in the age of patients recruited for TBI studies. In addition to the difficulties this presents in forming evidence-based decisions for the patient with TBI, it may also represent a wider problem for ICU research in an ever-ageing critical care population. More research needs to be conducted to establish the treatment end points for an ageing population. [ABSTRACT FROM PUBLISHER]

The aim of these studies was to provide reference data on intersubject variability and reproducibility of metabolite ratios for Choline/Creatine (Cho/Cr), N-acetyl aspartate/Choline (NAA/Cho) and N-acetyl aspartate/Creatine (NAA/Cr), and individual signal-intensity normalised metabolite concentrations of NAA, Cho and Cr. Healthy volunteers underwent imaging on two occasions using the same 3T Siemens Verio magnetic resonance scanner. At each session two identical Metabolic Imaging and Data Acquisition Software (MIDAS) sequences were obtained along with standard structural imaging. Metabolite maps were created and regions of interest applied in normalised space. The baseline data from all 32 volunteers were used to calculate the intersubject variability, while within session and between session reproducibility were calculated from all the available data. The reproducibility of measurements were used to calculate the overall and within session 95% prediction interval for zero change. The within and between session reproducibility data were lower than the values for intersubject variability, and were variable across the different brain regions. The within and between session reproducibility measurements were similar for Cho/Cr, NAA/Choline, Cho and Cr (11.8%, 11.4%, 14.3 and 10.6% vs. 11.9%, 11.4%, 13.5% and 10.5% respectively), but for NAA/Creatine and NAA between session reproducibility was lower (9.3% and 9.1% vs. 10.1% and 9.9%; p <0.05). This study provides additional reference data that can be utilised in interventional studies to quantify change within a single imaging session, or to assess the significance of change in longitudinal studies of brain injury and disease. [ABSTRACT FROM AUTHOR]

Head injury is common, sometimes requires intensive care unit admission, and is associated with significant mortality and morbidity. A gap still remains in the understanding of the molecular mechanism of this condition. This review is aimed at providing a general overview of the molecular mechanisms involved in traumatic brain injury to a busy clinician. It will encompass the pathophysiology in traumatic brain injury including apoptosis, the role of molecules and genes, and a brief mention of possible pharmacological therapies. [ABSTRACT FROM AUTHOR]

Diversion of cerebrospinal fluid (CSF) is a common neurosurgical procedure for control of intracranial pressure (ICP) in the acute phase after traumatic brain injury (TBI), where medical management is insufficient. CSF can be drained via an external ventricular drain (EVD) or, in selected patients, via a lumbar (external lumbar drain [ELD]) drainage catheter. Considerable variability exists in neurosurgical practice on their use. A retrospective service evaluation was completed for patients receiving CSF diversion for ICP control after TBI, from April 2015 to August 2021. Patients were included whom fulfilled local criteria deeming them suitable for either ELD/EVD. Data were extracted from patient notes, including ICP values pre/postdrain insertion and safety data including infection or clinically/radiologically diagnosed tonsillar herniation. Forty-one patients were retrospectively identified (ELD = 30 and EVD = 11). All patients had parenchymal ICP monitoring. Both modalities affected statistically significant decreases in ICP, with relative reductions at 1, 6, and 24 hour pre/postdrainage (at 24-hour ELD P < 0.0001, EVD P < 0.01). Similar rates of ICP control failure, blockage and leak occurred in both groups. A greater proportion of patients with EVD were treated for CSF infection than with ELD. One event of clinical tonsillar herniation is reported, which may have been in part attributable to ELD overdrainage, but which did not result in adverse outcome. The data presented demonstrate that EVD and ELD can be successful in ICP control after TBI, with ELD limited to carefully selected patients with strict drainage protocols. The findings support prospective study to formally determine the relative risk-benefit profiles of CSF drainage modalities in TBI. [ABSTRACT FROM AUTHOR]