Brain-damaged Patients Research Articles

The value of amide proton transfer imaging in assessing brain damage in patients with obstructive sleep apnea

ObjectiveTo investigate the application value of amide proton transfer (APT) magnetic resonance imaging in evaluating brain damage in patients with obstructive sleep apnea (OSA). Materials and methods49 OSA patients and 25 healthy individuals matched for age and sex were included as case and control groups. All study participants underwent conventional 3D T1WI and APT imaging of the head. The APT values were measured in each of the brain regions of interest (ROI). To compare the differences in APT values of each brain region between the case and control groups, to compare the differences in the efficacy of APT values of each brain region in diagnosing OSA, and to investigate the correlation between APT values of each brain region and Apnea Hypopnea Index (AHI) and minimum blood oxygen saturation. ResultsCompared to the control group, patients with OSA had elevated APT values in several brain regions (P < 0.05), and the diagnostic efficacy of the combined diagnosis of OSA by multiple brain regions is better than that by each brain region alone.Left frontal APT values were positively correlated with AHI in the case group (r = 0.33, P = 0.020).In the case group, the APT values of bilateral frontal lobe, parietal lobe, occipital lobe, left temporal lobe, right thalamus, left internal capsule, left lenticular nucleus, right cerebellar hemisphere and splenium of corpus callosum were negatively correlated with the minimum blood oxygen saturation, and the APT values for each of the above ROIs were positively correlated. ConclusionAPT imaging has a certain value in evaluating brain damage in OSA patients, which may provide a new objective imaging basis for the clinical diagnosis of OSA.

Graph theory network analysis reveals widespread white matter damage in brains of patients with classic ALS.

Objective: Amyotrophic lateral sclerosis (ALS) exhibits several different presentations and clinical phenotypes. Of these, classic ALS (ALS-Cl), which is the most common phenotype, presents with relatively equal amounts of upper motor neuron and lower motor neuron signs. Magnetic resonance imaging (MRI) provides a noninvasive way to assess central nervous system damage in these patients. To our knowledge no study is available where exploratory whole brain grey matter (GM) and white matter (WM) network analysis is performed considering only the ALS-Cl subgroup of ALS patients. Methods: GM voxel-based morphometry analysis and WM network analysis using graph theory was performed in the MRI dataset of 14 neurologic controls and 25 ALS-Cl patients. Results and Conclusions: No significant GM differences were observed between ALS-Cl and neurologic controls. WM network revealed significant (p < 0.05) reduction and increase in degree measure in several extramotor brain regions of ALS-Cl patients. Both global and local graph metrics revealed significant abnormal values in ALS-Cl patients when compared to neurologic controls. Significant WM changes in ALS-Cl patients with no significant GM changes suggest that neurodegeneration may onset as an "axonopathy" in this ALS subtype.

Optimal Targeted Temperature Management for Patients with Post-Cardiac Arrest Syndrome.

Background: To prevent hypoxic-ischemic brain damage in patients with post-cardiac arrest syndrome (PCAS), international guidelines have emphasized performing targeted temperature management (TTM). However, the most optimal targeted core temperature and cooling duration reached no consensus to date. This study aimed to clarify the optimal targeted core temperature and cooling duration, selected according to the time interval from collapse to return of spontaneous circulation (ROSC) in patients with PCAS due to cardiac etiology. Methods: Between 2014 and 2020, the targeted core temperature was 34 °C or 35 °C, and the cooling duration was 24 h. If the time interval from collapse to ROSC was within 20 min, we performed the 35 °C targeted core temperature (Group A), and, if not, we performed the 34 °C targeted core temperature (Group B). Between 2009 and 2013, the targeted core temperature was 34 °C, and the cooling duration was 24 or 48 h. If the interval was within 20 min, we performed the 24 h cooling duration (Group C), and, if not, we performed the 48 h cooling duration (Group D). Results: The favorable neurological outcome rates at 30 days following cardiac arrest were 45.7% and 45.5% in Groups A + B and C + D, respectively (p = 0.977). In patients with ROSC within 20 min, the favorable neurological outcome rates at 30 days following cardiac arrest were 75.6% and 86.4% in Groups A and C, respectively (p = 0.315). In patients with ROSC ≥ 21 min, the favorable neurological outcome rates at 30 days following cardiac arrest were 29.3% and 18.2% in Groups B and D, respectively (p = 0.233). Conclusions: Selecting the optimal target core temperature and the cooling duration for TTM, according to the time interval from collapse to ROSC, may be helpful in patients with PCAS due to cardiac etiology.

Ecological assessment of unilateral spatial neglect in immersive virtual reality: A multiple-case study to assess the feasibility and relevance of a Baking Tray Task

ABSTRACT The assessment of unilateral spatial neglect (USN) primarily relies on paper-and-pencil tests, which do not fully represent daily life difficulties. To address this limitation, ecological tests, like the Baking Tray Test (BTT), have been developed. However, the original BTT identifies the presence of USN without providing information on its severity. In this aim, a new severity measure, the Centre of Mass (CoM), has been proposed, but its calculation in real environments poses challenges. Immersive virtual reality (VR) offers a promising solution for implementing a BTT in which measures are automatically calculated. This study aimed to assess the feasibility and relevance of an immersive VR BTT. Nineteen right brain-damaged patients with and without USN and 25 healthy participants were included. Group analyses showed an equivalence between the two BTT versions. Individual analyses revealed that all USN patients, except one, had pathological results in both versions. They also underlined pathological scores in patients without USN signs on paper-and-pencil tests. Finally, the CoM strongly correlated with paper-and-pencil tests and appeared to be a good indicator of USN severity. These findings support the relevance of implementing the BTT in an immersive VR version, suggesting its potential to enhance USN assessment.

Organization of conceptual tool knowledge following left and right brain lesions: Evidence from neuropsychological dissociations and multivariate disconnectome symptom mapping

The aim of this work was to better understand the organization of conceptual tool knowledge following stroke. We explored specifically the link between manipulation kinematics and manipulation hand posture; and the link between manipulation kinematics and function relations in left brain-damaged (n = 30) and right brain-damaged (n = 30) patients. We examined the performance of brain-damaged patients in conceptual tool tasks using neuropsychological dissociations and disconnectome symptom mapping. Our results suggest that manipulation kinematics is more impaired than function relations, following left or right brain lesions. We also observed that manipulation kinematics and manipulation hand posture are dissociable dimensions but are still highly interrelated, particularly in left brain-damaged patients. We also found that the corpus callosum and bilateral superior longitudinal fasciculus are involved in action and semantic tool knowledge following left brain lesions. Our results provide evidence that the right hemisphere contains conceptual tool representations. Further studies are needed to better understand the mechanisms supporting the cognitive recovery of conceptual tool knowledge. An emerging hypothesis is that the right hemisphere may support functional recovery through interhemispheric transfer following a left hemisphere stroke.

Quantifying the Use of Space in the Clock Drawing Test: Validity in Hemispatial Neglect.

The Clock Drawing Test (CDT) is a widely used test for cognitive screening as its execution taps into a large number of cognitive functions. Because of the involvement of visuospatial abilities, the CDT is also commonly used to assess hemispatial neglect. In the present study, we introduce a new quantitative scoring method for the CDT that aims to measure the use of space for each half of the clock face and asymmetries of space use. Two measures are introduced: the explored space (ES) and used space (US) for each half of the clock, as well as two derived asymmetry indices. Such new measures were applied to CDTs of four groups of participants: right brain-damaged patients without visuospatial neglect, two groups of right brain-damaged patients with varying degrees of visuospatial neglect, and a group of neurologically healthy participants. Analyses showed that only neglect patients explored and used the left clock half significantly less than the right one. This result was also confirmed by the asymmetry indices, where neglect patients showed a stronger rightward bias. For neglect patients, the US asymmetry index correlated with the patients' scores on the neuropsychological tests. The analyses of receiver operating characteristic curves showed that left US and left ES scores had good accuracy in categorizing neglect patients. The present work provides new quantitative indices of CDT space usage in hemispatial neglect. Cutoffs are provided for clinical practice.

Boronic Acid-Rich Lanthanide Metal-Organic Frameworks Enable Deep Proteomics with Ultratrace Biological Samples.

Label-free proteomics is widely used to identify disease mechanism and potential therapeutic targets. However, deep proteomics with ultratrace clinical specimen remains a major technical challenge due to extensive contact loss during complex sample pretreatment. Here, a hybrid of four boronic acid-rich lanthanide metal-organic frameworks (MOFs) with high protein affinity is introduced to capture proteins in ultratrace samples jointly by nitrogen-boronate complexation, cation-π and ionic interactions. A MOFs Aided Sample Preparation (MASP) workflow that shrinks sample volume and integrates lysis, protein capture, protein digestion and peptide collection steps into a single PCR tube to minimize sample loss caused by non-specific absorption, is proposed further. MASP is validated to quantify ≈1800 proteins in 10 HEK-293T cells. MASP is applied to profile cerebrospinal fluid (CSF) proteome from cerebral stroke and brain damaged patients, and identified ≈3700 proteins in 1µL CSF. MASP is further demonstrated to detect ≈9600 proteins in as few as 50µg mouse brain tissues. MASP thus enables deep, scalable, and reproducible proteome on precious clinical samples with low abundant proteins.

Have I Been Touched? Subjective and Objective Aspects of Tactile Awareness.

Somatosensory tactile experience is a key aspect of our interaction with the environment. It is involved in object manipulation, in the planning and control of actions and, in its affective components, in the relationships with other individuals. It is also a foundational component of body awareness. An intriguing aspect of sensory perception in general and tactile perception in particular is the way in which stimulation comes to consciousness. Indeed, although being aware of something seems a rather self-evident and monolithic aspect of our mental states, sensory awareness may be in fact modulated by many different processes that impact on the mere stimulation of the skin, including the way in which we perceive our bodies as belonging to us. In this review, we first took into consideration the pathological conditions of absence of phenomenal experience of touch, in the presence of implicit processing, as initial models for understanding the neural bases of conscious tactile experience. Subsequently, we discussed cases of tactile illusions both in normal subjects and in brain-damaged patients which help to understand which high-order processes impact tactile awareness. Finally, we discussed the observations reported in the review in light of some influential models of touch and body representation.

Long-Term Effects of Intensive Rehabilitation on Memory Functions in Acquired Brain-Damaged Patients.

Memory difficulties after brain injury are a frequent and concerning outcome, affecting a wide range of daily activities, employment, and social reintegration. Despite the importance of functional memory capacities throughout life, most studies examined the short-term effects of memory interventions in brain-damaged patients who underwent a rehabilitation program. In the present study, we investigated the long-term outcomes and intensity of memory interventions in acquired (traumatic brain injury [TBI] and non-TBI) brain-damaged patients who participated in an intensive cognitive rehabilitation program and either suffered or did not suffer from memory impairments. We measured pre-post-treatment memory performance of patiients (N = 24) suffering from memory deficits in four common and validated memory tasks (e.g. ROCFT). We compared them to other acquired brain injury patients treated at the same rehabilitation facility who did not suffer from memory impairments (N = 16). Patients with memory deficits showed long-term improvements in three out of four tasks, while patients without memory deficits showed memory enhancements in only one task. In addition, rehabilitation intensity and type of brain damage predicted the extent of the memory change over time. Long-term improvements in objective memory measures can be observed in patients suffering from brain injury. These improvements can be enhanced by intensifying the treatment program. Findings also suggest that these memory improvements are more pronounced in non-TBI than TBI patients. We discuss the implications of these results in designing optimal memory rehabilitation interventions.

Unilteral Spatial Neglect: Clinical Manifestations and Neural Correlates

Unilateral spatial neglect is the failure of brain-damaged patients to report, respond, or orient to novel or meaningful stimuli presented to the contralateral side of the lesion. This usually involves the right cerebral hemisphere. Neglect presents with no restriction in gaze direction and results in difficulty across various aspects of daily activities, distinguishing it from simple homonymous hemianopia. The basic mechanisms underlying neglect is rightward bias of spatial attention, while non-direction-specific cognitive problems may contribute to clinical expressions of neglect.

Features of the Background EEG of Alcohol Dependent Patients with Comorbid Exogenous Organic Brain Damage

Background: the range and prevalence of complicating pathologies in alcoholism indicate the need for a thorough examination of patients using modern diagnostic approaches. The aim was to study the indicators of spontaneous electrical activity of the brain in patients with alcohol dependence with comorbid exogenous organic brain damage non-alcoholic nature. Patients and methods: a study of electroencephalograms of 148 men with alcohol dependence using the classification of E.A. Zhirmunskaya (1984) was conducted. Results: based on the hystory data, 85 (57.4%) patients were found to have exogenous organic vascular brain damage (including hypertension in 57 (38.5%) cases, chronic cerebral circulation disorder — in 8 (5.4%), somatoform autonomic dysfunction — in 7 (4.7%)) and traumatic character (mild traumatic brain injury) in 13 (8.8%)) patients. The analysis using Fisher’s exact criterion revealed statistically significant differences between patients with alcohol dependence and alcoholism patients with comorbid exogenous organic brain damage in the frequency of occurrence of various types of electroencephalograms (p &lt; 0.001). The study clearly showed that the presence of exogenous organic brain damage in patients with alcoholism leads to more pronounced functional changes in the brain. Conclusion: early detection of pathological activity on the EEG in patients with alcohol dependence will allow clinicians to carry out appropriate therapeutic and diagnostic measures in a timely manner and will provide additional information necessary for the development of personalized medical rehabilitation programs for patients taking into account their neurophysiological profile.

Typical and atypical MRI abnormalities in Wernicke's encephalopathy: Correlation with blood vitamin B1 levels

PurposeClinical features of Wernicke's encephalopathy (WE) confirmed strictly through the low blood vitamin B1 (VB1) levels are limited. This study aimed to analyse magnetic resonance imaging (MRI) findings, and clinical characteristics, in patients with WE who have confirmed low blood VB1 levels. MethodsClinical and laboratory records of 12 consecutive patients with WE admitted to our hospital during the past 11 years were reviewed. The WE diagnosis was confirmed based on low blood VB1 levels and the presence of at least one of the classical triad. ResultsOphthalmoplegia and nystagmus were recorded in 75% and 50% of the patients, respectively. Eleven of 12 patients presented with consciousness disturbance/memory loss. All patients experienced gait disturbances. Eight of the 12 patients exhibited MRI abnormalities at typical sites (the dorsal midbrain [n = 7], medial thalamus [n = 6], mammillary bodies [n = 5], and dorsal pons [n = 5]). Of the 12 patients, six showed abnormalities at atypical sites (the splenium of the corpus callosum [n = 4], fornix [n = 3], cerebral cortex [n = 2], cerebellar vermis [n = 2], and dorsal medulla [n = 1]). Patients with positive MRI abnormalities had significantly lower blood VB1 levels than those without abnormalities (9.5 vs. 16.0 ng/mL). ConclusionsIn cases of confirmed WE with low blood VB1 levels, the corpus callosum, fornix, and cerebral cortex were more frequently involved than in previous studies. MRI abnormalities at both typical and atypical sites were correlated with low blood VB1 levels in WE, suggesting that lower blood VB1 levels are associated with more severe brain damage in patients with WE.

A new method for detecting unilateral spatial neglect with tracing tasks using the Rey-Osterrieth complex figure: a pilot study.

To explore efficacy of the "Rey-Osterrieth complex figure (ROCF) tracing task" as a new test to detect unilateral spatial neglect (USN). Subjects were 40 healthy control (HC) and 20 right brain-damaged patients with (USN + , n = 10) or without USN (USN - , n = 10). After the ROCF copying task, the tracing task was performed under conditions that did not leave any tracing lines on the sample figure. Evaluation used the conventional 36-point scoring system, laterality index (LI) as the ratio of the left and right structure scores, and the number of overlaps for each of the left and right structures scored. In the tracing task, USN + showed a lower LI than HC. Furthermore, left-sided neglect was sometimes more evident than in the copying task. Regarding the total overlapping score, USN + showed a greater score than HC. The right-sided overlapping scores in USN + and USN - were also greater than that in HC. In the right brain-damaged subjects, clinically meaningful correlations were not found between evaluations in the ROCF tracing task and in conventional USN screening tests. Receiver-operating-characteristic analysis to test the power of detection showed moderate performance for the tracing LI (AUC = 0.76, 95% CI = 0.54-0.97), which was greater than that of other tests. Further, the total overlapping score in the tracing task showed sensitivity 0.9 (highest among the tests performed), specificity 0.5, and AUC 0.68 (95% CI = 0.43-0.92). The ROCF tracing task might be a convenient method to detect USN and to reveal the extent of spatial working memory impairment.

White matter network underlying semantic processing: evidence from stroke patients.

The hub-and-spoke theory of semantic representation fractionates the neural underpinning of semantic knowledge into two essential components: the sensorimotor modality-specific regions and a crucially important semantic hub region. Our previous study in patients with semantic dementia has found that the hub region is located in the left fusiform gyrus. However, because this region is located within the brain damage in patients with semantic dementia, it is not clear whether the semantic deficit is caused by structural damage to the hub region itself or by its disconnection from other brain regions. Stroke patients do not have any damage to the left fusiform gyrus, but exhibit amodal and modality-specific deficits in semantic processing. Therefore, in this study, we validated the semantic hub region from a brain network perspective in 79 stroke patients and explored the white matter connections associated with it. First, we collected data of diffusion-weighted imaging and behavioural performance on general semantic tasks and modality-specific semantic tasks (assessing object knowledge on form, colour, motion, sound, manipulation and function). We then used correlation and regression analyses to examine the association between the nodal degree values of brain regions in the whole-brain structural network and general semantic performance in the stroke patients. The results revealed that the connectivity of the left fusiform gyrus significantly predicted general semantic performance, indicating that this region is the semantic hub. To identify the semantic-relevant connections of the semantic hub, we then correlated the white matter integrity values of each tract connected to the left fusiform gyrus separately with performance on general and modality-specific semantic processing. We found that the hub region accomplished general semantic processing through white matter connections with the left superior temporal pole, middle temporal gyrus, inferior temporal gyrus and hippocampus. The connectivity between the hub region and the left hippocampus, superior temporal pole, middle temporal gyrus, inferior temporal gyrus and parahippocampal gyrus was differentially involved in object form, colour, motion, sound, manipulation and function processing. After statistically removing the effects of potential confounding variables (i.e. whole-brain lesion volume, lesion volume of regions of interest and performance on non-semantic control tasks), the observed effects remained significant. Together, our findings support the role of the left fusiform gyrus as a semantic hub region in stroke patients and reveal its crucial connectivity in the network. This study provides new insights and evidence for the neuroanatomical organization of semantic memory in the human brain.

Entrectinib in the treatment of ROS1-positive lung cancer

The possibilities in the treatment of patients with non–small cell lung cancer are constantly expanding – thanks to high-performance genomic profiling methods, we are discovering new targets in the tumor for drug action, as a result, new targeted drugs appear, some of them have several application points. Multipurpose drugs have a number of advantages and therefore have become the main direction of drug development. Entrectinib is an oral low molecular weight multikinase inhibitor that blocks three targets at once – the receptors of tyrosine kinases ROS1, NTRK1/2/3 and ALK, in 2023 was approved by the Ministry of Health of the Russian Federation for the treatment of adult patients with ROS1-positive metastatic non-small cell lung cancer. This form of lung cancer is classified as a rare orphan disease, which usually occurs in younger people (about 50 years old), more often in women and non-smokers. Until recently , we had the only active targeted drug – crizotinib. It provided a sufficiently high immediate effect and long-term control of the disease. However, his intracranial activity was not evaluated prospectively, and a retrospective analysis showed modest results. Entrectinib is distinguished from its competitor by high intracranial activity, and, as is known, metastatic brain damage in patients with activating mutations is quite common. With comparable indicators of objective response, its duration and time to progression, entrectinib provides a high level of intracranial control and reduces the risks of progression in the central nervous system in patients who did not have brain metastases at the beginning of therapy. In addition, entrectinib demonstrates good tolerability.

Impairment of executive functions in patients with alcohol use disorders

To study the features of executive functions in patients with alcohol use disorders and comorbid exogenous organic brain damage of non-alcoholic nature. Sixty-five men, aged 24 to 55 years, with alcohol use disorders were examined. Thirty mentally healthy men were examined as a control group. To assess executive functioning, standard neuropsychological tests were used: the Go/No-Go task, the Corsi test and the Stroop Color Test. Patients with alcohol use disorders and comorbid exogenous organic brain damage made significantly more errors in the Go/No-Go task (skipping the Go signal: p=0.004) and performed the Stroop Color test longer (task completion time: p=0.003). According to multivariate regression analysis, the presence of exogenous organic brain damage predicted the worst indicators of psychomotor reaction (p=0.009) and cognitive flexibility (p=0.021). Comorbid exogenous organic brain damage in patients with alcohol use disorders leads to a significant deterioration of executive functions, including psychomotor reaction and cognitive flexibility, compared with patients suffering only from alcohol use disorders.

Colors in the mind’s eye

The famous "Piazza del Duomo" paper, published in Cortex in 1978, inspired a considerable amount of research on visual mental imagery in brain-damaged patients. As a consequence, single-case reports featuring dissociations between perceptual and imagery abilities challenged the prevailing model of visual mental imagery. Here we focus on mental imagery for colors. A case study published in Cortex showed perfectly preserved color imagery in a patient with acquired achromatopsia after bilateral lesions at the borders between the occipital and temporal cortex. Subsequent neuroimaging findings in healthy participants extended and specified this result; color imagery elicited activation in both a domain-general region located in the left fusiform gyrus and the anterior color-biased patch within the ventral temporal cortex, but not in more posterior color-biased patches. Detailed studies of individual neurological patients, as those often published in Cortex, are still critical to inspire and constrain neurocognitive research and its theoretical models.

Resting-state EEG microstates as electrophysiological biomarkers in post-stroke disorder of consciousness.

Ischemic stroke patients commonly experience disorder of consciousness (DOC), leading to poorer discharge outcomes and higher mortality risks. Therefore, the identification of applicable electrophysiological biomarkers is crucial for the rapid diagnosis and evaluation of post-stroke disorder of consciousness (PS-DOC), while providing supportive evidence for cerebral neurology. In our study, we conduct microstate analysis on resting-state electroencephalography (EEG) of 28 post-stroke patients with awake consciousness and 28 patients with PS-DOC, calculating the temporal features of microstates. Furthermore, we extract the Lempel-Ziv complexity of microstate sequences and the delta/alpha power ratio of EEG on spectral. Statistical analysis is performed to examine the distinctions in features between the two groups, followed by inputting the distinctive features into a support vector machine for the classification of PS-DOC. Both groups obtain four optimal topographies of EEG microstates, but notable distinctions are observed in microstate C. Within the PS-DOC group, there is a significant increase in the mean duration and coverage of microstates B and C, whereas microstate D displays a contrasting trend. Additionally, noteworthy variations are found in the delta/alpha ratio and Lempel-Ziv complexity between the two groups. The integration of the delta/alpha ratio with microstates' temporal and Lempel-Ziv complexity features demonstrates the highest performance in the classifier (Accuracy = 91.07%). Our results suggest that EEG microstates can provide insights into the abnormal brain network dynamics in DOC patients post-stroke. Integrating the temporal and Lempel-Ziv complexity microstate features with spectral features offers a deeper understanding of the neuro mechanisms underlying brain damage in patients with DOC, holding promise as effective electrophysiological biomarkers for diagnosing PS-DOC.

The Arousal-Related "Central Thalamus" Stimulation Site Simultaneously Innervates Multiple High-Level Frontal and Parietal Areas.

In human and nonhuman primates, deep brain stimulation applied at or near the internal medullary lamina of the thalamus [a region referred to as "central thalamus," (CT)], but not at nearby thalamic sites, elicits major changes in the level of consciousness, even in some minimally conscious brain-damaged patients. The mechanisms behind these effects remain mysterious, as the connections of CT had not been specifically mapped in primates. In marmoset monkeys (Callithrix jacchus) of both sexes, we labeled the axons originating from each of the various CT neuronal populations and analyzed their arborization patterns in the cerebral cortex and striatum. We report that, together, these CT populations innervate an array of high-level frontal, posterior parietal, and cingulate cortical areas. Some populations simultaneously target the frontal, parietal, and cingulate cortices, while others predominantly target the dorsal striatum. Our data indicate that CT stimulation can simultaneously engage a heterogeneous set of projection systems that, together, target the key nodes of the attention, executive control, and working-memory networks of the brain. Increased functional connectivity in these networks has been previously described as a signature of consciousness.SIGNIFICANCE STATEMENT In human and nonhuman primates, deep brain stimulation at a specific site near the internal medullary lamina of the thalamus ["central thalamus," (CT)] had been shown to restore arousal and awareness in anesthetized animals, as well as in some brain-damaged patients. The mechanisms behind these effects remain mysterious, as CT connections remain poorly defined in primates. In marmoset monkeys, we mapped with sensitive axon-labeling methods the pathways originated from CT. Our data indicate that stimulation applied in CT can simultaneously engage a heterogeneous set of projection systems that, together, target several key nodes of the attention, executive control, and working-memory networks of the brain. Increased functional connectivity in these networks has been previously described as a signature of consciousness.

Brain Oxygenation Response to Hypercapnia in Patients with Acute Brain Injury.

Cerebral hypoxia is a frequent cause of secondary brain damage in patients with acute brain injury. Although hypercapnia can increase intracranial pressure, it may have beneficial effects on tissue oxygenation. We aimed to assess the effects of hypercapnia on brain tissue oxygenation (PbtO2). This single-center retrospective study (November 2014 to June 2022) included all patients admitted to the intensive care unit after acute brain injury who required multimodal monitoring, including PbtO2 monitoring, and who underwent induced moderate hypoventilation and hypercapnia according to the decision of the treating physician. Patients with imminent brain death were excluded. Responders to hypercapnia were defined as those with an increase of at least 20% in PbtO2 values when compared to their baseline levels. On a total of 163 eligible patients, we identified 23 (14%) patients who underwent moderate hypoventilation (arterial partial pressure of carbon dioxide [PaCO2] from 44 [42-45] to 50 [49-53] mm Hg; p < 0.001) during the study period at a median of 6 (4-10) days following intensive care unit admission; six patients had traumatic brain injury, and 17 had subarachnoid hemorrhage. A significant overall increase in median PbtO2 values from baseline (21 [19-26] to 24 [22-26] mm Hg; p = 0.02) was observed. Eight (35%) patients were considered as responders, with a median increase of 7 (from 4 to 11) mm Hg of PbtO2, whereas nonresponders showed no changes (from - 1 to 2mm Hg of PbtO2). Because of the small sample size, no variable independently associated with PbtO2 response was identified. No correlation between changes in PaCO2 and in PbtO2 was observed. In this study, a heterogeneous response of PbtO2 to induced hypercapnia was observed but without any deleterious elevations of intracranial pressure.