Critical dynamics in spontaneous EEG predict anesthetic-induced loss of consciousness and perturbational complexity.

Consciousness has been proposed to be supported by electrophysiological patterns poised at criticality, a dynamical regime which exhibits adaptive computational properties, maximally complex patterns and divergent sensitivity to perturbation. Here, we investigate dynamical properties of the resting-state electroencephalogram (EEG) of healthy subjects undergoing general anesthesia with propofol, xenon or ketamine. Importantly, all participants were unresponsive under anesthesia, while consciousness was retained only during ketamine anesthesia (in the form of vivid dreams), enabling an experimental dissociation between unresponsiveness and unconsciousness. For each condition, we measure (i) avalanche criticality, (ii) chaoticity, and (iii) criticality-related metrics, revealing that states of unconsciousness are characterized by a distancing from both avalanche criticality and the edge of chaos. We then ask whether these same dynamical properties are predictive of the perturbational complexity index (PCI), a TMS-based measure that has shown remarkably high sensitivity in detecting consciousness independently of behavior. We successfully predict individual subjects' PCI values with considerably high accuracy from resting-state EEG dynamical properties alone. Our results establish a firm link between perturbational complexity and criticality, and provide further evidence that criticality is a necessary condition for the emergence of consciousness.

Differentiating loss of consciousness causes through artificial intelligence-enabled decoding of functional connectivity.

Differential diagnosis of acute loss of consciousness (LOC) is crucial due to the need for different therapeutic strategies despite similar clinical presentations among etiologies such as nonconvulsive status epilepticus, metabolic encephalopathy, and benzodiazepine intoxication. While altered functional connectivity (FC) plays a pivotal role in the pathophysiology of LOC, there has been a lack of efforts to develop differential diagnosis artificial intelligence (AI) models that feature the distinctive FC change patterns specific to each LOC cause. Three approaches were applied for extracting features for the AI models: three-dimensional FC adjacency matrices, vectorized FC values, and graph theoretical measurements. Deep learning using convolutional neural networks (CNN) and various machine learning algorithms were implemented to compare classification accuracy using electroencephalography (EEG) data with different epoch sizes. The CNN model using FC adjacency matrices achieved the highest accuracy with an AUC of 0.905, with 20-s epoch data being optimal for classifying the different LOC causes. The high accuracy of the CNN model was maintained in a prospective cohort. Key distinguishing features among the LOC causes were found in the delta and theta brain wave bands. This research advances the understanding of LOC's underlying mechanisms and shows promise for enhancing diagnosis and treatment selection. Moreover, the AI models can provide accurate LOC differentiation with a relatively small amount of EEG data in 20-s epochs, which may be clinically useful.

The problem of unconscious and unidentified patients in emergency department admissions; a 3-year retrospective study.

Unidentified patients present a medical information dilemma for all medical departments but can be a major problem in Emergency Departments (EDs). This study aimed to determine the clinical and socio-demographic profile of 'unidentified' patients admitted to the ED with altered consciousness and to define the outcomes of these patients. All ED presentations were analyzed retrospectively for the unidentified patients brought to the hospital by ambulance with altered consciousness. We assessed demographic data, clinical presentation, discharge information, and major clinical outcomes. In this study, 1324 unidentified patients were admitted with altered consciousness to the ED. Of these, 1048 (80.1%) were foreign nationals. In this patient group, the most common diagnoses were; traffic accidents, assault or sharp object injuries, drug addicts, or syncope-epilepsy. In addition, the number of patients who left the hospital without permission or escaped and therefore could not be diagnosed was higher in the foreign nationalities group and constituted approximately one-fifth of the patients (18.9% vs. 5.4%, p:0.001). Of the unidentified patients, 903 (68.2%) were discharged after treatment. 351 (26.5%) patients left the ED unattended. 32 (2.4%) patients were hospitalized. 38 (2.9%) patients died in ED. The majority of the unidentified patients admitted to the ED with altered consciousness were immigrant males. Unidentified patients are a high-need population, most commonly presenting with substance misuse or trauma. Although most of the patients were seeking urgent treatment, more than one-fourth of the patients left the hospital without appropriate treatment and most of these patients were also immigrants. We believe that economic, linguistic, and social disadvantages played an important role in this outcome.

Intracranial dissemination of Klebsiella pneumoniae originating from pulmonary infection: a case report.

BACKGROUND: Metastatic brain abscesses caused by Klebsiella pneumoniae are extremely rare but life-threatening conditions. To depict a unique case of the middle-aged hypertensive man with an unusual presentation of metastatic brain abscesses originating from a pleural abscess caused by Klebsiella pneumoniae and subsequently leading to loss of consciousness (LOC). CASE REPORT: A 52-year-old Iranian man with a history of hypertension presented to the emergency department with a five-day history of worsening cough, high-grade fever, shortness of breath, chest pain, fatigue, and a productive cough. Laboratory tests revealed leukocytosis, elevated C-reactive protein, and respiratory alkalosis. A chest computed tomography scan confirmed pneumonia, and a brain scan revealed multiple hypodense lesions. Despite antibiotic therapy, the patient's condition worsened, leading to confusion, disorientation, and loss of consciousness. Magnetic resonance imaging revealed multiple ring-enhancing lesions, suggesting an abscess formation. Bronchial washings and BAL samples confirmed a lower respiratory tract infection. Cultures from the bronchial washings grew Klebsiella pneumoniae. CONCLUSIONS: Metastatic brain abscesses caused by Klebsiella pneumoniae are exceedingly rare but life-threatening conditions. Timely diagnosis and effective antimicrobial treatment are critical for patient outcomes. This case underscores the significance of recognizing atypical presentations of bacterial infections, as early detection and appropriate management can significantly impact patient outcomes.

Globus pallidus externus drives increase in network-wide alpha power with propofol-induced loss-of-consciousness in humans.

States of consciousness are likely mediated by multiple parallel yet interacting cortico-subcortical recurrent networks. Although the mesocircuit model has implicated the pallidocortical circuit as one such network, this circuit has not been extensively evaluated to identify network-level electrophysiological changes related to loss of consciousness (LOC). We characterize changes in the mesocircuit in awake versus propofol-induced LOC in humans by directly simultaneously recording from sensorimotor cortices (S1/M1) and globus pallidus interna and externa (GPi/GPe) in 12 patients with Parkinson disease undergoing deep brain stimulator implantation. Propofol-induced LOC is associated with increases in local power up to 20 Hz in GPi, 35 Hz in GPe, and 100 Hz in S1/M1. LOC is likewise marked by increased pallidocortical alpha synchrony across all nodes, with increased alpha/low beta Granger causal (GC) flow from GPe to all other nodes. In contrast, LOC is associated with decreased network-wide beta coupling and beta GC from M1 to the rest of the network. Results implicate an important and possibly central role of GPe in mediating LOC-related increases in alpha power, supporting a significant role of the GPe in modulating cortico-subcortical circuits for consciousness. Simultaneous LOC-related suppression of beta synchrony highlights that distinct oscillatory frequencies act independently, conveying unique network activity.

A neurophysiological profiling of the heartbeat-evoked potential in severe acquired brain injuries: A focus on unconsciousness.

Unconsciousness in severe acquired brain injury (sABI) patients occurs with different cognitive and neural profiles. Perturbational approaches, which enable the estimation of proxies for brain reorganization, have added a new avenue for investigating the non-behavioural diagnosis of consciousness. In this prospective observational study, we conducted a comparative analysis of the topological patterns of heartbeat-evoked potentials (HEP) between patients experiencing a prolonged disorder of consciousness (pDoC) and patients emerging from a minimally consciousness state (eMCS). A total of 219 sABI patients were enrolled, each undergoing a synchronous EEG-ECG resting-state recording, together with a standardized consciousness diagnosis. A number of graph metrics were computed before/after the HEP (Before/After) using the R-peak on the ECG signal. The peak value of the global field power of the HEP was found to be significantly higher in eMCS patients with no difference in latency. Power spectrum was not able to discriminate consciousness neither Before nor After. Node assortativity and global efficiency were found to vary with different trends at unconsciousness. Lastly, the Perturbational Complexity Index of the HEP was found to be significantly higher in eMCS patients compared with pDoC. Given that cortical elaboration of peripheral inputs may serve as a non-behavioural determinant of consciousness, we have devised a low-cost and translatable technique capable of estimating causal proxies of brain functionality with an endogenous, non-invasive stimulus. Thus, we present an effective means to enhance consciousness assessment by incorporating the interaction between the autonomic nervous system (ANS) and central nervous system (CNS) into the loop.

Effects of mTBI with loss of consciousness on neurobehavioral symptoms, depression, and insomnia in former collegiate and NFL football athletes.

OBJECTIVE: Considering that diagnostic decisions about mTBI are often predicated on clinical symptom criteria, it is imperative to determine which initial presentation features of mTBI have prognostic significance for identifying those at high risk for long-term functional impairment. SETTING: Zoom interview Participants: Male, former NCAA Division I, and professional-level National Football League (NFL) athletes (n = 177) between the ages of 27 and 85 (M = 54.1, SD = 14.7). DESIGN: Cross-sectional case-control. Main Measures: History of mild TBI, history of loss of consciousness (LOC), depression symptoms, insomnia, neurobehavioral symptoms. RESULTS: Number of mTBI exposures did not predict neurobehavioral symptoms (B = 0.21, SE = 0.18, p = 0.23), but number of mTBI + LOC events did (B = 2.27, SE = 0.64, p = <.001). Further analysis revealed that the number of mTBI + LOC events predicted neurobehavioral symptoms indirectly through both depression (B = 0.85, 95% CI = [0.27, 1.52) and insomnia (B = 0.81, 95% CI = [0.3, 1.4]). Further, the direct effect of mTBI + LOC events on neurobehavioral symptoms became non-significant when depression and insomnia were added to the model (B = 0.78, SE = 0.45, p = 0.08). CONCLUSIONS: Findings support LOC at time of injury as an important predictor of long-term outcomes. Additionally, results suggest depression and insomnia as potential mediators in the association between mTBI + LOC and neurobehavioral symptoms. These findings provide justification for early depression and insomnia symptom monitoring following mTBI + LOC.

Electrical stimulation of the ventral tegmental area restores consciousness from sevoflurane-, dexmedetomidine-, and fentanyl-induced unconsciousness in rats.

BACKGROUND: Dopaminergic neurons in the ventral tegmental area (VTA) are crucially involved in regulating arousal, making them a potential target for reversing general anesthesia. Electrical deep brain stimulation (DBS) of the VTA restores consciousness in animals anesthetized with drugs that primarily enhance GABAA receptors. However, it is unknown if VTA DBS restores consciousness in animals anesthetized with drugs that target other receptors. OBJECTIVE: To evaluate the efficacy of VTA DBS in restoring consciousness after exposure to four anesthetics with distinct receptor targets. METHODS: Sixteen adult Sprague-Dawley rats (8 female, 8 male) with bipolar electrodes implanted in the VTA were exposed to dexmedetomidine, fentanyl, ketamine, or sevoflurane to produce loss of righting, a proxy for unconsciousness. After receiving the dopamine D1 receptor antagonist, SCH-23390, or saline (vehicle), DBS was initiated at 30 µA and increased by 10 µA until reaching a maximum of 100 µA. The current that evoked behavioral arousal and restored righting was recorded for each anesthetic and compared across drug (saline/SCH-23390) condition. Electroencephalogram, heart rate and pulse oximetry were recorded continuously. RESULTS: VTA DBS restored righting after sevoflurane, dexmedetomidine, and fentanyl-induced unconsciousness, but not ketamine-induced unconsciousness. D1 receptor antagonism diminished the efficacy of VTA stimulation following sevoflurane and fentanyl, but not dexmedetomidine. CONCLUSIONS: Electrical DBS of the VTA restores consciousness in animals anesthetized with mechanistically distinct drugs, excluding ketamine. The involvement of the D1 receptor in mediating this effect is anesthetic-specific.

Taking consciousness for real: Increasing the ecological validity of the study of conscious vs. unconscious processes.

The study of consciousness has developed well-controlled, rigorous methods for manipulating and measuring consciousness. Yet, in the process, experimental paradigms grew farther away from everyday conscious and unconscious processes, which raises the concern of ecological validity. In this review, we suggest that the field can benefit from adopting a more ecological approach, akin to other fields of cognitive science. There, this approach challenged some existing hypotheses, yielded stronger effects, and enabled new research questions. We argue that such a move is critical for studying consciousness, where experimental paradigms tend to be artificial and small effect sizes are relatively prevalent. We identify three paths for doing so-changing the stimuli and experimental settings, changing the measures, and changing the research questions themselves-and review works that have already started implementing such approaches. While acknowledging the inherent challenges, we call for increasing ecological validity in consciousness studies.

An 11-month-old boy with tuberculous meningitis presenting as progressive limb weakness, fever, developmental retardation, and loss of consciousness: a case report.

BACKGROUND: Tuberculous meningitis (TBM) accounts for about 1% of all tuberculosis cases and about 5% of extrapulmonary tuberculosis cases. However, it poses major importance because approximately half of those affected die or become severely disabled. Herein, the successful treatment of an 11-month-old boy with progressive limb weakness, fever, developmental retardation, and loss of consciousness due to tuberculosis, was reported. CASE PRESENTATION: An 11-month-old (Iranian Turk) boy was referred to Loghman Hakim hospital for progressive limb weakness and loss of previously attained developmental milestones for the past 2 months. He also had persistent fever and loss of consciousness for about 14 to 21 days. Before being referred to our center, the patient had been diagnosed with hydrocephalus at another center due to possible acute bacterial meningitis based on a CT scan and MRI imaging. On physical examination, anterior fontanel bulging and neck stiffness were observed on the admission. His body temperature and heart rate were 38.1 C and 86 beats per minute (bpm), respectively. He had left 6 cranial nerve palsy and spastic quadriparesis with a power of grade 3/5. Other systemic examinations were normal. Endoscopic third ventriculostomy (ETV) (and leptomeningeal biopsy) revealed diffuse thickening of the floor and lateral walls of the 3rd ventricle and also a cobblestone appearance in the form of multiple white patchy lesions was detected on the floor of the 3rd ventricle. CSF analysis and polymerase chain reaction confirmed the TB meningitis. During hospitalization, a temporary EVD (external ventricular drain) was initially inserted. Eventually, defervescence was denoted 5-6 days after initiation of anti-TB medications, and a permanent ventriculoperitoneal shunt was inserted due to hydrocephalus. Gradually his truncal and limb tone and motor function improved, as did his emotional responses to his parents and ability to eat. The patient can walk without help in the 15th month following the operation and resolved hydrocephalus demonstrated on follow-up imaging. CONCLUSION: Over half of treated TB meningitis patients die or suffer severe neurological sequelae, mainly due to late diagnosis. Hence, early diagnosis and prompt initiation of TB treatment offer the best chance of a good neurological outcome.

Clinical presentation and management of methanol poisoning outbreaks in Riyadh, Saudi Arabia: a retrospective analysis.

BACKGROUND: Acute methanol intoxication, whether unintentional or deliberate, necessitates prompt intervention to prevent severe morbidity and mortality. Homemade alcoholic beverages are a frequent source of such poisoning. This retrospective analysis examined two outbreaks of methanol intoxication in Saudi Arabia. It investigated the clinical presentation, implemented management strategies, and any lasting complications (sequelae) associated with these cases. The aim was to assess the potential impact of different treatment modalities and the timeliness of their initiation on patient outcomes. METHODS: This was a retrospective case series of methanol poisoning cases which presented to the adult emergency department (ED) at King Abdulaziz Medical City (KAMC) in Riyadh, Saudi Arabia. There were two separate outbreaks in the city, the first one was from September 1 to September 10, 2020 and the second one was from May 14 to May 20, 2021. Electronic charts were reviewed, and data were extracted to previously prepared data extraction sheets. RESULT: From the 22 patients who arrived in the ED alive, the most common complaints were nausea or vomiting followed by altered level of consciousness. About 9% from the patient were hypotensive, 36% were tachycardic, 41% were tachypneic and 4% were having SpO2 < 94%. Brain CT was abnormal in 6 patients. Vision impairment was the most common sequalae of methanol poisoning (7 out of 12 patients who were assessed by ophthalmologist, 58%). When the patients were divided based on severity (mild, moderate, severe), nausea or vomiting and loss of consciousness were the most common complaints among the moderate group while loss of consciousness predominated in the severe group. Two patients presented with low blood pressure and were in the sever group. The severe group had a mean Glasgow Coma Scale (GCS) of 8. Most of the patients in the severity groups underwent the same management apart from those who died or deposited. Eight patients in the severe group had to be intubated. CONCLUSION: This study demonstrates the multifaceted clinical presentation of methanol poisoning, culminating in a 17.4% mortality rate. Notably, our findings emphasize the critical role of prompt diagnosis and swift initiation of combined fomepizole therapy and hemodialysis in mitigating mortality and minimizing the potential for chronic visual sequelae associated with methanol poisoning.

Exploring the Median Effective Dose of Ciprofol for Anesthesia Induction in Elderly Patients: Impact of Frailty on ED50.

Purpose: Explore the median effective dose of ciprofol for inducing loss of consciousness in elderly patients and investigate how frailty influences the ED50 of ciprofol in elderly patients. Patients and Methods: A total of 26 non-frail patients and 28 frail patients aged 65-78 years, with BMI ranging from 15 to 28 kg/m2, and classified as ASA grade II or III were selected. Patients were divided into two groups according to frailty: non-frail patients (CFS<4), frail patients (CFS≥4). With an initial dose of 0.3 mg/kg for elderly non-frail patients and 0.25 mg/kg for elderly frail patients, using the up-and-down Dixon method, and the next patient's dose was dependent on the previous patient's response. Demographic information, heart rate (HR), oxygen saturation (SpO2), mean blood pressure (MBP), and bispectral index (BIS) were recorded every 30 seconds, starting from the initiation of drug administration and continuing up to 3 minutes post-administration. Additionally, the total ciprofol dosage during induction, occurrences of hypotension, bradycardia, respiratory depression, and injection pain were recorded. Results: The calculated ED50 (95% confidence interval [CI]) and ED95 (95% CI) values for ciprofol-induced loss of consciousness were as follows: 0.267 mg/kg (95% CI 0.250-0.284) and 0.301 mg/kg (95% CI 0.284-0.397) for elderly non-frail patients; and 0.263 mg/kg (95% CI 0.244-0.281) and 0.302 mg/kg (95% CI 0.283-0.412) for elderly frail patients. Importantly, no patients reported intravenous injection pain, required treatment for hypotension, or experienced significant bradycardia. Conclusion: Frailty among elderly patients does not exert a notable impact on the median effective dose of ciprofol for anesthesia induction. Our findings suggest that anesthesiologists may forego the necessity of dosage adjustments when administering ciprofol for anesthesia induction in elderly frail patients.

Consistency in Reporting of Loss of Righting Reflex for Assessment of General Anesthesia in Rats and Mice: A Systematic Review.

General anesthesia induces a reversible loss of consciousness (LOC), a state that is characterized by the inability to feel pain. Identifying LOC in animals poses unique challenges, because the method most commonly used in humans, responding to questions, cannot be used in animals. For over a century, loss of righting reflex (LORR) has been used to assess LOC in animals. This is the only animal method that correlates directly with LOC in humans and has become the standard proxy measure used in research. However, the reporting of how LORR is assessed varies extensively. This systematic literature review examined the consistency and completeness of LORR methods used in rats and mice. The terms 'righting reflex,' 'anesthesia,' 'conscious,' 'rats,' 'mice,' and their derivatives were used to search 5 electronic databases. The abstracts of the 985 articles identified were screened for indications that the study assessed LORR in mice or rats. Full texts of selected articles were reviewed for LORR methodological completeness, with reported methods categorized by 1) animal placement method, 2) behavioral presence of righting reflex, 3) duration of LORR testing, 4) behavioral LORR, and 5) animal position for testing LORR. Only 22 papers reported on all 5 methodological categories. Of the 22 papers, 21 used unique LORR methodologies, with descriptions of LORR methods differing in at least one category as compared with all other studies. This variability indicates that even papers that included all 5 categories still had substantial differences in their methodological descriptions. These findings reveal substantial inconsistencies in LORR methodology and reporting in the biomedical literature likely compromising study replicability and data interpretation.

Adaptation to numerosity affects the pupillary light response.

We recently showed that the gain of the pupillary light response depends on numerosity, with weaker responses to fewer items. Here we show that this effect holds when the stimuli are physically identical but are perceived as less numerous due to numerosity adaptation. Twenty-eight participants adapted to low (10 dots) or high (160 dots) numerosities and subsequently watched arrays of 10-40 dots, with variable or homogeneous dot size. Luminance was constant across all stimuli. Pupil size was measured with passive viewing, and the effects of adaptation were checked in a separate psychophysical session. We found that perceived numerosity was systematically lower, and pupillary light responses correspondingly smaller, following adaptation to high rather than low numerosities. This is consistent with numerosity being a primary visual feature, spontaneously encoded even when task irrelevant, and affecting automatic and unconscious behaviours like the pupillary light response.

Precise detection of awareness in disorders of consciousness using deep learning framework.

Diagnosis of disorders of consciousness (DOC) remains a formidable challenge. Deep learning methods have been widely applied in general neurological and psychiatry disorders, while limited in DOC domain. Considering the successful use of resting-state functional MRI (rs-fMRI) for evaluating patients with DOC, this study seeks to explore the conjunction of deep learning techniques and rs-fMRI in precisely detecting awareness in DOC. We initiated our research with a benchmark dataset comprising 140 participants, including 76 unresponsive wakefulness syndrome (UWS), 25 minimally conscious state (MCS), and 39 Controls, from three independent sites. We developed a cascade 3D EfficientNet-B3-based deep learning framework tailored for discriminating MCS from UWS patients, referred to as "DeepDOC", and compared its performance against five state-of-the-art machine learning models. We also included an independent dataset consists of 11 DOC patients to test whether our model could identify patients with cognitive motor dissociation (CMD), in which DOC patients were behaviorally diagnosed unconscious but could be detected conscious by brain computer interface (BCI) method. Our results demonstrate that DeepDOC outperforms the five machine learning models, achieving an area under curve (AUC) value of 0.927 and accuracy of 0.861 for distinguishing MCS from UWS patients. More importantly, DeepDOC excels in CMD identification, achieving an AUC of 1 and accuracy of 0.909. Using gradient-weighted class activation mapping algorithm, we found that the posterior cortex, encompassing the visual cortex, posterior middle temporal gyrus, posterior cingulate cortex, precuneus, and cerebellum, as making a more substantial contribution to classification compared to other brain regions. This research offers a convenient and accurate method for detecting covert awareness in patients with MCS and CMD using rs-fMRI data.

Comparative brain-wide mapping of ketamine- and isoflurane-activated nuclei and functional networks in the mouse brain.

Ketamine (KET) and isoflurane (ISO) are two widely used general anesthetics, yet their distinct and shared neurophysiological mechanisms remain elusive. In this study, we conducted a comparative analysis of the effects of KET and ISO on c-Fos expression across the mouse brain, utilizing hierarchical clustering and c-Fos-based functional network analysis to evaluate the responses of individual brain regions to each anesthetic. Our findings reveal that KET activates a wide range of brain regions, notably in the cortical and subcortical nuclei involved in sensory, motor, emotional, and reward processing, with the temporal association areas (TEa) as a strong hub, suggesting a top-down mechanism affecting consciousness by primarily targeting higher order cortical networks. In contrast, ISO predominantly influences brain regions in the hypothalamus, impacting neuroendocrine control, autonomic function, and homeostasis, with the locus coeruleus (LC) as a connector hub, indicating a bottom-up mechanism in anesthetic-induced unconsciousness. KET and ISO both activate brain areas involved in sensory processing, memory and cognition, reward and motivation, as well as autonomic and homeostatic control, highlighting their shared effects on various neural pathways. In conclusion, our results highlight the distinct but overlapping effects of KET and ISO, enriching our understanding of the mechanisms underlying general anesthesia.

Unconsciousness as the main nonfocal symptom of anterior circulation transient ischemic attack: A case report.

RATIONALE: Unconsciousness is a nonfocal symptom of transient ischemic attack (TIA) that is frequently observed in patients with vertebrobasilar artery stenosis or occlusion. Conversely, loss of consciousness due to anterior circulation involvement (e.g., middle cerebral artery [MCA]) is a rare occurrence in TIA. PATIENT CONCERNS: This report describes a rare case in a 59-year-old woman who experienced recurrent episodes of altered consciousness because of the occlusion or stenosis of her MCAs. DIAGNOSES: The diagnosis of the case was updated from TIA to acute cerebral infarction, finally. Following initial loss of consciousness, cranial magnetic resonance imaging (MRI) did not reveal any evidence of acute cerebral infarction. However, following the second and third episodes of unconsciousness, the MRI revealed multiple new acute cerebral infarcts affecting both the cerebral hemispheres. Further evaluation through digital subtraction angiography disclosed complete occlusion of the left MCA and severe stenosis of the right MCA. INTERVENTIONS: Early in her illness, the patient was treated with vasodilators, aspirin and atorvastatin. Finally, 2 stents in her right and left MCAs were placed respectively, followed by treatment with aspirin, clopidogrel, and double-dosed atorvastatin calcium. Meanwhile, the patient focused on avoiding conditions which may lead to dehydration in her daily life routine. OUTCOMES: The episodes of unconsciousness of this patient were completely resolved. During the 1-year postoperative follow-up, the patient remained clinically stable without any symptoms of unconsciousness, limb numbness or weakness, or dizziness. LESSONS: These findings suggested that hypoperfusion in the bilateral cerebral hemispheres played a pivotal role in precipitating the patient episodes of unconsciousness. This case underscores the possibility that occlusion or severe stenosis in both MCAs can contribute to recurrent episodes of unconsciousness due to hypoperfusion. Moreover, it emphasizes the association between these episodes of unconsciousness and an increased risk of subsequent ischemic stroke.

Role of corpus callosum in unconscious vision.

The existence of unconscious visually triggered behavior in patients with cortical blindness (e.g., homonymous hemianopia) has been amply demonstrated and the neural bases of this phenomenon have been thoroughly studied. However, a crosstalk between the two hemispheres as a possible mechanism of unconscious or partially conscious vision has not been so far considered. Thus, the aim of this study was to assess the relationship between structural and functional properties of the corpus callosum (CC), as shown by probabilistic tractography (PT), behavioral detection/discrimination performance and level of perceptual awareness in the blind field of patients with hemianopia. Twelve patients were tested in two tasks with black-and-white visual square-wave gratings, one task of movement and the other of orientation. The stimuli were lateralized to one hemifield either intact or blind. A PT analysis was carried out on MRI data to extract fiber properties along the CC (genu, body, and splenium). Compared with a control group of participants without brain damage, patients showed lower FA values in all three CC sections studied. For the intact hemifield we found a significant correlation between PT values and visual detection/discrimination accuracy. For the blind hemifield the level of perceptual awareness correlated with PT values for all three CC sections in the movement task. Importantly, significant differences in all three CC sections were found also between patients with above-vs. chance detection/discrimination performance while differences in the genu were found between patients with and without perceptual awareness. Overall, our study provides evidence that the properties of CC fibers are related to the presence of unconscious stimulus detection/discrimination and to hints of perceptual awareness for stimulus presentation to the blind hemifield. These results underline the importance of information exchange between the damaged and the healthy hemisphere for possible partial or full recovery from hemianopia.

Assessing Susceptibility to Carbon Dioxide Gas in Three Rat Strains Using the Loss of Righting Reflex.

Overdose of carbon dioxide gas (CO2) is a common euthanasia method for rodents; however, CO2 exposure activates nociceptors in rats at concentrations equal to or greater than 37% and is reported to be painful in humans at concentrations equal to or greater than 32.5%. Exposure of rats to CO2 could cause pain before loss of consciousness. We used 2 standardized loss of righting reflex (LORR) methods to identify CO2 concentrations associated with unconsciousness in Wistar, Long???Evans, and Sprague???Dawley rats (n = 28 animals per strain). A rotating, motorized cylinder was used to test LORR while the rat was being exposed to increasing concentrations of CO2. LORR was defined based on a 15-second observation period. The 2 methods were 1) a 1-Paw assessment (the righting reflex was considered to be present if one or more paws contacted the cylinder after the rat was positioned in dorsal recumbency), and 2) a 4-Paw assessment (the righting reflex was considered to be present if all 4 paws contacted the cylinder after the rat was positioned in dorsal recumbency). Data were analyzed with Probit regression, and dose-response curves were plotted. 1-Paw EC95 values (CO2 concentration at which LORR occurred for 95% of the population) were Wistar, 27.2%; Long???Evans, 29.2%; and Sprague???Dawley, 35.0%. 4-Paw EC95 values were Wistar, 26.2%; Long???Evans, 25.9%, and Sprague???Dawley, 31.1%. Sprague???Dawley EC95 values were significantly higher in both 1- and 4-Paw tests as compared with Wistar and Long???Evans rats. No differences were detected between sexes for any strain. The 1-Paw EC95 was significantly higher than the 4-Paw EC95 only for Sprague-Dawley rats. These results suggest that a low number of individual rats from the strains studied may experience pain during CO2 euthanasia.

Intracerebral hemorrhage in methanol toxicity patients during COVID-19 pandemic: case report and review of literature.

PURPOSE: The aim of this study is to examine the clinical and imaging manifestations of methanol toxicity during the COVID-19 pandemic, as well as to review existing studies on this topic. The most common cause of methanol intoxication is methanol-adulterated liquor. The primary metabolite of methanol, formic acid, is responsible for pathological changes. Symptoms typically present within 6-24 h of consumption and can include visual disturbances, acute neurological symptoms, and gastrointestinal issues. During the initial year of the COVID-19 pandemic, methanol poisoning cases increased significantly. METHODS: In this study, We present six different patients with methanol intoxication and their clinical and imaging features. RESULTS: In the literature review, the most common clinical presentation was loss of consciousness and obtundation and the other was vision loss. CT scan findings showed bilateral putaminal necrosis and hemorrhage in 55% of methanol toxicity patients. CONCLUSION: Methanol intoxication, causing bilateral putaminal involvement and a 50% mortality rate in intracerebral hemorrhage patients, warrants urgent toxicological analysis due to potential putaminal hemorrhage.