Deep Brain Stimulation for Recovery of Consciousness in Minimally Conscious Patients After Traumatic Brain Injury: A Systematic Review

Thalamic burst and tonic firing selectively indicate patients' consciousness level and recovery

Patients with disorders of consciousness suffer from severe impairments in arousal and awareness alongside anomalous brain connections and aberrant neuronal activities. The thalamus, a crucial hub in the brain connectome, has been empirically inferred to maintain consciousness and wakefulness. Here, we investigated thalamic spiking, brain connectivity, consciousness states, and recovery outcomes following deep brain stimulation in 29 patients. Our study reveals that thalamic neuronal activity serves as a marker of consciousness state. Patients diagnosed with vegetative state/unresponsive wakefulness syndrome exhibited less-active neurons, with longer and more variable burst discharges, than those in a minimally conscious state. Furthermore, neuronal profiles in the intralaminar thalamus, the direct stimulation site, predicted whether electrostimulation here improved recovery. Stronger tonic firing was correlated with enhanced thalamocortical connectivity and better recovery outcomes in patients. These findings suggest that thalamic spiking signatures, including single-neuron burst discharge and tonic firing, selectively indicate the representation and alteration of consciousness.

A Review of Advances in Multimodal Treatment Strategies for Chronic Disorders of Consciousness Following Severe Traumatic Brain Injury

Background

Chronic disorders of consciousness (cDoC) resulting from severe traumatic brain injury (sTBI) are associated with significant challenges in treatment and recovery. This review explores multimodal interventions aimed at improving patient outcomes.

Methods

A systematic review was conducted on peer-reviewed studies from PubMed and Google Scholar published between 2000 and 2023. The review included clinical trials, observational studies, and case series that assessed interventions for improving consciousness and cognitive function in patients with cDoC following sTBI. Interventions considered included pharmacological treatments, non-invasive neuromodulation, rehabilitation therapies, and traditional medicine approaches.

Results

The review identifies several promising interventions. Hyperbaric oxygen therapy (HBOT), when combined with physical rehabilitation and non-invasive brain stimulation techniques like transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), has shown positive effects on consciousness and cognitive recovery. Non-invasive neuromodulation techniques have been linked to improvements in cortical activity and consciousness, with taVNS emerging as a novel approach. Additionally, traditional Chinese medicine, particularly herbal therapies, has demonstrated complementary benefits when integrated with modern rehabilitation methods. Personalized treatment strategies based on clinical characteristics, biomarkers, and genetic data were found to enhance recovery. Notably, integrating these modalities into personalized care protocols has shown enhanced efficacy, suggesting that individualized approaches are critical for improving outcomes.

Conclusion

Multimodal therapies show promise in enhancing recovery in cDoC patients after sTBI, but further research is needed to optimize treatment protocols and standardize clinical practices. The integration of traditional and modern therapies represents a potentially effective strategy for improving patient outcomes.

Medical and surgical treatments in disorders of consciousness

Ever since a 2012 landmark study showed positive effects of amantadine in people with disorders of consciousness (DOC), there has been a shift in research efforts from merely improving diagnostics and prognostication of DOC to also include therapeutic trials, in the quest to improve consciousness recovery after brain injury. Stimulation of residual consciousness in the intensive care unit is critical because failure to do so may lead to unwarranted pessimistic prognosis and premature withdrawal of life-sustaining therapies. Similarly, it is crucial to harvest the potential of chronic DOC patients for late consciousness recovery, which is increasingly reported. To this end, medical and nonpharmacologic, including surgical, treatment strategies are being tested. These include dopaminergic and GABAergic drugs (medical), vagal nerve stimulation (noninvasive or surgical), and deep brain stimulation (surgical). In addition, transcranial magnetic stimulation, transcranial direct current stimulation, and low-intensity ultrasound (nonpharmacologic and nonsurgical) are covered in another chapter in this volume of the Handbook. Although overall, DOC treatment studies are subject to small sample sizes, unblinded protocols, and limited follow-up, this will likely change in the foreseeable future with the advent of adequately powered multicenter studies, randomized, double-blind, placebo-controlled designs, and standardized outcome measures. This chapter discusses the present state and outlooks of the field of medical and surgical options to boost arousal and awareness in patients with DOC, indicating the future of DOC treatment is bright.

Revolutionizing treatment for disorders of consciousness: a multidisciplinary review of advancements in deep brain stimulation

Among the existing research on the treatment of disorders of consciousness (DOC), deep brain stimulation (DBS) offers a highly promising therapeutic approach. This comprehensive review documents the historical development of DBS and its role in the treatment of DOC, tracing its progression from an experimental therapy to a detailed modulation approach based on the mesocircuit model hypothesis. The mesocircuit model hypothesis suggests that DOC arises from disruptions in a critical network of brain regions, providing a framework for refining DBS targets. We also discuss the multimodal approaches for assessing patients with DOC, encompassing clinical behavioral scales, electrophysiological assessment, and neuroimaging techniques methods. During the evolution of DOC therapy, the segmentation of central nuclei, the recording of single-neurons, and the analysis of local field potentials have emerged as favorable technical factors that enhance the efficacy of DBS treatment. Advances in computational models have also facilitated a deeper exploration of the neural dynamics associated with DOC, linking neuron-level dynamics with macroscopic behavioral changes. Despite showing promising outcomes, challenges remain in patient selection, precise target localization, and the determination of optimal stimulation parameters. Future research should focus on conducting large-scale controlled studies to delve into the pathophysiological mechanisms of DOC. It is imperative to further elucidate the precise modulatory effects of DBS on thalamo-cortical and cortico-cortical functional connectivity networks. Ultimately, by optimizing neuromodulation strategies, we aim to substantially enhance therapeutic outcomes and greatly expedite the process of consciousness recovery in patients.

Deep brain stimulation mitigates memory deficits in a rodent model of traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a major life-threatening event. In addition to neurological deficits, it can lead to long-term impairments in attention and memory. Deep brain stimulation (DBS) is an established therapy for movement disorders that has been recently investigated for memory improvement in various disorders. In models of TBI, stimulation delivered to different brain targets has been administered to rodents long after the injury with the objective of treating motor deficits, coordination and memory impairment.

OBJECTIVE

To test the hypothesis that DBS administered soon after TBI may prevent the development of memory deficits and exert neuroprotective effects.

METHODS

Male rats were implanted with DBS electrodes in the anterior nucleus of the thalamus (ANT) one week prior to lateral fluid percussion injury (FPI). Immediately after TBI, animals received active or sham stimulation for 6 h. Four days later, they were assessed in a novel object/novel location recognition test (NOR/NLR) and a Barnes maze paradigm. After the experiments, hippocampal cells were counted. Separate groups of animals were sacrificed at different timepoints after TBI to measure cytokines and brain derived neurotrophic factor (BDNF). In a second set of experiments, TBI-exposed animals receiving active or sham stimulation were injected with the tropomyosin receptor kinase B (TrkB) antagonist ANA-12, followed by behavioural testing.

RESULTS

Rats exposed to TBI given DBS had an improvement in several variables of the Barnes maze, but no significant improvements in NOR/NLR compared to Sham DBS TBI animals or non-implanted controls. Animals receiving stimulation had a significant increase in BDNF levels, as well as in hippocampal cell counts in the hilus, CA3 and CA1 regions. DBS failed to normalize the increased levels of TNFα and the proinflammatory cytokine IL1β in the perilesional cortex and the hippocampus of the TBI-exposed animals. Pharmacological experiments revealed that ANA-12 administered alongside DBS did not counter the memory improvement observed in ANT stimulated animals.

CONCLUSIONS

DBS delivered immediately after TBI mitigated memory deficits, increased the expression of BDNF and the number of hippocampal cells in rats. Mechanisms for these effects were not related to an anti-inflammatory effect or mediated via TrkB receptors.

Complementary therapy with Chinese aromatic herbs to promote awakening in a comatose patient: A case report

RATIONALE

Traumatic brain injury frequently leads to prolonged coma, posing significant medical management challenges. Complementary therapies, including traditional Chinese herbal medicine, have been investigated as potential interventions in comatose patients. Chinese aromatic herbs, such as Borneolum (Bingpian), Moschus (Shexiang), and Acori tatarinowii rhizoma (Shichangpu), have long been believed to be "resuscitation with aromatics" based on traditional Chinese medicines theory.

PATIENT CONCERNS

A 16-year-old male was admitted to the intensive rehabilitation unit for further treatment due to prolonged coma and frequent seizures following traumatic brain injury.

DIAGNOSES

Western medicine diagnosed the patient as coma, diffuse axonal injury, and epilepsy. According to traditional Chinese medicine theory, the syndrome differentiation indicates a Yin-closed disease.

INTERVENTIONS

According to the patient's condition, we use the Chinese aromatic herbs as a complementary therapy.

OUTCOMES

Following a month-long administration, the patient's consciousness and electroencephalogram (EEG) background progressively improved. A 6-month follow-up demonstrated full arousal, though with ambulatory EEG revealing mild to moderate abnormality in the background.

LESSONS

The addition of Chinese aromatic herbs appears to have a beneficial effect on the patient's consciousness and EEG background. This could be attributed to the herbs' inherent pharmacological properties, as well as their potential to enhance the permeability of the blood-brain barrier to other drugs. This makes them a promising option for complementary therapy.

Deep Brain Stimulation for Consciousness Disorders; Technical and Ethical Considerations

Disorders of Consciousness (DoC) result in profound functional impairment, adversely affecting the lives of a predominantly younger patient population. Currently, effective treatment options for those who have reached chronicity (prolonged symptom duration over 4 weeks) are extremely limited, with the majority of such cases facing life-long dependence on carers and a poor quality of life. Here we briefly review the current evidence on caseload, diagnostic and management options in the United Kingdom (UK), United States of America (USA) and the European Union (EU). We identify key differences as well as similarities in these approaches across respective healthcare systems, highlighting unmet needs in this population. We subsequently present past efforts and the most recent advances in the field of surgical modulation of consciousness through implantable neurostimulation systems. We examine the ethical dilemmas that such a treatment approach may pose, proposing mediating solutions and methodological adjustments to address these concerns. Overall, we argue that there is a strong case for the utilisation of deep brain stimulation (DBS) in the DoC patient cohort. This is based on both promising results of recent clinical trials as well as technological developments. We propose a revitalization of surgical neuromodulation for DoC with a multicenter, multidisciplinary approach and strict monitoring guidelines, in order to not only advance treatment options but also ensure the safeguarding of patients' welfare and dignity.

Brain Temporal-Spectral Functional Variability Reveals Neural Improvements of DBS Treatment for Disorders of Consciousness

Deep brain stimulation (DBS) is establishing itself as a promising treatment for disorders of consciousness (DOC). Measuring consciousness changes is crucial in the optimization of DBS therapy for DOC patients. However, conventional measures use subjective metrics that limit the investigations of treatment-induced neural improvements. The focus of this study is to analyze the regulatory effects of DBS and explain the regulatory mechanism at the brain functional level for DOC patients. Specifically, this paper proposed a dynamic brain temporal-spectral analysis method to quantify DBS-induced brain functional variations in DOC patients. Functional near-infrared spectroscopy (fNIRS) that promised to evaluate consciousness levels was used to monitor brain variations of DOC patients. Specifically, a fNIRS-based experimental procedure with auditory stimuli was developed, and the brain activities during the procedure from thirteen DOC patients before and after the DBS treatment were recorded. Then, dynamic brain functional networks were formulated with a sliding-window correlation analysis of phase lag index. Afterwards, with respect to the temporal variations of global and regional networks, the variability of global efficiency, local efficiency, and clustering coefficient were extracted. Further, dynamic networks were converted into spectral representations by graph Fourier transform, and graph energy and diversity were formulated to assess the spectral global and regional variability. The results showed that DOC patients under DBS treatment exhibited increased global and regional functional variability that was significantly associated with consciousness improvements. Moreover, the functional variability in the right brain regions had a stronger correlation with consciousness enhancements than that in the left brain regions. Therefore, the proposed method well signifies DBS-induced brain functional variations in DOC patients, and the functional variability may serve as promising biomarkers for consciousness evaluations in DOC patients.

Traumatic Brain Injury and Neuromodulation Techniques in Rehabilitation: A Scoping Review

BACKGROUND AND OBJECTIVES

Traumatic Brain Injury (TBI) is a condition in which an external force, usually a violent blow to the head, causes functional impairment in the brain. Neuromodulation techniques are thought to restore altered function in the brain, resulting in improved function and reduced symptoms. Brain stimulation can alter the firing of neurons, boost synaptic strength, alter neurotransmitters and excitotoxicity, and modify the connections in their neural networks. All these are potential effects on brain activity. Accordingly, this is a promising therapy for TBI. These techniques are flexible because they can target different brain areas and vary in frequency and amplitude. This review aims to investigate the recent literature about neuromodulation techniques used in the rehabilitation of TBI patients.

MATERIALS AND METHODS

The identification of studies was made possible by conducting online searches on PubMed, Web of Science, Cochrane, Embase, and Scopus databases. Studies published between 2013 and 2023 were selected. This review has been registered on OSF (JEP3S).

RESULTS

We have found that neuromodulation techniques can improve the rehabilitation process for TBI patients in several ways. Transcranial Magnetic Stimulation (TMS) can improve cognitive functions such as recall ability, neural substrates, and overall improved performance on neuropsychological tests. Repetitive TMS has the potential to increase neural connections in many TBI patients but not in all patients, such as those with chronic diffuse axonal damage.

CONCLUSIONS

This review has demonstrated that neuromodulation techniques are promising instruments in the rehabilitation field, including those affected by TBI. The efficacy of neuromodulation can have a significant impact on their lives and improve functional outcomes for TBI patients.

Research hotspots and frontiers of neuromodulation techniques in disorders of consciousness: a bibliometric analysis

Background

The characteristics of disorders of consciousness (DOC) are changes in arousal and/or awareness caused by severe brain injuries. To date, the management of DOC patients remains a complex and challenging task, and neuromodulation techniques offer a promising solution. However, a bibliometric analysis focusing on neuromodulation techniques in DOC is currently absent. The aim of this study is to provide a bibliometric visualization analysis to investigate the research hotspots and frontiers in the field of neuromodulation techniques in DOC from 2012 to 2022.

Methods

The publications were collected and retrieved from the Web of Science (WoS) from 2012 to 2022. CiteSpace and Microsoft Excel were utilized perform the first global bibliographic analysis of the literature related to neuromodulation techniques for DOC.

Results

The analysis included a total of 338 publications. From 2012 to 2022, a consistent yet irregular increase in the number of articles published on neuromodulation techniques in DOC was observed. Frontiers in Neurology published the highest number of papers (n = 16). Neurosciences represented the main research hotspot category (n = 170). The most prolific country, institution, and author were the USA (n = 105), the University of Liege (n = 41), and Laureys Steven (n = 38), respectively. An analysis of keywords revealed that UWS/VS, MCS, and TMS constituted the primary research trends and focal points within this domain.

Conclusion

This bibliometric study sheds light on the current progress and emerging trends of neuromodulation techniques in DOC from 2012 to 2022. The focal topics in this domain encompass the precise diagnosis of consciousness levels in patients suffering from DOC and the pursuit of efficacious neuromodulation-based evaluation and treatment protocols for such patients.

Current status and prospect of transcutaneous auricular vagus nerve stimulation for disorders of consciousness

Disordered Consciousness (DOC) is among neurological disorders for which there is currently no admitted treatment. The pathogenesis of DOC is still unclear, covering a variety of indistinguishable types of diseases, high misdiagnosis rate and poor prognosis. Most treatments remain to be clarified in the future to provide adequate evidence for clinical guidance. Neuromodulation technology aims to regulate neural circuits to promote awakening more directly. At present, it is confirmed that the potential of transcutaneous auricular vagus nerve stimulation (taVNS) as a therapeutic tool is worth exploring in the context of consciousness disorders, as previously proposed for invasive forms of VNS, in which the means of stimulating the vagus nerve to change the brain areas related to cosciousness have also received widespread attention. In this paper, we review the literature on taVNS and DOC to better understand the current status and development prospect of taVNS treament as a non-invasive neuromodulation method with sensitivity and/or specificity at the single subject.

Review of spinal cord stimulation for disorders of consciousness

PURPOSE OF REVIEW

High-cervical spinal cord stimulation can alter cortical activity and cerebral metabolism. These effects are potentially beneficial for disorders of consciousness. A better understanding of the effects of clinical application of stimulation is needed. We aimed to evaluate the existing literature to determine the state of available knowledge. We performed a literature review of clinical studies assessing cervical spinal cord epidural stimulation for disorders of consciousness. Only peer-reviewed articles reporting preoperative and postoperative clinical status were included.

RECENT FINDINGS

Nineteen studies were included. A total of 532 cases were reported, and 255 patients were considered responsive (47.9%). Considering only studies published after the definition of minimally conscious state (MCS) as an entity, 402 individuals in unresponsive wakefulness syndrome (UWS) and 113 in MCS were reported. Responsiveness to SCS was reported in 170 UWS patients (42.3%) and in 78 MCS cases (69.0%), although the criteria for responsiveness and outcome measures varied among publications.

SUMMARY

Cervical SCS yielded encouraging results in patients with disorders of consciousness and seems to be more effective in MCS. More extensive investigation is needed to understand its potential role in clinical practice.

Alternating current stimulation promotes neurite outgrowth and plasticity in neurons through activation of the PI3K/AKT signaling pathway

As a commonly used physical intervention, electrical stimulation (ES) has been demonstrated to be effective in the treatment of central nervous system disorders. Currently, researchers are studying the effects of electrical stimulation on individual neurons and neural networks, which are dependent on factors such as stimulation intensity, duration, location, and neuronal properties. However, the exact mechanism of action of electrical stimulation remains unclear. In some cases, repeated or prolonged electrical stimulation can lead to changes in the morphology or function of the neuron. In this study, immunofluorescence staining and Sholl analysis are used to assess changes in the neurite number and axon length to determine the optimal pattern and stimulation parameters of ES for neurons. Neuronal death and plasticity are detected by TUNEL staining and microelectrode array assays, respectively. mRNA sequencing and bioinformatics analysis are applied to predict the key targets of the action of ES on neurons, and the identified targets are validated by western blot analysis and qRT-PCR. The effects of alternating current stimulation (ACS) on neurons are more significant than those of direct current stimulation (DCS), and the optimal parameters are 3 μA and 20 min. ACS stimulation significantly increases the number of neurites, the length of axons and the spontaneous electrical activity of neurons, significantly elevates the expression of growth-associated protein-43 (GAP-43) without significant changes in the expression of neurotrophic factors. Furthermore, application of PI3K/AKT-specific inhibitors significantly abolishes the beneficial effects of ACS on neurons, confirming that the PI3K/AKT pathway is an important potential signaling pathway in the action of ACS.

Spinal cord stimulation and deep brain stimulation for disorders of consciousness: a systematic review and individual patient data analysis of 608 cases

The application of spinal cord stimulation (SCS) and deep brain stimulation (DBS) for disorders of consciousness (DoC) has been increasingly reported. However, there is no sufficient evidence to determine how effective and safe SCS and DBS are for DoC owing to various methodological limitations. We conducted a systematic review to elucidate the safety and efficacy of SCS and DBS for DoC by systematically reviewing related literature by searching PubMed, EMBASE, Medline, and Cochrane Library. Twenty eligible studies with 608 patients were included in this study. Ten studies with 508 patients reported the efficacy of SCS for DoC, and the estimated overall effectiveness rate was 37%. Five studies with 343 patients reported the efficacy of SCS for VS, and the estimated effectiveness rate was 30%. Three studies with 53 patients reported the efficacy of SCS for MCS, and the estimated effectiveness rate was 63%. Five studies with 92 patients reported the efficacy of DBS for DoC, and the estimated overall effectiveness rate was 40%. Four studies with 63 patients reported the efficacy of DBS for VS, and the estimated effectiveness rate was 26%. Three studies with 19 patients reported the efficacy of DBS for MCS, and the estimated effectiveness rate was 74%. The adverse event rate of DoC was 8.1% and 18.2% after SCS and DBS, respectively. These results suggest that SCS and DBS can be considered reasonable treatments for DoC with considerable efficacy and safety.

Ten-Year Change in Disorders of Consciousness: A Bibliometric Analysis

Objectives: Disorders of consciousness (DoC) is a dynamic and challenging discipline, presenting intriguing challenges to clinicians and neurorehabilitation specialists for the lack of reliable assessment methods and interventions. Understanding DoC keeps pace with scientific research is urgent to need. We quantitively analyzed publications on DoC over the recent 10 years via bibliometrics analysis, to summarize the intellectual structure, current research hotspots, and future research trends in the field of DoC. Methods: Literature was obtained from the Science Citation Index Expanded of Web of Science Core Collection (WoSCC). To illustrate the knowledge structure of DoC, CiteSpace 5.8.R3 was used to conduct a co-occurrence analysis of countries, institutions, and keywords, and a co-citation analysis of references and journals. Also, Gephi 0.9.2 contributed to the author and co-cited author analysis. We found the most influential journals, authors, and countries and the most talked about keywords in the last decade of research. Results: A total of 1919 publications were collected. Over the past 10 years, the total number of annual publications has continued to increase, with the largest circulation in 2018. We found most DoC research and close cooperation originated from developed countries, e.g., the USA, Canada, and Italy. Academics from Belgium appear to have a strong presence in the field of DoC. The most influential journals were also mainly distributed in the USA and some European countries. Conclusions: This bibliometric study sheds light on the knowledge architecture of DoC research over the past decade, reflecting current hotspots and emerging trends, and providing new insights for clinicians and academics interested in DoC. The hot issues in DoC were diagnosing and differentiating the level of consciousness, and detecting covert awareness in early severe brain-injured patients. New trends focus on exploring the recovery mechanism of DoC and neuromodulation techniques.

Neurostimulation for Functional Recovery After Traumatic Brain Injury: Current Evidence and Future Directions for Invasive Surgical Approaches

We aim to provide a comprehensive review of the current scientific evidence supporting the use of invasive neurostimulation in the treatment of deficits associated with traumatic brain injury (TBI), as well as to identify future directions for research and highlight important questions that remain unaddressed. Neurostimulation is a treatment modality with expanding applications in modern medical practice. Targeted electrical stimulation of specific brain regions has been shown to increase synaptogenesis and enhance structural reorganization of neuronal networks. This underlying therapeutic effect might be of high value for patients suffering from TBI because it could modulate neuronal connectivity and function of areas that are partially or completely spared after injury. The current published literature exploring the application of invasive neurostimulation for the treatment of functional deficits associated with TBI is scarce but promising. Rodent models have shown that targeted stimulation of the hippocampus or connecting structures can result in significant cognitive recovery, while stimulation of the motor cortex and deep cerebellar nuclei is associated with motor improvements. Data from clinical studies are extremely limited; single-patient reports and case series found neurostimulation to be effective in relieving motor symptoms, improving visuospatial memory, and supporting emotional adjustment. Looking forward, it will be important to identify stimulation targets and paradigms that can maximize improvement over multiple functional domains. It will also be important to corroborate the observed behavioral improvements with histological, electrophysiological, and radiological evidence. Finally, the impact of biological variables such as sex and age on the treatment outcomes needs to be explored.

Rhythmic musical-electrical trigeminal nerve stimulation improves impaired consciousness

Accumulating evidence shows that consciousness is linked to neural oscillations in the thalamocortical system, suggesting that deficits in these oscillations may underlie disorders of consciousness (DOC). However, patient-friendly non-invasive treatments targeting this functional anomaly are still missing and the therapeutic value of oscillation restoration has remained unclear. We propose a novel approach that aims to restore DOC patients' thalamocortical oscillations by combining rhythmic trigeminal-nerve stimulation with comodulated musical stimulation ("musical-electrical TNS"). In a double-blind, placebo-controlled, parallel-group study, we recruited 63 patients with DOC and randomly assigned them to groups receiving gamma, beta, or sham musical-electrical TNS. The stimulation was applied for 40 min on five consecutive days. We measured patients' consciousness before and after the stimulation using behavioral indicators and neural responses to rhythmic auditory speech. We further assessed their outcomes one year later. We found that musical-electrical TNS reliably lead to improvements in consciousness and oscillatory brain activity at the stimulation frequency: 43.5 % of patients in the gamma group and 25 % of patients in the beta group showed an improvement of their diagnosis after being treated with the stimulation. This group of benefitting patients still showed more positive outcomes one year later. Moreover, patients with stronger behavioral benefits showed stronger improvements in oscillatory brain activity. These findings suggest that brain oscillations contribute to consciousness and that musical-electrical TNS may serve as a promising approach to improve consciousness and predict long-term outcomes in patients with DOC.

Brain Metabolic Connectivity Patterns in Patients with Prolonged Disorder of Consciousness after Hypoxic-Ischemic Injury: A Preliminary Study

Understanding the patterns of brain glucose metabolism and connectivity in hypoxic-ischemic encephalopathy (HIE) patients with prolonged disorders of consciousness (DOC) may be of positive significance to the accurate assessment of consciousness and the optimization of neuromodulation strategy. We retrospectively analyzed the brain glucose metabolism pattern and its correlation with clinical Coma Recovery Scale-Revised (CRS-R) score in six HIE patients with prolonged DOC who had undergone 18F-deoxyglucose brain positron emission tomography scanning (FDG-PET). We also compared the differences in global metabolic connectivity patterns and the characteristics of several brain networks between HIE patients and healthy controls (HC). The metabolism of multiple brain regions decreased significantly in HIE patients, and the degree of local metabolic preservation was correlated with CRS-R score. The internal metabolic connectivity of occipital lobe and limbic system in HIE patients decreased, and their metabolic connectivity with frontal lobe, parietal lobe and temporal lobe also decreased. The metabolic connectivity patterns of default mode network, dorsal attention network, salience network, executive control network and subcortex network of HIE also changed compared with HC. The present study suggested that pattern of cerebral glucose metabolism and network connectivity of HIE patients with prolonged DOC were significantly different from those of healthy people.

Related Factors and Outcome of Spinal Cord Stimulation Electrode Deviation in Disorders of Consciousness

Background and Purpose

Spinal cord stimulation (SCS) has been reported to be a promising neuromodulation method for patients with disorders of consciousness (DOC). Our previous studies found that clinical characteristics of patients and SCS stimulation parameters could affect the therapeutic effects of SCS, while surgical-related factors remain unknown. Through the improvement of surgical procedures, most of the SCS electrodes are implanted in the middle, while a small number of electrodes have still deviated.

Methods

A total of 137 patients received SCS treatment in our institutions from 1 January 2010 to 31 December 2020. Among them, 27 patients were found with electrode deviation and met the inclusion criteria. Patients were grouped according to whether the electrode deviation angle (EDA) is >30°, respectively. Clinical characteristics of patients and SCS stimulation parameters were compared. Potential related factors and outcomes were evaluated by Chi-square test or two-way repeated measures analysis.

Results

Twenty seven patients receiving cervical SCS treatment were found to have electrode deviation postoperatively. Among them, 12 patients were classified into the more deviation group. No significant difference was found among age, sex, pathogeny, course of DOC, C2–C5 distance, spinal cord to spinal canal ratio at C2 level, and preoperative JFK Coma Recovery Scale-Revised (CRS-R) scores. We found that the electrode direction significantly deviated to the contralateral side in the lateral decubitus position (P = 0.025). The maximum tolerant stimulation intensity in the less deviation group (1.70 ± 0.41) was significantly higher than that in the more deviation group (1.25 ± 0.34) (P = 0.006). Under the strongest stimulation, less unilateral limb tremor (P = 0.049) and paroxysmal sympathetic hyperactivity (PSH) episodes (P = 0.030) were found. EDA had a significant effect on postoperative CRS-R in patients, and patients in the less deviation group had significantly higher postoperative CRS-R (P < 0.01). There was also an interaction effect between EDA and postoperative time. With the prolonged postoperative time, the CRS-R improvement rate of patients with different EDA was different, and the CRS-R improved faster in patients with less EDA (P < 0.05).

Conclusions

Electrode deviation will affect the outcome of patients receiving cervical SCS treatment. The intraoperative surgical position is associated with postoperative electrode deviation direction. The reduction of EDA under 30° can increase maximum tolerant stimulation intensity, reduce complications, and further improve patients' outcomes.

Methodological aspects of studying the mechanisms of consciousness

There are at least two approaches to the definition of consciousness. In the first case, certain aspects of consciousness, called qualia, are considered inaccessible for research from a third person and can only be described through subjective experience. This approach is inextricably linked with the so-called "hard problem of consciousness", that is, the question of why consciousness has qualia or how any physical changes in the environment can generate subjective experience. With this approach, some aspects of consciousness, by definition, cannot be explained on the basis of external observations and, therefore, are outside the scope of scientific research. In the second case, a priori constraints do not constrain the field of scientific investigation, and the best explanation of the experience in the first person is included as a possible subject of empirical research. Historically, in the study of cause-and-effect relationships in biology, it was customary to distinguish between proximate causation and ultimate causation existing in biological systems. Immediate causes are based on the immediate influencing factors [1]. Proximate causation has evolutionary explanations. When studying biological systems themselves, such an approach is undoubtedly justified, but it often seems insufficient when studying the interaction of consciousness and the brain [2,3]. Current scientific communities proceed from the assumption that the physical substrate for the generation of consciousness is a neural network that unites various types of neurons located in various brain structures. Many neuroscientists attach a key role in this process to the cortical and thalamocortical neural networks. This question is directly related to experimental and clinical research in the field of disorder of consciousness. Progress in this area of medicine depends on advances in neuroscience in this area and is also a powerful source of empirical information. In this area of consciousness research, a large amount of experimental data has been accumulated, and in this review an attempt was made to generalize and systematize.

Electrocorticography reveals thalamic control of cortical dynamics following traumatic brain injury

The return of consciousness after traumatic brain injury (TBI) is associated with restoring complex cortical dynamics; however, it is unclear what interactions govern these complex dynamics. Here, we set out to uncover the mechanism underlying the return of consciousness by measuring local field potentials (LFP) using invasive electrophysiological recordings in patients recovering from TBI. We found that injury to the thalamus, and its efferent projections, on MRI were associated with repetitive and low complexity LFP signals from a highly structured phase space, resembling a low-dimensional ring attractor. But why do thalamic injuries in TBI patients result in a cortical attractor? We built a simplified thalamocortical model, which connotes that thalamic input facilitates the formation of cortical ensembles required for the return of cognitive function and the content of consciousness. These observations collectively support the view that thalamic input to the cortex enables rich cortical dynamics associated with consciousness.

Treating Traumatic Brain Injuries with Electroceuticals: Implications for the Neuroanatomy of Consciousness

According to the Centers for Disease Control and Prevention (CDC), traumatic brain injury (TBI) is the leading cause of loss of consciousness, long-term disability, and death in children and young adults (age 1 to 44). Currently, there are no United States Food and Drug Administration (FDA) approved pharmacological treatments for post-TBI regeneration and recovery, particularly related to permanent disability and level of consciousness. In some cases, long-term disorders of consciousness (DoC) exist, including the vegetative state/unresponsive wakefulness syndrome (VS/UWS) characterized by the exhibition of reflexive behaviors only or a minimally conscious state (MCS) with few purposeful movements and reflexive behaviors. Electroceuticals, including non-invasive brain stimulation (NIBS), vagus nerve stimulation (VNS), and deep brain stimulation (DBS) have proved efficacious in some patients with TBI and DoC. In this review, we examine how electroceuticals have improved our understanding of the neuroanatomy of consciousness. However, the level of improvements in general arousal or basic bodily and visual pursuit that constitute clinically meaningful recovery on the Coma Recovery Scale-Revised (CRS-R) remain undefined. Nevertheless, these advancements demonstrate the importance of the vagal nerve, thalamus, reticular activating system, and cortico-striatal-thalamic-cortical loop in the process of consciousness recovery.

Wakefulness-Promoting Effects of Lateral Hypothalamic Area-Deep Brain Stimulation in Traumatic Brain Injury-Induced Comatose Rats: Upregulation of α1-Adrenoceptor Subtypes and Downregulation of Gamma-Aminobutyric Acid β Receptor Expression Via the Orexins Pathway

OBJECTIVE

Previous studies have shown that deep brain stimulation (DBS) can improve the level of consciousness of comatose patients with traumatic brain injuries (TBIs). However, the most suitable targets for DBS are unknown, and the mechanisms underlying recovery remain to be determined. The aim of the present study was to assess the effects of lateral hypothalamic area-DBS (LHA-DBS) in comatose rats with TBIs.

METHODS

A total of 55 Sprague-Dawley rats were randomly assigned to 5 groups: the control group, TBI group, stimulated (TBI+LHA-DBS) group, antagonist (TBI+SB334867+LHA-DBS) group, and antagonist control (TBI+saline+LHA-DBS) group. The rats in the control group had undergone a sham operation and anesthesia, without coma induction. Coma was induced using a free-fall drop method. The rats in the stimulated group received bilateral LHA stimulation (frequency, 200 Hz; voltage, 2-4 V; pulse width, 0.1 ms) for 1 hour, with 5-minute intervals between subsequent stimulations, which were applied alternately to the left and right sides of the lateral hypothalamus. The comatose rats in the antagonist group received an intracerebroventricular injection with an orexins receptor type 1 (OX1R) antagonist (SB334867) and then received LHA-DBS. A I-VI consciousness scale and electroencephalography were used to assess the level of consciousness in each group of rats after LHA-DBS. Western blotting and immunofluorescence were used to detect OX1R expression in the LHA and α1-adrenoceptor (α1-AR) subtype and gamma-aminobutyric acid β receptor (GABABR) expression in the prefrontal cortex.

RESULTS

In the TBI, stimulated, antagonist, and antagonist control groups, 5, 10, 6, and 9 rats were awakened. The electroencephalographic readings indicated that the proportion of δ waves was lower in the stimulated group than in the TBI and antagonist groups (P < 0.05). Western blotting and immunofluorescence analysis showed that OX1R expression was greater in the stimulated group than in the TBI group (P < 0.05). The expression of α1-AR was also greater in the stimulated group than in the TBI and antagonist groups (P < 0.05). In contrast, the GABABR levels in the stimulated group were lower than those in the TBI and antagonist groups (P < 0.05). A statistically significant difference was found between the antagonist and antagonist control groups.

CONCLUSIONS

Taken together, these results suggest that LHA-DBS promotes the recovery of consciousness in comatose rats with TBIs. Upregulation of α1-AR expression and downregulation of GABABR expression in the prefrontal cortex via the orexins and OX1R pathways might be involved in the wakefulness-promoting effects of LHA-DBS.

Clinical diagnosis guidelines and neurorestorative treatment for chronic disorders of consciousness (2021 China version)

Chronic disorders of consciousness (DOC) include the vegetative state and the minimally consciousness state. The DOC diagnosis mainly relies on the evaluation of clinical behavioral scales, electrophysiological testing, and neuroimaging examinations. No specifically effective neurorestorative methods for chronic DOC currently exist. Any valuable exploration therapies of being able to repair functions and/or structures in the consciousness loop (e.g., drugs, hyperbaric medicines, noninvasive neurostimulation, sensory and environmental stimulation, invasive neuromodulation therapy, and cell transplantation) may become effective neurorestorative strategies for chronic DOC. In the viewpoint of Neurorestoratology, this guideline proposes the diagnostic and neurorestorative therapeutic suggestions and future exploration direction for this disease following the review of the existing treatment exploration achievements for chronic DOC.

Multimodal treatment for spinal cord injury: a sword of neuroregeneration upon neuromodulation

Spinal cord injury is linked to the interruption of neural pathways, which results in irreversible neural dysfunction. Neural repair and neuroregeneration are critical goals and issues for rehabilitation in spinal cord injury, which require neural stem cell repair and multimodal neuromodulation techniques involving personalized rehabilitation strategies. Besides the involvement of endogenous stem cells in neurogenesis and neural repair, exogenous neural stem cell transplantation is an emerging effective method for repairing and replacing damaged tissues in central nervous system diseases. However, to ensure that endogenous or exogenous neural stem cells truly participate in neural repair following spinal cord injury, appropriate interventional measures (e.g., neuromodulation) should be adopted. Neuromodulation techniques, such as noninvasive magnetic stimulation and electrical stimulation, have been safely applied in many neuropsychiatric diseases. There is increasing evidence to suggest that neuromagnetic/electrical modulation promotes neuroregeneration and neural repair by affecting signaling in the nervous system; namely, by exciting, inhibiting, or regulating neuronal and neural network activities to improve motor function and motor learning following spinal cord injury. Several studies have indicated that fine motor skill rehabilitation training makes use of residual nerve fibers for collateral growth, encourages the formation of new synaptic connections to promote neural plasticity, and improves motor function recovery in patients with spinal cord injury. With the development of biomaterial technology and biomechanical engineering, several emerging treatments have been developed, such as robots, brain-computer interfaces, and nanomaterials. These treatments have the potential to help millions of patients suffering from motor dysfunction caused by spinal cord injury. However, large-scale clinical trials need to be conducted to validate their efficacy. This review evaluated the efficacy of neural stem cells and magnetic or electrical stimulation combined with rehabilitation training and intelligent therapies for spinal cord injury according to existing evidence, to build up a multimodal treatment strategy of spinal cord injury to enhance nerve repair and regeneration.

Non-invasive brain intervention techniques used in patients with disorders of consciousness

Aim of the study: With the development of emergency medicine and intensive care technology, the number of people who survive with disorders of consciousness (DOC) has dramatically increased. The diagnosis and treatment of such patients have attracted much attention from the medical community. From the latest evidence-based guidelines, non-invasive brain intervention (NIBI) techniques may be valuable and promising in the diagnosis and conscious rehabilitation of DOC patients.Methods: This work reviews the studies on NIBI techniques for the assessment and intervention of DOC patients.Results: A large number of studies have explored the application of NIBI techniques in DOC patients. The NIBI techniques include transcranial magnetic stimulation, transcranial electric stimulation, music stimulation, near-infrared laser stimulation, focused shock wave therapy, low-intensity focused ultrasound pulsation and transcutaneous auricular vagus nerve stimulation.Conclusions: NIBI techniques present numerous advantages such as being painless, safe and inexpensive; having adjustable parameters and targets; and having broad development prospects in treating DOC patients.

The clinical effect of vagus nerve stimulation in the treatment of patients with a minimally conscious state

Objective:

Vagus nerve stimulation (VNS) has recently been used in neurorehabilitation and the recovery of consciousness based on its effects on cortical plasticity. The aim of this study was to examine the therapeutic effects of VNS on patients with a minimally conscious state (MCS).

Methods:

All patients included in the study were assessed more than 5 months after injury and were receiving regular rehabilitation at our hospital from August 2018 to October 2019. Ten patients diagnosed with MCS by Coma Recovery Scale-Revised (CRS-R) test who underwent VNS surgery were enrolled. The scores on CRS-R evaluation at baseline (before VNS implantation) and 1, 3, and 6 months after VNS treatment were recorded. The stimulation parameters were chosen according to a previous study. All clinical rehabilitation protocols remained unchanged during the study. Furthermore, safety was assessed by analyzing treatment-emergent adverse events (TEAEs).

Results:

No significant improvement in the total CRS-R scores at the end of the 1-month follow-up was observed (p > 0.05). After 3 months of stimulation, a significant difference (p = 0.0078) was observed in the total CRS-R scores compared with the baseline. After 6 months of VNS treatment, CRS-R assessments showed a continuous significant improvement (p = 0.0039); one patient emerged from the MCS and recovered functional communication and object use. Interestingly, one item of CRS-R scores on visual domain was sensitive to VNS treatment (p = 0.0039). Furthermore, no serious adverse event occurred throughout the study.

Conclusion:

This exploratory study provides preliminary evidence suggesting that VNS is a safe and effective tool for consciousness recovery in patients with MCS.