Indicators and criteria of consciousness: ethical implications for the care of behaviourally unresponsive patients

Task-based EEG and fMRI paradigms in a multimodal clinical diagnostic framework for disorders of consciousness

Disorders of consciousness (DoC) are generally diagnosed by clinical assessment, which is a predominantly motor-driven process and accounts for up to 40 % of non-communication being misdiagnosed as unresponsive wakefulness syndrome (UWS) (previously known as prolonged/persistent vegetative state). Given the consequences of misdiagnosis, a more reliable and objective multimodal protocol to diagnosing DoC is needed, but has not been produced due to concerns regarding their interpretation and reliability. Of the techniques commonly used to detect consciousness in DoC, task-based paradigms (active paradigms) produce the most unequivocal result when findings are positive. It is well-established that command following (CF) reliably reflects preserved consciousness. Task-based electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) can detect motor-independent CF and reveal preserved covert consciousness in up to 14 % of UWS patients. Accordingly, to improve the diagnostic accuracy of DoC, we propose a practical multimodal clinical decision framework centered on task-based EEG and fMRI, and complemented by measures like transcranial magnetic stimulation (TMS-EEG).

Making It Count - Tracing Signs of Consciousness and Potentiality in Severe Brain Injury in Denmark

Healthcare professionals use various technologies to evaluate and support patients who have suffered severe brain injuries. They integrate monitoring and sensory assessments into their clinical practice, and these assessments can have an impact on treatment decisions and prognostication. Responses from patients during different interactions are interpreted as "signs of consciousness" when considered contextually relevant. This study is based on anthropological fieldwork conducted in specialized Danish intensive care units, where we explore how signs of consciousness are made to count through practices of enactment. We ethnographically trace how the clinical concept of potential influences the interpretation of signs of consciousness as a complex biosocial practice based on the biomedical assumption that consciousness is a vital indicator of what makes a life. The article provides insights into the potential for recovery as an emergent biosocial practice and contributes to a broader discussion within medical anthropology of the moral landscapes of clinical and experimental borderlands.

Brain microstate spatio-temporal dynamics as a candidate endotype of consciousness

Consciousness can be defined as a phenomenological experience continuously evolving. Current research showed how conscious mental activity can be subdivided into a series of atomic brain states converging to a discrete spatiotemporal pattern of global neuronal firing. Using the high temporal resolution of EEG recordings in patients with a severe Acquired Brain Injury (sABI) admitted to an Intensive Rehabilitation Unit (IRU), we detected a novel endotype of consciousness from the spatiotemporal brain dynamics identified via microstate analysis. Also, we investigated whether microstate features were associated with common neurophysiological alterations. Finally, the prognostic information comprised in such descriptors was analysed in a sub-cohort of patients with prolonged Disorder of Consciousness (pDoC). Occurrence of frontally-oriented microstates (C microstate), likelihood of maintaining such brain state or transitioning to the C topography and complexity were found to be indicators of consciousness presence and levels. Features of left-right asymmetric microstates and transitions toward them were found to be negatively correlated with antero-posterior brain reorganization and EEG symmetry. Substantial differences in microstates' sequence complexity and presence of C topography were found between groups of patients with alpha dominant background, cortical reactivity and antero-posterior gradient. Also, transitioning from left-right to antero-posterior microstates was found to be an independent predictor of consciousness recovery, stronger than consciousness levels at IRU's admission. In conclusions, global brain dynamics measured with scale-free estimators can be considered an indicator of consciousness presence and a candidate marker of short-term recovery in patients with a pDoC.

Neural coding of autonomic functions in different states of consciousness

Detecting signs of residual neural activity in patients with altered states of consciousness is a crucial issue for the customization of neurorehabilitation treatments and clinical decision-making. With this large observational prospective study, we propose an innovative approach to detect residual signs of consciousness via the assessment of the amount of autonomic information coded within the brain. The latter was estimated by computing the mutual information (MI) between preprocessed EEG and ECG signals, to be then compared across consciousness groups, together with the absolute power and an international qualitative labeling. One-hundred seventy-four patients (73 females, 42%) were included in the study (median age of 65 years [IQR = 20], MCS +: 29, MCS -: 23, UWS: 29). Electroencephalography (EEG) information content was found to be mostly related to the coding of electrocardiography (ECG) activity, i.e., with higher MI (p < 0.05), in Unresponsive Wakefulness Syndrome and Minimally Consciousness State minus (MCS -). EEG-ECG MI, besides clearly discriminating patients in an MCS - and +, significantly differed between lesioned areas (sides) in a subgroup of unilateral hemorrhagic patients. Crucially, such an accessible and non-invasive measure of residual consciousness signs was robust across electrodes and patient groups. Consequently, exiting from a strictly neuro-centric consciousness detection approach may be the key to provide complementary insights for the objective assessment of patients' consciousness levels and for the patient-specific planning of rehabilitative interventions.

Cortico-thalamo-cortical interactions modulate electrically evoked EEG responses in mice

Perturbational complexity analysis predicts the presence of consciousness in volunteers and patients by stimulating the brain with brief pulses, recording EEG responses, and computing their spatiotemporal complexity. We examined the underlying neural circuits in mice by directly stimulating cortex while recording with EEG and Neuropixels probes during wakefulness and isoflurane anesthesia. When mice are awake, stimulation of deep cortical layers reliably evokes locally a brief pulse of excitation, followed by a biphasic sequence of 120 ms profound off period and a rebound excitation. A similar pattern, partially attributed to burst spiking, is seen in thalamic nuclei and is associated with a pronounced late component in the evoked EEG. We infer that cortico-thalamo-cortical interactions drive the long-lasting evoked EEG signals elicited by deep cortical stimulation during the awake state. The cortical and thalamic off period and rebound excitation, and the late component in the EEG, are reduced during running and absent during anesthesia.

Perspectives on consciousness in patients with disorders of consciousness from brain injury: group concept mapping study across clinic, research, and families

BACKGROUND

An effective healthcare system depends on clinic, research, and patient/relatives interactions. Such interactions may at their core be challenged by misalignments of concepts and the practices that constitute them. The concept of consciousness and what is experienced and understood as signs of consciousness in patients with severe acquired brain injury is one of these potential areas of misalignment. Different perspectives and experiences of consciousness are challenging the delivery of care and the high-stake decision-making process on the potential withdrawal of treatment. The enhanced uncertainties call for reflections on how key stakeholders perceive and identify consciousness in current clinical encounters and practice.

METHODS

The study empirically explores the actual experiences and conceptions of consciousness concerning patients with disorders of consciousness (DoC) from the perspectives of researchers, health professionals, and relatives of patients, to understand the challenges of the diversity of understandings of consciousness. Engaging the stakeholders by employing Group Concept Mapping methodology, the study developed a situated conceptual map, which reflects nuances and the importance of perspectives on and signs of consciousness.

RESULTS

Twenty-seven participants contributed to the generation of ideas, 14 took part in the structuring of statements and 10 took part in the validation meeting to interpret the cluster rating map. A total of 85 unique statements were identified and organized into six clusters: (1) Presence, (2) Intentional Activity, (3) Experience of self, (4) Participation in Social Interaction, (5) (Repeated) Response, and (6) Unspecific Reaction. The conceptual mapping demonstrates an extensive overlap in perspectives on consciousness among participants, prioritizing signs that are observable at the bedside.

CONCLUSIONS

The study provides a first step toward a future framework for the difficult process of decision-making concerning a segment of patients with DoC. The study highlights the importance of repeatable signs of consciousness observed at the bedside and the patient's ability to participate in social interactions, while also considering the importance of non-clinically observable signs of consciousness.