Evoked and Event-Related Potentials as Biomarkers of Consciousness State and Recovery

Abstract

Summary: The definition of consciousness has been the subject of great interest for many scientists and philosophers. To better understand how evoked potentials may be identified as biomarkers of consciousness and recovery, the different theoretical models sustaining neural correlates of consciousness are reviewed. A multimodal approach can help to better predict clinical outcome in patients presenting with disorders of consciousness. Evoked potentials are inexpensive and easy-to-implement bedside examination techniques. Evoked potentials are an integral part of prognostic evaluation, particularly in cases of cognitive motor dissociation. Prognostic criteria are well established in postanoxic disorders of consciousness, especially postcardiac arrest but are less well determined in other etiologies. In the early examination, bilateral absence of N20 in disorder of consciousness patients is strongly associated with unfavorable outcome (i.e., death or unresponsive wakefulness syndrome) especially in postanoxic etiologies. This predictive value is lower in other etiologies and probably also in children. Both N20 and mismatch negativity are proven outcome predictors for acute coma. Many studies have shown that mismatch negativity and P3a are characterized by a high prognostic value for awakening, but some patients presenting unresponsive wakefulness syndrome also process a P3a. The presence of long-latency event-related potential components in response to stimuli is indicative of a better recovery. All neurophysiological data must be integrated within a multimodal approach combining repeated clinical evaluation, neuroimaging, functional imaging, biology, and neurophysiology combining passive and active paradigms.

Canonical Response Parameterization: Quantifying the structure of responses to single-pulse intracranial electrical brain stimulation

“…In the operating room, these are a realtime diagnostic electrophysiology that can dynamically reveal impending injury so the surgeon can stop an action before causing permanent injury. In the clinic and hospital setting, these can be used to diagnose brain function in coma (diminished level of consciousness) after anoxia or traumatic brain injury [45, 52, 53]. Parameterization would dramatically simplify the nuance required by the electrophysiological technician who assists in these surgical procedures.…”

“…ERPs have been studied exhaustively in EEG, ECoG, and MEG, to study sensation, perception, cognition, memory, and other aspects of brain function [37,[39][40][41][42][43]. Event-related potentials have been studied to understand injuries and diseases of the brain and spinal cord [44][45][46], and are also used intraoperatively to dynamically to study the function of the spinal cord and brainstem (e.g. somatosensory evoked potentials -SSEPs [47] and brainstem evoked auditory responses -BAERs [48]).…”

The Integration of Assistive Technology and Virtual Reality for Assessment and Recovery of Post-coma Patients With Disorders of Consciousness: A New Hypothesis

“…Neuropsychological procedures including event-related potentials such as P300 and/or mismatch negativity are also used to assess the responsiveness of patients with severe disorders of consciousness (Lancioni et al, 2009b , 2011 ). Thus, empirical evidences of P300 or mismatch negativity are usually viewed as basic signs of awareness or consciousness with meaningful implications for the recovery process (Estraneo et al, 2022 ; Pruvost-Robieux et al, 2022 ). Recent reviews (Pan et al, 2021 ; Aubinet et al, 2022 ) critically discussed the use of event-related potentials and emphasized the strengths to use multiple measures to enhance the significance of the findings (Calabrò et al, 2021 ).…”

Transcranial Direct Current Stimulation Improves Some Neurophysiological Parameters but not Clinical Outcomes after Severe Traumatic Brain Injury

“…Paradigms to detect consciousness by means of positron emission tomography (PET) functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) have been developed during the past two decades to supplement the clinical evaluation of DOC [10]. Neurophysiological tests (EEG and evoked potentials) are useful for assessing the degree of awareness especially in the difficult context of withdrawal of life-sustaining treatments [11]. In traumatic brain injury, brainstem auditory evoked potentials (BAEP) is a good prognostic indicator for traumatic brain injury, while the absence of all waves beyond wave 1 predicts an unpromising prognosis [12].…”