Unmasking Covert Language Processing in the Intensive Care Unit with Electroencephalography

Edlow, Brian L.; Naccache, Lionel

doi:10.1002/ana.26030

Cited by 14 publications

(9 citation statements)

References 35 publications

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“…99 A passive language-based paradigm was first demonstrated to have prognostic significance for acutely injured patients in 2021. 100,101 Sokoliuk and colleagues 100 found that the presence of EEG signatures corresponding to cortical processing of higher-level linguistic structures (i.e., sentences or phrases rather than single monosyllabic words) in acutely injured patients in the ICU correlated with higher GOSE scores at 3and 6-month follow-up (►Fig. 7).…”

Section: Stimulus-based Paradigmsmentioning

confidence: 99%

Conventional and Investigational Approaches Leveraging Clinical EEG for Prognosis in Acute Disorders of Consciousness

2022

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Prediction of recovery of consciousness after severe brain injury is difficult and limited by a lack of reliable, standardized biomarkers. Multiple approaches for analysis of clinical electroencephalography (EEG) that shed light on prognosis in acute severe brain injury have emerged in recent years. These approaches fall into two major categories: conventional characterization of EEG background and quantitative measurement of resting state or stimulus-induced EEG activity. Additionally, a small number of studies have associated the presence of electrophysiologic sleep features with prognosis in the acute phase of severe brain injury. In this review, we focus on approaches for the analysis of clinical EEG that have prognostic significance and that could be readily implemented with minimal additional equipment in clinical settings, such as intensive care and intensive rehabilitation units, for patients with acute disorders of consciousness.

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Section: Stimulus-based Paradigmsmentioning

confidence: 99%

Conventional and Investigational Approaches Leveraging Clinical EEG for Prognosis in Acute Disorders of Consciousness

2022

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“…Other 18 (7) single-photon emission computerized tomography, or functional MRI. The lack of access to these diagnostic tools in clinical settings is notable because part of the suggested definition of coma devised by the expert panel includes absence of cognitive motor dissociation, which is typically diagnosed with either functional imaging or quantitative EEG analyses [6,[35][36][37]. Although functional neuroimaging may be logistically challenging for patients who may not be medically stable for transport and may not be economically or technically viable at most sites, conversely EEG techniques for assessing covert consciousness may be more broadly available.…”

Section: Discussionmentioning

confidence: 99%

The Curing Coma Campaign International Survey on Coma Epidemiology, Evaluation, and Therapy (COME TOGETHER)

et al. 2022

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Background Although coma is commonly encountered in critical care, worldwide variability exists in diagnosis and management practices. We aimed to assess variability in coma definitions, etiologies, treatment strategies, and attitudes toward prognosis. Methods As part of the Neurocritical Care Society Curing Coma Campaign, between September 2020 and January 2021, we conducted an anonymous, international, cross-sectional global survey of health care professionals caring for patients with coma and disorders of consciousness in the acute, subacute, or chronic setting. Survey responses were solicited by sequential emails distributed by international neuroscience societies and social media. Fleiss κ values were calculated to assess agreement among respondents. Results The survey was completed by 258 health care professionals from 41 countries. Respondents predominantly were physicians (n = 213, 83%), were from the United States (n = 141, 55%), and represented academic centers (n = 231, 90%). Among eight predefined items, respondents identified the following cardinal features, in various combinations, that must be present to define coma: absence of wakefulness (81%, κ = 0.764); Glasgow Coma Score (GCS) ≤ 8 (64%, κ = 0.588); failure to respond purposefully to visual, verbal, or tactile stimuli (60%, κ = 0.552); and inability to follow commands (58%, κ = 0.529). Reported etiologies of coma encountered included medically induced coma (24%), traumatic brain injury (24%), intracerebral hemorrhage (21%), and cardiac arrest/hypoxic-ischemic encephalopathy (11%). The most common clinical assessment tools used for coma included the GCS (94%) and neurological examination (78%). Sixty-six percent of respondents routinely performed sedation interruption, in the absence of contraindications, for clinical coma assessments in the intensive care unit. Advanced neurological assessment techniques in comatose patients included quantitative electroencephalography (EEG)/connectivity analysis (16%), functional magnetic resonance imaging (7%), single-photon emission computerized tomography (6%), positron emission tomography (4%), invasive EEG (4%), and cerebral microdialysis (4%). The most commonly used neurostimulants included amantadine (51%), modafinil (37%), and methylphenidate (28%). The leading determinants for prognostication included etiology of coma, neurological examination findings, and neuroimaging. Fewer than 20% of respondents reported routine follow-up of coma survivors after hospital discharge; however, 86% indicated interest in future research initiatives that include postdischarge outcomes at six (85%) and 12 months (65%). Conclusions There is wide heterogeneity among health care professionals regarding the clinical definition of coma and limited routine use of advanced coma assessment techniques in acute care settings. Coma management practices vary across sites, and mechanisms for coordinated and sustained follow-up after acute treatment are inconsistent. There is an urgent need for the development of evidence-based guidelines and a collaborative, coordinated approach to advance both the science and the practice of coma management globally.

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“…Nevertheless, as stated above, without explicit report from the listener, the term “comprehension” may be an inference too far. Indeed, this challenge reflects the more general challenge of inferring consciousness without explicit report in disorders of consciousness ( Edlow and Naccache, 2021 ).…”

Section: Discussionmentioning

confidence: 99%

“…Note, however, as stated above, there is evidence that awareness is required for grouping visually presented individual words into larger linguistic units ( Rabagliati et al, 2018 ). Furthermore, the fact that high-level cortical tracking can be observed during passive listening is also a strength of the paradigm for use in unresponsive patients as it is entirely passive with low cognitive demands, and yet, it provides a valuable insight into the patient’s relative neurocognitive preservation ( Edlow and Naccache, 2021 ). Our results indicate first that sentence/phrase-rate tracking has relatively low cognitive demands and can be elicited during passive listening, and therefore is likely to have good sensitivity in unresponsive patients.…”

Section: Discussionmentioning

confidence: 99%

The Influence of Auditory Attention on Rhythmic Speech Tracking: Implications for Studies of Unresponsive Patients

Sokoliuk

Degano

Melloni

et al. 2021

Front. Hum. Neurosci.

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Language comprehension relies on integrating words into progressively more complex structures, like phrases and sentences. This hierarchical structure-building is reflected in rhythmic neural activity across multiple timescales in E/MEG in healthy, awake participants. However, recent studies have shown evidence for this “cortical tracking” of higher-level linguistic structures also in a proportion of unresponsive patients. What does this tell us about these patients’ residual levels of cognition and consciousness? Must the listener direct their attention toward higher level speech structures to exhibit cortical tracking, and would selective attention across levels of the hierarchy influence the expression of these rhythms? We investigated these questions in an EEG study of 72 healthy human volunteers listening to streams of monosyllabic isochronous English words that were either unrelated (scrambled condition) or composed of four-word-sequences building meaningful sentences (sentential condition). Importantly, there were no physical cues between four-word-sentences. Rather, boundaries were marked by syntactic structure and thematic role assignment. Participants were divided into three attention groups: from passive listening (passive group) to attending to individual words (word group) or sentences (sentence group). The passive and word groups were initially naïve to the sentential stimulus structure, while the sentence group was not. We found significant tracking at word- and sentence rate across all three groups, with sentence tracking linked to left middle temporal gyrus and right superior temporal gyrus. Goal-directed attention to words did not enhance word-rate-tracking, suggesting that word tracking here reflects largely automatic mechanisms, as was shown for tracking at the syllable-rate before. Importantly, goal-directed attention to sentences relative to words significantly increased sentence-rate-tracking over left inferior frontal gyrus. This attentional modulation of rhythmic EEG activity at the sentential rate highlights the role of attention in integrating individual words into complex linguistic structures. Nevertheless, given the presence of high-level cortical tracking under conditions of lower attentional effort, our findings underline the suitability of the paradigm in its clinical application in patients after brain injury. The neural dissociation between passive tracking of sentences and directed attention to sentences provides a potential means to further characterise the cognitive state of each unresponsive patient.

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Unmasking Covert Language Processing in the Intensive Care Unit with Electroencephalography

Cited by 14 publications

References 35 publications

Conventional and Investigational Approaches Leveraging Clinical EEG for Prognosis in Acute Disorders of Consciousness

Conventional and Investigational Approaches Leveraging Clinical EEG for Prognosis in Acute Disorders of Consciousness

The Curing Coma Campaign International Survey on Coma Epidemiology, Evaluation, and Therapy (COME TOGETHER)

The Influence of Auditory Attention on Rhythmic Speech Tracking: Implications for Studies of Unresponsive Patients

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