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Young MJ, Fecchio M, Bodien YG, Edlow BL. Covert cortical processing: a diagnosis in search of a definition. Neurosci Conscious 2024; 2024:niad026. [PMID: 38327828 PMCID: PMC10849751 DOI: 10.1093/nc/niad026] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 10/22/2023] [Accepted: 12/10/2023] [Indexed: 02/09/2024] Open
Abstract
Historically, clinical evaluation of unresponsive patients following brain injury has relied principally on serial behavioral examination to search for emerging signs of consciousness and track recovery. Advances in neuroimaging and electrophysiologic techniques now enable clinicians to peer into residual brain functions even in the absence of overt behavioral signs. These advances have expanded clinicians' ability to sub-stratify behaviorally unresponsive and seemingly unaware patients following brain injury by querying and classifying covert brain activity made evident through active or passive neuroimaging or electrophysiologic techniques, including functional MRI, electroencephalography (EEG), transcranial magnetic stimulation-EEG, and positron emission tomography. Clinical research has thus reciprocally influenced clinical practice, giving rise to new diagnostic categories including cognitive-motor dissociation (i.e. 'covert consciousness') and covert cortical processing (CCP). While covert consciousness has received extensive attention and study, CCP is relatively less understood. We describe that CCP is an emerging and clinically relevant state of consciousness marked by the presence of intact association cortex responses to environmental stimuli in the absence of behavioral evidence of stimulus processing. CCP is not a monotonic state but rather encapsulates a spectrum of possible association cortex responses from rudimentary to complex and to a range of possible stimuli. In constructing a roadmap for this evolving field, we emphasize that efforts to inform clinicians, philosophers, and researchers of this condition are crucial. Along with strategies to sensitize diagnostic criteria and disorders of consciousness nosology to these vital discoveries, democratizing access to the resources necessary for clinical identification of CCP is an emerging clinical and ethical imperative.
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Affiliation(s)
- Michael J Young
- Center for Neurotechnology and Neurorecovery, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, 101 Merrimac Street, Suite 310, Boston, MA 02114, USA
| | - Matteo Fecchio
- Center for Neurotechnology and Neurorecovery, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, 101 Merrimac Street, Suite 310, Boston, MA 02114, USA
| | - Yelena G Bodien
- Center for Neurotechnology and Neurorecovery, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, 101 Merrimac Street, Suite 310, Boston, MA 02114, USA
- Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Harvard Medical School, 300 1st Ave, Charlestown, Boston, MA 02129, USA
| | - Brian L Edlow
- Center for Neurotechnology and Neurorecovery, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, 101 Merrimac Street, Suite 310, Boston, MA 02114, USA
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, 149 13th St, Charlestown, Charlestown, MA 02129, USA
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Hermann B, Salah AB, Perlbarg V, Valente M, Pyatigorskaya N, Habert MO, Raimondo F, Stender J, Galanaud D, Kas A, Puybasset L, Perez P, Sitt JD, Rohaut B, Naccache L. Habituation of auditory startle reflex is a new sign of minimally conscious state. Brain 2020; 143:2154-2172. [PMID: 32582938 PMCID: PMC7364741 DOI: 10.1093/brain/awaa159] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 03/05/2020] [Accepted: 03/30/2020] [Indexed: 02/07/2023] Open
Abstract
Neurological examination of non-communicating patients relies on a few decisive items that enable the crucial distinction between vegetative state (VS)-also coined unresponsive wakefulness syndrome (UWS)-and minimally conscious state. Over the past 10 years, this distinction has proven its diagnostic value as well as its important prognostic value on consciousness recovery. However, clinicians are currently limited by three factors: (i) the current behavioural repertoire of minimally conscious state items is limited and restricted to a few cognitive domains in the goldstandard revised version of the Coma Recovery Scale; (ii) a proportion of ∼15-20% clinically VS/UWS patients are actually in a richer state than VS/UWS as evidenced by functional brain imaging; and (iii) the neurophysiological and cognitive interpretation of each minimally conscious state item is still unclear and debated. In the current study we demonstrate that habituation of the auditory startle reflex (hASR) tested at bedside constitutes a novel, simple and powerful behavioural sign that can accurately distinguish minimally conscious state from VS/UWS. In addition to enlarging the minimally conscious state items repertoire, and therefore decreasing the low sensitivity of current behavioural measures, we also provide an original and rigorous description of the neurophysiological basis of hASR through a combination of functional (high density EEG and 18F-fluorodeoxyglucose PET imaging) and structural (diffusion tensor imaging MRI) measures. We show that preservation of hASR is associated with the functional and structural integrity of a brain-scale fronto-parietal network, including prefrontal regions related to control of action and inhibition, and meso-parietal areas associated with minimally conscious and conscious states. Lastly, we show that hASR predicts 6-month improvement of consciousness. Taken together, our results show that hASR is a cortically-mediated behaviour, and suggest that it could be a new clinical item to clearly and accurately identify non-communicating patients who are in the minimally conscious state.
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Affiliation(s)
- Bertrand Hermann
- Institut du Cerveau et de la Moelle épinière - ICM, Inserm U1127, CNRS UMR 7225, F-75013, Paris, France
- Department of Neurology, Groupe hospitalier Pitié-Salpêtrière, AP-HP, F-75013, Paris, France
- Faculté de Médecine Pitié-Salpêtrière, Sorbonne Universités, UPMC Université Paris 06, Paris, France
| | - Amina Ben Salah
- Institut du Cerveau et de la Moelle épinière - ICM, Inserm U1127, CNRS UMR 7225, F-75013, Paris, France
| | - Vincent Perlbarg
- Sorbonne Université, CNRS, INSERM, Laboratoire d’Imagerie Biomédicale, LIB, F-75006, Paris, France
- BrainTale SAS, F-75013, Paris, France
| | - Mélanie Valente
- Institut du Cerveau et de la Moelle épinière - ICM, Inserm U1127, CNRS UMR 7225, F-75013, Paris, France
- Department of Clinical Neurophysiology, Groupe hospitalier Pitié-Salpêtrière, AP-HP, F-75013, Paris, France
| | - Nadya Pyatigorskaya
- Institut du Cerveau et de la Moelle épinière - ICM, Inserm U1127, CNRS UMR 7225, F-75013, Paris, France
- Faculté de Médecine Pitié-Salpêtrière, Sorbonne Universités, UPMC Université Paris 06, Paris, France
- Department of Neuroradiology, Groupe hospitalier Pitié-Salpêtrière, AP-HP, F-75013, Paris, France
| | - Marie-Odile Habert
- Sorbonne Université, CNRS, INSERM, Laboratoire d’Imagerie Biomédicale, LIB, F-75006, Paris, France
- Department of Nuclear Medicine, Groupe hospitalier Pitié-Salpêtrière, AP-HP, F-75013, Paris, France
| | - Federico Raimondo
- Institut du Cerveau et de la Moelle épinière - ICM, Inserm U1127, CNRS UMR 7225, F-75013, Paris, France
- Coma Science Group, GIGA Consciousness, University of Liège, Belgium
- Centre du Cerveau, University Hospital of Liège, Belgium
| | - Johan Stender
- Institut du Cerveau et de la Moelle épinière - ICM, Inserm U1127, CNRS UMR 7225, F-75013, Paris, France
| | - Damien Galanaud
- Institut du Cerveau et de la Moelle épinière - ICM, Inserm U1127, CNRS UMR 7225, F-75013, Paris, France
- Faculté de Médecine Pitié-Salpêtrière, Sorbonne Universités, UPMC Université Paris 06, Paris, France
- Department of Neuroradiology, Groupe hospitalier Pitié-Salpêtrière, AP-HP, F-75013, Paris, France
| | - Aurélie Kas
- Sorbonne Université, CNRS, INSERM, Laboratoire d’Imagerie Biomédicale, LIB, F-75006, Paris, France
- Department of Nuclear Medicine, Groupe hospitalier Pitié-Salpêtrière, AP-HP, F-75013, Paris, France
| | - Louis Puybasset
- Faculté de Médecine Pitié-Salpêtrière, Sorbonne Universités, UPMC Université Paris 06, Paris, France
- Sorbonne Université, CNRS, INSERM, Laboratoire d’Imagerie Biomédicale, LIB, F-75006, Paris, France
- Department of Anesthesia and Critical Care, Multidisciplinary Intensive Care Unit, Groupe hospitalier Pitié-Salpêtrière, AP-HP, F-75013, Paris, France
| | - Pauline Perez
- Institut du Cerveau et de la Moelle épinière - ICM, Inserm U1127, CNRS UMR 7225, F-75013, Paris, France
| | - Jacobo D Sitt
- Institut du Cerveau et de la Moelle épinière - ICM, Inserm U1127, CNRS UMR 7225, F-75013, Paris, France
| | - Benjamin Rohaut
- Institut du Cerveau et de la Moelle épinière - ICM, Inserm U1127, CNRS UMR 7225, F-75013, Paris, France
- Department of Neurology, Groupe hospitalier Pitié-Salpêtrière, AP-HP, F-75013, Paris, France
- Faculté de Médecine Pitié-Salpêtrière, Sorbonne Universités, UPMC Université Paris 06, Paris, France
- Department of Neurology, Columbia University, New York, NY 10027, USA
| | - Lionel Naccache
- Institut du Cerveau et de la Moelle épinière - ICM, Inserm U1127, CNRS UMR 7225, F-75013, Paris, France
- Department of Neurology, Groupe hospitalier Pitié-Salpêtrière, AP-HP, F-75013, Paris, France
- Faculté de Médecine Pitié-Salpêtrière, Sorbonne Universités, UPMC Université Paris 06, Paris, France
- Department of Clinical Neurophysiology, Groupe hospitalier Pitié-Salpêtrière, AP-HP, F-75013, Paris, France
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Benghanem S, Mazeraud A, Azabou E, Chhor V, Shinotsuka CR, Claassen J, Rohaut B, Sharshar T. Brainstem dysfunction in critically ill patients. Crit Care 2020; 24:5. [PMID: 31907011 PMCID: PMC6945639 DOI: 10.1186/s13054-019-2718-9] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 12/23/2019] [Indexed: 02/06/2023] Open
Abstract
The brainstem conveys sensory and motor inputs between the spinal cord and the brain, and contains nuclei of the cranial nerves. It controls the sleep-wake cycle and vital functions via the ascending reticular activating system and the autonomic nuclei, respectively. Brainstem dysfunction may lead to sensory and motor deficits, cranial nerve palsies, impairment of consciousness, dysautonomia, and respiratory failure. The brainstem is prone to various primary and secondary insults, resulting in acute or chronic dysfunction. Of particular importance for characterizing brainstem dysfunction and identifying the underlying etiology are a detailed clinical examination, MRI, neurophysiologic tests such as brainstem auditory evoked potentials, and an analysis of the cerebrospinal fluid. Detection of brainstem dysfunction is challenging but of utmost importance in comatose and deeply sedated patients both to guide therapy and to support outcome prediction. In the present review, we summarize the neuroanatomy, clinical syndromes, and diagnostic techniques of critical illness-associated brainstem dysfunction for the critical care setting.
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Affiliation(s)
- Sarah Benghanem
- Department of Neurology, Neuro-ICU, Sorbonne University, APHP Pitié-Salpêtrière Hospital, Paris, France
- Medical ICU, Cochin Hospital, AP-HP, Paris, France
| | - Aurélien Mazeraud
- Department of Neuro-ICU, GHU-Paris, Paris-Descartes University, Paris, France
- Laboratory of Experimental Neuropathology, Pastuer Institute, Paris, France
| | - Eric Azabou
- Department of Physiology, Clinical Neurophysiology Unit, APHP, Raymond Poincaré Hospital, University of Versailles Saint Quentin en Yvelines, Garches, France
| | - Vibol Chhor
- Department of Intensive Care Medicine, Saint-Joseph Hospital, Paris, France
| | - Cassia Righy Shinotsuka
- Intensive Care Unit and Postgraduate Program, Instituto Nacional de Câncer, Rio de Janeiro, Brazil
- D'Or Institute for Research and Education, Rio de Janeiro, Rio de Janeiro, Brazil
| | - Jan Claassen
- Department of Neurology, Neuro-ICU, Columbia University, New York, NY, USA
| | - Benjamin Rohaut
- Department of Neurology, Neuro-ICU, Sorbonne University, APHP Pitié-Salpêtrière Hospital, Paris, France
- Department of Neurology, Neuro-ICU, Columbia University, New York, NY, USA
- Institut du Cerveau et de la Moelle épinière, ICM, INSERM UMRS 1127, CNRS UMR 7225, Pitié- Salpêtrière Hospital, Paris, F-75013, France
| | - Tarek Sharshar
- Department of Neuro-ICU, GHU-Paris, Paris-Descartes University, Paris, France.
- Laboratory of Experimental Neuropathology, Pastuer Institute, Paris, France.
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Zasler ND, Aloisi M, Contrada M, Formisano R. Disorders of consciousness terminology: history, evolution and future directions. Brain Inj 2019; 33:1684-1689. [DOI: 10.1080/02699052.2019.1656821] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Nathan D. Zasler
- Concussion Care Centre of Virginia, LTD; Tree of Life Services, Inc., Richmond, Virginia, USA
- Department of Physical Medicine and Rehabilitation, Virginia Commonwealth University, Richmond, Virginia, USA
- Department of Physical Medicine and Rehabilitation, University of Virginia, Charlottesville, Virginia, USA
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Naccache L. Why and how access consciousness can account for phenomenal consciousness. Philos Trans R Soc Lond B Biol Sci 2018; 373:20170357. [PMID: 30061470 PMCID: PMC6074081 DOI: 10.1098/rstb.2017.0357] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/21/2018] [Indexed: 11/12/2022] Open
Abstract
According to a popular distinction proposed by the philosopher Ned Block in 1995, our conscious experience would overflow the very limited set of what we can consciously report to ourselves and to others. He proposed to coin this limited consciousness 'Access Consciousness' (A-Cs) and to define 'Phenomenal Consciousness' as a much richer subjective experience that is not accessed but that would still delineate the extent of consciousness. In this article, I review and develop five major problems raised by this theory, and show how a strict A-Cs theory can account for our conscious experience. I illustrate such an A-Cs account within the global workspace (GW) theoretical framework, and revisit some seminal empirical findings and neuropsychological syndromes. In this strict A-Cs perspective, subjective reports are not conceived as the mere passive broadcasting of information to the GW, but as resulting from a dynamic and active chain of internal processes that notably include interpretative and belief attribution stages. Finally, I list a set of testable predictions, of unsolved questions and of some counterintuitive hypotheses.This article is part of the theme issue 'Perceptual consciousness and cognitive access'.
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Affiliation(s)
- Lionel Naccache
- Department of Neurology, AP-HP, Groupe hospitalier Pitié-Salpêtrière, 75013 Paris, France
- Department of Neurophysiology, AP-HP, Groupe hospitalier Pitié-Salpêtrière, 75013 Paris, France
- Sorbonne Université, INSERM, U 1127, 75013 Paris, France
- Institut du Cerveau et de la Moelle épinière, ICM, PICNIC Lab, 75013 Paris, France
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