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Dissociations between spontaneous EEG features and the Perturbational Complexity Index in the minimally conscious state
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  • Silvia Casarotto,
  • Gabriel Hassan,
  • Mario Rosanova,
  • Simone Sarasso,
  • Chiara-Camilla Derchi,
  • Pietro Trimarchi,
  • Alessandro Viganò,
  • Simone Russo,
  • Matteo Fecchio,
  • Guya Devalle,
  • Jorge Navarro,
  • Marcello Massimini,
  • Angela Comanducci
Silvia Casarotto
University of Milan
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Gabriel Hassan
University of Milan
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Mario Rosanova
University of Milan
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Simone Sarasso
Università degli Studi di Milano
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Chiara-Camilla Derchi
Fondazione Don Carlo Gnocchi Onlus
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Pietro Trimarchi
Fondazione Don Carlo Gnocchi Onlus
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Alessandro Viganò
Fondazione Don Carlo Gnocchi Onlus
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Simone Russo
University of Milan
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Matteo Fecchio
Massachusetts General Hospital
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Guya Devalle
Fondazione Don Carlo Gnocchi Onlus
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Jorge Navarro
Fondazione Don Carlo Gnocchi Onlus
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Marcello Massimini
University of Milan
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Angela Comanducci
Fondazione Don Carlo Gnocchi Onlus

Corresponding Author:acomanducci@dongnocchi.it

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Abstract

The analysis of spontaneous EEG is a cornerstone in the assessment of patients with disorders of consciousness (DoC). Alterations in specific frequency bands have been reported, including a predominance of delta power in vegetative state/unresponsive wakefulness syndrome (VS/UWS) patients in contrast with a predominance of alpha activity in minimally conscious state patients (MCS). Although preserved EEG patterns are highly suggestive of consciousness even in unresponsive patients, moderately or severely abnormal patterns are difficult to interpret. Indeed, growing evidence shows that consciousness can be present despite either large delta or reduced alpha activity in spontaneous EEG. Quantifying the complexity of EEG responses to direct cortical perturbations (Perturbational Complexity Index; PCI) may complement the observational approach and provide a reliable assessment of consciousness even when spontaneous EEG features are inconclusive. To systematically test this hypothesis, we compared PCI to EEG spectral measures in the same population of MCS patients (n=40) hospitalized in rehabilitation facilities. We found a remarkable EEG background variability across MCS patients as compared to healthy controls and a non-negligible number of patients with predominant delta and highly reduced alpha power in spontaneous EEG. Conversely, PCI values invariably suggested a capacity for consciousness in all MCS patients, consistent with the presence of clearly discernible, albeit fleeting, behavioral signs of awareness. These results confirm that spontaneous EEG rhythms may dissociate from the actual capacity for consciousness and suggest that a perturbational approach can effectively compensate for this pitfall with practical implications for the individual patient’s stratification and tailored rehabilitation.
22 Mar 2023Submitted to European Journal of Neuroscience
23 Mar 2023Submission Checks Completed
23 Mar 2023Assigned to Editor
23 Mar 2023Review(s) Completed, Editorial Evaluation Pending
13 Apr 2023Reviewer(s) Assigned
05 Sep 2023Editorial Decision: Revise Major