Epidural electrocorticography for monitoring of arousal in locked-in state.
Electroencephalography (EEG) often fails to assess both the level (i.e., arousal) and the content (i.e., awareness) of pathologically altered consciousness in patients without motor responsiveness. This might be related to a decline of awareness, to episodes of low arousal and disturbed sleep patterns, and/or to distorting and attenuating effects of the skull and intermediate tissue on the recorded brain signals. Novel approaches are required to overcome these limitations. We introduced epidural electrocorticography (ECoG) for monitoring of cortical physiology in a late-stage amytrophic lateral sclerosis patient in completely locked-in state (CLIS). Despite long-term application for a period of six months, no implant-related complications occurred. Recordings from the left frontal cortex were sufficient to identify three arousal states. Spectral analysis of the intrinsic oscillatory activity enabled us to extract state-dependent dominant frequencies at <4, ~7 and ~20 Hz, representing sleep-like periods, and phases of low and elevated arousal, respectively. In the absence of other biomarkers, ECoG proved to be a reliable tool for monitoring circadian rhythmicity, i.e., avoiding interference with the patient when he was sleeping and exploiting time windows of responsiveness. Moreover, the effects of interventions addressing the patient's arousal, e.g., amantadine medication, could be evaluated objectively on the basis of physiological markers, even in the absence of behavioral parameters. Epidural ECoG constitutes a feasible trade-off between surgical risk and quality of recorded brain signals to gain information on the patient's present level of arousal. This approach enables us to optimize the timing of interactions and medical interventions, all of which should take place when the patient is in a phase of high arousal. Furthermore, avoiding low-responsiveness periods will facilitate measures to implement alternative communication pathways involving brain-computer interfaces (BCI).
Division of Functional and Restorative Neurosurgery and Division of Translational Neurosurgery, Department of Neurosurgery, Eberhard Karls University Tuebingen Tuebingen, Germany ; Neuroprosthetics Research Group, Werner Reichardt Center for Integrative Neuroscience, Eberhard Karls University Tuebingen Tuebingen, Germany ; Department of Empirical Inference, Max Planck Institute for Intelligent Systems Tuebingen, Germany ; Department of Medical Physics, University Medical Center Utrecht, Utrecht University Utrecht, Netherlands.
Suzanne
S
Martens
Department of Computer Engineering, Wilhelm-Schickard Institute for Computer Science, Eberhard Karls University Tuebingen Tuebingen, Germany.
Michael
M
Bensch
Institute of Medical Psychology and Behavioral Neurobiology, Eberhard Karls University Tuebingen Tuebingen, Germany ; Institute of Psychology, University of Wuerzburg Wuerzburg, Germany.
Sebastian
S
Halder
Department of Empirical Inference, Max Planck Institute for Intelligent Systems Tuebingen, Germany.
Jeremy
J
Hill
Research Group Human Media Interaction, Department of Electrical Engineering, Mathematics and Computer Science, University of Twente Enschede, Netherlands.
Femke
F
Nijboer
Institute of Medical Psychology and Behavioral Neurobiology, Eberhard Karls University Tuebingen Tuebingen, Germany ; Health and Quality of life Unit, Fatronik-Tecnalia San Sebastian, Spain.
Ander
A
Ramos-Murguialday
Department of Empirical Inference, Max Planck Institute for Intelligent Systems Tuebingen, Germany.
Bernhard
B
Schoelkopf
Institute of Medical Psychology and Behavioral Neurobiology, Eberhard Karls University Tuebingen Tuebingen, Germany ; Istituto di Ricovero e Cura a Carattere Scientifico, IRCCS Ospedale San Camillo Venezia, Italy.
Niels
N
Birbaumer
Division of Functional and Restorative Neurosurgery and Division of Translational Neurosurgery, Department of Neurosurgery, Eberhard Karls University Tuebingen Tuebingen, Germany ; Neuroprosthetics Research Group, Werner Reichardt Center for Integrative Neuroscience, Eberhard Karls University Tuebingen Tuebingen, Germany.
Alireza
A
Gharabaghi
brain-computer interface; coma; consciousness; electrocorticography; epidural recording; locked-in state; neuroprosthetic devices