Normal Brain Response to Propofol in Advance of Recovery from Unresponsive Wakefulness Syndrome.
Up to 40% of individuals with unresponsive wakefulness syndrome (UWS) actually might be conscious. Recent attempts to detect covert consciousness in behaviorally unresponsive patients via neurophysiological patterns are limited by the need to compare data from brain-injured patients to healthy controls. In this report, we pilot an alternative within-subject approach by using propofol to perturb the brain state of a patient diagnosed with UWS. An auditory stimulation series was presented to the patient before, during, and after exposure to propofol while high-density electroencephalograph (EEG) was recorded. Baseline analysis revealed residual markers in the continuous EEG and event-related potentials (ERPs) that have been associated with conscious processing. However, these markers were significantly distorted by the patient's pathology, challenging the interpretation of their functional significance. Upon exposure to propofol, changes in EEG characteristics were similar to what is seen in healthy individuals and ERPs associated with conscious processing disappeared. At the 1-month follow up, the patient had regained consciousness. We offer three alternative explanations for these results: (1) the patient was covertly consciousness, and was anesthetized by propofol administration; (2) the patient was unconscious, and the observed EEG changes were a propofol-specific phenomenon; and (3) the patient was unconscious, but his brain networks responded normally in a way that heralded the possibility of recovery. These alternatives will be tested in a larger study, and raise the intriguing possibility of using a general anesthetic as a probe of brain states in behaviorally unresponsive patients.
School of Physical and Occupational Therapy, McGill University Montreal, QC, Canada.
Stefanie
S
Blain-Moraes
Department of Linguistics and Languages, McMaster University Hamilton, ON, Canada.
Rober
R
Boshra
Department of Anesthesia, McMaster University Hamilton, ON, Canada.
Heung Kan
HK
Ma
Department of Linguistics and Languages, McMaster University Hamilton, ON, Canada.
Richard
R
Mah
Department of Linguistics and Languages, McMaster University Hamilton, ON, Canada.
Kyle
K
Ruiter
Department of Anesthesiology, Washington University St. Louis, MO, USA.
Michael
M
Avidan
Department of Linguistics and Languages, McMaster University Hamilton, ON, Canada.
John F
JF
Connolly
Department of Anesthesiology, University of Michigan Ann Arbor, MI, USA.
George A
GA
Mashour
anesthesia; consciousness; event-related potentials (ERPs); functional connectivity; propofol; unresponsive wakefulness syndrome/vegetative state (UWS/VS)