Wanderings of the mind and signs of consciousness

Detecting residual consciousness in patients that are severely brain-damaged represents a major challenge from a medical and ethical point of view.  It is also a difficult task given the risk of misdiagnosis which is a constant threat to medical professionals. In collaboration with the Massachusetts Institute of Technology, the Coma Science Group of the University of Liege and University Hospital of Liege recently showed that resting state functional MRI scanning is an efficient tool for establishing the level of consciousness of brain-damaged patients who are incapable to communicate.

IRMf etat reposDeclaring the state of consciousness of severely brain-damaged patients who are incapable of communication remains a challenge for physicians. Clinical evaluation of these people is traditionally based on examination of their motor responses with the help of behavioural scales. Interestingly, these patients can be paralysed, deaf, blind, suffering from aphasia or attention deficit disorders, which may lead to an underestimation of their level of consciousness. According to a study published in 2009 in BMC Neurology (1), the risk of misdiagnosis has been estimated at 40%. Nevertheless, the systematic use of the “Coma Recovery Scale-Revised” (CRS-R), a standardised and sensitive behavioural scale developed in the US by Joseph Giacino at the New Jersey Neuroscience Institute and validated in French and Dutch by Caroline Schnakers and Steven Laureys of the Coma Science Group, reduced the percentage of misdiagnosis rate to 31%.

This figure is obviously far from satisfactory. Also, researchers have continuously been working on the development of objective, motor-independent control tools for detecting possible signs of consciousness which may be missed during clinical examination. For any given patient, distinguishing between the two conditions known as the vegetative state/unresponsive wakefulness syndrome (VS/UWS) and the minimally conscious state (MCS) is at the heart of the problem. At the same time, diagnostic errors may also concern patients in a locked-in syndrome (LIS). Indeed, LIS patients are trapped in a motionless body, which sometimes can lead to be mistakenly considered as unconscious or minimally conscious even though their level of consciousness is actually intact.

“This is a grey area, the boundaries between the two conditions VS/UWS and MCS are difficult to diagnose by merely examining the patient’s motor response. Hence, the obligation is to develop irrefutable objective consciousness markers. And this is especially true because a patient’s future prognosis, namely her/his chances of recovery, is more favourable in the case of the MCS”. In addition, treatments differ, because, while patients in a VS/UWS are oblivious to physical pain, patients in a MCS can still feel pain (2). Therefore, the administration of painkillers in cases where medical cares could be painful is highly recommended for patients in MCS.

Wandering mind

The minimally conscious state was demonstrated in 2002 by Joseph Giacino. It describes patients who are capable of following simple instructions in a “reproducible” way but still have fluctuating consciousness with regard to their environment.  For example, they may execute voluntary movements from time to time, smile at family members or follow a moving object with their eyes; nevertheless, they will never succeed in communicating their thoughts. Patients in a vegetative/non-responsive state, on the other hand, have no consciousness of the external world and can only make involuntary reflex movements. As such, the results of clinical examination of the VS/UWS patients often remain clouded in uncertainty as discussed above.

Complementary use of Functional Magnetic Resonance Imaging (fMRI and/or Positron Emission Tomography) has made it possible to reduce the number of misdiagnoses around twenty per cent. In this type of examination, patients are usually asked to follow simple instructions during which their brain activity is recorded. But these tools are costly, relatively inaccessible and non-portable, very sensitive to patients’ movements while in the scanner and are hindered by the time-scale required to acquire data.
In the meantime, many projects have focussed on the use of brain-computer interfaces based on electroencephalography (EEG) and event related potentials.

(1) Schnakers, C., Vanhaudenhuyse, A., Giacino, J. T., Ventura, M., Boly, M., Majerus, S., Moonen, G., & Laureys, S. (2009). Diagnostic accuracy of the vegetative and minimally conscious state: clinical consensus versus standardized neurobehavioral assessment. BMC Neurol, 9, 35.
(2) Boly, M., Faymonville, M.-E., Schnakers, C., Peigneux, P., Lambermont, B., Phillips, C., Lancellotti, P., Luxen, A., Lamy, M., Moonen, G., Maquet, P., & Laureys, S. (2008). Perception of pain in the minimally conscious state with PET activation: an observational study. Lancet Neurol, 7, 1013-1020.

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