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A new test for consciousness in ‘comatose’ patients
09 November 2011
Liège, University of
The Coma Science Group (CRCyclotron, University of Liège /Liège University Hospital), led by Dr Steven Laureys, has developed, along with its partners in London, Ontario, (Canada) and Cambridge (England), a portable test which will permit a simpler and less expensive diagnosis of ‘vegetative’ patients who still have consciousness, despite the fact that they do not have the means to express it. The researchers’ conclusions are published this week in The Lancet.
The desire to develop this simple test of consciousness, at the patient’s bedside, follows on from previous research carried out by the Coma Science Group. Professor Steven Laureys and his colleagues had in effect already demonstrated, in 2009, that 40% of so-called ‘vegetative’ patients had been badly diagnosed and that in reality they retained a certain degree of consciousness. Following on from this study Laureys’ team at the University Hospital of Liège, on the recommendation of the Federal Health Service, was able to prescribe the compulsory use of a specially designed scale of consciousness (the coma recovery scale), now used in every coma specialist centre in Belgium.
In 2010 the Coma Science Group researchers and their colleagues at Cambridge (England) made another fundamental breakthrough in showing that it was possible to communicate with ‘vegetative’ patients through the means of scanners whose technology was based on functional magnetic resonance imaging (fMRI). Classically, the clinical evaluation of coma always proceeded via a muscular response to a stimulus. This study showed that, thanks to fMRI, a doctor could detect traces of consciousness and even communicate with so-called ‘vegetative’ patients due to the fact that they mentally responded in an appropriate manner to a task suggested by the evaluator. Scientifically revolutionary, using functional magnetic resonance imaging in the evaluation of comas is nevertheless very expensive, and not every hospital is equipped with or has access to it.
The new test described this week in The Lancet should change this situation. ‘As doctors, we as a rule ask the patient to respond to a simple command, such as ‘pinch my hand,’ to assure us that the patient is conscious. When we obtain a response, everything is fine, but if we cannot detect a response that does not necessarily mean to say that the patient is unconscious. Sometimes he or she cannot move because injuries have affected the nerves, the spinal cord or the brain,’ explains Dr Laureys. ‘With our new test, we also ask patients to move their hand or their foot, but we no longer have confidence in the muscular response. We measure the activity of the motor cortex directly using electroencephalography (EEG), a cheaper method which is widespread throughout the hospital centres.’
‘That means that this portable test can be carried out in every health care centre and even at home!’ states Camille Chatelle, a neuropsychologist and one of the new study’s co-authors.
The activation of the motor cortex, highlighted in dark brown, is identical for a healthy subject and a ‘vegetative’ patient. © comascience.org ULg
Certain patients with severe traumatic damage can no longer control a single muscle, but the recording of the brain’s electrical responses (using high density electroencephalography – EEG) to simple demands (‘move your foot’ or ‘move your hand’) enables doctors to demonstrate that they are indeed conscious. © comascience.org ULg