By Dave Andrusko
Dr. Steven Laureys, one of the co-authors of the Lancet study
In recent years a number of ingenious studies have demonstrated that many patients in a so-called “Persistent Vegetative State” (PVS) have been misdiagnosed and that some actually in a PVS are consciously aware. More fascinating and suggestive evidence to buttress this comes from a study just published online hours ago.
The authors of “Bedside detection of awareness in the vegetative state: a cohort study” begin by noting that up to 43% of patients diagnosed to be in a PVS were discovered not to be when assessed by experienced teams. But that’s not where it ends. “A further subset of conscious patients could exist who are undetected even after extensive clinical investigations in specialized centers.” Such is the conclusion of the study that appears in the prestigious British medical journal the Lancet.
For both reasons of cost and physical stress to the patients, it is not always practical to use functional MRI studies. What to do? These researchers used EEG (electroencephalography) at the bedside.
Referring to patients assessed in two European centers who meet the ‘vegetative’ criteria, the authors conclude, “These findings confirm that a population of patients exists who meet all the behavioral criteria for the vegetative state, but nevertheless retain a level of covert awareness that cannot be detected by thorough behavioural assessment.”
Specifically, the teams assessed 16 patients diagnosed as “vegetative” and12 healthy “controls” at a center in Cambridge, UK, and a center in Belgium. All were directed to imagine that they were making a fist and wiggling toes.
They found that three of the 16 (or 19%) of the “vegetative” patients “could repeatedly and reliably generate appropriate EEG responses similar to those of the conscious controls,” according to the study’s authors. Put a slightly different way (as a commentary that accompanied the article put it), these patients “could generate EEG responses to two commands involving motor imagery, although the patient were otherwise behaviorally unresponsive.”
As the eight authors explain, this finding comes on top of previously published studies using more complex and less readily available functional magnetic resonance imaging technology that demonstrated some patients in a “vegetative” state, when instructed to imagine they were playing tennis, generated brain waves comparable to those of healthy “controls.”
As helpful as the study is there is an important caveat. While the Lancet study shows that EEGs could detect signs of consciousness in patients who had been diagnosed as “vegetative,” it does not follow that such patients are definitely unconscious if EEGs do not detect these signs.
As the study itself notes, the fact that the EEG did not pick up these signs of consciousness in 25% of the healthy and aware patients (the “controls”) “shows unequivocally that a null EEG outcome does not necessarily indicate an absence of awareness.”
Burke J. Balch, director of NRLC’s Powell Center for Medical Ethics, commented, “Many patients, probably thousands, have had their food and fluids cut off and died, based on what we now know may well have been mistaken assumptions that they had lost all capacity for consciousness. The Lancet EEG study, together with earlier functional MRI studies, holds out the hope that we may develop ways to communicate with aware patients who have routinely been diagnosed as ‘vegetative,’ much as today eye movements and blinks are used to communicate with some patients with paraplegia.”
Balch added, “Just as what were once generally accepted mental health diagnoses of ‘idiot’ and ‘moron’ have long been dropped from standard medical vocabulary, it is to be hoped that these studies will help lead to abandonment of the dehumanizing and inaccurate term ‘vegetative’ as an acceptable medical diagnostic term.”
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