Well Liège has made it into the news again!
The Coma Science Group here at our hospital, working with other centres,
has published another significant study of persistent disorders of consciousness. It’s worth having a look at this; in a subsequent post we’ll look at another very important paper by these researchers. I’ll also place these reports into some kind of context in terms of Michael Schumacher’s situation (or more correctly, presumed situation).
First a link to an article about today’s study:
And a link to the article itself:
Remember how we said that the vegetative state is defined as a state where the patient shows signs of wakefulness (notably open eyes) without behavioural responsiveness (as a marker of consciousness or awareness). Because of the emotionally laden and ambiguous nature of the word “vegetative”, some, including the Coma Science Group, prefer to use the term “unresponsive wakefulness syndrome” (henceforth UWS) for this state.
The key in differentiating a patient with unresponsive wakefulness syndrome from a minimally conscious state is the presence in the latter of fluctuating signs of awareness, with consistent but intermittent appropriate responses to stimuli.
Distinguishing these states can be difficult, but is absolutely crucial, medically, socially, ethically and therapeutically. A patient who is genuinely in a UWS, has, by definition, no self awareness. No voices are recognised, no sensation of hunger, none of pain, none of thirst. This is why clinicians caring for patients in a UWS are authorised almost everywhere to withdraw medical support, if and when appropriate, (including food and water – remember this is not cruel because there is no hunger or thirst perceived) from UWS patients. This is not the case once the patient has demonstrated any consciousness at all. Prognostically, as we’ve mentioned previously, persistence of a clinically correctly diagnosed (and that’s the point here) UWS for one year after the inciting trauma pretty much means any meaningful recovery is impossible. On the other hand, a minimally conscious state raises the possibility of continued progress.
Unfortunately, it can sometimes be remarkably difficult to show conclusively what state the patient is in. The problem is double.
First of all, there is the fluctuating nature of awareness. Episodes of interaction can appear randomly, or might be associated with a certain time of day, the presence of certain people, etc. The key is to do sufficient evaluations, sufficiently often, to reliably ascertain what the patient’s best level of awareness is.
Second, let’s remember that these patients have suffered devastating brain damage, whether caused by trauma (as is the case with Michael), infections, massive strokes, global anoxia, etc. This means that these patients will almost always have severe restrictions in their ability to show their responses to external (and internal) stimuli – spastic limbs which preclude reliable movements, visual or auditory deficits, etc.
Because of this, current guidelines for the management of patients with prolonged disorders of consciousness are becoming more and more insistent as to the FREQUENCY and QUALITY of the evaluations that are done. Standardised measurement scales are used, and the training necessary to administer them are well defined. Despite this, doubt remains at the edges between the diagnoses. Help is clearly needed to reliably diagnose the presence of these difficult-to-demonstrate degrees of awareness.
The study published today is an attempt to validate the use of imaging techniques, in addition to clinical evaluation, to help determine whether a patient is or is not AWARE.
Steve’s study looked at the ability of two imaging techniques, FDG PET scanning and fMRI imaging, to help distinguish between UWS and minimally conscious states. FDG PET images show brain areas that are actively using glucose. This is known to correlate with activity in those same areas. FDG PET images show the pattern of brain activity at rest. On the other hand, fMRI images look for use of oxygen in the brain. It is particularly useful to do when asking the subject to do a mental task – whether visualising something, imagining something, or DOING something moving fingers, pressing buttons, etc).
It is also known with high confidence that certain brain areas show normal activity in normally conscious patients, essentially no activity in UWS patients, and intermediate (but significantly reduced) activity in patients who are minimally conscious.
This study looked at the reliability of using activity in these areas to help confirm the diagnosis made clinically, and to help determine the patient’s prognosis.
Briefly, the study showed that FDG PET imaging is highly correlated with a previously validated (and widely if not universally used) clinical scoring scale. Importantly, one third of patients (13 of 41) diagnosed clinically as being in a UWS were shown by FDG PET to have activity in centres associated with awareness. Over the next year, nine of these 13 patients (remember, they were classified clinically as UWS!) had moved “up” to a clinical diagnosis of minimal consciousness or better, while of those with an imaging “confirmation” of UWS had terribly dismal outcomes. Of these 26 patients, 35% were still unconscious after one year . . . and 56% were dead. This shows that these images may well sensitively show the possibility of awareness, and seem to contain the same prognostic information that a clinical diagnosis of minimally conscious state contains. Further the numbers track what I’ve said in previous posts in terms of prognosis.
It is absolutely vital that we understand what the study didn’t show. It did NOT show that these 32% of patients were aware, or conscious. It showed that these patients, who clinically were felt to be unconscious, “had cerebral activity compatible with consciousness” (the authors’ words). But importantly, these patients had significantly better CLINICAL courses subsequently than those in whom PET confirmed an absence of activity compatible with consciousness.
Conclusion: it’s looking like at some point in the not distant future FDG PET imaging may well be a standard test in addition to clinical scoring, to determine whether awareness is or is not present in patients with disorders of consciousness. Remember: 1) it’s not yet fully validated, meaning more research is necessary before making this a standard tool with fully accepted statistical notions of reliability and validity; 2) until it IS validated, it remains a research tool.
Implications for Michael Schumacher
Actually, to the extent that Michael has been reliably shown clinically to have signs of awareness/consciousness (this would appear to be the case based on direct quotes of Sabine Kehm), this type of imaging would have no real utility, as a diagnosis of minimally conscious state would then have been made clinically. On the other hand, my next post will deal with another paper by our Coma Science Group, one with fascinating clinical and even philosophical implications.