Discovering Awareness in Vegetative State Patients: What to Do Next?

    “Is he still there, somewhere we can’t reach?” For many people whose loved ones are in a vegetative state, this might be one of the most asked questions. For doctors and researchers studying human consciousness, this is always a hard question to answer. Thanks to the development in methods of neuroimaging, we are now able to detect awareness in some patients who used to be thought of having no consciousness. Furthermore, these advanced techniques also indicate revision in medical terminology and the care of those patients in a vegetative state.

    The definition of “vegetative state” varies by technical or laymen’s usage, and by legislative concerns in different countries.  A definition widely recommended by medical practitioners these days is that patients in a vegetative state (VS) show no awareness of self and the environment, but have sleep-awake cycle, as well as complete or partial functions of hypothalamus and the brain-stem. (1) There are some characteristics that distinguish vegetative state with other consciousness disorders such as coma and minimally conscious state. Unlike patients in a coma who are unconscious and “sleeping”, VS patients appear to be “awake”. They may automatically reflect to stimuli, occasionally move their bodies, or even smile and cry. However, in contrast with patients in a minimally conscious state (MCS), these movements all take place in the absence of awareness. As the name suggests, patients in a minimally conscious state preserve some consciousness, exhibiting contingent, inconsistent, but purposeful movements. (2) In other words, they are able to move “at their own will”, whereas VS patients move – if they move – without knowing it.

    Doctors also use more specific terms to describe different state of VS. In the US, a patient is diagnosed to be in a persistent vegetative state (PVS) if a series of tests shows that the chance for the patient to achieve functions higher than vegetative state is very unlikely. A patient may also be established to be in permanent vegetative state, if the doctors envision his state to be irreversible. However, since we can only prove the presence but not the absence of consciousness, the diagnosis of VS and PVS patients is still a grey zone.  According to a previous study, the misdiagnosis of PVS is not uncommon. In retrospect, a considerable number of patients are actually able to communicate but misdiagnosed as PVS due to the limitation of diagnostic approaches in the past (3). Such a situation seems to be an implication of the question underlying the diagnosis of vegetative state: “Is it possible that the person is still there, but somehow locked in his broken body, so we can’t find him?”

    In February 2010, a report posted on New England Journal of Medicine by Monti et al. draws people’s attention to this question again. With the help of functional Magnetic Resonance Imaging (fMRI), scientists are able to “communicate” with 5 of 54 patients who are diagnosed as being in PVS or MCS.  During the research, the patients are asked to perform two sets of mental tasks. First, the researchers instruct the patients to imagine they are playing tennis, and then imagine they are at home; the scan shows that several patients show brain activities in related areas. After that, the researchers let these patients associate the said tasks with yes or no, and answer the questions. In this set of experiment, one patient is able to answer questions with this technique (4).

     The results of the research show strong evidence that a small proportion of patients in PVS or MCS has some level of consciousness.  Although they appear to have no control over their bodies, their brains still preserve some ability to process questions, therefore they can “think”. Seeing the potential of this discovery, researchers conclude that, in the future, this method could help to address important clinical questions, such as determining whether analgesic agents should be administered by asking whether the patient can feel pain. Moreover, “with further development, this technique could be used by some patients to express their thoughts, control their environment, and increase their quality of life.” (4)

    Although impressed by the result, I don’t feel as optimistic as the researchers in the matter of employing fMRI as the “thoughts translator” for VS and MCS patients. This attempt would only add to the already hot ethical debates. For example, many people are concerned with pain relief for the terminal patients; some people think that it is justifiable to alleviate the pain even at the cost of the patients’ life span, but others may view it as unacceptable. Not all doctors agree to perform palliative sedation. Even with the verbal request by patients who are fully conscious and communicative, some medical decisions are still made in a way against the patients’ will. Although consciousness disorders are very different from terminal diseases such as cancer, the fate of their patient can be similar – most PVS patients die in 2-5 years (1). When it comes to clinical decision making, it is likely that the response of this very small proportion of patients who can only communicate through brain imaging would be considered not persuasive enough.

    In my opinion, instead of tackling the ethical and technical problems to enable these patients to administrate their care, it is more practical and important to reconsider the criteria of diagnosing persistent vegetative state, as well as the care of patients in a vegetative state.

    For many medical practitioners, it’s probably not easy to diagnose a patient as in PVS. Because of its implication in law, the diagnosis of PVS can greatly influence the future of a patient – if the family starts a petition, the court may support the withdrawal of nutrition and hydration, which will eventually terminate the patient’s life (5). Even from a technical perspective, the diagnosis is difficult – PVS patients are expected to have no prospective recovery, which is impossible to prove. And as the results of previous studies (3) suggest, the chance of misdiagnosis is actually rather high. With new techniques made available through time, we might find more patients who used to be thought as unconscious but turn out to be aware. In the report by Monti et al., two of the five patients show no voluntary movement according to the bedside assessment, suggesting that the current bedside assessment is not sufficient in determining the presence of awareness in patient (4). Therefore, if condition permits, clinicians should consult neuroimaging results before diagnosing a patient to be in PVS in the future.

    Since techniques such as fMRI are not currently available to every patient with severe consciousness disorders, I think we should also pay attention to the care of patients already diagnosed as in vegetative state. Patients can come into a vegetative state with various causes – acute brain injuries such as car accidents or stroke, degenerative and metabolic brain disorders such as Alzheimer syndrome, as well as nervous system malformations. According to different causes, the patients’ prospect of recovery varies greatly. Although most patients have poor chance of recovery after several months in vegetative state, patients who underwent acute traumatic head injuries sometimes are more likely to show improvement in consciousness. Therefore, when planning for the care of VS patients, doctors should take the cause and possibility of recovery into account. Those patients who newly enter vegetative state or have higher chance of recovery should be given priority if new evaluation techniques are available.

    The advanced neuroimaging techniques open a door for us to the unknown realm of human brain. With the discovery of the “hidden awareness” in the vegetative state patients, we are empowered and challenged in the study of consciousness. I believe that with further knowledge of the interaction between our bodies and brains, our definition of consciousness disorders such as vegetative state and the care of those patients will change accordingly.





References

1. The Multi-Society Task Force on PVS, . "Medical Aspects of the Persistent Vegetative State." New England Journal of Medicine 330. (1994): 1499-1508. Web. 23 Feb 2010. <http://content.nejm.org/cgi/content/full/330/21/1499>.

2. Giacino, J.T. et al. "The minimally Conscious State: Definition and Diagnostic Criteria." Neurology 58 (2002): 349-53. Web. 23 Feb 2010. <http://www.neurology.org/cgi/reprint/58/3/349>.

3. Andrews, K. et al. "Misdiagnosis of the Vegetative State: Retrospective Study in a Rehabilitation Unit." British Medical Journal 313.7408 (1996): 13-16. Web. 23 Feb 2010. <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2351462/?tool=pubmed>.

4. Monti, Martin M. et al. "Willful Modulation of Brain Activity in Disorders of Consciousness." New England Journal of Medicine 362. 579-89. Web. 23 Feb 2010. <http://content.nejm.org/cgi/content/short/362/7/579>.

5. Kovacs, Richard. "Vegetative State-Background and Ethics." Journal of the Royal Society of Medicine 90. (1997): 593-96. Web. 23 Feb 2010. <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1296667/pdf/jrsocmed00034-0009.pdf>.