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Showing entries tagged coma.  Show all entries

December 3, 2011

Buried Alive: Finding cognizance in unresponsive patients


It's a horrible thought, one that undoubtedly haunts people's nightmares: the idea of being buried alive. The idea that someone might be taken against their will and forced, alive, into the depths of the earth, is terrifying. Personally, I have a similar but slightly altered phobia: asylums. The thought of being held against my will and, by physical or pharmaceutical restraints, forced to submission, scares the bejeebies out of me.

Many people in hospital rooms all over the world are facing a fate not unlike these scenarios. Over the years, evidence has accumulated that many of the people diagnosed as being in a persistent vegetative state, or coma, are at least somewhat conscious. That is, these people are trapped inside their own bodies - awake, but in such a state of unresponsiveness that they are thought to be in a coma! These people are not a small minority, either. In fact, as many as 43% of people diagnosed as vegetative are later reclassified as at least minimally conscious.

A new paper published in the November 10th issue of The Lancet outlines a very accessible new method for accurately diagnosing these people. Doctors used "bedside" electroencephalography (EEG) to look at the brains of sixteen vegetative patients. The doctors asked the patients to envision producing simple motor actions at precise times. Three of the patients "were found to be aware and capable of substantially and consistently modulating their EEG responses to command". The study was designed so that any response by the patients required higher order "top down" brain function - meaning that responsiveness was indicative of at least some level of cognizance.
This study is very important, not for it's novelty, but for it's practical implications. Functional magnetic resonance imaging (fMRI) has been used for a while to recognize cognizance in unresponsive patients. In fact, EEG has also appeared in the literature as recognizing cognition in individual unresponsive patients. This study is important in that the doctors used a group of patients (rather than a single patient) to show that EEG can be used as an effective replacement for fMRI.

For unresponsive patients, there are a number of potential hurdles that that make using fMRI difficult or impossible: cost, scanner availability, the physical stress associated with traveling to a suitably equipped fMRI facility, movement artifacts, and interference from metal implants (present in many brain damaged patients) are all serious hindrances to using fMRI. EEG, on the other hand, is much less expensive, is unaffected by metal implants and, possibly most importantly, can be done at the bedside. The method introduced in this study can both bring brain imaging to patients who do not have access, and can supplement or replace the current system of diagnosing a vegetative state.
Currently, vegetative state is diagnosed by a team of specialists who use the coma recovery scale-revised (CRS-R) to access the patient's auditory, visual, motor, oromotor, communication, and arousal functions. This method is highly subjective and prone to misdiagnosis. Each of the patients in this study, including the three cognizant patients, met the CRS-R requirements for vegetative state.

While the prospects of this study are exciting, there are limitations, say the authors. Of the twelve healthy controls in the study, only 9 (75%) were capable of producing brain activity that met the study's criteria for responsiveness. This means that, while using EEG can recognize cognizance, its failure to do so is not indicative of a lack of cognizance.

The authors of the study say that this method can lead to new technologies that allow the patient to interact with their environment and loved ones in meaningful ways. For some patients, this study might be the first step in regaining some form of freedom, some sort of escape from the prison of their bodies.


article link: http://www.sciencedirect.com/science/article/pii/S0140673611612245
Edited by      Kyle K. at 4:41 AM MST
Tags: coma, eeg, vegetative




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