A new study shows that 42 really is the answer to life, the universe, and everything. OK, not really, but it does show that 42% of healthy brain activity is the minimum threshold for consciousness.
Disorders of consciousness, also referred to as coma when severe enough, can be a difficult situation to assess sufficiently to make reliable predictions about outcome. Part of the problem is that once someone is not able to maintain consciousness, we lose much of the neurological exam, and therefore it becomes more difficult to assess brain function other than to say that they are not conscious.
Types of coma
Two types of coma in particular are of interest: the persistent vegetative state, also called unresponsive wakefulness syndrome (UWS), and the minimally conscious state (MCS). Both are severe impairments of consciousness. In UWS, by definition, the patient may have sleep-wake cycles, open their eye, have roving eye movements, and grimace, but they do not have any interaction with their environment. They do not respond to voice, look at faces, or move in response to stimuli.
People in a vegetative state, usually as a result of brain trauma or anoxia (lack of oxygen) by definition have no signs of conscious awareness or activity. The definition, therefore, is based largely on the absence of evidence for consciousness.
Of course, arguments based upon the absence of evidence are only as compelling as the degree to which evidence has been properly searched for. In recent years technology has advanced to the point that our ability to detect the possible subtle signs of consciousness in those presumed to be vegetative has increased – mainly through functional MRI scans (fMRI) and electroencephalograms (EEGs).
There has been a steady stream of studies demonstrating that a small minority of patients thought to be vegetative actually display some signs of minimal consciousness. The latest such study was recently published in Neuroimage: Clinical by a research team from the University of Cambridge.
But let’s back up a bit first. Even prior to evaluating vegetative patients with fMRI and advanced EEG techniques, several studies showed that a detailed neurological exam specifically designed to detect the most subtle clinical signs of consciousness could find such signs in some patients who were diagnosed as being vegetative by more standard neurological exam. According to one study as many as 41% of patients diagnosed as vegetative were really minimally conscious, meaning they had subtle signs of consciousness, but still cannot wake up, converse, or act purposefully. (more…)
I don’t know. The mainstream media is doing a wonderful job sensationalizing this case, presenting it without skepticism. Some outlets are doing a good job of discussing the relevant issues – but they don’t have the information to have a meaningful discussion of this particular case. Details are tantalizing but thin.
The case is that of Rom Houben. The story was broke, as far as I can tell, by the Mail Online – yes, that is a huge red flag. It does not make the story wrong, it just doesn’t instill in me confidence in the reporting.
Mr. Houben was in a terrible motor vehicle accident 23 years ago and has been paralyzed ever since. His diagnosis has been PVS – persistent vegetative state. However, recently, we are told, his mother insisted on a neurological re-evaluation. This is actually quite reasonable, generally speaking (again, without knowing specific details of this case).