Background to the 20 year coma recovery

When a man wakes up after a 20 year coma, you know that people are going to pay attention. Particularly after the Terry Schiavo business, I think it is important to add some facts to this debate as early as possible before it gets completely out of control.

So let's talk about this guy. In 1984, Terry Wallis has a car accident where he was thrown from his pickup. He goes into a coma. Despite his family's objections, it would appear he was misdiagnosed as being in a persistent vegetative state rather than a minimally conscious state:

But improvements in the care of patients could be made without putting every patient into a brain scanner, says Schiff. There is currently no system for even a bedside re-examination from 8 weeks after an initial diagnosis, despite the fact that "their whole prognosis might change", he says.

Wallis was frequently classified as being in a permanent vegetative state. Though his family fought for a re-evaluation after seeing many promising signs that he was trying to communicate, their requests were turned down.

"A careful bedside examination at 6 months [after the accident] would have unequivocally said he was not in a vegetative state," says Schiff. There is a much greater chance of a late recovery from a minimally conscious state, he adds, although such recoveries are still rare. "The Wallis case will force the issue," he believes.

What is the difference between a persistent vegetative state and a minimally conscious state? Here are the American Academy of Neurology's criterion for a persistent vegetative state:

-- No evidence of awareness of self or environment and an inability to interact with others;

-- No evidence of sustained, reproducible, purposeful, or voluntary behavioral responses to visual, auditory, tactile, or noxious stimuli;

-- No evidence of language comprehension or expression;

-- Intermittent wakefulness manifested by the presence of sleep-wake cycles;

-- Sufficiently preserved hypothalamic and brainstem autonomic functions to permit survival with medical and nursing care;

-- Bowel and bladder incontinence; and

-- Variably preserved cranial nerve (pupillary, oculocephalic, corneal, vestibulo-ocular, gag) and spinal reflexes.

The criterion for a minimally conscious state are different. Here is a chart comparing the physical signs of each (and another syndrome called locked-in syndrome). (Ed. The original link for this chart is dead. Here is a link to the appropriate paper.)

Click on image below for larger chart:


i-921601a491ef3ae0c1416e4ab9322331-chart.jpg

The key difference, as summarized in a quote from an article about the Terry Schiavo case, is "the difference...between autonomic activity and episodic conscious activity," said Fins.

To emphasize the point, there is a huge area of difference between someone who has essentially only the housekeeping functions in the brain and someone who -- for reasons metabolic or traumatic -- comes in and out of consciousness intermittently. It is very unfortunate that Terry Wallis was misdiagnosed in this case, because the prognosis for individuals with minimally conscious state -- while not fabulous -- is much better than for a persistent vegetative state. I just thought I would get the distinction out of the way early lest people go into a flurry of speculation about how all people in comas now have the possibility of recovery. Terry Wallis had a possibility of recovery because he had a condition that allowed for recovery. Terry Schiavo did not.

But what caused Mr. Wallis to go into a minimally conscious state; what about his disease allowed for the possibility of recovery? I have never looked at his chart, and it is difficult to tell from the article but it looks like he had Diffuse Axonal Injury:

To try and find out what was going on inside Wallis's brain, Nicholas Schiff and colleagues from the Weill Medical College of Cornell University in New York City, used a new brain imaging technique called diffusion tensor imaging (DTI). The system tracks water molecules and so reveals the brain's white matter tracts - akin to a wiring diagram. They combined this with more traditional PET scanning, to show which brain areas were active.

The team's findings suggest that Wallis's brain had, very gradually, developed new pathways and completely novel anatomical structures to re-establish functional connections, compensating for the brain pathways lost in the accident.

They found that new axons - the branches that connect neurons together - seemed to have grown, establishing novel working brain circuits.

Surprisingly, the circuits look nothing like normal brain anatomy. A lot of the damage had been to axons that passed from one side of the brain to the other, torn by the force of the accident. But Schiff says that new connections seem to have grown across around the back of the brain, forming structures that do not exist in normal brains. (Emphasis mine.)

The axons going from one side of the brain to another refers to the corpus callosum, and injuries to the corpus callosal axons is one relatively common problem resulting from torsion in car accidents. Diffuse Axonal Injury results from shearing of the axons when the head is rotated very rapidly. Axons are sort of like the telephone lines that connect neurons to one another. They are processes that neuron cell bodies grow in order to communicate with other neuron cell bodies, sometimes very far away in the body or brain. The corpus callosum is an area in the brain with a great many of these axons that are transversing from one side of the brain to the other.

i-2b05633bf827675e121f9c7deba2df2a-neuron.JPG

The fact that this is DAI as opposed to something else may explain why there was recovery in this case. We know that neurons in your brain very rarely divide, but under some circumstances axons can regrow -- provide the neuron cell body is intact. It is possible that if the damage were restricted solely to the axons and you waited long enough, they would just regrow back to their old targets. This appears to be what happened here.

What is extraordinary about this case is that such widespread rewiring is nearly unheard of. The classical belief is that in the central nervous system (CNS) -- as opposed to the peripheral nervous system (PNS) -- regrowth of axons is suppressed by a signaling pathway that is at least partially known (involving proteins like Nogo and Nogo-R). Under this system regrowth of this nature should not occur. Even more than that, it is remarkable that after the axons started growing they managed to find their original targets. The process of axon pathfinding is complicated and involves many signalling molecules that direct the axons to the right place. It is not what I would have expected that those signals would still be present in the brain of an adult.

In any case, it is OK to get excited about cases like this. The human body can do a lot more than we thought. It is important, however, to remember that most evidence suggests that normal brain regeneration is rather limited in scope.

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My husband was in a car crash August 2005. He sustained a right subdural hematoma with diffuse subarachnoid hemorrhage. The neurologist also used the term diffuse axonal injury. His most recent CT scan shows progressive encephalomalacia of the brain and loss of volume. The ventrical system is larger referred to as hydrocephalus ex vacuo. There is also evidence of areas of low attenuation sulci in both frontal lobes and bilateral frontal lobe damage. This story has given his father continual false hope. I think all of the facts should be given during the television broadcasts so that families with similar situations won't think this can happen to their loved one.

The possiblity of their loved ones being involved in a car accident is quite high, but the point of this blog it seems is to say that the recovery of said loved one is not as likely. Espcially if they suffer from certain types of injury where recovery simply is not possible.

By Benjamin Breen (not verified) on 21 Sep 2008 #permalink

Terry Wallis is a prove of natural brain healing but he failed to get more functions due to long perioud he passed as MCS. Look at another point.People who live long in coma,if they awaken they are not PVS or MCS, That is natural healing also. You can see maps of brain and reading but no body can say even a word about consciousness of a man in PVS or MCS state.Actually PVs or MCS are only signs and due to weakness and shock of brain injury these patients are unable to show their awareness.There shoud be new studies from the basic. I am here struggling in this field for my son Jawad Pasha who is improved as fully conscious but still without motor function. Family of another boy Muammad Hussain of Pishin Quetta Pakistan is also working on same lines and we hope to see better recovery in his case also.

By Anwer Kamal Pasha (not verified) on 07 Jul 2009 #permalink

forget the brain it sucks

By lindsey lohammers (not verified) on 12 Oct 2009 #permalink

I saw Mr. Wallis on a BBC World News report last night. Is he in fact communicating? What was shown was an assistant who appeared to be the one actually doing all the "communication". Mr. Wallis was providing a finger that was being moved around on the touch-screen by the assistant. In fact, it looked an awful lot like the "facilitated communication" for autistic children that proved to be nothing more than the facilitators doing all the communication. It will be interesting to see how this story develops.

By Whiskyjack (not verified) on 24 Nov 2009 #permalink

My mistake. The man I saw was Rom Houben, not this Mr. Wallis. Getting my "man-awakes-from-a-20-year-coma" stories mixed up.

By Whiskyjack (not verified) on 24 Nov 2009 #permalink

im interest in science that i study hard in science and all the subjects that was im looking in the internet or in my books and i study my lessons in school
:)

...........thanks............

By denisecel mari… (not verified) on 23 Jun 2010 #permalink

Hi,

Just wondering where you got your figure of a neuron from. I would like to use it in my thesis and wondering who to contact.

Cheers,

Tom