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Question about checking for brain life

chillzero

Penultimate Amazing
chillzero
Joined
Dec 11, 2002
Messages
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I'm reading one of my usual trashy crime thriller books, and came across something I hadn't heard of before, so i was hoping someone could explain. (I'm sorry if this is a really dumb question, by the way)

Two characters are taking about a person who has been taken off life support, as they were brain dead. During the discussion they mention checking pupil response, pain response, touching the eyeball; all of which I am aware of and understand the mechanisms as to why they are used to check for life responses.

They also mentioned putting water in the ear. That was a newer one on me. How does this work? I mean, people fall asleep in the bath even with water in their ears. Is there a definite, defined response to doing this, or is it just something else to try that might get a reaction? I would have thought it less ... sensitive/reliable ... than the eye tests?
 
Cold or warm water or air is irrigated into the external auditory canal, usually using a syringe. The temperature difference between the body and the injected water creates a convective current in the endolymph of the nearby horizontal semicircular canal. Hot and cold water produce currents in opposite directions and therefore a horizontal nystagmus in opposite directions
...
In comatose patients with cerebral damage, the fast phase of nystagmus will be absent as this is controlled by the cerebrum. As a result, using cold water irrigation will result in deviation of the eyes toward the ear being irrigated. If both phases are absent, this suggests the patient's brainstem reflexes are also damaged and carries a very poor prognosis
Click to expand...
http://en.wikipedia.org/wiki/Caloric_reflex_test
 
chillzero said:
I'm reading one of my usual trashy crime thriller books, and came across something I hadn't heard of before, so i was hoping someone could explain. (I'm sorry if this is a really dumb question, by the way)

Two characters are taking about a person who has been taken off life support, as they were brain dead. During the discussion they mention checking pupil response, pain response, touching the eyeball; all of which I am aware of and understand the mechanisms as to why they are used to check for life responses.

They also mentioned putting water in the ear. That was a newer one on me. How does this work? I mean, people fall asleep in the bath even with water in their ears. Is there a definite, defined response to doing this, or is it just something else to try that might get a reaction? I would have thought it less ... sensitive/reliable ... than the eye tests?
Click to expand...

V. S. Ramachandran talked about putting cold water in the ears of stroke patients who suffered from the delusion that they were perfectly healthy. I can't remember the name of the condition...the patients would make all kinds of excuses as to why they couldn't walk or tie their shoes just right now, but they would not admit that they were handicapped in any way.

Ramachandran found that cold water in the ear temporarily relieved them of this delusion.
 
Professor Yaffle said:
http://en.wikipedia.org/wiki/Caloric_reflex_test
Click to expand...

Thank you. :)
I really ought to remember to google or use Wiki before the forum, but usually I get good answer here and some extra info as well.


... ummm .... does that basically mean that the person's eyes look toward the ear if you squirt in some cold water?

I don't understand much of that text (like this: "the fast phase of nystagmus will be absent as this is controlled by the cerebrum."). :blush:
 
I wonder if it is related to the diagnostic test for benign positional vertigo which I had recently. In that condition there is some debris in the ear canal and if you lie with your head tilted back and turn your head to the side it moves the debris into the area where the hairs (I forget the technical word for them) are and sets off a vertigo episode, accompanied by vertical (I think, because it feels like you are spinning in that orientation) nystagmus.

ETA nystagmus is rapid movements of the eye - so a horizontal nystagmus would be rapid eye movements from centre to one side and back repeatedly with the direction depending on whether it is hot or cold water. And in comatose patients where the nystagmus is absent, yes, just a deviation of the eyes towards one side. And if even that doesn't happen, there's not much hope for you. It basically seems to be looking for different levels of reflex to see how far gone the brain is.
 
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chillzero said:
Thank you. :)
I really ought to remember to google or use Wiki before the forum, but usually I get good answer here and some extra info as well.


... ummm .... does that basically mean that the person's eyes look toward the ear if you squirt in some cold water?

I don't understand much of that text (like this: "the fast phase of nystagmus will be absent as this is controlled by the cerebrum."). :blush:
Click to expand...

I think it means saccades, which are fast, jurky movements of the eye. So the eye moves slowly over to the side of the head which has the cold water in, then there are saccades towards the other side. The directions are reversed with warm water.
 
aggle-rithm said:
V. S. Ramachandran talked about putting cold water in the ears of stroke patients who suffered from the delusion that they were perfectly healthy. I can't remember the name of the condition...the patients would make all kinds of excuses as to why they couldn't walk or tie their shoes just right now, but they would not admit that they were handicapped in any way.

Ramachandran found that cold water in the ear temporarily relieved them of this delusion.
Click to expand...

Interesting .... ok ... I was interested enough to remember to go to wiki first before asking.
http://en.wikipedia.org/wiki/Vilayanur_S._Ramachandran
but it doesn't seem to cover the same thing you are telling me about? Any other references (or did I miss it on that page?)?
 
Professor Yaffle said:
I wonder if it is related to the diagnostic test for benign positional vertigo which I had recently. In that condition there is some debris in the ear canal and if you lie with your head tilted back and turn your head to the side it moves the debris into the area where the hairs (I forget the technical word for them) are and sets off a vertigo episode, accompanied by vertical (I think, because it feels like you are spinning in that orientation) nystagmus.

<snip>
Click to expand...

Cilia.
 
Interesting side note...when I was looking up Ramachandran to make sure I was getting the spelling right, I noticed a list of testimonials from famous scientists, praising Ramachandran's work. One of them was Richard Dawkins, author of "The Blind Phantoms of the Brain".

I think they got two book titles mixed up.
 
Ivor the Engineer said:
I think it means saccades, which are fast, jurky movements of the eye. So the eye moves slowly over to the side of the head which has the cold water in, then there are saccades towards the other side. The directions are reversed with warm water.
Click to expand...

I think nystagmus is more pronounced than saccades, more like the rapid eye movements during the dream phase of sleep.

ETA: Ah here we go:

Physiologic nystagmus is a form of involuntary eye movement that is part of the vestibulo-ocular reflex (VOR). It is characterized by alternating smooth pursuit in one direction and saccadic movement in the other direction.
Click to expand...
http://en.wikipedia.org/wiki/Physiologic_nystagmus

So you're totally correct Ivor.

I used to work with a girl with congenital pathologic nystagmus - her eyes were constantly moving like that.
 
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So this test is used as part of the clinical diagnosis of brain death. Its based upon examing the mechanism for how we keep our eyes looking in the direction we want.

In normal circumstances if I turn your head slightly to one direction or the other, you can still continue to look straight ahead, or in any direction you choose - while we are awake and healthy the direction of our gaze is under our conscious control.

There are also unconscious controls of gaze, which arise from the brainstem - lower down in the nervous system. These controls act to keep our eye movements linked together to prevent double vision, and compensate for head movements to keep our gaze fixed. These act entirely involuntarily, almost like an automatic pilot.

Imagine you are examining a comatose patient, and you want to determine the location of the injury that has rendered them unsconscious - is it in the cerebrum, or lower down in the brainstem? If you hold their eyes open and move their head from side to side and their pupils remain looking straight ahead, this indicates that their "autopilot" or brainstem controls are functioning normally - there is just no conscious control.
If, on the other hand, their eyes move with the head - (this is called an absent occulocephalic reflex, or dolls eye response), then the brainstem has been damaged.

The cold water in the ear tests exactly the same thing, but gives a much stronger stimulus than head turning, which is why it is used as part of the diagnosis of brain death. Ice cold water is used, and any movement of the eyes over a 1 minute observation means the patient cannot be diagnosed brain dead - it doesn't mater in which direction the movement is.
 
Criticalist said:
The cold water in the ear tests exactly the same thing, but gives a much stronger stimulus than head turning, which is why it is used as part of the diagnosis of brain death. Ice cold water is used, and any movement of the eyes over a 1 minute observation means the patient cannot be diagnosed brain dead - it doesn't mater in which direction the movement is.
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Thank you for all that info!

So ... does this work even when the eyes are non-responsive to the other tests done specifically on them?
 
chillzero said:
Thank you for all that info!

So ... does this work even when the eyes are non-responsive to the other tests done specifically on them?
Click to expand...

Yes, it will still work. Part of deciding if someone is brain dead involves testing the cranial nerves - the nerves that come directly from the brainstem. The cold water test examines the function of cranial nerves III, IV, VI and VIII. The other tests that involve the eyes are the pupillary light test (to see if the pupils respond to light) and the corneal reflex (to see if the eyes blink when gently touched). These examine different nerves - II, III, V and VII. Its possible that the eyes may not respond to the light test but respond to the cold water test as different nerves are being tested. To declare someone brain dead all the tests must show no function.
 
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Yes, no argument there.:) Brain death itself is a fascinating concept as well - I'm also quite impressed with an author getting that much detail right. Sounds like a good book!
 
Criticalist said:
Yes, no argument there.:) Brain death itself is a fascinating concept as well - I'm also quite impressed with an author getting that much detail right. Sounds like a good book!
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It was ok. It's called Soul Murder by Daniel Blake.
I've read much more gripping thrillers, and I worked out the few twists in it in advance, but it wasn't objectionable.

Oh - in fact - the lead character is an atheist surrounded by very religious people, and he comes out of the whole story much stronger than the rest. Quite refreshing in that respect.
 
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