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brain herniation

Wise Young wisey at nyc.pipeline.com
Wed Jul 19 11:46:56 EST 1995

In article <Pine.SUN.3.91.950717190202.23411A-100000 at meded.com.uci.edu>,
Neal Prakash writes: 
>does anyone know a good technique for preventing/reducing brain  
>herniation in rats? 
>i currently remove roughly a 4mm by 3mm window of parietal skull and then 

>peel back the dura. prior to skull removal i do a cm (cisterna magna)  
>punch. lately i seemed to be having more rapid herniation than usual. 
>any suggestions? 
In my experience, peeling back of the dura itself seems to contribute
significantly to the development of brain edema.  I don't know why but
certainly it seems to accelerate the process, just, as I am sure you know,
it seems to do so in humans.  One suggestion, if this does not interfere
with the experiment in any way, is to allow the brain to cool down or to
increase the level of anesthesia (reducing blood pressure).   Continuous
washing of the brain surface during the durotomy may also help although I
am not sure that this is not due to some local cooling of the brain. 
Theoretically, hemorrhage and blood products may contribute to release of
nitric oxide, prostaglandins, and other edemagenic substances.  Edema is
much less prominent when there is no hemorrhage. Incidentally, the fact
that you are lately having more rapid herniation may be related to ambient
room temperature and humidity during summertime... the brain is probably
not cooling off as much as it would be during winter time and dryer
weather.  What are you using to open the skull? Sometimes, drilling may
heat the brain underneath.  Even a 5 C increase in brain temperature
contributes significantly to the edema.  We use a hand-drill and rongeurs
only.  Incidentally, the swelling seems to be largely localized to the side
of the surgery rather than a generalized swelling.  I hope that this is

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