Structural vs. metabolic cause of coma

[Basch]

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Hello comrades, this is my first post o this forum and I have a question regarding the definitions of structural and metabolic causes of coma (or loss of conciousness in general). If this is posted in the wrong place please let me know.

What is the exact definition of structural and metabolic causes? Everwhere I can read that this and that belong to one category or the other. But I can't find the definitions anywhere!

Please help me out,
Medical student in Sweden

 

[danielmd06]

Hello comrades, this is my first post o this forum and I have a question regarding the definitions of structural and metabolic causes of coma (or loss of conciousness in general). If this is posted in the wrong place please let me know.

What is the exact definition of structural and metabolic causes? Everwhere I can read that this and that belong to one category or the other. But I can't find the definitions anywhere!

Please help me out,
Medical student in Sweden

Try this:

http://www.amazon.com/Posners-Diagnosis-Stupor-Contemporary-Neurology71/dp/0195321316

This is the gold standard text on coma, and is actually not too hard a read. It is one of those books that is helpful for physicians from essentially any branch of medicine.

Structural means there is an anatomical reason for the coma, metabolic means that there is a metabolic derangement responsible for the coma. Both are quite broad terms.

 

[Basch]

Try this:

http://www.amazon.com/Posners-Diagnosis-Stupor-Contemporary-Neurology71/dp/0195321316

This is the gold standard text on coma, and is actually not too hard a read. It is one of those books that is helpful for physicians from essentially any branch of medicine.

Structural means there is an anatomical reason for the coma, metabolic means that there is a metabolic derangement responsible for the coma. Both are quite broad terms.

Thank's for your answer, it makes sense now. Actually I have read the first chapter in that book, however I could not find a good definition.

But what about ischemia, because of arterial occlusion for instance. That is a metabolic cause of tissue dysfunction in my opinion, i.e. oxygen insufficency. However it is classified as structural cause, as far as I am concerned. How can that be?

 

[danielmd06]

Thank's for your answer, it makes sense now. Actually I have read the first chapter in that book, however I could not find a good definition.

But what about ischemia, because of arterial occlusion for instance. That is a metabolic cause of tissue dysfunction in my opinion, i.e. oxygen insufficency. However it is classified as structural cause, as far as I am concerned. How can that be?

That is because the first chapter of the book is dedicated to the definition of consciousness (a great topic for those of us with philosophical tendencies), the neuroanatomy of sleep and wake (my favorite section of the whole book), and the general approach to the comatose patient.

The answer to what you just asked is in Chapter 3. A stroke is a clot or hemorrhage that results in a structural affectation of the brainstem tissue (or bilateral thalami or bilateral hemispheres). Hence, it's a mechanical/anatomical reason for coma...like herniation.

 

[neurodoc]

Try this:

Structural means there is an anatomical reason for the coma, metabolic means that there is a metabolic derangement responsible for the coma. Both are quite broad terms.

That's pretty much it, with a clarification that "anatomical reason" includes such things as traumatic injury to the brain, mass lesions (tumors, hematomas, etc.), infections and inflammatory lesions, and lesions due to compromise of vascular supply (basically "strokes"). These lesions will generally be apparent on neuroimaging studies (MRI and CT). In order for these sorts of lesions to cause coma, they will have to affect either both cerebral hemispheres or the brainstem reticular activating system.

"Metabolic" causes of coma include "systemic" disorders that do not produce visible damage to neural circuits, but which impair their "function.." Theoretically this impairment may be "reversible." Examples include hypoglycemia, drug toxicities, hypothermia ,hyperammoninemia, etc./I].