# Trismus - What exactly causes it?



## AeroClinician (Oct 25, 2013)

It seems like trismus (jaw clenching), results from multiple things. But does anyone understand the pathophysiology behind it? 

Most commonly I have seen it in head injuries, but have heard about it happening in other situations as well.


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## sir.shocksalot (Oct 25, 2013)

I couldn't tell you the exact pathophys for each etiology of trismus since you are correct in that a number of conditions can cause it. As far as a head injury goes, from what I've read/been told, is that as the brain swells and begins to herniate it can place pressure on the trigeminal nerve. The pressure on the nerve results in activation of the motor neurons and causes the involved muscles to contract and the jaw to clench shut. That's my understanding. I'm sure some more people can add more or correct me if I'm mistaken.


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## vasile (Oct 25, 2013)

Thats sound interesting,I wander if we have a trismus presentation with transtentorial herniation...


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## AeroClinician (Oct 25, 2013)

I can find a lot of threads on this website were people talk about seeing truisms in their patients. But I don't see anyone talking about the pathophysiology of it.


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## AeroClinician (Nov 2, 2013)

Can anyone direct me to were I can find more info on this? 

Thanks


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## mycrofft (Nov 3, 2013)

Since it is a symptom and not a disease or pathology, you will need to run down every cause for the "bigger picture". Sort of like looking up "fever" or "jaundice".

Some I know of: trigeminal injury, tetanus, seizure. I've seen it in psych meds potpourri overdose but unsure why. I think malignant hyperthermia also.


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## Carlos Danger (Nov 3, 2013)

Firehazmedic said:


> It seems like trismus (jaw clenching), results from multiple things. But does anyone understand the pathophysiology behind it?
> 
> Most commonly I have seen it in head injuries, but have heard about it happening in other situations as well.



It is a common finding in head injuries, and also malignant hyperthermia. Transient jaw rigidity is considered a normal response to succinylcholine in young pediatrics. There are also cases in the literature of severe idiopathic trismus in patients under anesthesia which was NOT associated with any other signs of MH.

As mycrofft say, the patho varies based on the cause. I do not know what causes it in children who receive sux.


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## AEMTstudent (Dec 1, 2013)

My question is: how do you ventilate someone presenting with trismus, who has sustained traumatic injury, due to an MVC?  Yourself and your partner are both licensed to deliver Basic Life Support services.


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## EMT B (Dec 2, 2013)

call for a medic and do the best you can with a couple NPAs


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## TheLocalMedic (Dec 2, 2013)

EMT B said:


> call for a medic and do the best you can with a couple NPAs



Calling for ALS may not do you any good…  Here we don't carry any paralytics so we cannot RSI, and I have had no luck in using Versed to relieve the trismus.  From what I understand, the amount of Versed I would need to use to achieve the relaxation you need is higher than our max dosage anyhow (20-30 mg).  The other issue with using that much Versed is causing hypotension and decreasing Cerebral Perfusion Pressure, which is already compromised by the swelling that is causing the trismus.  

Best bet for BLS is NPAs and making like a tree and getting the F out of there.  Even then, if they are already at the point where they've got trismus they're pretty well screwed anyway.  Pretty high mortality rate for a head injury severe enough to cause trismus.


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## AEMTstudent (Dec 2, 2013)

NPAs are contraindicated to a patient with head trauma or significant MOI (follow your scope) . Because of the patient's current state, you are unable to use any type of adjunct OPA/NPA/combi-tube,LMA.  ETT and cricothyroidomotomy is out of the question because it's out of your scope.  ALS might be an option, but what if you are rural and it is not.  I am trying to generate a discussion here.


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## TheLocalMedic (Dec 2, 2013)

Maybe NPAs are contraindicated for facial trauma, but a blunt closed head injury is a different story.  And many areas have moved away from nasal tubes and crics other than needle-crics.  And why wait for an ALS provider?  A medic isn't going to fix their problem, they need a surgeon.


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## Handsome Robb (Dec 2, 2013)

AEMTstudent said:


> NPAs are contraindicated to a patient with head trauma or significant MOI (follow your scope) . Because of the patient's current state, you are unable to use any type of adjunct OPA/NPA/combi-tube,LMA.  ETT and cricothyroidomotomy is out of the question because it's out of your scope.  ALS might be an option, but what if you are rural and it is not.  I am trying to generate a discussion here.



The contraindication of nasal tubes in head trauma comes from NG tubes breaking through an already fractured cribriform plate and ending up in the brain. Problem with an NG tube is that it has a stiff, blunt tip and a small diameter. An NPA is too flexible as well as being too large so it's not an issue.   

You're correct though, by the book they are generally contraindicated.

If I'm rural and not ALS or even am ALS but don't have RSI I'm calling for HEMS to meet me somewhere. 

Urban NPA(s) or do what you can with aggressive suctioning and without an adjunct and boogy p1 to the hospital. 

If I can't oxygenate, ventilate or intubate I'm cutting. Wait you said I can't do that.


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## Tigger (Dec 2, 2013)

AEMTstudent said:


> NPAs are contraindicated to a patient with head trauma or significant MOI (follow your scope) . Because of the patient's current state, you are unable to use any type of adjunct OPA/NPA/combi-tube,LMA.  ETT and cricothyroidomotomy is out of the question because it's out of your scope.  ALS might be an option, but what if you are rural and it is not.  I am trying to generate a discussion here.



Maybe facial trauma but this scenario sounds about perfect for an NPA.


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## 18G (Feb 2, 2014)

I think the benefit of controlling an airway and ventilating a patient outweighs the minimal risk of shoving an NPA into someones brain. This is more of a hypothetical that got carried away. There is some literature out there describing about the very low incidence and extremely rare nature of this. 

If a patient has trismus and ALS does not have RSI its a surgical airway or needle cric situation. It's the only option left. Waiting for a helicopter to RSI would probably kill the patient since they need intervention NOW. Depending on the cause of the trismus and breathing status you could consider a nasal intubation.


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## mycrofft (Feb 2, 2014)

18G said:


> I think the benefit of controlling an airway and ventilating a patient outweighs the minimal risk of shoving an NPA into someones brain. This is more of a hypothetical that got carried away. There is some literature out there describing about the very low incidence and extremely rare nature of this.
> 
> If a patient has trismus and ALS does not have RSI its a surgical airway or needle cric situation. It's the only option left. Waiting for a helicopter to RSI would probably kill the patient since they need intervention NOW. Depending on the cause of the trismus and breathing status you could consider a nasal intubation.



We have maintained trismus cases with active respiration by a side-lying position, suctioning the lower buccal cavity, and supp oxygen. Most people can breath through their teeth.

 Now, teeth plus vomitus…another matter.

Don't remember if I mentioned this, but we started suctioning a pt who went into trismus as we were working. He bit off the tip of the Yankauer suction handpiece and it was rattling around in his oropharynx the entire time.  h34r:


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