Sunday, January 08, 2012

Trigger point model deconstruction, models in general

Today I noticed a retweet from a (Spanish, by the look of things) twitterer,  @argoicoechea, who keeps a blog (Goicoechea arturo, his own name, surname first. Here is his bio). 

(Thank you, Chome browser, for making translation so darn simple.) 

What caught my eye about this tweet was that it was about trigger points. So I checked it out. Fibromyalgia, myofascial pain, tender points and trigger points: splitting or lumping?
Open access. I had not seen it yet, when I wrote Why I don't buy the idea that trigger points are in muscle, in July '11. (I don't retract anything I said in that blog post, just in case anyone is thinking I might.)

The paper is co-authored by a pair of researchers, one of whom represents the staunch mesodermalist assertion by the look of it (Bennett), and the other not so much (Goldenberg); it is written in debate-style, point-counterpoint format. 

ABSTRACT: Myofascial trigger points (MTPs) have long been a contentious issue in relation to fibromyalgia, and poorly defined pain complaints in general. Can MTPs be reproducibly identified? Do MTPs have valid objective findings, such as spontaneous electromyographic activity, muscle microdialysis evidence for an inflammatory milieu or visualization with newer ultrasound techniques? Is fibromyalgia a syndrome of multiple MTPs, or is focal muscle tenderness a manifestation of central sensitization? These issues are discussed with relevance to a recent paper reporting that manual palpation of active MTPs elicits the spontaneous pain experienced by fibromyalgia patients.

One of the papers cited by Goldenberg is by a few people I know online.
Lucas N, Macaskill P, Irwig L, Moran R, Bogduk N. Reliability of physical examination for diagnosis of myofascial trigger points: a systematic review of the literature. Clin J Pain.2009;25:80–89. doi: 10.1097/AJP.0b013e31817e13b6. [PubMed] [Cross Ref]

What is a "model"?
I think of a model as a thought bubble. The more variables it can account for, the bigger and shinier will be the bubble, the more opportunities it will provide more people (bigger 'surface area') to see through, to clarify their ideas of physical existence. 
Stephen Hawking, who just celebrated his 70th birthday in spite of having had ALS for decades, is quoted as saying,  “A model is a good model if first it interprets a wide range of observations in terms of a simple and elegant model, and second if the model makes definite predictions that can be tested, and possibly falsified, by observation.”    

So, here's the thing: a model that posits muscles as being bad guys and giving rise to "pain" is a poor model. Problems with the model include:
1. It was built on palpation! 
2. The palpators who push the current muscle (mesodermal derivative) model either deliberately ignored highly innervated custis/subcutis they were palpating through, and therefore didn't explain how they could subtract it as a freakishly unconstrainable confounding variable (bad on them) or else never thought to include it in the first place (still bad on them, but perhaps a bit more forgivable). 
3. Its perpetuators still refuse to consider that the nervous system itself is a probable confounding variable, or how to constrain it (probably because they can't (!) so they keep hoping no one notices. Hey! I notice!) 
4. As Goldenberg points out, interrater reliability is a problem. It stands to reason it would be; unless and until palpators from any school of thought figure out someday how to remove the blubber layer, with all its embedded cutaneous neural structure and unpredictable fractal nervous system qualities which derive from the nervous system's own strong opinions about protecting its organism in each and every moment from exteroceptive environmental threat, models built on palpation only are doomed to be consigned to that category known as belief systems or pseudoscience. The only other way to study sore spots via palpation, in an honest way, would be to include that layer.  
5. Goldenberg: "Just like fibrositis and fibositic nodules have become historical curiosities, MTPs will eventually be discounted as discrete pathologic abnormalities in the muscle." 

I see this image: a triggerpointer injector or investigator who insists trigger points are caused by muscle misbehaviour or pathology sits up on top of a silo, his "model", high and dry, eyes covered by blinkers and ears stuffed by fingers, while a big wet tsunami of neuroscience and biopsychosocial investigation of nociception and pain swells and surges around him. As long as he can artificially control the height of the silo upon which he is perched, by adding more "research" purporting his pet model, the wet won't touch him. But man oh man, that silo will rot away one of these days, and he'll fall in. 


Carlos said...

Arturo is a famous neurologist here in Spain. You should check his books about migraine.

Nice post, by the way :)


kevin minney said...

There is more to TRPs than merely palpatory evidence.Elsevier published a peer demonstarting biochemical signatures of Trigger Point using site-specific biochemical analysis:
Uncovering the biochemical milieu of myofascial
trigger points using in vivo microdialysis:
An application of muscle pain concepts to
myofascial pain syndrome
Jay P. Shah, MD
, Elizabeth A. Gilliams, BA

Here's the url:

Diane Jacobs said...

Thank you kevin: I must point out that even Shah admits that no actual proof exists that:
1. trigger points exist
2. in muscles
3. or cause pain

It's all correlative. Correlation is not causation.

Inés said...

Hi there,

I just wanted to let you know that Arturo Goicoechea's blog is also available in English (or at least some of his most popular entries). His bio is in English too, there.

Here you go, just in case you'd like to take a look at it: