Sunday, September 23, 2007

Pain For Dummies - Part II

The Multidimensionality of Pain and the Biopsychosocial Model.

With the arrival of brain scanning techniques like fMRI and PET-Scans the Neurosciences really took off. Until a few years ago the brain was still just a black box doing mysterious things and the only clues we got as to it's inner workings was done by observing the output it produced.

That's why there are still some who think that there are pain fibres in the body or specific pain centers in the brain. Anatomy and all the other sciences had nothing else to work with and postulated their findings as the "only truth".

Today we know that pain is a multidimensional problem - it has biological causes and consequences, psychological components and acts itself out in a complex social environment.
It's not longer sufficient to draw a picture of a boy burning his foot and following a line to his brain that represents the pathway the pain travels to be a successful therapist.

In order to be able to treat pain - especially chronic pain conditions - you have to be aware of all the components of the pain experience. The best approach to date to describe this complex interplay of different fields and specialties is the so-called "Biopsychsocial Model" (of Health and Illness).

It postulates that in a lot of situations the pain itself isn't the biggest problem - but the way the person in pain or those around him/her perceive and deal with the pain. This goes all the way from family members who offer too much help to doctors and therapists who don't take the patient seriously and even society as a whole when it comes to things like sick leave and sick pay.

Let's look at some of the parts that make up the pain experience:
The biology is very complex - from nerves to neurotransmitters and even specific genes that make some people more likely to experience (chronic) pain.

These are the stages an acute trauma goes through:
Tissue is damaged - leading to local inflammation to initiate the healing response; the immune system is activated to combat infection, a general and short term stress response is activated to enable us to get away from the pain quickly and to prevent further damage.

In this case - acute pain - nociceptive signals are sent to the spinal cord that modifies these signals according to their importance and sends them up to the brain for further processing. At the spinal cord level reflexes kick in - stereotypical motor patterns to protect the limb or the body.

The brain - based on experience and the circumstances the trauma occurs in decides whether or not to "label" the incoming signals as "pain producing signals". If for instance you are in a serious car accident there are more important things than the abrasions or contusions you have - the brain is more concerned with your survival - hence people after serious injuries don't feel any pain - what we call "shock". The nociceptive signals are all there all right - as are the other responses your body initiated to repair the damage - but no pain - at least initially.

If all goes well the damage is eventually repaired, the stress response is shut of very quickly since it is only useful during the traumatic event itself, nociception stops and the pain goes away.

This short outline is already able to give us a lot of clues as to what and where things can go wrong after we have hurt ourselves. The most important thing however is that the biological part is only one piece of the pain experience. As we have seen it's not enough to have nociception - you need a brain to process that information; and if that brain decides to ignore the peripheral input it can do so. It can also decide to produce pain without nociception.

This is where the biopsychosocial model comes in - it recognizes that pain really is an experience that has different factors that contribute to it.

I think most people can relate to the fact that pain is especially painful after we have done something really really stupid - it hurts more because we are ashamed:


Pain For Dummies - Part I

or: what you always wanted to know about pain but were afraid to ask.

What's this pain thing all about then?

Well - acute pain has a lot of useful functions: it is a warning signal that draws our attention towards a damaged area (or to the potential of damage occurring in the future). It enables our brain to react even before we become aware of it. It protects us from doing more damage, and signals - by way of muscular action - other people that we have a problem in a specific part of our bodies (just think of the way you hold your arm when it hurts).

It also interferes with cognitive processes by altering Emotions and Mood - which is another way that other people can tell that there is something "wrong" with us. What good is pain if you can't communicate it to the world around you?

Some used to think that there is a pain center in the brain. But all the brain imaging studies done over the past 10 or more years show a different picture: pain processing centers are everywhere. Pain is a so-called multidimensional sensation - it's the unique combination of effects it has that makes it so powerful.
It invades every aspect of life - and vanishes just as quickly when the danger is gone.

The most dramatic way to show how important pain is in everyday life is in people who are born without the ability to feel pain (congenital insensitivity to pain); it is a very rare disorder - but with very dramatic effects. If one of their bones is broken they still use it as if it were alright - leading to more and more damage and life threatening infections.

The best definition so far is the one provided by the IASP:
"An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage."

Notice the "described in terms of such damage" - that's my favorite part. Think about a visit to the dentists office; for a lot of people there doesn't have to be pain in order to feel it. The smell, the sounds, the faces of others in the waiting area and the (bad) memories one has about previous visits is enough to elicit a stress response - and lead to "imaginary" pain.

There are two important lessons here:
1) our brains are pattern seeking and prediction making machines
2) the link between stress and pain

1) our brains start looking for patterns the moment we are born. Babies will smile at anything that resembles a face - even a piece of cardboard with two eyes and a mouth. Our brains are hardwired to look for faces especially - that's why we are able to see them anywhere - in clouds, in trees, ...
That's why highkey portraits work so well - they reduce a (human) face to the most basic structures our brains seek - eyes, a mouth and a bit of skull outlined.

Windows To The Soul

So if you brought your brain with you to the dentist it starts analyzing the situation: the smell of antiseptic, the high-pitched sounds of the drill, the facemask (very uncool and unintentionally threatening) - and perhaps bad memories from past visits.

How can your brain not see a pattern that says: "Beware - Pain ahead!". It has to do this - it's hardwired to protect you.
The same goes for every other painful experience you ever had - if your brain recognizes a similar pattern it will make you uncomfortable in advance of the actual experience. It prepares you for action.

2) The "stress response". How does your brain prepare you for such a situation when you are - based on the brains prediction - likely to experience pain?:
by up-regulating your natural stress response - changing the heart rate, shutting down digestion, pumping adrenaline into the bloodstream, ... - all the reactions your body needs in order to flee and or to survive.

You have to remember that our brains developed over several hundred million years - so they still expect sabre-tooth tigers to jump at us from behind mailboxes - not dentists who want to help you. Our brains have learned that overreacting is better than the other way round and essential for survival.

So today any stressful situation leads to the full array of stress responses.
And this is the simple link between stress and pain. Stress makes you more likely to experience pain - and as such relaxation techniques are helpful - they remove part of the pain experience which can make pain easier to live with.
Actually short term stress reduces pain (think the "shock" after a traumatic event) - but long term stress heightens it.

In the next posting we will look at the multidimensional nature of pain.

Sunday, September 2, 2007

Work Issues and Pain

Work Issues and Pain. "How does pain affect your work life? Are you able to work? Has pain forced you to give up work?"

I was invited to address a topic related to these questions, along with several other people who blog about pain, by How To Cope With Pain. See my post here. To see all the other posts in this carnival, go to the How To Cope With Pain blog.

Stop and think about work for a moment.
Not about your work - but about what work means, what it is and what it could be like.
If you look at some of the more common family names in Germany for example you'll find a lot of people that have a profession as their family name - "Müller" (Miller), "Zimmermann" (Carpenter), "Schuster" (Shoemaker), "Metzger" (Butcher), ...
That means that at one time people where defined by what they did for a living.

How about you?
Does your work give you your identity - or at least part of it?
If it doesn't - what does that say about your whole life situation?
I think that it is absolutely impossible for someone just to have a job. Work does so much more: it structures the day, gives you an income, provides you with social support, takes your mind of things, ...

Not all jobs are created equal though. Some even add to the problem - or are the cause of all the trouble you experience. If that is the case it's time to leave - fast. The stress response we all have is a wonderful thing - it helps us get out of trouble by preparing our body to fight or to get away quickly.

However - if the stress response is turned on constantly our bodies start to suffer very badly. Tissue breaks down and isn't rebuilt properly, oxygenation is surpressed in certain areas, digestion is shut down, bones become brittle - all leading to severe stress related diseases that crop up later in life in a lot of people.

If you can't get out - you have to find something that takes your mind of things in your free time. Yes - you have to - otherwise things will turn out bad. Being under chronic stress makes you more vulnerable to develop chronic pain problems. And if you already suffer from chronic pain the additional stress of the workplace doesn't help either.

In an ideal world - or "fantasy world" as some would call it work is a big help. Apart from the financial aspect distraction is the factor that is most important. Our brains have only a very limited working memory. That means we can only focus on one thing at a time. If you have a chronic painful condition your attention is automatically drawn towards the painful experience. If you have a demanding task at hand however your brain can't deal with these two things at once - it has to shut out one of them.
Ideally the painful one of course.

Regardless of what you are doing for a living - try to do everything - even movements that you have done for years - with a fresh "mind" - starting from scratch. Analyze the movement, pay attention to it. That way you "overload" your brain with fresh visual and sensory information - hopefully distracting yourself and your brain away from the pain.

Do this long enough and some (all) of the painful movements you experienced before might be re-wired (or overwritten) - in a non-painful way.

If you had to stop working because of the injury or the pain - find something that gives you some of the same positive things work provides: a sense of purpose, structure, motivation, a creative outlet - anything but doing nothing! Like I said - Distraction is the key.

Happy Labor Day!

It's a tough job but somebody has to do it: ;-)

Another Bloody Day At Work


"Filling-in" - könnte man mit "Ergänzung" ins Deutsche übersetzen - ist ein sehr interessantes Phänomen. Man beschreibt damit den Effekt der Komplettierung/Ergänzung/Auffüllung von "leeren" Stellen die - laut unserem Gehirn - nicht leer sein dürfen oder es aller Wahrscheinlichkeit nach nicht sind.

Beispiel: wenn wir vor einer Hecke stehen und sich dahinter ein Objekt befindet dann ergänzt unser Gehirn automatisch die Teile die wir nicht sehen können. Wir nehmen das Objekt als Ganzes war - nicht nur die kleinen Puzzleteile die wir tatsächlich sehen können.
Aus Erfahrung (und Wahrscheinlichkeit) heraus ergänzt unser Gehirn die fehlende Information.
Ein harmloser und hilfreicher Prozess.
Auf diese Art und Weise nehmen wir immer eine komplette zusammenhängende Umwelt war.

Staring Contest

Die Stelle an der unser Sehnerv das Auge verlässt empfängt keine visuellen Informationen - wir sind an diesem Punkt blind. Das Gehirn nutzt die Informationen angrenzender Bereiche um diesen Punkt so aufzufüllen dass ein einheitliches Bild entsteht.
Man kann diesen Effekt hier sehr schön testen und gleichzeitig seine Grösse ausmessen (linkes Auge schliessen und mit dem rechten das Kreuz fixieren, Kopf vor und zurück bewegen bis der Punkt auf der rechten Seite verschwindet).

Wie all diese Phänomene ist "Filling-in" nicht nur auf das Auge beschränkt - wir hören auch Töne die es nicht gibt - verschiedene Beispiele hier.

Auch der Bereich der taktilen Wahrnehmung ist betroffen: die "Cutaneous Rabbit Illusion" ist hier das beste Beispiel; es handelt sich um eine klassische Illusion bei der man 2 voneinander entfernte Hautstellen schnell hintereinander stimuliert - z.b. das Handgelenk und dann den Ellenbogen - und es sich für die Probanden so anfühlt als ob auch der Unterarm dazwischen in bestimmten Abständen berührt worden wäre - als ob ein Hase den Arm hinaufhüpft.

Diese Illusion wird direkt vom Gehirn selbst erzeugt: der Somatosensorische Cortex - der unter anderem für die Verarbeitung von taktilen Reizen zuständig ist - wird in den Bereichen aktiv in denen die Illusion gefühlt wird.
Ich bin nach wie vor überzeugt dass man diese Illusion theraputisch nutzen kann wie ich hier vor längerer Zeit spekuliert habe.

Wenn ein Körperteil bei chronischen Schmerzpatienten so empfindlich ist, dass man ihn nicht mehr anfassen kann weil sofort Schmerz ausgelöst wird, könnte man an den Stellen, die direkt daneben liegen Reize setzen, die dann "durch" den Schmerzbereich laufen.
So müsste man den krankhaft veränderten Teil der Gehirnrinde erreichen können ohne mehr Schmerz auszulösen. Wäre wahrscheinlich schon mit einem TENS Gerät machbar.

Bewegung und Erfahrung

Mein Bruder hat in einem Kommentar folgenden Textauszug gepostet:

"It's amazing, even with 16 pixels, how much our subjects have been able to do," says Professor Mark Humayun who has developed the device at the Doheny Eye Institute at the University of Southern California in San Francisco. "We were completely wrong... We thought from simulations that 16 would give you distinction only between light and dark and maybe some greyscale." In fact patients are able to tell the difference between objects such as a cup, a plate and a knife. They can also tell in which direction objects are moving in front of them. "The brain is able to fill in a lot of the information," he adds. (Spotlight, August 2007, "A second chance for sight", S. 28ff)

Man kann hier sehr eindrucksvoll sehen wie wenig Information unser Auge liefern muss damit wir uns in unserer Umgebung zurechtfinden können. Der Rest wird nach Bedarf von unserem Gehirn ergänzt ("Filling-in"); Erfahrung spielt hier die grösste Rolle.

Der Bereich unseres Auges mit dem wir scharf sehen können - die Fovea ist winzig. Um das auszugleichen und uns trotzdem einen guten Überblick über unsere Umwelt zu verschaffen nutzt unser Gehirn einen anderen Mechanismus: aufgrund von als wichtig eingestuften Informationen (v.a. Bewegung, laute Geräusche) wird ein Orientierungsreflex aktiviert der die Augen (und evtl. den ganzen Körper) in die Richtung des relevanten Stimulus lenkt.

Das sieht man sehr schön wenn ein Auto mit Sirene vorbeifährt - die meisten Menschen schauen in die Richtung des Geräusches und drehen sich oft sogar um.
Daraus lassen sich für den Alltag gleich ein paar Lektionen ableiten:

- es wird nicht nur der Körper auf den Reiz (Bewegung, Geräusch) ausgerichtet - sondern auch die Aufmerksamkeit umgelenkt. Die Produktivität sinkt also deutlich wenn man an einem Schreibtisch arbeitet an dem immer wieder jemand vorbeigeht. Jede Bewegung die man nur aus dem Augenwinkel heraus wahrnimmt lenkt ungemein ab. Das ist auch zu beachten wenn man z.b. Spiegeltherapie zuhause durchführt - möglichst in ruhiger Umgebung arbeiten.

- Damit man schnell genug reagieren kann ist die Bewegung der Augen mit der Aktivität der Nackenmuskulatur gekoppelt, d.h. die Augen bestimmen zu einem Grossteil was die Nackenmuskeln machen. Wer also Verspannungen im Bereich des Hinterkopfes hat sollte beim Training/zur Entspannung dies berücksichtigen und Augenbewegungen ins Training mit einbeziehen. "Augengymnastik" eignet sich natürlich auch für zwischendurch um die Verspannungen gleich gar nicht entstehen zu lassen.

Auf dieser Seite findet sich ein sehr interessantes Experiment:
anhand von nur 15 Punkten die sich bewegen und an den Gelenken angebracht sind können wir verschiedenste Qualitäten unterscheiden - ist es ein Mann oder eine Frau? schwer, leicht?, traurig, fröhlich? nervös, entspannt?
Unser Gehirn interessiert sich in diesem Fall nicht für die Punkte an sich - sondern für das Verhältnis der Punkte zueinander.

Auch diesen Effekt kann man im Alltag ausnutzen:
will man als Radfahrer oder Jogger besser gesehen werden ist es am besten die Leuchtmarkierungen (die man haben sollte) in Gelenknähe anzubringen.