Central Sensitization - Pain 101

February 17, 2021

Your body registers more pain than what an injury deserves, and especially for long term pain, or recurrent injuries, it can become “sensitized” but the question is why, and how do we settle it back down to normal again?

Disclaimer: This description is the most un-anatomical description of pain pathways you're likely to come across, but the intention is to introduce or consolidate concepts to talk about with your FLEX Physiotherapist, without using lots of jargon and technical terms.  

We hope you find it helpful.

Pain is Helpful

Pain is normal, and is designed to be helpful.  It's sensible to have a system that protects our bodies and warns us not to do things that will cause injury.  However, when pain persists, it is difficult to see how it can be serving any useful purpose. Sometimes your body registers more pain than what an injury deserves, and especially for long term pain, or recurrent injuries, it can become “sensitized” but the question is why, and how do we settle it back down to normal again?

Chinese Whispers - The Message System

In an acute injury, it is a normal and helpful reaction for your body to try and protect itself.  Information from sensors in your skin and tissues send a “potential threat” message through nerves, which “synapse” (or tag team) at several points along the way on their way up the spinal column, up to your brain, back down the spinal column, and back into the original body area.  

At each synapse, the message can be amplified or reduced, depending on the hormones and chemicals in the “synapse juice”.  In fact, if the nerves have been sending the same message for a while, they actually get better at sending it too, so send a stronger message.

When the message gets to the brain, the “potential threat” message is then interpreted.  It can choose to ignore the message if your brain does not consider it a significant threat, and has lots of happy and relaxed hormones floating around, or it can register it as pain, and send the message back down the spinal cord to the local tissues about how to respond.  

For example, for lower back pain it is common for the message to be “Uh oh, tense up surrounding back muscles to prevent further damage” this will stop you from bending over and sitting too long (they hurt too much, or you just can't physically reach!) but after a while, if you avoid things that place stress on your back, and gently start walking and moving around, your brain will gradually reduce the amount of muscle guarding protection it deems necessary.

The Message System In Summary:

Tissue sensors  > nerve signal towards spinal cord

> up the spinal cord (few synapses in spinal cord)

> brain (lots and lots of synapses in the brain mixed with other information and interpretation)

> new message from brain

> travels back down spinal cord (a few more synapses)

> back to the original tissue

Why is My Pain Volume Turned Up?

  • Lack of quality sleep, or difficulty getting to sleep
  • Anxiety or stress
  • Negative thoughts and worry
  • Feeling that it's out of your control, and nothing you do helps

Even if it seems totally unrelated, the chemicals in the “synapse juice” when you're stressed, anxious, tired, worried or feeling low amplify the volume of the “potential threat” signal that goes to your brain.  

  • A traumatic history or stressful event.  This can be a physical or emotional trauma, often at a similar time to the injury onset, but sometimes many years earlier, or under similar circumstances.
  • Long term, chronic or recurrent injuries
  • Nerve irritation – either by direct injury to the nerves, posture that overloads them, overstretching, or by not being moved and wriggled around as much as they're used to!  Nerves can be really sensitive structures!
  • Lack of activity – a lack of movement and blood flow to an area can increase the acidity of the tissues, which makes them more sensitive to pain
  • Muscle guarding or protective movement strategies  - These are helpful in the short term to protect a brand new injury, but if your muscles keep on protecting the injury this way for too long, the body can't remember the normal healthy pattern, and you often experience muscular pain or aching too.
  • Your brain's “virtual body map” isn't very clear, or has become more sensitive

Your Brain's Body Map

Your brain contains virtual map of your body, where important and sensitive parts like your face and fingertips have lots of brain space.  As you use a certain part of body regularly, your brain gets lots of information from that body part, and the map in your brain gets bigger and clearer.  So we would expect that in a violinist's brain there would be very large, clearly defined fingertips.

However when you have pain, or don't move a body part normally for a while, that part of the body map can become “smudged”, so your brain isn't as good at knowing how to recognize information from it, or send helpful information for how to control it.  If you have pain for a long time, or strong pain, that area can grow so it becomes more sensitive, but unfortunately that means the affected area also becomes more sensitive to pain.

The good news is that Physiotherapists can choose exercises to improve your body map, practicing normal movement patterns will help bring back normal clarity to that body area in the brain.  There are also some other weird and wonderful ways to do this too!

On High Alert

Sometimes your body gets so good at protecting itself, amplifying “potential threat” messages, and interpreting them as pain, that something that wouldn't normally cause pain, and isn't a real threat, like feather-light touch, or ice does cause pain.  It's a typical sign of central sensitization.

Sound Familiar?

How many of these statements resonate with you?

“The pain is spreading”

“The pain is worsening”

“Lots of movements hurt, even small ones”

“The pain moves around my body”

“No one seems to believe me”

“It comes on when I think about it”

“It's worse when I'm tired”

“I have difficulty getting to sleep”

“I find it difficult to relax”

“I sometimes get headaches, especially when my pain is bad”

Turning the volume back down

Our Physiotherapists can assess if “central sensitization” is a part of your injury, and help you find ways of “turning the pain volume back down”.

Ensuring you are sleeping well, have realistic goals and timeframes and are committed to doing physio exercises regularly, is a great place to start.

We also need to reduce the stress hormones and neurotransmitters in the “synapse juice” that have been amplifying the threat signal, so taking some deep breaths, using relaxation strategies for stress or anxiety, and finding something enjoyable and relaxing can be helpful for changing the chemical imbalance, and sometimes we suggest you see a psychologist for a few sessions to give you some tools to manage these.

Some exercises your physio gives you may seem strange, (deep breathing, visualisations, mirrors and iPhone apps just to mention a few!) but remember we need to retrain the brain about how it interprets and responds to the messages it receives.

It is also important to have the right amount and type of medication to manage the pain, so we often recommend you talk about this with your GP or pain specialist.

So, don't lose hope, there are lots we can do to help you, and lots you can do to help yourself.

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