Above is a diagram of the Neuromatrix model of pain. It was proposed over a decade ago by Dr. Ronald Melzack. Ever heard of it? Or him? Maybe not. But in school, you likely learned about the gate control theory of pain and somewhere along the way, used the McGill Pain Questionnaire. Well he also developed these.
So as a PT, what does this model mean to us? In my opinion, A LOT. It is a conceptual framework for every one of our patient’s who presents to us with complaints of pain. Acute pain. Chronic pain. Dull Pain. Stabbing Pain. Neuropathic pain. You get the point.
Pain is always an output from the brain (specifically the individual regions which make up the “neuromatrix”) based upon many different variables. Simply the brain’s suspicion that a tissue has the potential for damage, will cause it to react. TISSUE INJURY IS NOT NECESSARY. This statement is important. We often search for a “root” cause of our patients pain. And we often blame tissues. Heck, we always blame tissues. Well, research indicates pain is more than mechanical deformation of tissues. As a profession, we must understand and accept this. To do so will improve our scientific validity.
The neuromatrix, is a framework made up of cortical areas of the brain which we know to be active when one experiences pain (as well as other processes which cause one to possess a sense of self). To complicate things, everyones neuromatrix is slightly different (there are some areas that are consistently active though). The reaction of the neuromatrix to stimuli or input described below, results in a conscious, and arguably fantastic, communication response, which is crucial for our safety, well-being and survival.
INPUT to the neuromatrix:
These are on the left side of the image above. Each of these input is sufficient in causing the neuromatrix to determine that there is a sufficient threat to the body’s tissues, and causes the brain to react. In the latest neuromatrix model, the following inputs can trigger the neuromatrix:
1. Memories of past experiences, attention, meaning and anxiety.
ex. The context of an injury is important. Imagine a patient that you have treated with chronic whiplash-associated disorder. They come to therapy and tell you that their drive to therapy caused pain. Why do you suspect this happened? Many of us, would suspect that turning the neck to back up or the prolonged driving posture resulted in pain. But consider the context of the car. The car itself is a contextual threat to that individuals brain. The car is what injured them. The car has meaning. The brain potentially could be protecting the neck from a threatening environment. And we know the brain can and will do this.
2. Cutaneous, visceral and musculoskeletal inputs
ex. This is the input which all of us learns can cause pain. Stress and strain to tissue will result in pain. And it does. A lot. But not always.
3. Limbic system and associated homeostatic/stress mechanisms
ex. Emotional, hormonal and stress regulatory systems can also contribute to reaction from the neuromatrix.
One, two or all three types of input can sufficiently cause an output.
So as a PT we must understand that many times, it is more than tissue. Our patient interactions and their improvement may be due to what you are doing, but the effects may be different than you would suspect. You’re treatment environment may be warm and inviting (and non-threatening). The patient may be widowed and your touch to their painful neck is the first human interaction they have had in 3 months. Your communication skills are pleasant and the patient expects your treatments, which they don’t completely understand, will get them better. All the therapeutic input which you provide to the neuromatrix, may cause it, to not react.
Iannetti GD, Mouraux A. From the neuromatrix to the pain matrix (and back).Exp Brain Res 2010; 205; 1-12
Moseley GL. A pain neuromatrix approach to patients with chronic pain.Manual Therapy 2003;8:130-140