Neuroscience

An Introduction to Current Concepts of Pain (Lester Jones) in Recent Advances in Physiotherapy (Cecily Partridge Ed.).

Key concept 1 - Peripheral mechanisms

Nociceptive transmission is not pain

• If we stub our toe, special nerve fibres respond to the forceful compression of the soft tissue by transmitting an electrical impulse towards the spinal cord.
• This is not pain – it is an electrical impulse.

Key concept 2 - Central mechanisms (spinal)

Modulation of nociceptive transmission can occur in the dorsal horn of spinal cord (i.e. Rexed's laminae)

• Often the spinal cord is described as a relay station for electrical impulses travelling between the brain and the periphery.
• But it is not just a relay station – interesting things happen here!

Read:

Campbell, J.N. & Meyer, R.A. (2008). Mechanisms of neuropathic pain. Neuron, 52(1), 77-92. doi:10.1016/j.neuron.2006.09.021

Lewis, J. S., Kersten, P., McPherson, K. M., Taylor, G. J., Harris, N., McCabe, C. S., & Blake, D. R. (2010). Wherever is my arm? Impaired upper limb position accuracy in Complex Regional Pain Syndrome. Pain, 149(3), 463-469. doi:10.1016/j.pain.2010.02.007

Key concept 3 - Central mechanisms (brain)

Pain is created by the brain in response to central and peripheral mechanisms (i.e. pain is an output of the brain and not in the tissues)

• When we feel pain, the brain has concluded that we need to do something to avoid injury or worse – death! However, if it is really death we are facing, the brain can also conclude that pain is not a good idea and that we need to run away. But once we are safe, we will feel the pain!
   
• This is only part of the story. Do you believe that people can create pain (and swelling) by imagining movement of their painful hand? Or have their pain disappear by seeing their non-painful limb move in a mirror?

Read:

Moseley, G. L., Zalucki, N., Birklein, F., Marinus, J., van Hilten, J. J., & Luomajoki, H. (2008). Thinking about movement hurts: The effect of motor imagery on pain and swelling in people with chronic arm pain. Arthritis Care & Research, 59(5), 623-631. doi:10.1002/art.23580

Ploghaus, A., Becerra, L., Borras, C., & Borsook, D. (2003). Neural circuitry underlying pain modulation: expectation, hypnosis, placebo. Trends in Cognitive Sciences, 7(5), 197-200. doi:10.1016/S1364-6613(03)00061-5

Sumitani, M., Miyauchi, S., McCabe, C. S., Shibata, M., Maeda, L., Saitoh, Y., . . . Mashimo, T. (2008). Mirror visual feedback alleviates deafferentation pain, depending on qualitative aspects of the pain: a preliminary report. Rheumatology, 47(7), 1038-1043. doi:10.1093/rheumatology/ken170

Key concepts 4 & 5

See 'Assessment and treatment' page.

Lorimer Mosely: Why things Hurt by TedxAdelaide (YouTube)