Chronic Back Pain Decreases Brain Size
Apkarian, et al (2004), and Acerra and Moseley (2005) found that chronic pain harms brain areas unrelated to pain, although the exact mechanism was not discovered in these studies. In the 2004 study the scientists found that chronic pain sufferers had 5-11% less neocortical gray matter compared to controls which is comparable to the decline in gray matter experienced over ten to twenty years of normal ageing. For every year of chronic pain there was a calculated loss of 1.3cm³. Similar alterations in the dorsolateral prefrontal cortex have also been noted in patients with fibromyalgia with some researchers recently proposing that this change in brain structure is at the root of the fibro-fog and other symptoms common in the syndrome.
Pain Changes the Brain
Changes in brain structure and adverse effects on behavior in chronic pain sufferers could be due to altered functional connectivity in the cortical regions considered the default mode network (DMN). These regions of the brain are active at rest but the balance of positive and negative activity in these regions is disrupted in several disorders, including chronic back pain. The DMN is thought to play a key role in interpreting, responding to, and predicting environmental demands but the constant presence of chronic pain results in disruption of the ‘at-rest’ brain and, therefore, this key system of homeostasis.
Scanning the Brain in Pain
Using functional MRI scans to study the default mode network (DMN), Baliki, et al (2008), had patients with chronic back pain carry out simple visual attention tasks in order to discern any differences from healthy controls. Patients with chronic back pain, which can be a symptom of spinal stenosis, performed the task just as well as controls but showed marked differences in brain function. Several important areas of the default mode network had reduced deactivation and the researchers contend that these alterations illustrate how cognitive and behavioral issues accompanying chronic back pain could be an effect of the pain on overall brain function.
A brain processing chronic pain is not, therefore, the same as a healthy brain processing acute pain. Instead, the brain of a chronic pain patient is altered in response to the pain creating changes in cognitive function most likely all too familiar to chronic back pain sufferers.
Baliki, M.N., Geha, P.Y., Apkarian, A.V., Chialvo, D.R., Beyond feeling: chronic pain hurts the brain, disrupting the default-mode network dynamics. J Neurosci. 2008 Feb 6;28(6):1398-403.
Apkarian, A.V., Sosa, Y., et al, (2004), Chronic Back Pain Is Associated with Decreased Prefrontal and Thalamic Gray Matter Density, The Journal of Neuroscience, 17 November 2004, 24(46):
Acerra, N.E., Moseley, G.L., (2005) Dysynchiria: watching the mirror image of the unaffected limb elicits pain on the affected side. Neurology, 65:751–753.