Apkarian AV, Baliki MN, Geha PY Towards a theory of chronic pain. Progress in Neurobiology 2009;87:81-97
- The Seltzer partial sciatic nerve injury model proposes that full-blown thermal hyperalgesia and mechanical allodynia begin with hours of the injury.
- In contrast, in the spared nerve injury model where the tibial and peroneal branches of the sciatic nerve are cut, stable and peak thermal hyperalgesia and mechanical allodynia are only observed at about 2 weeks after initial injury.
- To our knowledge there are no studies as to the mechanisms underlying these time delays.
- Management of chronic pain
- a 2000 meta-analysis of NSAID studies found no evidence that these drugs were effective in treating chronic low back pain.
- A systemic review of antidepressant treatment for chronic back pain also conclude that they produce only a moderate symptom reduction
- The world health organization advisory panel likewise concluded that there is no single treatment superior to others for relieving chronic back pain.
- In summary, there is long list of risk factors but no dominant physical or psychological parameter that can substantially explain chronic pain.
- We reported that, in contrast to age, sex, and education matched healthy control, chronic back pain and CRPS patients are significantly impaired on an emotional decision-making task.
- A long list of cognitive abnormalities has been described in chronic pain patient. The most noteworthy are attentional and memory deficits.
- In 2004 published the first brain morphometric study showing anatomical evidence for brain atrophy in chronic back pain patients.
- The sustained prefrontal activity is most likely related to the maladaptive psychological and behavioral cost associated with chronic pain.
- Acute pain appears to activate a fairly constant set of brain regions, as demonstrated in a meta-analysis.
- Meta-analysis confirms that overall brain activity patterns in chronic pain patients generally diverge from that seen in acute pain, particularly with respect to the emerging prominence of prefrontal cortex activations.
- Studying in a psoriatic arthritis patient we found that decreases in activity in S2 and anterior insula were tightly correlated with the changes in pain perception following ingesting the drug.
- There has been a historic divide between scientists identifying themselves as localizationists and those who considered the brain to be connected network, where the dynamics of the connected network characterize brain states.
- Recent animal studies show that cortical manipulations can modulate pain behavior. Results emphasize the role of the insula, anterior cingulated, mPFC, and amygdale in pain, which are limbic structures with strong interconnectivity.
- In terms of learning and memory one could recast this definition as:chronic pain is a persistence of the memory of pain and/or the inability to extinguish the memory of pain evoked by an initial injury.
- D-cycloserine(DCS) given systemically or centrally enhances cognitive process, improves attention and memory, and facilitates fear extinction through de novo memory trace formation involving n-methy-D-aspartic acid (NMDA) plasticity.
