What is the pathophysiology of complex regional pain syndrome type 1 (CRPS 1)?

Updated: Mar 09, 2021
  • Author: T P Sudha Rao, MD; Chief Editor: Herbert S Diamond, MD  more...
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Susceptibility factors are unknown and may include genetic predisposition (HLA typing) [3, 4, 5] and, in some patients, a tendency toward increased sympathetic activity. This includes cold hands, hyperhidrosis, or a history of fainting.

Healthy individuals have a sympathetic response to injury, with vasoconstriction designed to prevent blood loss and swelling. This initial response soon subsides and gives way to vasodilatation and increased capillary permeability, allowing tissue repair.

In patients with CRPS 1, this sympathetic response continues unabated. The reasons for the perpetuation of the response are unknown but may be related to central dysregulation of nociceptive impulses. This dysregulation may be mediated by wide dynamic range neurons in the spinal cord.

Prolonged ischemia caused by the vasoconstriction produces more pain, establishing a reflex arc that promotes further sympathetic discharge and vasospasm. This is compounded by the local response to trauma, with liberation of substantial amounts of proinflammatory mediators, such as histamine, serotonin, and bradykinin.

The result is a swollen, painful, stiff, nonfunctioning extremity. At least partial sympathetic mediation of this phenomenon is likely because of the ability of sympathetic nerve blockade to relieve pain and other features of CRPS 1 in some patients.

Numerous studies have reported altered brain function in CRPS 1. Researchers have also documented structural alterations in the brain. Pleger et al reported that magnetic resonance imaging (MRI) in patients with CRPS 1 showed altered gray matter structure in dorsomedial prefrontal cortex, as well as increases in gray matter density in the motor cortex contralateral to the affected limb, which were inversely related to decreased white matter density of the internal capsule within that brain hemisphere. [6]

A study by Barad that used structural MRI found that compared with controls, patients with complex regional pain syndrome had decreased gray matter volume in several pain-affect regions (including the dorsal insula, left orbitofrontal cortex, and several aspects of the cingulate cortex) and increased gray matter volume in the bilateral dorsal putamen and right hypothalamus. [7]

Lee et al found that the right dorsolateral prefrontal cortex and left ventromedial prefrontal cortex were significantly thinner in patients with CRPS than in healthy controls. In addition, CRPS patients had longer stop-signal task reaction times and made more perseveration errors on the Wisconsin Card Sorting Test. [8]

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