Behavioural therapy in patients with CRPS typ I induces cortical reorganisation and pain reduction

Introduction: The Complex regional pain syndrome (CRPS) is a serious complication that occurs after a trauma of a limb. Recent studies provide evidence for a shrinkage of cortical maps in primary somatosensory cortex contralateral to the CRPS affected limb. The degree of reduction thereby appeared to be linked to pain intensity. Combining functional magnetic resonance imaging with psychophysical tests and a pain adapted sensorimotor training program consisting of graded desensitization protocols and motor tasks in ascending difficulty, we studied cortical reorganization in the primary and secondary somatosensory cortex, and changes of tactile perception and pain intensity.

Methods: We recruited 6 patients with intractable pain due to definite CRPS type I of one upper limb. We paralleled fMRI measurement testing 2-point discrimination thresholds of both index fingers as a marker of tactile perception. Blood-oxygen-level-dependent (BOLD) signal during electrical stimulation of the CRPS-affected and the healthy IF was evaluated in separate sessions. Pain-adapted sensorimotor treatment protocols were applied to the patients 3 to 4 days a week over a period ranging from 1 to 6 month.

Results: Before therapy we found an elevated spatial discrimination threshold on the affected index finger. In parallel, BOLD signals from the corresponding IF representation in SI and SII were diminished. The individual threshold elevation was linearly correlated to the pain intensity. Both, sensory impairment and pain intensity were also linked to the shrinkage in SI and SII. The concept of sensorimotor retuning led to pain-relief which was paralleled by a restoration of the impaired tactile perception and a regain of BOLD contrast in contralateral SI and SII.

Conclusions: The results of this study provide further evidence that in CRPS cortical and perceptual alterations are correlated to pain intensity. Interestingly, pain, cortical reorganization and sensory impairment can be reversed by graded sensorimotor retuning.