Decreased perceptual learning ability in complex regional pain syndrome.

Recently, several functional imaging studies have shown that sensorimotor cortical representations may be changed in complex regional pain syndromes (CRPS). Therefore, we investigated tactile performance and tactile learning as indirect markers of cortical changes in patients with CRPS type I and controls. Patients had significant higher spatial discrimination thresholds at CRPS-affected extremities compared to both unaffected sides and control subjects. Furthermore, in order to improve tactile spatial acuity we used a Hebbian stimulation protocol of tactile coactivation. This consistently improved tactile acuity, both in controls and patients. However, the gain of performance was significantly lower on the CRPS-affected side implying an impaired perceptual learning ability. Therefore, we provide further support for an involvement of the CNS in CRPS, which may have implications to future neurorehabilitation strategies for this disease.