Association of Neglect-Like Symptoms with Anxiety, Somatization, and Depersonalization in Complex Regional Pain Syndrome.

Background: Many patients with complex regional pain syndrome (CRPS) report some foreignness of the affected limb, which is referred to as "neglect-like symptoms" (NLS). Despite similarities of the NLS reports to symptoms of body image disturbances in mental disorders, no study has been conducted to examine such associations. Methods: We investigated 50 patients with CRPS and 45 pain control patients (N = 27, chronic limb pain; N = 18, migraine headache). NLS, anxiety, depression, depersonalization, and somatization were assessed using validated questionnaires. Results: Seventy-two percent of the CRPS patients reported at least one NLS vs 29.6% and 33.3% in the two patient control groups. In limb pain controls, NLS correlated with pain intensity. In CRPS patients, NLS correlated with anxiety (rho = 0.658, P < 0.001), somatization (rho = 0.616, P < 0.001), depersonalization (rho = 0.634, P < 0.001), and pain catastrophizing (rho = 0.456, P < 0.01), but not with intensity of pain, duration of pain, or pain disability. Conclusions: In CRPS patients, NLS could be a result of somatization, depression, anxiety, and depersonalization, but probably not of pain. Whether these associations are causative must be clarified in longitudinal psychological studies.

Interaction of calcitonin gene related peptide (CGRP) and substance P (SP) in human skin.

Calcitonin gene related peptide (CGRP) and substance P (SP) are neuropeptides that are simultaneously released from nociceptive C-fibers. CGRP is a potent vasodilator, inducing a long-lasting increase in superficial skin blood flow, whereas SP induces only a brief vasodilation but a significant plasma extravasation. CGRP and SP may play important roles in the pathophysiology of various pain states but little is known about their interaction. Different concentrations of SP (ranging from 10-5M to 10-9M) were applied to the volar forearm of 24 healthy subjects via dermal microdialysis. SP was applied either alone or in combination with CGRP10-9M and CGRP 10-6M. As expected, SP induced a transient increase in skin blood flow that decayed shortly after application. This transient blood flow peak was blunted with co-application of CGRP 10-9M and inhibited with co-application of CGRP10-6M. SP alone induced plasma protein extravasation (PPE). However, when CGRP10-6M was added, the PPE significantly increased. Our results demonstrate a complex interaction of the neuropeptides CGRP and SP. CGRP10-6M prevented SP-induced early vasodilation but augmented SP-induced PPE. These interactions might explain why vascular symptoms in chronic pain can differ strikingly between individuals.