1 Department of Clinical Medicine - The Danish Pain Research Center, Department of Clinical Medicine, Health, Aarhus University2 Department of Clinical Medicine - The Spinal Cord Injury Centre of Western Danmark, Department of Clinical Medicine, Health, Aarhus University3 Department of Clinical Medicine - The Spinal Cord Injury Centre of Western Danmark, Department of Clinical Medicine, Health, Aarhus University
Aim of investigation: CRPS may spread from the primary affected limb to other body parts . Even without subjective reports of a spread of CRPS, a spread of pressure hyperalgesia from the affected limb to the ipsilateral forehead is present in the majority of patients [2-4]. This may indicate a disturbance in central nociceptive pathways processing input from hemilateral body sites. However, it may also be consistent with referred pain and cortical reorganization. Thus, it is important to assess whether sensory disturbances spread to ipsilateral body sites other than the forehead. The aim of this study was to investigate sensitivity to pressure and pinprick at multiple body sites remote from the CRPS limb. Methods: Preliminary results from 10 CRPS patients (F/M: 8/2; mean age 43.2, range 24-61) with lower (n=2) or upper (n=8) limb affection and 10 age and sex matched healthy controls is presented. Pressure-pain thresholds (PPTs) and ratings of sharpness (on a 0-10 scale) to a firm nylon bristle were investigated on each side of the forehead, in both shoulders, the affected and contralateral limb, the ipsilateral limb and the most remote contralateral limb of patients and at equivalent body sites in controls. Patients also rated spontaneous pain on a numeric rating scale (0-10). Results: Mean of all PPTs were lower in CRPS patients (119 ± 15 kPa) than in controls (166 ± 15 kPa; p = 0.04), and PPTs were in general lower on the body side ipsilateral to pain in the CRPS patients (107 ± 13 kPa vs. 129 ± 10 kPa; p = 0.01). This was irrespective of the level of the body assessed (forehead, shoulders, segmental or heterotopic level; p = 0.22). Sharpness ratings were greater in patients than controls (3.07 ± 0.44 vs. 0.98 ± 0.44; p = 0.003) and were greater on one side of the body in patients, but not in controls (p = 0.046). However, the side difference was at limb level only (p = 0.05) (CRPS limb (5.75 ± 1.18) vs. contralateral limb (2.25 ± 0.59) (p = 0.01); ipsilateral limb (3.2 ± 0.77) vs. remote contralateral limb (1.60 ± 0.50) (p = 0.02)). Ipsilateral pressure hyperalgesia and ipsilateral limb hyperalgesia to sharpness were not related to age, pain intensity, or pain duration. 2 Conclusions: The findings suggest the presence of heightened excitability in nociceptive pathways in CRPS, particularly those that provide hemilateral input, perhaps due to disturbances in pain control from thalamus or higher cortical centers. Acknowledgement: The study was supported by a grant from Lundbeckfonden (R54-A5765).