Spinal cord stimulation induces c-Fos expression in the dorsal horn in rats with neuropathic pain after partial sciatic nerve injury.

Spinal cord stimulation (SCS) is an established treatment for intractable neuropathic pain, especially CRPS-1. The mechanisms of action of SCS have only been partly elucidated and include suppression of the hyper-excitability of the Wide Dynamic Range neurons and a GABA increase in the dorsal horn. In the present study we demonstrate an increase of c-Fos immunoreactive cells in the dorsal horn after SCS, suggesting early cellular activation that may preclude earlier described electrophysiological and biochemical changes in the dorsal horn after SCS. In a rat model of neuropathic pain, allodynia was induced and quantified using the von Frey test. In 11 rats a SCS device was implanted and spinal cord stimulation performed. Withdrawal threshold were measured every 15 min up to 90 min. A sham group (n=6) also had a SCS device implanted, but did not receive SCS. After SCS the animals were perfused and histology was performed for quantification of c-Fos immunoreactivity in the dorsal horns. We found a significant increase in c-Fos in the SCS group compared to our sham group and control tissue, indicating late cellular activity in the dorsal horn after SCS.

Quality of life in chronic pain is more associated with beliefs about pain, than with pain intensity.

OBJECTIVES: The objectives of this study were to investigate pain cognitions and quality of life of chronic pain patients referred to a multi-disciplinary university pain management clinic and to search for predictors of quality of life. METHODS: A heterogeneous group of 1208 chronic pain patients referred to the Maastricht university hospital pain clinic participated in this cross-sectional study. At the initial assessment, all patients completed a set of questionnaires on demographic variables, cause, location, pain intensity (McGill pain questionnaire, MPQ), pain coping and beliefs (pain coping and cognition list, PCCL), pain catastrophising (pain catastrophising scale, PCS) and eight dimensions of quality of life (Rand-36). RESULTS: The results showed that the present sample of heterogeneous pain patients reported low quality of life on each domain and significantly lower scores than has been found in previous studies with other Dutch chronic pain populations. Patients with low back pain and multiple pain localisations experienced most functional limitations. Women reported more pain, more catastrophising thoughts about pain, more disability and lower vitality and general health. When tested in a multiple regression analysis, pain catastrophising turned out to be the single most important predictor of quality of life. Especially social functioning, vitality, mental health and general health are significantly associated with pain catastrophising. CONCLUSIONS: Patients from a multi-disciplinary university pain clinic experience strikingly low quality of life, whereby low back pain patients and patients with multiple pain localisations have the lowest quality of life. Pain catastrophising showed the strongest association with quality of life, and stronger than pain intensity.