Changes of Somatosensory Phenotype in the Course of Disease in Osteoarthritis Patients.

To investigate sensory changes, physical function (pF), quality of life (QoL) and pain intensity of patients with osteoarthritis (OA) in the natural course of disease, and patients undergoing total joint replacement therapy (TJR) 31 (20 females, mean age 64.6 ± 10.4 years), patients with OA were investigated with questionnaires and quantitative sensory testing (QST) in the area of referred pain at the thigh at baseline and follow-up 22-49 weeks later; changes were analyzed separately for patients with (n = 13) and without TJR (n = 18). In patients without TJR pain intensity, pF, QoL did not improve, and increased pain sensitivity to cold and a stronger loss of detection were observed. In patients after TJR, however, a reduction in mechanical pain sensitivity and allodynia occurred in accordance with a reduction of pain intensity and improvement of functionality while QoL did not improve. Additionally, an increased sensitivity to heat pain and a more pronounced loss of mechanical detection could be observed in this group. TJR seems to stop peripheral pain input leading to a reduction of pain intensity and central sensitization, but surgery-induced sensory changes such as peripheral sensitization and loss of detection occur. Furthermore, TJR has favorable effects on pain intensity and functionality but not QoL.

A-Fibers Mediate Cold Hyperalgesia in Patients with Oxaliplatin-Induced Neuropathy.

Cold hyperalgesia is a common side effect of oxaliplatin treatment; still, the pathophysiological and molecular mechanisms as well as the contribution of different primary afferent fiber systems are unclear. Therefore, patients with oxaliplatin-induced acute neuropathy with (n = 6) and without (n = 7) cold hyperalgesia were tested by applying a preferential blockade of peripheral myelinated A-fiber afferents in combination with quantitative sensory testing. Additionally, an interview-based questionnaire assessed the severity of symptoms and the impact on daily activities. Results indicate a deficit of cold perception in patients without cold hyperalgesia compared to patients with cold hyperalgesia prior to A-fiber blockade. In patients with cold hyperalgesia, a preferential blockade of A-fibers abolished cold hyperalgesia. This suggests that oxaliplatin-induced cold hyperalgesia is mediated by A-fibers and that a deficit in A-fiber function might prevent the development of cold hyperalgesia. The work supports findings in rodents and in human sural nerve biopsies indicating that oxaliplatin interferes with axonal ion conductance in intact A-fibers by sensitizing potassium and/or sodium channels. Drugs that act on these molecular targets might be of potential value to treat oxaliplatin-induced cold hyperalgesia.

Sensory symptoms in low back pain-how do they matter?

OBJECTIVE: Successful treatment of chronic low back pain (LBP) is difficult in clinical practice and hard to measure in trials. One reason might be the use of insufficient outcome parameters. The aim was to investigate the importance of typical clinical characteristics of chronic LBP on QoL and functionality. METHODS: A total of 51 patients with chronic LBP (19 with, 32 without radiculopathy) were investigated with different questionnaires. RESULTS: Burdening symptoms differed in frequency, intensity and impairment of QoL and functionality between patients with and without radiculopathy and between the area of pain within the same patient, i.e. between back and leg. Symptoms of nerve affection such as prickling pain and numbness were rated higher in the area of radiating pain than on the back in radiculopathy, and typical neuropathic pain symptoms such as burning pain, prickling, spontaneous pain, and feeling of deep pressure and pain at the beginning of movement were rated with a higher impairment of QoL and functionality in patients with compared to those without radiculopathy. Furthermore, intensity, impairment of QoL, and functionality were not necessarily reported in association with one another: some patients were highly impaired in QoL or functionality, despite a moderate-to-low pain intensity, whereas others suffered from severe pain, but were less impaired in QoL or functionality. CONCLUSION: Results suggest the consideration of impairment of QoL and functionality in addition to symptom intensity for treatment evaluation of chronic LBP. This can help to improve overall well-being of the patients and enhance efficacy in clinical pain trials and patient-centered treatment.

High concentration capsaicin for treatment of peripheral neuropathic pain: effect on somatosensory symptoms and identification of treatment responders.

BACKGROUND: Pain is usually assessed by spontaneous pain ratings. Time-dependent (brief attacks) or evoked (allodynia) phenomena, common in neuropathic pain, are not captured. To evaluate the overall effectiveness of a treatment, improvement of all sensory symptoms should be measured. Since the pattern of sensory abnormalities might hint at the underlying mechanisms of pain, this baseline information may aid in predicting the treatment effect. Data on sensory neuropathic abnormalities (painDETECT questionnaire) were analyzed aiming to (1) evaluate the frequency of neuropathic symptoms in different peripheral neuropathic pain syndromes, (2) assess the effect of capsaicin 8% patch on neuropathic symptoms and (3) identify treatment responders based on baseline values. METHODS: Data analysis of a prospective 12 week non-interventional trial in peripheral neuropathic pain treated with capsaicin 8% cutaneous patch. Average pain intensity during the past 24 hours, pain descriptors and qualities of neuropathic pain were assessed to characterize the patients' sensory symptoms at baseline and to document changes. RESULTS: (1) Characteristic symptoms of neuropathic pain were present in all peripheral neuropathic pain syndromes, but frequencies varied in the individual syndromes. (2) Topical capsaicin 8% treatment significantly reduced the overall pain intensity and resulted in a reduction of sensory abnormalities. (3) Short disease duration predicted a better treatment effect. High painDETECT scores, the presence of burning and pressure-evoked pain were weakly associated with treatment response. CONCLUSIONS: Topical capsaicin 8% treatment effectively reduced sensory abnormalities in peripheral neuropathic pain. The association of sensory symptoms and treatment response aids in understanding the mechanism of action of high concentration capsaicin. It is, however, not possible to use sensory symptom patterns to predict treatment response to capsaicin on an individual level. LIMITATIONS: Completion of painDETECT was optional and therefore data was not available for all patients. Further studies for confirmation of these results are needed.