Chronic Pain with Neuropathic Characteristic

Chronic pain conditions are often categorised into two major groups, namely nociceptive (caused by tissue damage) or neuropathic (caused by nerve damage) pain. In the past few years, this dichotomous approach (either neuropathic or nociceptive) has been questioned and it has been suggested that not only “typical” neuropathic pain syndromes but also otherwise chronic pain (e.g. back pain) may have neuropathic components of pain. This dimensional perspective is consistent with basic scientific opinion regarding chronic pain mechanisms; however, further studies are needed to examine it empirically. Neuropathic symptoms (e.g. burning and prickling sensations) have a central role in the clinical diagnosis of the neuropathic components of pain. The main aim of the first study was to assess the severity of self-reported neuropathic symptoms in different syndromes of chronic pain (e.g. headache, musculoskeletal pain, postsurgical pain). Using validated screening tools for neuropathic symptoms, a number of recent populationbased studies reported higher levels of pain intensity, as well as anxiety and depressive symptoms, in respondents who scored high on neuropathic symptoms, compared to those who scored low. Consequently, many authors have suggested the assumption of the uniqueness of neuropathic pain quality in its intensity and distressing characteristic. We aimed to further examine the association of the severity of neuropathic symptoms with pain-related (e.g. pain intensity and chronicity) and psychological factors (e.g. depression) in clinical samples of patients: one sample of patients with diverse types of chronic pain (study 1), and 4 samples of patients with typical neuropathic pain, radiculopathy, fibromyalgia or nociceptive back pain (study 2). In study 2, we also compared different patterns of neuropathic symptoms regarding pain and psychological factors. Seven hundred and six (study 1: n=400; study 2: n=306) patients suffering from a chronic pain condition enrolled for multidisciplinary pain treatment were considered for inclusion in the research project. The criteria for inclusion were: an age of over 18 years and having chronic pain according to ICD-10 criteria (F45.41 or R52.1-2). In study 2 only patients with typical neuropathic pain, back pain with (radiculopathy) or without (nociceptive back pain) clinical signs of nerve involvement, and fibromyalgia were included. The pain DETECT questionnaire was used to assess the severity of neuropathic symptoms in patients. A high severity of neuropathic symptoms was found not only in “typical neuropathic pain” but also in fibromyalgia and postsurgical pain (study 1). At first sight, our findings in a sample of patients with diverse types of chronic pain (study 1) suggested that neuropathic symptoms are associated with a high level of pain intensity, pain chronicity, functional disability and depression. However, in study 2 considering patients who had been diagnosed with typical neuropathic pain, radiculopathy or fibromyalgia, neither severity nor different patterns of neuropathic symptoms were correlated with the pain-related and psychological variables. A subgroup of nociceptive back pain patients who scored high on selfreported neuropathic symptoms reported high levels of pain intensity, depression, catastrophising and non-acceptance of pain suggesting a general response tendency (response bias) in this subgroup of nociceptive back pain patients. In summary, the results corroborate and support a dimensional perspective of neuropathic pain. Our findings lend no support to the assumption of many authors that a high severity of neuropathic symptoms principally results in high levels of pain intensity and psychological distress as it is not the case in patients with an underlying pathology of neuropathic symptoms. The results highlight the influence of cognitive-emotional factors on the experience and report of pain. The implications of these findings for research and clinical practice are discussed