Axial low back pain: one painful area--many perceptions and mechanisms

Abstract

Axial low back pain can be considered as a syndrome with both nociceptive and neuropathic pain components (mixed-pain). Especially neuropathic pain comprises a therapeutic challenge in practical experience and may explain why pharmacotherapy in back pain is often disappointing for both the patient and the therapist. This survey uses epidemiological and clinical data on the symptomatology of 1083 patients with axial low back pain from a cross sectional survey (painDETECT). Objectives were (1) to estimate whether neuropathic pain contributes to axial low back pain and if so to what extent. (2) To detect subgroups of patients with typical sensory symptom profiles and to analyse their demographic data and co-morbidities. (3) To compare patients with and without prior intervertebral disc surgery (IVD). Neuropathic pain components could be detected in 12% of the entire cohort. Cluster analyses of these patients revealed five distinct subgroups of patients showing a characteristic sensory profile, i.e. a typical constellation and combination of symptoms. All subgroups occurred in relevant numbers and some showed distinct neuropathic characteristics while others showed nociceptive features. Post-IVD-surgery patients showed a tendency to score more "neuropathic" than patients without surgery (not statistically significant). Axial low back pain has a high prevalence of co-morbidities with implication on therapeutic aspects. From these data it can be concluded that sensory profiles based on descriptor severity may serve as a better predictor for therapy assessment than pain intensity or sole diagnosis alone. Standardized phenotyping of pain symptoms with easy tools may help to develop an individualized therapy leading to a higher success rate in pharmacotherapy of axial low back pain.

Figure 1. Differences in PD-Q scores in the subgroups.

The different scores calculated from the PD-Q are shown, revealing the proportion of positive, i.e. neuropathic and negative, i.e. non-neuropathic as well as unclear results. Patients from clusters 3 and 4 showed the tendency to score more neuropathic than those from clusters 1, 2 and 5.

Figure 2. Subgroups of patients based on their sensory symptoms.

To identify relevant subgroups of patients who are characterized by a characteristic symptom constellation a hierarchical cluster analysis was performed. The clusters are represented by the patterns of questionnaire scores (A: adjusted individual mean; B: non-adjusted values), thus showing the typical pathological structure of the respecting group. By using this approach five clusters with distinct symptom profiles could be detected in the cohort. Sensory profiles show remarkable differences in the expression of the symptoms. Subgroup 5 does not show any outstanding symptoms and low prevalence of symptoms in general.

Figure 3. Differences in PD-Q scores after IVD-surgery.

The pie-chart depicts the proportion of patients with and without IVD-surgery scoring “positive”, “unclear” or “negative” in the PD-Q. There are no significant differences between the respective groups (χ²-Test, p = 0.2215).