Fibromyalgia and neuropathic pain--differences and similarities. A comparison of 3057 patients with diabetic painful neuropathy and fibromyalgia.

BACKGROUND: Patients with diabetic neuropathy (DPN) and fibromyalgia differ substantially in pathogenetic factors and the spatial distribution of the perceived pain. We questioned whether, despite these obvious differences, similar abnormal sensory complaints and pain qualities exist in both entities. We hypothesized that similar sensory symptoms might be associated with similar mechanisms of pain generation. The aims were (1) to compare epidemiological features and co-morbidities and (2) to identify similarities and differences of sensory symptoms in both entities. METHODS: The present multi-center study compares epidemiological data and sensory symptoms of a large cohort of 1434 fibromyalgia patients and 1623 patients with painful diabetic neuropathy. Data acquisition included standard demographic questions and self-report questionnaires (MOS sleep scale, PHQ-9, PainDETECT). To identify subgroups of patients with characteristic combinations of symptoms (sensory profiles) a cluster analysis was performed using all patients in both cohorts. RESULTS: Significant differences in co-morbidities (depression, sleep disturbance) were found between both disorders. Patients of both aetiologies chose very similar descriptors to characterize their sensory perceptions. Burning pain, prickling and touch-evoked allodynia were present in the same frequency. Five subgroups with distinct symptom profiles could be detected. Two of the subgroups were characteristic for fibromyalgia whereas one profile occurred predominantly in DPN patients. Two profiles were found frequently in patients of both entities (20-35%). CONCLUSIONS: DPN and fibromyalgia patients experience very similar sensory phenomena. The combination of sensory symptoms--the sensory profile--is in most cases distinct and almost unique for each one of the two entities indicating aetiology-specific mechanisms of symptom generation. Beside the unique aetiology-specific sensory profiles an overlap of sensory profiles can be found in 20-35% of patients of both aetiologies.

A cross-sectional survey of 3035 patients with fibromyalgia: subgroups of patients with typical comorbidities and sensory symptom profiles.

OBJECTIVES: Patients with FM are heterogeneous. They present with a variety of pain qualities, sensory abnormalities and additional comorbidities. The aim was to identify clinically distinguishable subgroups of patients. METHODS: This investigation uses epidemiological and clinical data of 3035 FM patients from a cross-sectional survey (painDETECT) to (i) describe characteristic epidemiological data and comorbidities and (ii) detect subgroups of patients with typical patterns of sensory symptoms and comorbidities. RESULTS: Clinically relevant sensory abnormalities (strongly, very strongly present) included pressure pain (58%), prickling (33%), burning (30%) and thermal hypersensitivity (24%). Pain attacks were complained by 40% of patients. Moderate to severe comorbid depression occurred in 66% of patients. Only approximately 30% of the patients had optimal sleep. A hierarchical cluster analysis using descriptors of sensory abnormalities as well as the extent of comorbidities revealed five distinct subgroups of patients showing a characteristic clinical profile. Four subgroups of patients suffer from severe sensory disturbances in various combinations but lack pronounced comorbidities. In one subgroup, however, severe comorbidities dominate the clinical picture. Differences in pathophysiological mechanisms of pain generation can be attributed to each subgroup. CONCLUSIONS: The results of this study indicate that FM patients can be classified on the basis of their sensory symptoms and comorbidities by the use of a patient-reported questionnaire. Subgrouping of patients with FM may be used for future research and to tailor optimal treatment strategies for the appropriate patient.