Sensory signs in complex regional pain syndrome and peripheral nerve injury.

This study determined patterns of sensory signs in complex regional pain syndrome (CRPS) type I and II and peripheral nerve injury (PNI). Patients with upper-limb CRPS-I (n=298), CRPS-II (n=46), and PNI (n=72) were examined with quantitative sensory testing according to the protocol of the German Research Network on Neuropathic Pain. The majority of patients (66%-69%) exhibited a combination of sensory loss and gain. Patients with CRPS-I had more sensory gain (heat and pressure pain) and less sensory loss than patients with PNI (thermal and mechanical detection, hypoalgesia to heat or pinprick). CRPS-II patients shared features of CRPS-I and PNI. CRPS-I and CRPS-II had almost identical somatosensory profiles, with the exception of a stronger loss of mechanical detection in CRPS-II. In CRPS-I and -II, cold hyperalgesia/allodynia (28%-31%) and dynamic mechanical allodynia (24%-28%) were less frequent than heat or pressure hyperalgesia (36%-44%, 67%-73%), and mechanical hypoesthesia (31%-55%) was more frequent than thermal hypoesthesia (30%-44%). About 82% of PNI patients had at least one type of sensory gain. QST demonstrates more sensory loss in CRPS-I than hitherto considered, suggesting either minimal nerve injury or central inhibition. Sensory profiles suggest that CRPS-I and CRPS-II may represent one disease continuum. However, in contrast to recent suggestions, small fiber deficits were less frequent than large fiber deficits. Sensory gain is highly prevalent in PNI, indicating a better similarity of animal models to human patients than previously thought. These sensory profiles should help prioritize approaches for translation between animal and human research.

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.

A case of neuropathic brachioradial pruritus caused by cervical disc herniation.

BACKGROUND: A 64-year-old woman presented to an outpatient clinic with a 2-year history of itch, burning sensation and intermittent paresthesias within the innervation territory of the sixth cervical nerve root on the right dorsal forearm. No dermatological diseases, trauma to the affected extremity or the spine, or familial pruritus were reported. INVESTIGATIONS: Dermatological examination, skin biopsy, laser Doppler imaging, neurological physical examination and cervical MRI scan. DIAGNOSIS: Brachioradial pruritus caused by cervical disc herniation. MANAGEMENT: Ventral spinal fusion with cage implantation.

Disease mechanisms in neuropathic itch.

Itch, also known as pruritus, is an unpleasant cutaneous sensation that provokes the desire to scratch. Itch is a common symptom of inflammatory skin disorders, but it can also occur in neurological diseases associated with injury to nervous tissue, in the absence of any skin disease and without any notable physiological stimuli in the periphery. This 'neuropathic' type of itch occurs either in combination with neuropathic pain or independently and is thought to be underdiagnosed. In this Review, we describe the physiological characteristics of specific neuronal systems in the PNS and CNS that transmit and process pruriceptive information, and we consider pathological changes that occur in these systems after nerve lesions. We then introduce a classification system for itch and highlight the similarities and differences between neuropathic itch and neuropathic pain. A summary of neuropathic syndromes in the PNS and CNS that are associated with itch is presented. Finally, we propose appropriate treatment strategies for neuropathic itch, in view of the fact that this condition has different mechanisms of itch generation to other types of itch and consequently requires different therapies.