Mechanical detection and pain thresholds: comparability of devices using stepped and ramped stimuli.

Quantitative sensory testing is used to assess somatosensory function in humans. The protocol of the German Research Network on Neuropathic Pain (DFNS) provides comprehensive normative values using defined tools; however, some of these may not be feasible in low-resource settings. OBJECTIVES: To compare the standard DFNS devices for assessment of mechanosensory function to a low resource tool, the Sorri-Bauru-monofilaments. METHODS: Mechanical detection thresholds (MDT), pain thresholds (MPT), and suprathreshold pinprick ratings (pain sensitivity: MPS) were measured over cheek, hand dorsum, and fingertip in 13 healthy subjects (7 female, aged 21-44 years). Mechanical detection threshold was assessed with DFNS standard glass monofilaments (0.25-512 mN, 0.5 mm tip) and nylon monofilaments (Sorri-Bauru; 0.5-3000 mN). MPT was assessed with DFNS standard cylindrical probes (8-512 mN, 0.25 mm tip), Sorri-Bauru monofilaments, and with ramped stimuli using an electronic von Frey aesthesiometer (10 mN/s or 100 mN/s, 0.20 mm tip). MPS was measured in response to stepped and ramped pinpricks (128 and 256 mN). RESULTS: Mechanical detection thresholds were the same for DFNS and Sorri-Bauru monofilaments. For MPT, Sorri-Bauru filaments yielded lower values than PinPricks over face but not hand. Pain thresholds were higher at all test sites for ramped than stepped pinpricks (P < 0.01). Suprathreshold ratings were lower for ramped than stepped pinpricks (P < 0.05). CONCLUSION: Sorri-Bauru filaments are acceptable substitutes for DFNS standards in estimating tactile sensitivity, but are not consistent with standard probes for pinprick sensitivity because of their nonstandardized tips. Ramped stimuli overestimated MPT and underestimated MPS due to reaction time artefacts and therefore need their own normative values.

Clinical characteristics of neuropathic pain in leprosy and associated somatosensory profiles: a deep phenotyping study in India.

This study investigated the clinical characteristics and somatosensory profiles of patients suffering from leprosy in Mumbai, India. A cross-sectional deep profiling study was conducted in 86 patients with leprosy (with and without pain) using an extensive battery of phenotyping measures including structured clinical examination, psychological state (General Health Questionnaire [GHQ-12]), and a quality-of-life condition-specific instrument (Brief Pain Inventory-short form). Quantitative sensory testing was performed according to the protocol of the German Research Network on Neuropathic Pain (DFNS) to assess the somatosensory profiles in the ulnar nerve innervation territory of all participants (dorsum of the hand). Reference data from 50 healthy Indian subjects were within the range of published DFNS values. Somatosensory profiles in leprosy patients with clinically or electroneurographically diagnosed neuropathy (with and without pain) revealed a profile of sensory loss to thermal and tactile stimuli combined with preservation of vibration and deep pressure detection. Sensory gain phenomena were not generally observed in patients with leprosy. In the group of subclinical neuropathy, a high degree of impaired thermal sensation was found, which could be clinically deployed to enhance identification of leprosy neuropathy at an early stage. Quantitative sensory testing can effectively document leprosy-associated neuropathy but does not distinguish between patients with or without pain. Patients with leprosy and neuropathic pain reported a poor quality of life and less psychological well-being compared with the pain-free patients with leprosy neuropathy.

Investigation of neuropathic pain in treated leprosy patients in Ethiopia: a cross-sectional study.

Pain can be a significant problem for treated leprosy patients. It can be nociceptive due to tissue inflammation occurring during episodes of immune mediated reactions, or neuropathic due to leprosy affecting the somatosensory system. There are sparse epidemiological data on the prevalence and impact of neuropathic pain in treated leprosy patients. Tools for assessing neuropathic pain have not been validated in leprosy. We have examined nature of pain in a cross-sectional study to determine the prevalence of neuropathic pain (NP) in 80 recently treated leprosy patients in Ethiopia. Pain and depression were evaluated using the General Health Questionnaire (GHQ-12) and the Brief Pain Inventory (BPI) questionnaire. The Douleur Neuropathique en 4 Questions (DN4) and the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) were used as screening tools for NP. Pain of any type was experienced by 60% of the patients. Pure nociceptive pain was experienced by 43%, pure NP by 11%, and mixed pain by 6%. Of the 14 patients who had NP either alone or in combination with nociceptive pain, 12 had high GHQ-12 scores, indicating possible depression. The DN4 had sensitivity and specificity of 100% and 45%, whereas the LANSS had 85% and 42%, respectively. This is the first study to differentiate nociceptive from NP in leprosy patients. The prevalence of NP is high in recently treated Ethiopian leprosy patients. We have validated the use of DN4 in leprosy and it is easier to use than LANSS. Depression is a common co-morbidity in patients with NP. The high prevalence and morbidity of NP in treated leprosy patients warrant clinical trials to assess the efficacy of pain therapies for leprosy-associated NP.