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Background In Swedish working life, exposure to cold and exposure to hand-arm vibration (HAV) are two common health hazards. Health effects of HAV in the neurosensory, vascular and musculoskeletal systems are collectively denoted hand-arm vibration syndrome (HAVS), and have been thoroughly studied. Effects of cold exposure in terms of effects on the peripheral neurosensory and vascular system are on the contrary limited, especially in an occupational setting. Effects of cold exposure or cold injury have not previously been assessed with quantitative sensory testing (QST). Commonly reported symptoms after exposure to HAV and after cold injuries, includes cold sensitivity and sensation of cold. Cold sensitivity can also occur without previous exposure to vibration or cold and may have a major impact on quality of life. Other possible risk factors for cold sensitivity need to be assessed. Sensation of cold hands could theoretically imply an early manifestation of damage to the neurosensory or vascular system, and therefore be of importance to enable early detection of vascular and neurosensory HAVS. The purpose of this thesis was to increase the knowledge about health effects from cold and HAV on the peripheral neurosensory and vascular system, with an occupational perspective. The aims were: first, to identify and evaluate health effects and sequelae in the peripheral neurosensory and vascular system due to cold injury and cold exposure; second, to investigate if sensation of cold hands is a predictor for future onset of Raynaud's phenomenon or paresthesia; and third, to identify possible risk factors associated with cold sensitivity. Methods A case series on 15 military conscripts with local cold injuries in the hands or feet, involving QST and symptom descriptions, was conducted to investigate the hypothesis that cold injuries can result in similar neurosensory and vascular impairments as in HAVS. To assess health effects of cold exposure, a cohort study on 54 military conscripts in cold winter military training, with cold exposure assessments, was conducted. Possible health effects were assessed after 14 months of military training, containing considerable cold exposure, by means of QST, Finger systolic blood pressure after local cooling (FSBP) and a questionnaire. To investigate if sensation of cold hands is a predictor for vascular or neurosensory HAVS we investigated a cohort of 178 employees at a manufacturing company where HAV was a common exposure. The cohort was followed during 21 years and both vibration exposure and health outcomes were assessed regularly. Questionnaire items were used to assess sensations of cold hands as well as signs of Raynaud’s phenomenon and paresthesia. To identify risk factors for cold sensitivity a case-control study was conducted involving 997iiiparticipants from the general population in northern Sweden. The study was cross-sectional and explored possible risk factors for cold sensitivity. Results Cold injuries and cold exposure were associated with reduced sensibility in QST and increase severity and prevalence of neurosensory and vascular symptoms. Our results did not show any impairment in peripheral blood flow due to cold exposure, detectable by FSBP. The risk of developing Raynaud's phenomenon was increased for workers previously reporting sensation of cold hands (OR 6.3, 95% CI 2.3-17.0). No increased risk for paresthesia in relation to a sensation of cold hands was observed. The identified risk factors for cold sensitivity were frostbite in the hands, rheumatic disease, nerve injury in upper extremities or neck, migraine and vascular disease. When analysing women and men separately, women’s risk factors were frostbite in the hands, rheumatic disease, migraine and cold exposure. Men’s risk factors were frostbite in the hands, vibration exposure and nerve injury in upper extremities or neck. BMI > 25 was a protective factor for both men and women. Conclusion Cold injury and cold exposure are associated with impairments in the neurosensory system, detectable by QST. Symptoms such as sensation of cold hands and white fingers indicate vascular involvement, even though no vascular impairments due to cold exposure could be detected by objective measurements. A sensation of cold hands is a risk factor for development of Raynaud´s phenomenon, but not for paresthesia. At the individual level, reporting cold hands does not appear to be useful information when considering the possibility of a future development of Raynaud’s phenomenon. Frostbite in the hands is a risk factor for cold sensitivity among both women and men. For women rheumatic disease, migraine and cold exposure are also independent risk factors, and for men, exposure to HAV. Being overweight is a protective factor for both women and men.

Objetivos: A dor neuropática crônica origina-se em consequência direta de uma lesão ou doença que afete o sistema somato-sensitivo. Pacientes que são refratários ao tratamento conservador são considerados candidatos a procedimentos invasivos, principalmente de ordem neuro-modulatória. A estimulação do gânglio da raiz dorsal é uma técnica recente de neuromodulação utilizada para o tratamento das dores neuropáticas crônicas de diferentes etiologias. Apesar do sucesso clínico da estimulação do gânglio da raiz dorsal no tratamento de dor neuropática já ter sido relatado em diversos trabalhos da literatura, os mecanismos neurofisiológicos responsáveis pelo alivio da dor ainda permanecem pouco esclarecidos. O presente trabalho avalia o efeito da estimulação do gânglio da raiz dorsal no processamento cortical da dor através do método de potenciais evocados a laser (PELs). Métodos: Avaliamos prospectivamente por 3 anos 34 doentes com dor inguinal (grupo 1), 62 doentes com dores neuropáticas diversas (grupo 2) que foram submetidos a estimulação do gânglio da raiz dorsal. Nestes 2 grupos foram analisadas variáveis relacionadas a intensidade da dor, incapacidade relacionada a dor, níveis de depressão e pensamentos catastróficos relacionados a dor. Adicionalmente, um subgrupo de 12 pacientes submetidos à cirurgia de estimulação do gânglio da raiz dorsal para tratamento de dor neuropática crônica unilateral da região inguinal, joelho ou perna por lesão direta de nervo periférico após procedimento cirúrgico, síndrome do insucesso da cirurgia espinhal ou síndrome dolorosa regional complexa tipo II foi avaliado de forma prospectiva (grupo 3). O lado normal foi utilizado como controle. PELs foram evocados por meio de estimulação a laser de CO2 na área desaferentada e normal. Latências e amplitudes dos componentes N2 e P2 e amplitudes do complexo N2-P2 foram correlacionados à intensidade da dor antes da terapia e após 1 e 6 meses de tratamento com estimulação do gânglio da raiz dorsal. Testes sensitivos quantitativos, escalas de intensidade da dor, incapacidade relacionada a dor, qualidade de vida, e depressão foram avaliadas. Resultados: Houve aumento significante das amplitudes do complexo N2-P2, igualando-se ao lado normal, e em paralelo diminuição significativa da intensidade de dor e na incapacidade relacionada à dor após 1 e 6 meses de tratamento em comparação com o estado pré-tratamento. Houve melhora significativa em 2 dos 8 itens de qualidade de vida avaliados. Não houve alteração significativa nos testes sensitivos quantitativos e na escala de depressão. Conclusão: A estimulação do gânglio da raiz dorsal restabeleceu as amplitudes dos PELs oriundos do giro do cíngulo anterior, ínsula e áreas temporais mediais, restaurando o processamento cortical fisiológico de dor em pacientes com dor neuropática crônica / Objectives: Chronic neuropathic pain originates as a direct consequence of an injury or disease that affects the somatosensory system. Patients who are refractory to conservative treatment are considered candidates for invasive procedures, mainly of neuro-modulatory order. Dorsal root ganglion stimulation is a recent neuromodulation technique used for the treatment of chronic neuropathic pain of different etiologies. Although the clinical success of dorsal root ganglion stimulation in the treatment of neuropathic pain has already been reported in several studies in the literature, the neurophysiological mechanisms responsible for pain relief remain unclear. The present study evaluates the effect of dorsal root ganglion stimulation on cortical pain processing through the use of laser evoked potentials (LEP). Methods: We evaluated prospectively during 3 years 34 patients with groin pain (group 1), 62 patients with various forms of neuropathic pain (group 2) who underwent dorsal root ganglion stimulation. In these 2 groups, variables related to pain intensity, pain-related disability, depression levels and painrelated catastrophic thoughts were analyzed. In addition, we prospectively analyzed a subgroup of 12 patients treated with dorsal root ganglion stimulation for treatment of chronic unilateral neuropathic pain of the groin region, knee or leg caused by direct injury of the peripheral nerve after surgical procedure, failed back surgery syndrome or complex regional pain syndrome type II (group 3). The healthy side was used as control. LEPs were evoked by means of CO2 laser stimulation in the deafferented and normal areas. Latencies and amplitudes of the N2 and P2 components and amplitudes of the N2-P2 complex were correlated to the pain intensity before therapy and after 1 and 6 months of treatment with dorsal root ganglion stimulation. Quantitative sensory testing, pain intensity scales, pain-related disability, quality of life, and depression were assessed. Results: There was a significant increase in N2-P2 complex amplitudes, matching the normal side, and in parallel a significant decrease in pain intensity and pain-related disability after 1 and 6 months of treatment compared to the pre-treatment state. There was a significant improvement in 2 out of 8 quality of life domains evaluated. There was no significant change in quantitative sensory testing and depression levels. Conclusion: Stimulation of the dorsal root ganglion reestablished the amplitudes of the LEPs originated from the anterior cingulate gyrus, insula, and medial temporal areas, restoring physiological cortical pain processing in patients with chronic neuropathic pain

Selon l’Association Internationale pour l’Étude de la Douleur, la douleur neuropathique est causée par « une lésion ou une maladie du système somatosensoriel ». Actuellement, il n’existe pas de test permettant de la diagnostiquer avec certitude. En médecine humaine, les suspicions cliniques reposent essentiellement sur les caractéristiques de la douleur perçue par le patient. En effet, le mélange de douleurs lancinantes et fulgurantes souvent de très forte intensité, et les termes utilisés pour les décrire, permettent de poser un diagnostic présomptif. En revanche, chez les personnes non-communicantes ainsi que chez nos patients en médecine vétérinaire, la douleur neuropathique devient extrêmement difficile à déceler. Elle pose aussi un problème éthique puisque ces douleurs sont souvent qualifiées d’insoutenables et sont notoirement réfractaires aux traitements analgésiques conventionnels. Faute de données spécifiques, le Conseil sur la douleur de l’Association internationale des vétérinaires pour les animaux de compagnie (WSAVA Global Pain Council) base ses recommandations thérapeutiques sur des succès anecdotiques relevés dans des rapports de cas ou des données tirées de la médecine humaine. Notre étude s’articulait autour de trois objectifs principaux : 1) Évaluer la fiabilité et la faisabilité des tests proposés pour explorer les profils somatosensoriels chez des chiens de propriétaires, incluant une nouvelle méthode dynamique permettant d’évaluer le système endogène de modulation de la douleur ; 2) Identifier une population de chiens de propriétaires présentant de la douleur neurologique chronique à composante neuropathique d’apparition spontanée, en se basant sur les recommandations données en médecine humaine, et caractériser la douleur neuropathique dans ce groupe, en comparant les profils somatosensoriels et les concentrations en cytokines inflammatoires de ces chiens avec ceux d’un groupe contrôle ; 3) Suivre l’évolution des profils somatosensoriels, des concentrations en cytokines inflammatoires et des scores de douleur/qualité de vie des chiens neuropathiques enrôlés dans un essai clinique croisé prospectif, partiellement masqué et randomisé, afin d’évaluer les effets du placebo, du gabapentin seul ou administré en combinaison avec le méloxicam sur ces paramètres. Nos hypothèses étaient que la méthodologie proposée serait fiable et faisable pour évaluer les profils somatosensoriels chez les chiens de propriétaires, et que la population de chiens souffrant de douleur neuropathique diffèrerait du groupe contrôle par leurs concentrations en cytokines inflammatoires, leurs seuils nociceptifs et leur capacité à moduler la douleur après application d’un stimulus conditionnant. Enfin, il était attendu que les traitements actifs (gabapentin et gabapentin-méloxicam) altèreraient les profils somatosensoriels, les scores de douleur/qualité de vie et les concentrations en cytokines inflammatoires des patients neuropathiques. Les tests quantitatifs sensoriels retenus pour évaluer la population de chiens neuropathiques dans la seconde partie du projet (stimulations mécanique et électrique) étaient fiables, faciles à réaliser et bien tolérés. L’évaluation du système inhibiteur descendant induit par les stimulations nociceptives (système endogène de modulation de la douleur; DNIC) a permis de mettre en évidence une dysfonction de la capacité de modulation de la douleur chez les chiens neuropathiques. L’administration de gabapentin combiné ou non avec le méloxicam a eu pour effet de « normaliser » les profils somatosensoriels dynamiques (augmentation du nombre de chiens présentant une inhibition après l’application d’un stimulus conditionnant). Les scores de douleur/qualité de vie ont évolué en faveur d’une amélioration avec l’administration de gabapentin seul ou en combinaison avec le méloxicam. Les concentrations en cytokines inflammatoires et les profils somatosensoriels statiques (les seuils nociceptifs), quant à eux, n’étaient pas différents entre les groupes et n’ont pas significativement varié avec les traitements étudiés. À travers ces études, nous avons présenté de nouvelles techniques de QST fiables et faisable chez le chien. Nous avons également montré que l’évaluation du DNIC est possible dans l’espèce canine, et que les chiens présentant une douleur chronique à composante neuropathique ont un DNIC déficient. L’évaluation des profils somatosensoriels dynamiques et des scores de douleur/qualité de vie supportent l’utilisation du gabapentin seul ou en combinaison avec le méloxicam pour le traitement médical de la douleur neuropathique chez le chien, tel que recommandé par les spécialistes du WSAVA. / According to the International Association for the Study of Pain, neuropathic pain is caused by "a lesion or a disease of the somatosensory system". Currently, there is no definitive test available to diagnose neuropathic pain. In humans, the presumptive diagnosis is essentially based on the characteristics of the pain perceived by the patient. In non-communicative individuals, on the other hand, just like in our patients in veterinary medicine, the diagnosis of neuropathic pain is difficult and poses an ethical problem because this type of pain is often qualified as unbearable and known to be refractory to conventional therapies. In the absence of specific data, the Global Pain Council of World Small Animal Veterinary Association (WSAVA) based its treatment recommendations of neuropathic pain on anecdotal veterinary reports, case reports or data from human medicine. This PhD program had three main objectives: 1) To assess the reliability and feasibility of the tests proposed to explore the somatosensory profiles in client-owned dogs, including a method to assess the descending noxious inhibitory controls; 2) To identify a population of client-owned dogs with naturally-occurring neuropathic pain, based on the recommendations from human medicine ; and to characterize neuropathic pain in this group, by comparing the somatosensory profiles and the serum levels of inflammatory cytokines of these dogs with those of a control group; 3) To determine the effects of placebo, gabapentin alone or in combination with meloxicam on the somatosensory profiles, concentrations of inflammatory cytokines and pain scores of dogs with naturally-occurring neuropathic pain managed medically, in a prospective, partially masked and randomized crossover clinical trial. Our hypotheses were that the proposed methodology would be feasible and reliable, allowing to assess somatosensory profiles of client-owned dogs, and that dogs with neuropathic pain would differ from the control group in their serum concentrations of inflammatory cytokines, their nociceptive thresholds and their ability to modulate pain after the application of a conditioning stimulus. Gabapentin and gabapentin-meloxicam would change somatosensory profiles, pain scores and serum concentrations of inflammatory cytokines of dogs with neuropathic pain. 7 The quantitative sensory tests (electrical and mechanical stimulations) were easy to perform, well tolerated and reliable. The evaluation of the diffuse noxious inhibitory control (endogenous pain modulation system; DNIC) revealed a dysfunction of the pain modulation capacity in neuropathic dogs. Administration of gabapentin with or without meloxicam had a "normalizing" effect on the dynamic somatosensory profiles (increase in the number of dogs showing inhibition after application of a conditioning stimulus). Pain / quality of life scores improved after gabapentin alone or in combination with meloxicam. On the other hand, serum concentrations of inflammatory cytokines and static somatosensory profiles (nociceptive thresholds) were not different between groups and did not vary significantly with treatments. Through these studies, we have presented new reliable and feasible QST techniques in dogs. We have also shown that the evaluation of the DNIC is possible in the canine species, and that dogs with chronic pain with a neuropathic component have a deficient DNIC. The assessment of the dynamic somatosensory profiles and pain / quality of life scores support the use of gabapentin alone or in combination with meloxicam for the medical management of neuropathic pain in dogs, as recommended by WSAVA specialists.