Sensory-Discriminative Three-Dimensional Body Pain Mobile App Measures Versus Traditional Pain Measurement With a Visual Analog Scale: Validation Study.

BACKGROUND: To quantify pain severity in patients and the efficacy treatments, researchers and clinicians apply tools such as the traditional visual analog scale (VAS) that leads to inaccurate interpretation of the main sensory pain. OBJECTIVE: This study aimed to validate the pain measurements of a neuroscience-based 3D body pain mobile app called GeoPain. METHODS: Patients with temporomandibular disorder (TMD) were assessed using GeoPain measures in comparison to VAS and positive and negative affect schedule (PANAS), pain and mood scales, respectively. Principal component analysis (PCA), scatter score analysis, Pearson methods, and effect size were used to determine the correlation between GeoPain and VAS measures. RESULTS: The PCA resulted in two main orthogonal components: first principal component (PC1) and second principal component (PC2). PC1 comprises a combination score of all GeoPain measures, which had a high internal consistency and clustered together in TMD pain. PC2 included VAS and PANAS. All loading coefficients for GeoPain measures in PC1 were above 0.70, with low loadings for VAS and PANAS. Meanwhile, PC2 was dominated by a VAS and PANAS coefficient >0.4. Repeated measure analysis revealed a strong correlation between the VAS and mood scores from PANAS over time, which might be related to the subjectivity of the VAS measure, whereas sensory-discriminative GeoPain measures, not VAS, demonstrated an association between chronicity and TMD pain in locations spread away from the most commonly reported area or pain epicenter (P=.01). Analysis using VAS did not detect an association at baseline between TMD and chronic pain. The long-term reliability (lag >1 day) was consistently high for the pain area and intensity number summation (PAINS) with lag autocorrelations averaging between 0.7 and 0.8, and greater than the autocorrelations for VAS averaging between 0.3 and 0.6. The combination of higher reliability for PAINS and its objectivity, displayed by the lack of association with PANAS as compared with VAS, indicated that PAINS has better sensitivity and reliability for measuring treatment effect over time for sensory-discriminative pain. The effect sizes for PAINS were larger than those for VAS, consequently requiring smaller sample sizes to assess the analgesic efficacy of treatment if PAINS was used versus VAS. The PAINS effect size was 0.51 SD for both facial sides and 0.60 SD for the right side versus 0.35 SD for VAS. Therefore, the sample size required to detect such effect sizes with 80% power would be n=125 per group for VAS, but as low as n=44 per group for PAINS, which is almost a third of the sample size needed by VAS. CONCLUSIONS: GeoPain demonstrates precision and reliability as a 3D mobile interface for measuring and analyzing sensory-discriminative aspects of subregional pain in terms of its severity and response to treatment, without being influenced by mood variations from patients.

Immediate effects of tDCS on the µ-opioid system of a chronic pain patient.

We developed a unique protocol where transcranial direct current stimulation (tDCS) of the motor cortex is performed during positron emission tomography (PET) scan using a µ-opioid receptor (µOR) selective radiotracer, [(11)C]carfentanil. This is one of the most important central neuromechanisms associated with pain perception and regulation. We measured µOR non-displaceable binding potential (µOR BP(ND)) in a trigeminal neuropathic pain patient (TNP) without creating artifacts, or posing risks to the patient (e.g., monitoring of resistance). The active session directly improved in 36.2% the threshold for experimental cold pain in the trigeminal allodynic area, mandibular branch, but not the TNP patient's clinical pain. Interestingly, the single active tDCS application considerably decreased µORBP(ND) levels in (sub)cortical pain-matrix structures compared to sham tDCS, especially in the posterior thalamus. Suggesting that the µ-opioidergic effects of a single tDCS session are subclinical at immediate level, and repetitive sessions are necessary to revert ingrained neuroplastic changes related to the chronic pain. To our knowledge, we provide data for the first time in vivo that there is possibly an instant increase of endogenous µ-opioid release during acute motor cortex neuromodulation with tDCS.

Reduced basal ganglia µ-opioid receptor availability in trigeminal neuropathic pain: a pilot study.

BACKGROUND: Although neuroimaging techniques have provided insights into the function of brain regions involved in Trigeminal Neuropathic Pain (TNP) in humans, there is little understanding of the molecular mechanisms affected during the course of this disorder. Understanding these processes is crucial to determine the systems involved in the development and persistence of TNP. FINDINGS: In this study, we examined the regional µ-opioid receptor (µOR) availability in vivo (non-displaceable binding potential BPND) of TNP patients with positron emission tomography (PET) using the µOR selective radioligand [11C]carfentanil. Four TNP patients and eight gender and age-matched healthy controls were examined with PET. Patients with TNP showed reduced µOR BPND in the left nucleus accumbens (NAc), an area known to be involved in pain modulation and reward/aversive behaviors. In addition, the µOR BPND in the NAc was negatively correlated with the McGill sensory and total pain ratings in the TNP patients. CONCLUSIONS: Our findings give preliminary evidence that the clinical pain in TNP patients can be related to alterations in the endogenous µ-opioid system, rather than only to the peripheral pathology. The decreased availability of µORs found in TNP patients, and its inverse relationship to clinical pain levels, provide insights into the central mechanisms related to this condition. The results also expand our understanding about the impact of chronic pain on the limbic system.

Dores neuropáticas: classificação, diagnóstico, mecanismos e importância para o cirurgião-dentista / Neuropathic pain: classification, diagnosis, mechanisms and clinical importance

As dores neuropáticas podem ser definidas, segundo a International Association for the Study of Pain (IASP), como "dor iniciada ou causada por uma lesão ou disfunção primária no sistema nervoso". Elas estão presentes em um grupo heterogêneo de condições como diabetes, deficiências imunológicas, doenças malignas, desordens traumáticas e isquêmicas, câncer, doenças degenerativas ou alterações neurológicas, podendo ainda ser agudas ou crônicas. Na região orofacial, elas ainda podem surgir após injúrias aos ramos do nervo trigêmeo, durante procedimentos odontológicos, tais como cirurgias ortognáticas, cirurgias pré-protéticas, tratamentos endodônticos e a colocação de implantes dentais. Devido a esse fato é de extrema importância que não só os profissionais especializados em Dor Orofacial, mas toda a classe odontológica conheça as principais características dessas dores, possibilitando um melhor manejo dos pacientes, contribuindo para se alcançar o sucesso no tratamento. O objetivo desse artigo é apresentar as características das dores neuropáticas e seus mecanismos de desenvolvimento; seus sinais e sintomas; apresentar o papel do cirurgião-dentista no desenvolvimento e prevenção destas alterações e possibilitar o diagnóstico destas alterações no tratamento clínico da dor orofacial, por meio da revisão da literatura dos artigos mais adequados ao tema