Pain
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Multicenter Study
Intraoral somatosensory abnormalities in patients with atypical odontalgia--a controlled multicenter quantitative sensory testing study.
Intraoral somatosensory sensitivity in patients with atypical odontalgia (AO) has not been investigated systematically according to the most recent guidelines. The aims of this study were to examine intraoral somatosensory disturbances in AO patients using healthy subjects as reference, and to evaluate the percent agreement between intraoral quantitative sensory testing (QST) and qualitative sensory testing (QualST). Forty-seven AO patients and 69 healthy control subjects were included at Universities of Washington, Malmö, and Aarhus. ⋯ The most frequent LossGain code was L0G2 (no somatosensory loss with gain of mechanical somatosensory function) (31.9% of AO patients). Percent agreement between corresponding QST and QualST measures of thermal and mechanical sensitivity ranged between 55.6% and 70.4% in AO patients and between 71.1% and 92.1% in control subjects. In conclusion, intraoral somatosensory abnormalities were commonly detected in AO patients, and agreement between quantitative and qualitative sensory testing was good to excellent.
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Pain is a frequently observed non-motor symptom of patients with Parkinson's disease. In some patients, Parkinson's-related pain responds to dopaminergic treatment. In the present study, we aimed to elucidate whether subthalamic deep brain stimulation has a similar beneficial effect on pain in Parkinson's disease, and whether this effect can be predicted by a pre-operative l-dopa challenge test assessing pain severity. ⋯ In the remaining 6 patients, pain was not improved by dopaminergic treatment nor by deep brain stimulation. Thus, we conclude that pain relief following subthalamic deep brain stimulation is superior to that following dopaminergic treatment, and that the response of pain symptoms to deep brain stimulation can be predicted by l-dopa challenge tests assessing pain severity. This diagnostic procedure could contribute to the decision on whether or not a Parkinson's patient with severe pain should undergo deep brain stimulation for potential pain relief.
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The enzyme catechol-O-methyltransferase (COMT) metabolizes catecholamine neurotransmitters involved in a number of physiological functions, including pain perception. Both human and mouse COMT genes possess functional polymorphisms contributing to interindividual variability in pain phenotypes such as sensitivity to noxious stimuli, severity of clinical pain, and response to pain treatment. In this study, we found that the effects of Comt functional variation in mice are modality specific. ⋯ The ancestral Comt variant, without a B2 SINE insertion, was more strongly associated with sensitivity to capsaicin in female vs male mice. In humans, the haplotype coding for low COMT activity increased capsaicin-induced pain perception in women, but not men. These findings reemphasize the fundamental contribution of COMT to pain processes, and provide a fine-grained resolution of this contribution at the genetic level that can be used to guide future studies in the area of pain genetics.
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Limb amputation may lead to chronic painful sensations referred to the absent limb, ie phantom limb pain (PLP), which is likely subtended by maladaptive plasticity. The present study investigated whether transcranial direct current stimulation (tDCS), a noninvasive technique of brain stimulation that can modulate neuroplasticity, can reduce PLP. In 2 double-blind, sham-controlled experiments in subjects with unilateral lower or upper limb amputation, we measured the effects of a single session of tDCS (2 mA, 15 min) of the primary motor cortex (M1) and of the posterior parietal cortex (PPC) on PLP, stump pain, nonpainful phantom limb sensations and telescoping. ⋯ PLP is associated primarily with cortical excitability shifts in the sensorimotor network; increasing excitability in this system by anodal tDCS has an antalgic effect on PLP. Conversely, nonpainful phantom sensations are associated to a hyperexcitation of PPC that can be normalized by cathodal tDCS. This evidence highlights the relationship between the level of excitability of different cortical areas, which underpins maladaptive plasticity following limb amputation and the phenomenology of phantom limb, and it opens up new opportunities for the use of tDCS in the treatment of PLP.