The journal of pain : official journal of the American Pain Society
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Trigeminal neuralgia, painful trigeminal neuropathy, and painful temporomandibular disorders (TMDs) are chronic orofacial pain conditions that are thought to have fundamentally different etiologies. Trigeminal neuralgia and neuropathy are thought to arise from damage to or pressure on the trigeminal nerve, whereas TMD results primarily from peripheral nociceptor activation. This study sought to assess the volume and microstructure of the trigeminal nerve in these 3 conditions. In 9 neuralgia, 18 neuropathy, 20 TMD, and 26 healthy controls, the trigeminal root entry zone was selected on high-resolution T1-weighted magnetic resonance images and the volume (mm(3)) calculated. Additionally, using diffusion-tensor images (DTIs), the mean diffusivity and fractional anisotropy values of the trigeminal nerve root were calculated. Trigeminal neuralgia patients displayed a significant (47%) decrease in nerve volume but no change in DTI values. Conversely, trigeminal neuropathy subjects displayed a significant (40%) increase in nerve volume but again no change in DTI values. In contrast, TMD subjects displayed no change in volume or DTI values. The data suggest that the changes occurring within the trigeminal nerve are not uniform in all orofacial pain conditions. These structural and volume changes may have implications in diagnosis and management of different forms of chronic orofacial pain. ⋯ This study reveals that neuropathic orofacial pain conditions are associated with changes in trigeminal nerve volume, whereas non-neuropathic orofacial pain is not associated with any change in nerve volume.
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The aim of this study was to investigate the relevance of the basal ganglia (BG) in pathogenesis of migraine by assessing the abnormal volume and resting-state networks of the BG in migraine patients without aura (MWoA). The volume of the subsets in the BG was compared between 40 MWoA and 40 age- and gender-matched healthy controls. The resting-state functional connectivity of BG subsets with abnormal volume was also investigated. Reduced volume in the left caudate and the right nucleus accumbens (NAc) was detected in the migraine group compared with healthy controls; meanwhile, increased functional connectivity between the BG and several brain regions within nociceptive and somatosensory processing pathways was observed. Correlation analysis revealed significant correlations between the volume of the bilateral caudate and right NAc and disease duration. In addition, an increased monthly frequency of migraine attack was associated with increased functional connectivity between the bilateral caudate and left insula, and longer disease duration was correlated with increased functional connectivity between the right NAc and bilateral anterior cingulate cortex. Our results revealed abnormal volume of BG and dysfunctional dynamics during interictal resting state within pain pathways of the BG in MWoA, which validated the association between the BG and migraine. ⋯ Our findings revealed the presence of reduced volume in NAc and caudate of the BG and interictal dysfunctional dynamics within BG networks in MWoA. The abnormal structure and function within the pain-related pathways of the BG were possibly associated with impaired pain processing and modulatory processes in MWoA.
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Randomized Controlled Trial
How good is the neurophysiology of pain questionnaire? A Rasch analysis of psychometric properties.
The Neurophysiology of Pain Questionnaire (NPQ) was devised to assess how an individual conceptualizes the biological mechanisms that underpin his or her pain. Despite its widespread use, its psychometric properties have not been comprehensively interrogated. Rasch analysis was undertaken on NPQ data from a convenience sample of 300 spinal pain patients, and test-retest reliability was assessed in a sample of 45 low back pain patients. The NPQ effectively targeted the ability of the sample and had acceptable internal consistency and test-retest reliability. However, some items functioned erratically for persons of differing abilities or were psychometrically redundant. The NPQ was reanalyzed with 7 questionable items excluded, and superior psychometric properties were observed. These findings suggest that the NPQ could be improved, but future prospective studies including qualitative measures are needed. In summary, the NPQ is a useful tool for assessing a patient's conceptualization of the biological mechanisms that underpin his or her pain and for evaluating the effects of cognitive interventions in clinical practice and research. These findings suggest that it has adequate psychometric properties for use with chronic spinal pain patients. ⋯ Rasch analysis was used to analyze the NPQ. Despite several limitations, these results suggest that it is a useful tool with which to assess a patient's conceptualization of the biological mechanisms that underpin his or her pain and to evaluate the effects of cognitive interventions in clinical practice and research.
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The rostroventromedial medulla (RVM) is an important area of the endogenous pain-regulating system, in which 5-hydroxytryptamine (5-HT) and gamma-aminobutyric acid (GABA) are 2 main transmitters involved in pain modulation. However, whether 5-HT and GABA are colocalized is poorly understood. By using glutamate decarboxylase 67-green fluorescence protein (GAD67-GFP) knock-in mouse, we confirmed the colocalization of 5-HT and GABA in the RVM, with a main distribution in the raphe magnus nucleus and paragigantocellular reticular nucleus. Interestingly, more than half (51.6%) of the 5-HT/GABA-immunoreactive (ir) neurons expressed neurokinin-1 receptors (NK-1R) and one-third (30.1%) of the 5-HT/GABA/NK-1R-ir neurons projected to the spinal cord, suggesting that substance P (SP) should regulate the activity of 5-HT/GABA-ir spinal cord-projecting neurons. By combining retrograde and anterograde tracing methods, we observed that the cuneiform nucleus, dorsal raphe nucleus, and lateral periaqueductal gray are the main origin nuclei for the SP-ir fibers and terminals in the RVM. Finally, after formalin injection into the mice hind paw, 29.2% SP-ir RVM-projecting neurons from supra-RVM nuclei and 33.1% NK-1R-ir spinal cord-projecting neurons in the RVM were activated. The present study provides potent morphological evidence that 5-HT and GABA are coexistent in RVM-spinal cord-projecting neurons that are also regulated by SPergic projections. ⋯ The results will greatly enhance our understanding for the modulation of nociceptive information in the descending pain-regulating system.
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Formalin injected in the knee joint of rats produces concentration-dependent nociception, edema, and plasma leakage (PL). Herein, we investigated the effect of histamine H1 receptor (H1R) antagonists in this model. Articular nociception was inferred from the paw elevation time (PET; seconds) during 1-minute periods of stimulated walking, determined every 5 minutes, throughout a 60-minute experimental session. Edema was evaluated by the increase in articular diameter (AD; mm), and PL was measured by the amount of Evans blue dye in the synovial fluid (PL; μg/mL). Loratadine and cetirizine, given systemically, both increased the PET. None of the treatments changed the AD and PL. Loratadine given locally with formalin increased the PET but was without effect when given in the contralateral knee. Systemic loratadine was also without effect when formalin was coinjected with sodium cromoglycate. Histamine and the selective H1R agonist 2-pyridylethylamine decreased the PET and potentiated morphine spinal analgesia, but did not affect the AD and PL. Cetirizine prevented the antinociceptive effect of the H1R agonist. The N-methyl-D-aspartate/histamine-site agonist tele-methylhistamine coinjected with formalin only increased PET. Serotonin alone had no effect on the PET and increased the AD, and the highest dose increased the PL. When coinjected with formalin, serotonin only caused hypernociception, and the highest dose also increased AD. NAN 190, cyproheptadine, and ondansetron (respectively, 5-HT1, 5-HT2, and 5-HT3 receptor antagonists) decreased the PET without changing the AD or PL. Collectively, these results suggest that in rats, the H1R plays an antinociceptive role within the knee joint, while serotonin receptors play a pronociceptive role. ⋯ The present study revealed an antinociceptive mechanism that has previously not been detected by traditional nociceptive tests. Our observations may help to improve the development of new pharmacological strategies for the treatment of clinically relevant pains that generally originate in deep structures.