Are hot-burning sensations produced by the axonal damage of afferent unmyelinated fibres?
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AIM: Pain resulting from nerve lesions is classically referred to as a ''burning pain''. Both the axonal damage and sensitization of unmyelinated C-fibres have been considered as the possible generators of this sensation. The aim of this study was to verify the hypothesis that hot-burning sensations are produced by the axonal damage of afferent unmyelinated fibres in peripheral nerves. METHODS: A total of 122 patients with pain localised in the distal parts of the upper limbs (hand, forearm) and lower limbs (leg or foot) were enrolled in the study. The intensity of pain and hot-burning sensations was measured using a numerical scale (range 0-10). The relationship between the presence of warm hypoesthesia (related to the loss of afferent unmyelinated fibres) and hot-burning sensations was assessed. Warm hypoesthesia was identified by Quantitative Sensory Testing employing thermal stimulation (QST-t) and the patients were divided into 2 groups: group A, with hypoesthesia and group B with normoesthesia. Patients with a central nervous impairment were excluded. RESULTS: No significant differences in the intensity of pain and hot-burning sensations was observed between the group of patients with warm hypoesthesia and that with warm normoesthesia. CONCLUSIONS: This study does not confirm the hypothesis that hot-burning sensations are produced by the axonal damage of afferent amyelinated fibres in peripheral nerves. It agrees with clinical evidence suggesting that patients with different clinical conditions can complain of hot-burning sensations, independently of the presence of a nerve lesion. (+info)
Immediate effects of spinal manipulation on thermal pain sensitivity: an experimental study.
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BACKGROUND: The underlying causes of spinal manipulation hypoalgesia are largely unknown. The beneficial clinical effects were originally theorized to be due to biomechanical changes, but recent research has suggested spinal manipulation may have a direct neurophysiological effect on pain perception through dorsal horn inhibition. This study added to this literature by investigating whether spinal manipulation hypoalgesia was: a) local to anatomical areas innervated by the lumbar spine; b) correlated with psychological variables; c) greater than hypoalgesia from physical activity; and d) different for A-delta and C-fiber mediated pain perception. METHODS: Asymptomatic subjects (n = 60) completed baseline psychological questionnaires and underwent thermal quantitative sensory testing for A-delta and C-fiber mediated pain perception. Subjects were then randomized to ride a stationary bicycle, perform lumbar extension exercise, or receive spinal manipulation. Quantitative sensory testing was repeated 5 minutes after the intervention period. Data were analyzed with repeated measures ANOVA and post-hoc testing was performed with Bonferroni correction, as appropriate. RESULTS: Subjects in the three intervention groups did not differ on baseline characteristics. Hypoalgesia from spinal manipulation was observed in lumbar innervated areas, but not control (cervical innervated) areas. Hypoalgesic response was not strongly correlated with psychological variables. Spinal manipulation hypoalgesia for A-delta fiber mediated pain perception did not differ from stationary bicycle and lumbar extension (p > 0.05). Spinal manipulation hypoalgesia for C-fiber mediated pain perception was greater than stationary bicycle riding (p = 0.040), but not for lumbar extension (p = 0.105). CONCLUSION: Local dorsal horn mediated inhibition of C-fiber input is a potential hypoalgesic mechanism of spinal manipulation for asymptomatic subjects, but further study is required to replicate this finding in subjects with low back pain. (+info)
Neuronavigator-guided percutaneous radiofrequency thermocoagulation in the treatment of intractable trigeminal neuralgia.
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BACKGROUND: Percutaneous radiofrequency thermocoagulation of the trigeminal ganglion (PRTTG) is regarded as the first choice for most patients with trigeminal neuralgia (TN) because of its safety and feasibility. However, neuronavigator-guided PRTTG has been seldom reported. The purpose of this study was to assess the safety and efficacy of neuronavigator-guided PRTTG for the treatment of intractable TN. METHODS: Between January 2000 and December 2004, 54 patients with intractable TN were enrolled into this study and were randomly divided into two groups. The patients in navigation group (n = 26) underwent PRTTG with frameless neuronavigation, and those in control group (n = 28) received PRTTG without neuronavigation. Three months after the operation, the efficacy, side effects, and complications of the surgery were recorded. The patients in the control group were followed up for 10 to 54 months (mean, 34 +/- 5), and those in the navigation group were followed up for 13 to 58 months (mean, 36 +/- 7). Kaplan-Meier analyses of the pain-free survival curves were used for the censored survival data, and the log-rank test was used to compare survival curves of the two groups. RESULTS: The immediate complete pain-relief rate of the navigation group was 100%, whereas it was 95% in the control. The proportion of sustained pain-relief rates at 12, 24 and 36 months after the procedure were 85%, 77%, and 62% in the navigation group, and 54%, 40%, and 35% in the control. Recurrences in the control group were more common than that in the navigation group. Annual recurrence rate in the first and second years were 15% and 23% in the navigation group, and 46%, 60% in the control group. No side-effect and complication was noted in the navigation group except minimal facial hypesthesia. CONCLUSION: Neuronavigator-guided PRTTG is a safe and promising method for treatment of intractable TN with better short- and long-term outcomes and lower complication rate than PRTTG without neuronavigation. (+info)
Physiological properties of spinal lamina II GABAergic neurons in mice following peripheral nerve injury.
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Aberrant GABAergic inhibition in spinal dorsal horn may underlie some forms of neuropathic pain. Potential, but yet unexplored, mechanisms include reduced excitability, abnormal discharge patterns or altered synaptic input of spinal GABAergic neurons. To test these hypotheses, we quantitatively compared active and passive membrane properties, firing patterns in response to depolarizing current steps and synaptic input of GABAergic neurons in spinal dorsal horn lamina II of neuropathic and of control animals. Transgenic mice were used which expressed enhanced green fluorescent protein (EGFP) controlled by the GAD67 promoter, thereby labelling one-third of all spinal GABAergic neurons. In all neuropathic mice included in this study, chronic constriction injury of one sciatic nerve led to tactile allodynia and thermal hyperalgesia. Control mice were sham-operated. Membrane excitability of GABAergic neurons from neuropathic or sham-treated animals was indistinguishable. The most frequent firing patterns observed in neuropathic and sham-operated animals were the initial burst (neuropathic: 46%, sham-treated: 42%), the gap (neuropathic: 31%, sham-treated: 29%) and the tonic firing pattern (neuropathic: 16%, sham-treated: 24%). The synaptic input from dorsal root afferents was similar in neuropathic and in control animals. Thus, a reduced membrane excitability, altered firing patterns or changes in synaptic input of this group of GABAergic neurons in lamina II of the spinal cord dorsal horn are unlikely causes for neuropathic pain. (+info)
Cold-provocation testing for the vascular component of hand-arm vibration syndrome in health surveillance.
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The aim was to investigate whether the use of infra-red thermography (I-R) and measurement of temperature gradients along the finger could improve the diagnostic accuracy of cold-provocation testing (15 degrees C for 5 min) in vascular hand-arm vibration syndrome (HAVS). Twenty-one controls and 33 individuals with stages 2/3V HAVS were studied. The standard measurement of time to rewarm by 4 degrees C (T4 degrees C) and temperature gradients between the finger tip, base and middle (measured using I-R) were calculated. Receiver Operating Characteristics (ROC) analysis to distinguish between the two groups revealed that for T4 degrees C the area under the ROC curve was not statistically significantly different from 0.5 (0.64 95% confidence interval 0.49-0.76). The difference between the tip and middle portion of the finger during the sixth minute of recovery was the most promising gradient with an area of 0.76 (95% confidence interval 0.62-0.87), and sensitivity and specificity of 57.6% and 85.7% respectively. However, this was not significantly different from that for the time to rewarm by 4 degrees C. In conclusion, the cold-provocation test used in this study does not appear to discriminate between individuals with stage 2/3V HAVS and controls and this is not improved by the measurement of temperature gradients along the fingers using I-R. (+info)
Impaired pain sensation in mice lacking prokineticin 2.
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Prokineticins (PKs), consisting of PK1 and PK2, are a pair of newly identified regulatory peptides. Two closely related G-protein coupled receptors, PKR1 and PKR2, mediate the signaling of PKs. PKs/PKRs participate in the regulation of diverse biological processes, ranging from development to adult physiology. A number of studies have indicated the involvement of PKs/PKRs in nociception. Here we show that PK2 is a sensitizer for nociception. Intraplantar injection of recombinant PK2 resulted in a strong and localized hyperalgesia with reduced thresholds to nociceptive stimuli. PK2 mobilizes calcium in dissociated dorsal root ganglion (DRG) neurons. Mice lacking the PK2 gene displayed strong reduction in nociception induced by thermal and chemical stimuli, including capsaicin. However, PK2 mutant mice showed no difference in inflammatory response to capsaicin. As the majority of PK2-responsive DRG neurons also expressed transient receptor potential vanilloid (TRPV1) and exhibited sensitivity to capsaicin, TRPV1 is likely a significant downstream molecule of PK2 signaling. Taken together, these results reveal that PK2 sensitize nociception without affecting inflammation. (+info)
Clinical profile, electrodiagnosis and outcome in patients with carpal tunnel syndrome: a Singapore perspective.
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INTRODUCTION: Carpal tunnel syndrome (CTS ) is the most common entrapment neuropathy seen in our neurodiagnostic laboratory referrals. We describe the clinical profile, and outcome in patients with electrophysiological diagnosis of CTS seen in our centre over a six month period. METHODS: A retrospective study was carried out and included 134 consecutive patients with CTS referred to the Neurodiagnostic Laboratory, National Neuroscience Institute, from October 2003 to March 2004, for the confirmatory testing. Severity grade was assigned following American Association of Electrodiagnostic Medicine criteria of CTS. RESULTS: The majority of patients were female (81.3 percent) with mean age of presentation being 53.6 years. Chinese women constitute the majority racial group. Paraesthesia (70.1 percent) and numbness (19.4 percent) were the presenting sensory symptoms. In the nerve conduction study, 108 patients had bilateral CTS with 35 having unilateral symptoms. Dominant hand involvement was present in 92.3 percent. Overall, 40.3 percent had mild, 46.3 percent had moderate and 13.4 percent had severe CTS, with median duration of symptoms of two, four and 12 months, respectively. Follow-up data were available for 115 patients. 27 patients with surgical treatment showed resolution or improvement in 53.3 percent with moderate CTS, and 83.3 percent with severe CTS, at three-month follow-up. 14 patients turned up for six-month follow-up and 92.9 percent showed improvement in symptoms. 88 patients were managed conservatively; symptoms were unchanged or worsened in 80.6 percent with mild CTS, 65.9 percent with moderate CTS, and 62.5 percent with severe CTS at three-month follow-up. Of the 54 patients who turned up for six-month follow-up, the clinical symptom remain unchanged or worsened in 68.5 percent. CONCLUSION: The severity of CTS is associated with longer duration of symptoms. Sensory symptoms and dominant hand involvement is more common. There is a high default rate in the clinical follow-up. Early surgical intervention results in either resolution or improvement in symptoms, whereas conservative management does not affect the natural history with symptoms that persisted or worsened with time. (+info)
Comparison of sensorineural symptoms between UK orthopaedic surgeons and gynaecologists.
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BACKGROUND: We have previously described significant differences in self-reported neurological symptoms of orthopaedic surgeons when compared to a group of gynaecologists. We suggested that this may be secondary to occupational sources of hand-transmitted vibration. The original study was intentionally brief and failed to address potential confounders. AIMS: To compare the prevalence of sensorineural symptoms between UK orthopaedic surgeons and gynaecologists and adjust for potential confounding factors. METHODS: Postal questionnaires were sent to 2040 members of the British Orthopaedic Association and 1797 members of the Royal College of Gynaecologists requesting information about demographics and self-reported neurological symptoms. Demographics of the orthopaedic surgeons and gynaecologists were compared using chi-squared tests and independent t-tests. Multiple logistic regressions were carried out to compare the prevalence of symptoms while adjusting for potential confounding factors. RESULTS: Differences in the demographic profile of the orthopaedic surgeons and gynaecologists were identified: orthopaedic surgeons were predominantly male, were more junior in grade, were younger, used double gloving more often, had larger glove size, were more likely to be ambidextrous, to use vibrating tools outside of work and to consume greater amounts of alcohol. Orthopaedic surgeons reported a higher prevalence of tingling and numbness of fingers while at work and at other times. These differences were significant even after adjusting for potential confounding factors. CONCLUSION: Observed differences could be related to exposure to hand-transmitted vibration at work. Further assessment of risk to orthopaedic surgeons from hand-held power tools used in the course of their work is recommended. (+info)