Pain
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The mechanisms underlying the relief of neuropathic pain of peripheral origin by spinal cord stimulation (SCS) are poorly understood. The present study was designed to investigate the effects of SCS on evoked and spontaneous discharges in dorsal horn neurons in intact and in nerve-injured rats subjected to partial sciatic nerve ligation according to Seltzer et al. (1990). Tactile sensitivity in the hind paw was assessed in behavioral tests using von Frey filaments. ⋯ In non-allodynic and control rats, SCS had no significant depressive effects on the evoked responses and spontaneous discharge. The results suggest that SCS may provide a suppressive action on dorsal horn neuronal hyperexcitability associated with signs of peripheral neuropathy. The suppressive effect of SCS on tactile allodynia, as previously observed in behavioral experiments, presumably corresponds to a normalization of the excitability of WDR cells in response to innocuous stimuli.
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Previous work demonstrated that, in rats, intrathecal GR89696, a putative kappa-2 opioid receptor agonist, inhibited hyperalgesia to noxious heat in an inflamed hind paw (anti-hyperalgesic effect). Non-inflamed paws were not influenced by kappa-2 receptor activation. The question addressed in this study was whether GR89696 was as effective in blocking hyperalgesia and allodynia in nerve injury models as it was in the inflammation model. ⋯ Naloxone (1 mg/kg, i.p.) reversed the anti-hyperalgesic and anti-allodynic effects of GR89696. The mu agonist DAMGO (6 nmoles, i.t.) and the kappa-1 agonist U69593 (100 nmoles, i.t.) only partially reversed hyperalgesia and allodynia. These findings suggest that kappa-2 opioid receptors may be a useful target for the pharmacological control of hyperalgesia and allodynia.
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Clinical Trial Controlled Clinical Trial
A prospective, longitudinal study on patients with trigeminal neuralgia who underwent radiofrequency thermocoagulation of the Gasserian ganglion.
Outcome after radiofrequency thermocoagulation in patients with trigeminal neuralgia was assessed in a prospective, longitudinal study. Forty-eight consecutive patients with chronic facial pain presenting for surgery to a neurosurgeon were studied. Patients were assessed preoperatively by an independent clinician both clinically, and with the use of two questionnaires: the McGill Pain Questionnaire (MPQ) and the Hospital Anxiety and Depression (HAD) scale. ⋯ Careful selection of patients for surgery using objective assessments will decrease morbidity and improve satisfaction. Physical morbidity and recurrence rates are insufficient to gauge outcomes. Psychological, sociological and patients' views must be included in evaluations.
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Clinical Trial
A blinded pilot study investigating the use of diagnostic ultrasound for detecting active myofascial trigger points.
Myofascial trigger points (MFTPs) have been cited by numerous authors as the cause of local and referred pain which arises from muscle and its surrounding fascia. At present there is no reliable objective test which is capable of determining their presence. ⋯ Eleven subjects with clinically identified, unilateral, active MFTPs were examined with diagnostic ultrasound at the site of the trigger point as well as the asymptomatic, contralateral side. The analysis of the results of this pilot study found no correlation between the clinical identification of active MFTPs and diagnostic ultrasound.
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The role of nerve growth factor (NGF) and glial-derived neurotrophic factor (GDNF) in sympathetic sprouting within the dorsal root ganglion was investigated. In nerve-intact rats, intrathecal NGF (1 mg/ml, 14 days) but not GDNF (1 mg/ml, 14 days) induced extensive sprouting of tyrosine hydroxylase immunoreactive (TH-IR) fibres and formation of pericellular TH-IR baskets within lumbar DRGs. TH-IR baskets were distributed equally to trkA-expressing and trkA-negative neuronal profiles. ⋯ Distribution of sympathetic sprouts within the DRG is independent of whether target neurons are injured or express trkA. Sequestration of NGF at the peripheral injury site does not influence basket formation within the DRG. It is likely that functional noradrenergic connections exist between sympathetic sprouts and sensory neuron cell bodies following exogenous NGF.