Pain
-
Intraspinal injections of the AMPA-metabotropic receptor agonist quisqualic acid (QUIS) were made in an effort to simulate injury induced elevations of excitatory amino acids (EAAs), a well documented neurochemical change following spinal cord injury (SCI). The progressive pathological sequela associated with QUIS injections closely resembles the cascade of events described following ischemic and traumatic SCI and the pathogenesis of cavities in the clinical condition of post-traumatic syringomyelia. ⋯ Thus, the present results provide a morphological correlate of spontaneous and evoked pain related behaviors following excitotoxic SCI. The behavioral characteristics combined with the similarities between QUIS induced injury and the clinical pathology of SCI support the use of the excitotoxic model in studies related to the central mechanism(s) of altered sensation, including pain, following spinal injury.
-
The psychological assessment of chronic pain is often accomplished using questionnaires such as the (West Haven-Yale) Multidimensional Pain Inventory ((WHY)MPI) which is constructed to capture the multidimensionality of chronic pain. The (WHY)MPI theoretically originates from behavioural and cognitive behavioural theories of pain. It is divided into three parts and measures psychosocial and behavioural consequences of pain. ⋯ This part of the inventory is designed to measure the extent of different types of activities, and our results suggest that this section may only be used for assessing general activity level. We conclude that, with a few adjustments, the analyses yielded satisfactory results for sections 1 and 2 of the MPI-S regarding its factor structure, reliability and generalisability. For section 3 the hypothesised factor structure could not be confirmed.
-
Nociceptive electrical stimuli were applied to the sural nerve during hypnotically-suggested analgesia in the left lower limb of 18 highly susceptible subjects. During this procedure, the verbally reported pain threshold, the nociceptive flexion (RIII) reflex and late somatosensory evoked potentials were investigated in parallel with autonomic responses and the spontaneous electroencephalogram (EEG). The hypnotic suggestion of analgesia induced a significant increase in pain threshold in all the selected subjects. ⋯ No modification in the autonomic parameters or the EEG was observed. These data suggest that different strategies of modulation can be operative during effective hypnotic analgesia and that these are subject-dependent. Although all subjects may shift their attention away from the painful stimulus (which could explain the decrease of the late somatosensory evoked potentials), some of them inhibit their motor reaction to the stimulus at the spinal level, while in others, in contrast, this reaction is facilitated.
-
Twenty patients suffering from complex regional pain syndrome (CRPS) and 21 healthy control subjects were examined to evaluate sympathetic reflex vasoconstriction. The mean age of the 12 female and eight male patients was 48.9 (21-72) years. At the time of investigation the median duration of the disease was 8.5 weeks (2-70). ⋯ Sympathetic reflex vasoconstriction triggered by MA which represents cortical generated, moderate vasoconstrictor stimulus, was significantly reduced on the affected limb (102.9% of prestimulus period) when compared to the control limb (85.0%, P < 0.002) or to controls (84.8%, P < 0.001). VAR (pure postganglionic), IG and CP (both spinal and supraspinal), representing stronger vasoconstrictor stimuli, revealed no significant side to side difference of sympathetic vasoconstriction and no significant difference as compared to controls. In conclusion our findings prove impairment of sympathetic vasoconstrictor activity after central vasoconstrictor stimulation in CRPS, and possible mechanisms are discussed.
-
Little is known concerning the mechanisms underlying the perception of cold pain in humans. An appreciation of these mechanisms is important to understand and possibly treat those disorders in which cold stimuli evoke unpleasant sensations. To study cold pain, I have conducted psychophysical experiments on 16 healthy subjects. ⋯ The block did not consistently affect the total pain at the hairy sites. However, most subjects reported more pain during the block at the glabrous sites. These data suggest that noxious cold stimuli affect a mosaic of primary afferent input and central processing resulting in a complex pain experience which may differ in glabrous and hairy skin.