Pain
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Comparative Study
Differentiating sensory and affective-sensory pain descriptions in patients undergoing magnetic resonance imaging for persistent low back pain.
The study design is a cross-sectional survey with psychometric analysis. The objective is to determine the validity of a modified version of the Short-Form McGill Pain Questionnaire (SF-MPQ). The SF-MPQ has been widely used to differentiate between reports of sensory and affective pain. ⋯ Correlations with measures of pain intensity and the RM were significant, but slightly lower, for the subscales of the modified 2-factor solution (0.26-0.40) than for the subscales of the previously described 2-factor solutions (0.34-0.45). The MSF-MPQ can be used as a brief tool to differentiate the language used to describe pain in patients who are undergoing lumbar MRI. The evidence indicates that this clinical tool can be used to categorize how these patients describe their pain and potentially may be very valuable in determining the optimal course of treatment.
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Comparative Study
Exaggerated nociceptive responses on morphine withdrawal: roles of protein kinase C epsilon and gamma.
On withdrawal from opioids many patients experience a heightened sensitivity to stimuli and an exaggerated pain response. The phenomenon has been little studied in infants. We present evidence that in postnatal day 7 rats an exaggerated nociceptive ventral root response of spinal cords in vitro and withdrawal-associated thermal hyperalgesia in vivo are dependent on protein kinase C (PKC), and we document the roles of PKC and gamma isozymes. ⋯ In contrast, thermal hyperalgesia during spontaneous withdrawal was inhibited by both PKC and gamma inhibitors. The consistency between the in vivo and in vitro findings with respect to naloxone-precipitated withdrawal provides further evidence that the sVRP reflects nociceptive neurotransmission. In addition the difference between naloxone-precipitated and spontaneous withdrawal in vivo suggests that in postnatal day 7 rats, morphine exposure produces an early phase of primary afferent sensitization dependent upon PKC translocation, followed by a later phase involving spinal sensitization mediated by PKC gamma.
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Comparative Study
P300-amplitudes in upper limb amputees with and without phantom limb pain in a visual oddball paradigm.
The aim of the study was to investigate to what extent cortical hyper-reactivity to visual stimuli is present in upper limb amputees. Five amputees with phantom limb pain (PLP), five amputees without PLP (Non-PLP) and 10 healthy controls (HC) were investigated using a visual oddball paradigm. Two hundred visual stimuli were presented with target stimuli occurring at a probability of 25% and standard stimuli at a probability of 75%. ⋯ The size of the P300-amplitude was positively correlated with the intensity of PLP. These findings suggest a higher magnitude of non-specific cortical excitability in amputees with PLP and a reduced excitability in amputees without PLP. This extends previous findings of differences in cortical excitability in PLP and non-PLP patients in the sensorimotor domain.
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Comparative Study
Block of NMDA and non-NMDA receptor activation results in reduced background and evoked activity of central amygdala neurons in a model of arthritic pain.
The latero-capsular division of the central nucleus of the amygdala (CeA) is now defined as the 'nociceptive amygdala' because of its high content of neurons activated exclusively or preferentially by noxious stimuli. Multireceptive (MR) neurons that respond to innocuous and, more strongly, to noxious stimuli become sensitized in arthritis pain. This form of nociceptive plasticity involves presynaptic group I metabotropic glutamate receptors, which increase glutamate release. ⋯ All neurons examined received excitatory input from the knee(s) and were MR neurons. A selective NMDA receptor antagonist (AP5) inhibited responses to noxious stimuli more potently in the arthritic pain state (n = 6) than under control conditions before arthritis (n = 8) AP5 also inhibited the enhanced background activity and increased responses to normally innocuous stimuli in arthritis, but had no significant effects on these parameters under control conditions. A selective non-NMDA receptor antagonist (NBQX) inhibited background activity and evoked responses under normal control conditions (n = 6) and in arthritis (n = 8) These data suggest that activation of both NMDA and non-NMDA receptors contributes to pain-related sensitization of amygdala neurons.
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Comparative Study
Distraction from chronic pain during a pain-inducing activity is associated with greater post-activity pain.
The aim of this study was to investigate the effects of distraction from pain during and after a pain-inducing lifting task in a sample of chronic low back pain (CLBP) patients. Fifty-two CLBP patients (25 males, 27 females; mean age=46.30 years) performed a pain-inducing lifting task twice, once alone and once with a simultaneous cognitive distraction task. ⋯ Further investigation of the catastrophizing data showed that the effect of catastrophizing about pain during the lifting task on the cognitive distraction task was mediated by the amount of attention paid to pain. Clinical implications of these findings are discussed.