European journal of pain : EJP
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Temporal summation of "second pain" (TSSP) is the result of C-fiber-evoked responses of dorsal-horn neurons, termed "windup". This phenomenon is dependent on stimulus frequency (0.33 Hz) and relevant for central sensitization as well as chronic pain. Whereas, our previous functional magnetic resonance imaging (fMRI) study characterized neural correlates of TSSP in 11 healthy volunteers, the present study was designed to compare brain responses associated with TSSP across these healthy participants and 13 fibromyalgia (FM) patients. ⋯ Subsequently, the fMRI-data of both groups were combined to increase the power of our statistical comparisons. fMRI-statistical maps identified several brain regions with stimulus and frequency dependent activation consistent with TSSP, including ipsilateral and contralateral thalamus, medial thalamus, S1, bilateral S2, mid- and posterior insula, rostral and mid-anterior cingulate cortex. However, the stimulus temperatures necessary to evoke equivalent levels of TSSP and corresponding brain activity were less in FM patients. These results suggest that enhanced neural mechanisms of TSSP in FM are reflected at all pain related brain areas, including posterior thalamus, and are not the result of selective enhancement at cortical levels.
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In adults, evidence is accumulating that migraine is associated with altered central processing of pain stimuli and, possibly, changes in the allocation of attentional resources to such stimuli. In pediatric migraine, however, little is known about altered pain processing. We examined 15 children with migraine and 15 controls (age 10-15) in an oddball standards task. ⋯ Habituation across trials was similar in both groups. Hence, children with migraine may display an automatic attentional bias towards painful and potentially painful somatosensory stimuli. Consistent with the psychobiological perspective of chronic pain, such an attentional bias could constitute an important mechanism for migraine becoming a chronic problem.
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Randomized Controlled Trial Multicenter Study Comparative Study
Sustained-release oral morphine versus transdermal fentanyl and oral methadone in cancer pain management.
The aim of this study was to compare the analgesic and adverse effects, doses, as well as cost of opioid drugs, supportive drug therapy and other analgesic drugs in patients treated with oral sustained-release morphine, transdermal fentanyl, and oral methadone. ⋯ All the three opioids used as first-line therapy were effective, well tolerated, and required similar amounts of symptomatic drugs or co-analgesics. Methadone was significantly less expensive, but required more changes, up and down, of the doses, suggesting that dose titration of this drug requires major clinical expertise.
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The middle cingulate cortex (MCC) has been implicated in pain processing by studies of cingulotomy for chronic pain and imaging studies documenting increased MCC blood flow in response to acute pain. The only previous report of quantitative sensory testing following cingulotomy described increased intensity and unpleasantness ratings of painful hot and cold stimuli in a single patient with psychiatric disease. We now report a case in which perception of pain and temperature was assessed before and after cingulotomy for obsessive-compulsive disorder (OCD). ⋯ Postoperative pain-evoked activation was demonstrated in the right (ipsilateral) parasylvian cortex but not of the MCC/SMA. Prior studies of forebrain lesions, and of cortical synchrony during the application of painful stimuli suggest the presence of functional connectivity between components of the MCC/SMA and the fronto-parietal opercula. Therefore present results suggest that cingulate lesions disinhibit ipsilateral parasylvian cortex and so are independent evidence of functional connectivity between these cortical areas, the defining characteristic of modules in a pain network.
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An appropriate bedside test for small fiber neuropathy does not exist so far. Cold hypaesthesia occurs as an early onset symptom, and the new handheld device NeuroQuick (NQ) was recently claimed to be a valid and reliable screening tool for its quantitative assessment. ⋯ This study demonstrates that the NeuroQuick is not an adequate screening device for cold hypaesthesia in patients with chronic neuropathic pain. It exhibits a high specificity but only low sensitivity in the identification of such small fiber dysfunction; a reliable and valid screening tool should necessarily provide opposite features.