Concentration-effect relationship of intravenous lidocaine on the allodynia of complex regional pain syndrome types I and II.
BACKGROUND: Several lines of evidence suggest that neuropathic pain (including Complex Regional Pain Syndrome [CRPS] I and CRPS II) is mediated in part by an increase in the density of voltage-sensitive sodium channels in injured axons and the dorsal root ganglion of injured axons. This study sought to characterize the effects of intravenous lidocaine (a sodium channel blocker) on acute sensory thresholds within the painful area and the size of the painful area in patients suffering from CRPS I and II. METHODS: This study used a randomized, double-blind, placebo-controlled design in 16 subjects suffering from CRPS I and II with a prominent allodynia. Each subject received an intravenous infusion of lidocaine and diphenhydramine separated by 1 week. A computer-controlled infusion pump targeted stair-step increases in plasma levels of lidocaine of 1, 2, and 3 microg/ml. At baseline and at each plasma level, spontaneous and evoked pain scores and neurosensory testing within the painful area were measured. The neurosensory testing consisted of thermal thresholds, tactile thresholds and the area of allodynia to punctate, and stroking and thermal stimuli. RESULTS: Intravenous lidocaine and diphenhydramine had no significant effect on the cool, warm, or cold pain thresholds. However, lidocaine caused a significant elevation of the hot pain thresholds in the painful area. Intravenous lidocaine caused a significantly decreased response to stroking and cool stimuli in the allodynic area. There was also a significant decrease in pain scores to cool stimuli at all plasma levels and the spontaneous pain at the highest plasma level. CONCLUSIONS: This study demonstrates that intravenous lidocaine affects pain in response to cool stimuli more than mechanical pain in subjects with neuropathic pain. There is a lesser effect on spontaneous pain and pain induced by stroking stimuli and no effect on the pain induced by punctate stimuli. (+info)
Pain and the body schema: evidence for peripheral effects on mental representations of movement.
Some accounts of body representations postulate a real-time representation of the body in space generated by proprioceptive, somatosensory, vestibular and other sensory inputs; this representation has often been termed the 'body schema'. To examine whether the body schema is influenced by peripheral factors such as pain, we asked patients with chronic unilateral arm pain to determine the laterality of pictured hands presented at different orientations. Previous chronometric findings suggest that performance on this task depends on the body schema, in that it appears to involve mentally rotating one's hand from its current position until it is aligned with the stimulus hand. We found that, as in previous investigations, participants' response times (RTs) reflected the degree of simulated movement as well as biomechanical constraints of the arm. Importantly, a significant interaction between the magnitude of mental rotation and limb was observed: RTs were longer for the painful arm than for the unaffected arm for large-amplitude imagined movements; controls exhibited symmetrical RTs. These findings suggest that the body schema is influenced by pain and that this task may provide an objective measure of pain. (+info)
Local sympathetic denervation in painful diabetic neuropathy.
This study assessed whether painful diabetic neuropathy is associated with abnormal sympathetic nervous function in the affected limbs. Nine patients with diabetes (four men, five women; age 61 +/- 7 years) and painful peripheral neuropathy of the feet, but without evidence of generalized autonomic neuropathy, underwent intravenous infusion of tritiated norepinephrine (NE) and sampling of arterial and venous blood in both feet and in one arm to quantify the rate of entry of NE into the local venous plasma (NE spillover). In the same patients, positron emission tomography (PET) scanning after intravenous injection of the sympathoneural imaging agent 6-[(18)F]fluorodopamine was used to visualize sympathetic innervation and after intravenous [(13)N]ammonia to visualize local perfusion. The results were compared with those in the feet of normal volunteers and in an unaffected foot of patients with unilateral complex regional pain syndrome (CRPS). In addition, neurochemical results obtained in painful diabetic neuropathy were compared with those obtained in diabetic control patients with painless neuropathy and diabetic control patients without neuropathy. Local arteriovenous difference in plasma NE levels (DeltaNE(AV)) and NE spillover in the arms did not differ across the groups. However, DeltaNE(AV) in the feet was significantly less in the group with painful diabetic neuropathy than in the control groups. Also NE spillover in the feet tended to be lower in painful neuropathy. DeltaNE(AV) of diabetic control patients without neuropathy (n = 6) resembled values in the control groups without diabetes, whereas patients with painless diabetic neuropathy (n = 6) had evidence suggesting partial loss of sympathetic innervation. PET scanning revealed decreased flow-corrected 6-[(18)F]fluorodopamine-derived radioactivity in patients with painful diabetic neuropathy, compared with values in normal volunteers and patients with CRPS. The results provide neurochemical and neuroimaging evidence for regionally selective sympathetic denervation in the painful feet of patients with diabetic neuropathy. (+info)
Infrared thermographic imaging in the assessment of successful block on lumbar sympathetic ganglion.
This study examined the net changes in temperature at various regions of the lower extremities in an attempt to identify the regions demonstrating the most significant temperature changes following a lumbar sympathetic ganglion block (LSGB). Thermography was performed before and after the LSGB in 26 sympathetic nerve system disorder cases. The inspection points were the anterior and posterior surfaces of the thigh, the knee and leg, and the dorsal and plantar surfaces of the feet. The net increases in skin temperature following the LSGB (deltaT(net)) at the plantar and dorsal surfaces of the feet, were 6.2 +/- 2.68 degrees C (mean +/- SD) and 3.9 +/- 1.89 degrees C, respectively, which were higher than those observed in the other regions of the lower extremities (p < 0.05). The areas, in order of decreasing deltaT(net), are as follows: the plantar surface of the foot, the dorsal surface of the foot, the shin, the anterior surface of the knee, the calf, the posterior surface of the knee, the anterior surface of the thigh, and the posterior surface of the thigh. There was one case of orthostatic hypotension during the thermography procedure. In conclusion, thermographic imaging is a useful method for demonstrating the success of a LSGB in various diseases. An evaluation of the deltaT(net) on the plantar surface of the feet using thermographic imaging is the most effective, simple, and safe method for assessing a successful LSGB. (+info)
Referred sensations in patients with complex regional pain syndrome type 1.
OBJECTIVES: This study sought to explore and characterize referred sensations (RS) in patients with complex regional pain syndrome (CRPS) type 1 and test the hypothesis that pain in CRPS is associated with central sensory changes. METHODS: Subjects underwent standardized neurological examination involving light touch, pinprick and vibration sense with eyes closed and then with eyes open. The subjects described the location and sensation emanating from the stimulated site and whether they experienced any sensations (similar or different) elsewhere. RESULTS: Five of 16 subjects recruited demonstrated RS. These were experienced in real time, were modality specific (touch and pinprick) and were located on the body part immediately adjacent, on Penfield's cortical homunculus, to the stimulated site. The RS were diminished or absent when the subject visualized the stimulated area. They disappeared when stimulation ceased and on clinical improvement. CONCLUSIONS: This is the first report of RS in CRPS and provides further evidence of central reorganization in what was previously thought to be a peripheral disorder. (+info)
Persistence of pain induced by startle and forehead cooling after sympathetic blockade in patients with complex regional pain syndrome.
BACKGROUND: Stimuli arousing sympathetic activity can increase ratings of clinical pain in patients with complex regional pain syndrome (CRPS). OBJECTIVE: To determine whether the increase in pain is mediated by peripheral sympathetic activity. METHODS: The effect of sympathetic ganglion blockade on pain evoked by a startle stimulus and cooling the forehead was investigated in 36 CRPS patients. RESULTS: Loss of vasoconstrictor reflexes and warming of the limb indicated that sympathetic blockade was effective in 26 cases. Before sympathetic blockade, pain increased in 12 of these 26 patients when they were startled. Pain increased in seven of the 12 patients and in another five cases when their forehead was cooled. As expected, pain that increased during sympathetic arousal generally subsided in patients with signs of sympathetic blockade. However, pain still increased in three of 12 of patients after the startle stimulus and in six of 12 of patients during forehead cooling, despite indisputable sympathetic blockade. CONCLUSIONS: These findings suggest that stimuli arousing sympathetic activity act by a central process to exacerbate pain in some patients, independent of the peripheral sympathetic nervous system. This may account for the lack of effect of peripheral sympathetic blockade on pain in some CRPS patients. (+info)
Spinal cord stimulation in complex regional pain syndrome: cervical and lumbar devices are comparably effective.
BACKGROUND: Spinal cord stimulation (SCS) has been used since 1967 for the treatment of patients with chronic pain. However, long-term effects of this treatment have not been reported. The present study investigated the long-term effects of cervical and lumbar SCS in patients with complex regional pain syndrome type I. METHODS: Thirty-six patients with a definitive implant were included in this study. A pain diary was obtained from all patients before treatment and 6 months and 1 and 2 years after implantation. All patients were asked to complete a seven-point Global Perceived Effect (GPE) scale and the Euroqol-5D (EQ-5D) at each post-implant assessment point. RESULTS: The pain intensity was reduced at 6 months, 1 and 2 years after implantation (P<0.05). However, the repeated measures ANOVA showed a statistically significant, linear increase in the visual analogue scale score (P=0.03). According to the GPE, at least 42% of the cervical SCS patients and 47% of the lumbar SCS patients reported at least 'much improvement'. The health status of the patients, as measured on the EQ-5D, was improved after treatment (P<0.05). This improvement was noted both from the social and from the patients' perspective. Complications and adverse effects occurred in 64% of the patients and consisted mainly of technical defects. There were no differences between cervical and lumbar groups with regard to outcome measures. CONCLUSION: SCS reduced the pain intensity and improves health status in the majority of the CRPS I patients in this study. There was no difference in pain relief and complications between cervical and lumbar SCS. (+info)
Complex regional pain syndrome: a review.
Complex regional pain syndrome (CRPS) is a challenging neuropathic pain state, quite difficult to comprehend and treat. Its pathophysiological mechanisms are unclear and its treatment is difficult. Multiple factors play a role in the generation and maintenance of CRPS. A close interdisciplinary collaboration amongst the psychologist, physical and occupational therapists, neurologist and pain medicine consultants is necessary to achieve optimal treatment effects. The primary goals of managing patients with this syndrome are to: 1) perform a comprehensive diagnostic evaluation, 2) be prompt and aggressive in treatment interventions, 3) assess and reassess the patient's clinical and psychological status, 4) be consistently supportive, and 5) strive for the maximal amount of pain relief and functional improvement. This article reviews the different aspects of CRPS including definition, classification, epidemiology and natural history, clinical presentation, pathophysiology and management. (+info)