Impact of spinal cord stimulation on sensory characteristics in complex regional pain syndrome type I: a randomized trial.

BACKGROUND: A randomized trial was performed to assess the effect of spinal cord stimulation (SCS) on detection and pain thresholds for pressure, warmth, and cold and on the extent of mechanical hyperalgesia in patients with chronic complex regional pain syndrome type I. METHODS: Fifty-four chronic complex regional pain syndrome type I patients were randomized to receive both SCS and physical therapy (SCS+PT; n = 36), or to receive only physical therapy (PT; n = 18). Twenty-four SCS+PT patients responded positively to trial stimulation and underwent SCS implantation. During a 12-month follow-up period, six quantitative sensory testing sessions were performed. The main analysis compared 24 SCS patients with 29 nonimplanted patients--one PT patient was excluded. RESULTS: SCS showed no effect on detection thresholds for warmth and cold or on pain thresholds for any sensation. The pressure detection threshold initially increased by SCS, but after 3 months, pressure detection thresholds returned to normal. Mechanical hyperalgesia, both dynamic and static, was reduced slightly with SCS. CONCLUSIONS: Although SCS has previously been shown to cause a significant pain reduction in complex regional pain syndrome type I, the treatment has no long-term effect on detection and pain thresholds for pressure, warmth, or cold. The treatment seems to have only minimal influence on mechanical hyperalgesia.

Randomized controlled trial of percutaneous intradiscal radiofrequency thermocoagulation for chronic discogenic back pain: lack of effect from a 90-second 70 C lesion.

STUDY DESIGN: A prospective double-blind randomized trial in 28 patients. OBJECTIVES: To assess the clinical effect of percutaneous intradiscal radiofrequency thermocoagulation for reducing pain, functional disability, and physical impairment in patients with chronic discogenic low back pain. SUMMARY OF BACKGROUND DATA: Chronic discogenic low back pain is a challenging problem in western countries. A treatment option is radiofrequency heating of the affected disc. Its clinical efficacy has never been formally tested in a controlled trial. METHODS: Twenty-eight patients with a history of at least 1 year of chronic low back pain were selected on the basis of a diagnostic anesthetization of the lower intervertebral discs. Only patients with one putative painful level were selected and randomly assigned to one of two treatment groups. Each patient in the radiofrequency treatment group (n = 13) received a 90-second 70 C lesion of the intervertebral disc. Patients in the control group (n = 15) underwent the same procedure, but without use of radiofrequency current. Both the treating physician and the patients were blinded to the group assignment. Before treatment, physical impairment, rating of pain, the degree of disability, and quality of life were assessed by a blinded investigator. RESULTS: Eight weeks after treatment, there was one success in the radiofrequency group (n = 13) and two in the control group (n = 15). The adjusted and unadjusted odds ratio was 0.5 and 1.1, respectively (not significant). Also, visual analog scores for pain, global perceived effect, and the Oswestry disability scale showed no differences between the two groups. CONCLUSIONS: Percutaneous intradiscal radiofrequency thermocoagulation (90 seconds, 70 C) is not effective in reducing chronic discogenic low back pain.

Thermal thresholds in complex regional pain syndrome type I: sensitivity and repeatability of the methods of limits and levels.

OBJECTIVES: To study whether the method of levels (MLE) or the method of limits (MLI) is preferable as a method of measuring thermal perception thresholds in patients with complex regional pain syndrome type I (CRPS I). METHODS: Perception thresholds for warmth and cold were measured twice, with both MLE and MLI, at a 1 month interval, both at unaffected and affected wrists (n=33) or feet (n=20) of patients with CRPS I of one extremity. RESULTS: (1) Sensitivity for pathology was equal for both methods. (2) The agreement between thresholds measured by both methods was low at all locations, except for the unaffected wrist. Since thresholds measured with the MLI always contain reaction time artefacts, this lack of agreement favours the MLE. (3) At both unaffected and affected wrists, the MLE showed significantly better coefficients of repeatability as compared to the MLI for both sensations. However, at both unaffected and affected feet, there was no preference for either method as far as threshold measurement repeatability was concerned. CONCLUSIONS: Abnormal thermal perception thresholds occurred in 20% (foot) to 36% (wrist) of the CRPS I patients on the affected side and in 15% (foot, wrist) on the unaffected side. The MLE is considered to be the preferable method to assess thermal perception thresholds in CRPS I.

Spinal cord stimulation in patients with chronic reflex sympathetic dystrophy.

BACKGROUND: Chronic reflex sympathetic dystrophy (also called the complex regional pain syndrome) is a painful, disabling disorder for which there is no proven treatment. In observational studies, spinal cord stimulation has reduced the pain associated with the disorder. METHODS: We performed a randomized trial involving patients who had had reflex sympathetic dystrophy for at least six months. Thirty-six patients were assigned to receive treatment with spinal cord stimulation plus physical therapy, and 18 were assigned to receive physical therapy alone. The spinal cord stimulator was implanted only if a test stimulation was successful. We assessed the intensity of pain (on a visual-analogue scale from 0 cm [no pain] to 10 cm [very severe pain]), the global perceived effect (on a scale from 1 [worst ever] to 7 [best ever]), functional status, and the health-related quality of life. RESULTS: The test stimulation of the spinal cord was successful in 24 patients; the other 12 patients did not receive implanted stimulators. In an intention-to-treat analysis, the group assigned to receive spinal cord stimulation plus physical therapy had a mean reduction of 2.4 cm in the intensity of pain at six months, as compared with an increase of 0.2 cm in the group assigned to receive physical therapy alone (P<0.001 for the comparison between the two groups). In addition, the proportion of patients with a score of 6 ("much improved") for the global perceived effect was much higher in the spinal cord stimulation group than in the control group (39 percent vs. 6 percent, P=0.01). There was no clinically important improvement in functional status. The health-related quality of life improved only in the 24 patients who actually underwent implantation of a spinal cord stimulator. Six of the 24 patients had complications that required additional procedures, including removal of the device in 1 patient. CONCLUSIONS: In carefully selected patients with chronic reflex sympathetic dystrophy, electrical stimulation of the spinal cord can reduce pain and improve the health-related quality of life.

Pain relief in complex regional pain syndrome due to spinal cord stimulation does not depend on vasodilation.

BACKGROUND: Spinal cord stimulation (SCS) is known to relieve pain in patients with complex regional pain syndrome (CRPS) and, in general, to cause vasodilation. The vasodilatory effect of SCS is hypothesized to be secondary to inhibition of sympathetically mediated vasoconstriction, or through antidromic impulses resulting in release of vasoactive substances. The aim of the present study was to assess whether pain relief in CRPS after SCS is, in fact, dependent on vasodilation. In addition, we tried to determine which of the potential mechanisms may cause the vasodilatory effect that is generally found after SCS. METHODS: Twenty-four of 36 patients with unilateral CRPS responded to the test of SCS. Twenty-two of these 24 responders (hand, n = 14; foot, n = 8) who had undergone previous sympathectomy were enrolled for the study. In addition, 20 control subjects (10 controls for each extremity) were studied. By means of laser Doppler flowmetry, the skin microcirculation of the patients was measured bilaterally while the SCS system was switched off and while it was activated. Control subjects (n = 20) were tested once only. The ratio of the rest flow at heart level and the dependent position was defined as the vasoconstriction index. RESULTS: Both in affected hands and feet, patients were found to have lower vasoconstriction indices (P < 0.01) as compared with controls, indicating a decreased sympathetic tone. Applying SCS did not result in any microcirculatory change as compared with baseline or the contralateral clinically unaffected side. CONCLUSIONS: The current study failed to show that SCS influences skin microcirculation in patients with CRPS and a low sympathetic tone. Therefore, we may conclude that pain relief in CRPS due to SCS is possible without vasodilation. Because sympathetic activity was greatly decreased in our patients, these results support the hypothesis that the vasodilation that is normally found with SCS is due to an inhibitory effect on sympathetically maintained vasoconstriction.

HLA-DQ1 associated with reflex sympathetic dystrophy.

Reflex sympathetic dystrophy (RSD) is a relatively common disabling disorder of unknown pathophysiology. From a cohort of 52 patients, carefully selected to fulfill the recently formulated diagnostic criteria for RSD, venous blood samples were taken for typing of class I and II major histocompatibility antigens. The frequency of HLA-DQ1 was found to be significantly increased compared with control frequencies. The association provides an indication for an organic basis of RSD.

Randomized trial of radiofrequency lumbar facet denervation for chronic low back pain.

STUDY DESIGN: A prospective double-blind randomized trial in 31 patients. OBJECTIVES: To assess the clinical efficacy of percutaneous radiofrequency denervation of the lumbar zygapophysial joints in reducing pain, functional disability, and physical impairment in patients with back pain originating from the lumbar zygapophysial joints. SUMMARY OF BACKGROUND DATA: Chronic low back pain is a major health problem in the industrialized world. A treatment option is percutaneous radiofrequency denervation of the lumbar zygapophysial joints. Its clinical efficacy has never been formally tested in a controlled trial. METHODS: Thirty-one patients with a history of at least 1 year of chronic low back pain were selected on the basis of a positive response to a diagnostic nerve blockade and subsequently randomly assigned to one of two treatment groups. Each patient in the radiofrequency treatment group (15 patients) received an 80 C radiofrequency lesion of the dorsal ramus of the segmental nerve roots L3, L4, and L5. Patients in the control group (n = 16) underwent an the same procedure but without use of a radiofrequency current. Both the treating physician and the patients were blinded to the group assignment. Before treatment, physical impairment, rating of pain, the degree of disability, and quality of life were assessed by a blinded investigator. RESULTS: Eight weeks after treatment, there were 10 success patients in the radiofrequency group (n = 15) and 6 in the sham group (n = 16). The unadjusted odds ratio was 3.3 (P = 0.05, not significant), and the adjusted odds ratio was 4.8 (P < 0.05, significant). The differences in effect on the visual analog scale scores, global perceived effect, and the Oswestry disability scale were statistically significant. Three, 6, and 12 months after treatment, there were significantly more success patients in the radiofrequency group compared with the sham group. CONCLUSIONS: Radiofrequency lumbar zygapophysial joint denervation results in a significant alleviation of pain and functional disability in a select group of patients with chronic low back pain, both on a short-term and a long-term basis.

Electrical spinal cord stimulation in reflex sympathetic dystrophy: retrospective analysis of 23 patients.

OBJECT: The aim of the study was to assess retrospectively the clinical efficacy and possible adverse effects of electrical spinal cord stimulation (SCS) for the treatment of patients with reflex sympathetic dystrophy (RSD). METHODS: Twenty-three patients who suffered severe pain due to RSD were included in the study. The SCS system was implanted only after a positive 1-week test period. The visual analog scale (VAS) score for pain (1-10) was obtained in all patients prior to treatment, 1 month postimplantation, and at last follow up. At final follow-up examination, patients were asked to rate the effect of their treatment on the 7-point global perceived effect scale. Eighteen (78%) of 23 patients treated between 1991 and 1997 reported improvement during the test period. Permanent implantation of SCS system was not performed in the other five patients. Complications occurred in nine (50%) of 18 patients. The system was removed in three patients after implantation (17%). At the end of follow up (mean 32 months) 15 patients still had an implanted system. The mean pain score had decreased from 7.9 to 5.4 (p<0.001). In the other eight patients the pain score had not changed significantly. In 13 patients (57%) in whom the SCS system was implanted, clinical status had much improved or improved; these cases were regarded as successful. CONCLUSIONS: In this retrospective series, the majority of patients with RSD reported a subjective improvement after implantation of an SCS system.

Relapsing ulcerative colitis associated with spinal cord stimulation.

Spinal cord stimulation is an increasingly popular form of pain treatment. An electrode positioned on the dorsal aspect of the spinal cord at the level of the nerve roots from the painful area stimulates the spinal cord. Current from the electrode is supplied by a pulse generator in the lower anterior abdominal wall. Spinal cord stimulation has not previously been associated with ulcerative colitis. A man with left-sided ulcerative colitis in remission experienced two successive relapses related to the use of a spinal cord stimulation system. After removal of the system, remission returned and remained. This case suggests that electrical current may influence the course of ulcerative colitis.

Radiofrequency cervical zygapophyseal joint neurotomy for cervicogenic headache: a prospective study of 15 patients.

The present study assessed the clinical efficacy of radiofrequency cervical zygapophyseal joint neurotomy in patients with cervicogenic headache. Fifteen consecutive patients with cervicogenic headache were treated and then assessed one week prior to treatment and, at short-term (8 weeks), intermediate (mean 8.8 months) and long-term (mean 16.8 months) follow-ups. The following were taken as outcome parameters: Visual Analogue Scale (VAS), 7-point Verbal Rating Scale (VRS), number of headache days per week and analgesic intake per week. The results of this study showed that radiofrequency neurotomy of the cervical zygapophyseal joints significantly reduced headache severity in 12 (80%) patients, both at short-term and long-term follow-up assessed by 7-point VRS. Mean VAS decrease was 31.4 mm (p < 0.001) and 53.5 mm (p < 0.0001) respectively in this period. The average mean number of headache days per week decreased from 5.8 days to 2.8 days (p = 0.001) and the average analgesic intake per week showed a reduction from a mean of 17.5 tablets to a mean of 3.4 tablets (p = 0.003). A definitive conclusion about the clinical efficacy of this treatment can only be drawn from a randomized controlled trial.

Effects of producing a radiofrequency lesion adjacent to the dorsal root ganglion in patients with thoracic segmental pain.

OBJECTIVE: To evaluate the effectiveness of a radiofrequency lesion adjacent to the dorsal root ganglion (RF-DRG) on a consecutive group of patients presenting with chronic thoracic pain. DESIGN: Retrospective study by a disinterested third party. SETTING: Clinical outcome study. PATIENTS: Forty-three patients with a minimum of 6 months history of unilateral thoracic segmental pain, unresponsive to conservative therapy were involved. INTERVENTIONS: Patients were selected for a radiofrequency lesion adjacent to the dorsal root ganglion after two or more prognostic nerve blocks had been performed under fluoroscopic control. The level which provided the best analgesic response was selected. At this level, a radiofrequency lesion was made at 67 degrees for 60 s immediately adjacent to the dorsal root ganglion. OUTCOME MEASURES: Rating of pain was done on a four-step verbal rating scale. RESULTS: A radiofrequency lesion adjacent to the dorsal root ganglion provided short-term (8 weeks) relief of pain in 67% and long-term relief (> 36 weeks) of pain in 52% of patients with a limited segmental distribution of pain. If more than two segmental levels were involved, the procedure was found to be less effective. CONCLUSIONS: There was a significantly (p < 0.05) better short-term and long-term pain relief in patients with a clearly localized pain that was confined to one or two thoracic segmental levels, compared to patients with more than two segmental levels involved in the pain syndrome.

Effects and side effects of a percutaneous thermal lesion of the dorsal root ganglion in patients with cervical pain syndrome.

Twenty consecutive patients with intractable chronic pain in the cervical region were treated with a radiofrequency lesion of the dorsal root ganglion on level C4, C5 or C6. Electromyography (EMG) and sensory evoked potentials (SEP) were recorded before and 3 weeks after the radiofrequency lesion. Side effects were studied 3 weeks, 6 weeks and 3 months after the procedure. Pain scores were evaluated on Numeric Rating Scales (NRS) before and 6 weeks after treatment. The patient was interviewed 3, 6 and 9 months after the radiofrequency lesion. The most common side effect was burning pain in the dermatome of the treated nerve root. Hyposensibility in the dermatome was noticed in 35% of patients. Except in 1 patient, these side effects had disappeared 6 weeks after treatment. The EMG showed no signs of denervation. One SEP recording remained abnormal after treatment. There was initial pain relief in 75% of patients after 3 months and in 50% of the patients after 6 months. In conclusion, this study did not reveal any signs of motor denervation after a percutaneous partial rhizotomy. There were no long-term signs of deafferentation. Initial pain relief was found in 75% of patients, but there was a marked tendency for pain to recur in a period from 3 to 9 months after treatment.

Myocardial metabolism, catecholamine balance, and left ventricular function during coronary artery surgery: effects of nitroprusside and nifedipine.

The effects of nitroprusside and nifedipine on myocardial oxygen consumption (MVO2), catecholamine release, and left ventricular (LV) function (using 2D transesophageal echocardiography) were compared. Thirty-seven patients undergoing coronary artery surgery, anesthetized with fentanyl, 100 micrograms/kg, were studied. All had good LV function and had been receiving long-term oral beta-blocking therapy. Patients were randomly allocated to one of three groups. Group C (n = 12) received no vasodilator and served as control. Group S (n = 13) received nitroprusside at an initial rate of 1 microgram/kg/min. Group N (n = 12) received nifedipine at an initial rate of 0.7 microgram/kg/min. Baseline measurements were obtained ten minutes after intubation. Vasodilator therapy was then started in groups S and N. Infusion rates were adjusted to maintain systolic blood pressure (SBP) between 80% and 120% of baseline values. Additional measurements were made ten minutes after the start of the infusion, ie, before surgery (in group C immediately before surgery), and after sternotomy when the pericardium was opened. The mean (+/- SD) total dose requirements were 1.9 +/- 0.5 micrograms/kg/min for nitroprusside and 1.1 +/- 0.2 micrograms/kg/min for nifedipine. The mean (+/- SD) total infusion time was 31 +/- 5 minutes for nitroprusside and 32 +/- 11 minutes for nifedipine. After sternotomy, heart rate increased in all groups. At this time arterial blood pressure and systemic vascular resistance (SVR) increased in group C. SVR was decreased after the first ten minutes of nitroprusside infusion and after sternotomy in group S. Coronary sinus blood flow, MVO2, and myocardial norepinephrine release increased in group N, but not in groups C or S. After sternotomy, LV percentage area reduction increased in groups S and N, but not in group C. In group N there was a significant correlation (r = 0.65; P less than .05) between the increases in MVO2 and LV percentage area reduction, an estimate of myocardial function. Lactate production occurred in two patients in group C after sternotomy. This was not associated with ECG changes, but in one patient regional wall motion abnormalities developed. No evidence of myocardial ischemia was observed in groups S and N. However, in contrast to nitroprusside, the use of nifedipine was associated with increases in MVO2, myocardial norepinephrine release, and inotropy.

Myocardial metabolism and coronary sinus blood flow during coronary artery surgery: effects of nitroprusside and nifedipine.

The effects of nitroprusside and nifedipine on hemodynamics, coronary dynamics, and global myocardial metabolism were compared in two groups of patients undergoing elective coronary artery surgery, who were anesthetized with fentanyl, 100 micrograms/kg. After induction of anesthesia, either nitroprusside or nifedipine was started as follows: group S (n = 11) received nitroprusside at an initial rate of 1.3 micrograms/kg/min; group N (n = 9) received nifedipine at an initial rate of 0.7 micrograms/kg/min. Infusion rates were adjusted to maintain systolic blood pressure (SBP) between 80% and 120% of preinfusion (control) values. Control measurements were obtained 10 minutes after intubation. Then vasodilator infusion was started. Additional measurements were obtained 10 minutes after the start of infusion (before surgery) and after sternotomy. The mean (+/- SD) total dose requirements were: nitroprusside, 1.6 +/- 0.3 micrograms/kg/min; and nifedipine 1.1 +/- 0.7 micrograms/kg/min. The mean (+/- SD) total infusion time was: nitroprusside, 32 +/- 5 minutes; and nifedipine, 37 +/- 7 minutes. After 10 minutes of infusion there were decreases in SBP (p less than 0.001) and diastolic blood pressure (DBP; p less than 0.01) in group S. In group N only SBP decreased (p less than 0.01). At this time there were no significant changes in coronary sinus blood flow (CSBF) or myocardial oxygen consumption (MVO2) in either group. After stenotomy DBP remained decreased (p less than 0.05) in group S.(ABSTRACT TRUNCATED AT 250 WORDS)