VPL-DBS on neuropathic pain rat model is effective in mechanical allodynia than cold allodynia

Recently, deep brain stimulation (DBS) is widely used in various types of neurodegenerative disorders for minimal invasiveness and safety of the procedure. Deep brain stimulation is consistently applied for the treatment of patients with neuropathic pain even though the success rate is not as high as other neurodegenerative disorders. Furthermore, it is also unclear how DBS improves neuropathic pain. In this study, we investigated the role of DBS following the stimulation parameter for analgesic effect on mechanical allodynia and cold allodynia in neuropathic pain rats. We used a sciatic nerve injury model to induce neuropathic pain, and observed responses to mechanical and cold stimulation by the von Frey test and acetone test, respectively. We classified the rats into four groups: na?ve (na?ve, n?=?10), na?ve?+?DBS (N?+?DBS, n?=?10), neuropathic pain (NP, n?=?10), and neuropathic pain?+?DBS (NP?+?DBS, n?=?10). We inserted the DBS electrode into the ventral posterolateral nucleus (VPL) into the rats (VPL-DBS). The score for mechanical allodynia was significantly decreased in NP?+?DBS group (p?<?0.01). However, the score for cold allodynia did not significantly drop in any groups including NP?+?DBS group (p?>?0.05). In this study, we found that the electrical stimulation of the VPL works more effectively with mechanical allodynia than cold one, and pain signal induced by mechanical stimulus and cold stimulus may be processed through different pathways in the brain.     

Analysis of Failed Spinal Cord Stimulation Trials in the Treatment of Intractable Chronic Pain

Objective

The purpose of this study is to identify the factors affecting the failure of trials (<50% pain reduction in pain for trial period) to improve success rate of spinal cord stimulation (SCS) trial.

Methods

A retrospective review of the failed trials (44 patients, 36.1%) among the patients (n=122) who underwent SCS trial between January 1990 and December 1998 was conducted. We reviewed the causes of failed trial stimulation, age, sex, etiology of pain, type of electrode, and third party support.

Results

Of the 44 patients, 65.9% showed unacceptable pain relief in spite of sufficient paresthesia on the pain area with trial stimulation. Four of six patients felt insufficient paresthesia with stimulation had the lesions of the spinal cord. Seventy five percent of the patients experienced unpleasant or painful sensation during stimulation had allodynia dominant pain. Third-party involvement, sex, age and electrode type had no influence on the outcome.

Conclusion

We conclude that SCS trial is less effective for patients with neuropathic pain of cord lesions, postherpetic neuropathy or post-amputation state. Further, patients with allodynia dominant pain can feel unpleasant or painful during trial stimulation.     

Factors Associated with the Success of Trial Spinal Cord Stimulation in Patients with Chronic Pain from Failed Back Surgery Syndrome

Objective

Spinal cord stimulation (SCS) is an effective means of treatment of chronic neuropathic pain from failed back surgery syndrome (FBSS). Because the success of trial stimulation is an essential part of SCS, we investigated factors associated with success of trial stimulation.

Methods

Successful trial stimulation was possible in 26 of 44 patients (63.6%) who underwent insertion of electrodes for the treatment of chronic pain from FBSS. To investigate factors associated with successful trial stimulation, patients were classified into two groups (success and failure in trial). We investigated the following factors : age, sex, predominant pain areas (axial, limb, axial combined with limbs), number of operations, duration of preoperative pain, type of electrode (cylindrical/paddle), predominant type of pain (nociceptive, neuropathic, mixed), degree of sensory loss in painful areas, presence of motor weakness, and preoperative Visual Analogue Scale.

Results

There were no significant differences between the two groups in terms of age, degree of pain, number of operations, and duration of pain (p>0.05). Univariate analysis revealed that the type of electrode and presence of severe sensory deficits were significantly associated with the success of trial stimulation (p<0.05). However, the remaining variable, sex, type of pain, main location of pain, degree of pain duration, degree of sensory loss, and presence of motor weakness, were not associated with the trial success of SCS for FBSS.

Conclusion

Trial stimulation with paddle leads was more successful. If severe sensory deficits occur in the painful dermatomes in FBSS, trial stimulation were less effective.     

Involvement of Selective Alpha-2 Adrenoreceptor in Sympathetically Maintained Pain

Objective

Peripheral nerve injury often leads to neuropathic pain, which is characterized by burning pain, allodynia, and hyperalgesia. The role of the sympathetic nervous system in neuropathic pain is a complex and controversial issue. It is generally accepted that the alpha adrenoreceptor (AR) in sympathetic nerve system plays a significant role in the maintenance of pain. Among alpha adrenoreceptor, alpha-1 receptors play a major role in the sympathetic mediated pain. The primary goal of this study is to test the hypothesis that sympathetically maintained pain involves peripheral alpha-2 receptors in human.

Methods

The study was a randomized, prospective, double-blinded, crossover study involving twenty patients. The treatments were : Yohimbine (30 mg mixed in 500 mL normal saline), and Phentolamine (1 mg/kg in 500 mL normal saline) in 500 mL normal saline at 70 mL/hr initially then titrated. The patients underwent infusions on three different appointments, at least one month apart. Thus, all patients received all 2 treatments. Pain measurement was by visual analogue scale, neuropathic pain questionnaire, and McGill pain questionnaire.

Results

There were significant decreases in the visual analogue scale, neuropathic score, McGill pain score of yohimnine, and phentolamine.

Conclusion

We conclude that alpha-2 adrenoreceptor, along with alpha-2 adrenoreceptor, may be play role in sympathetically maintained pain in human.     

Brain Activation Evoked by Sensory Stimulation in Patients with Spinal Cord Injury : Functional Magnetic Resonance Imaging Correlations with Clinical Features

Objective

The purpose of this study is to determine whether the changes of contralateral sensorimotor cortical activation on functional magnetic resonance imaging (fMRI) can predict the neurological outcome among spinal cord injury (SCI) patients when the great toes are stimulated without notice.

Methods

This study enrolled a total of 49 patients with SCI and investigated each patient''s preoperative fMRI, postoperative fMRI, American Spinal Injury Association (ASIA) score, and neuropathic pain occurrence. Patients were classified into 3 groups according to the change of blood oxygenation level dependent (BOLD) response on perioperative fMRI during proprioceptive stimulation with repetitive passive toe movements : 1) patients with a response of contralateral sensorimotor cortical activation in fMRI were categorized; 2) patients with a response in other regions; and 3) patients with no response. Correlation between the result of fMRI and each parameter was analyzed.

Results

In fMRI data, ASIA score was likely to show greater improvement in patients in group A compared to those belonging to group B or C (p<0.001). No statistical significance was observed between the result of fMRI and neuropathic pain (p=0.709). However, increase in neuropathic pain in response to the signal change of the ipsilateral frontal lobe on fMRI was statistically significant (p=0.030).

Conclusion

When there was change of BOLD response at the contralateral sensorimotor cortex on perioperative fMRI after surgery, relief of neurological symptoms was highly likely for traumatic SCI patients. In addition, development of neuropathic pain was likely to occur when there was change of BOLD response at ipsilateral frontal lobe.     

Axial Neck Pain after Cervical Laminoplasty

Objective

It has been demonstrated that cervical laminoplasty is an effective and safe method of treating multi-level cervical spondylotic myelopathy and ossification of the posterior longitudinal ligament. However, recent reports have suggested that axial neck pain is frequently encountered after cervical laminoplasty. The aim of the present study was to determine clinical significance of the C7 spinous process on axial neck pain after cervical laminoplasty.

Methods

A total of 31 consecutive patients that underwent cervical laminoplasty between March 2002 and December 2008 were reviewed. The authors evaluated and compared axial neck pain and lordotic angle in patients that underwent C7 spinous process preserving surgery (group 1, n = 16) and in patients in which the C7 spinous process was sacrificed (group 2, n = 15).

Results

Severe or moderate early axial pain occurred in 56.2% of patients in group 1 and in 86.6% in group 2. Severe or moderate late axial pain occurred in 12.5% in group 1 and in 73.3% in group 2. Eighty-Six percent of patients in group 2 and 43% in group 1 experienced aggravation of their axial neck pain during the early postoperative period. Aggravation of axial neck pain during early postoperative period was less common in group 1 but not statistically significant (p = 0.073). Sixty-six percent of patients in group 2 and 12% in group 1 had aggravated axial neck pain at late postoperative period and aggravation of late axial neck pain was significantly less common in group 1 (p = 0.002).

Conclusion

The present study demonstrates that C7 spinous process preserving laminoplasty decreases the incidence of aggravated axial neck pain after cervical laminoplasty.     

Microdecompression for Extraforaminal L5-S1 Disc Herniation; The Significance of Concomitant Foraminal Disc Herniation for Postoperative Leg Pain

Objective

To analyze the relationship of concomitant foraminal lumbar disc herniation (FLDH) with postoperative leg pain after microdecompression for extraforaminal lumbar disc herniation (EFLDH) at the L5-S1 level.

Methods

Sixty-five patients who underwent microdecompression for symptomatic EFLDH at the L5-S1 level were enrolled. According to the severity of accompanying FLDH, EFLDH was classified into four categories (Class I : no FLDH; Class II : mild to moderate FLDH confined within a lateral foraminal zone; Class III : severe FLDH extending to a medial foraminal zone; Class IV : Class III with intracanalicular disc herniation). The incidence of postoperative leg pain, dysesthesia, analgesic medication, epidural block, and requirement for revision surgery due to leg pain were evaluated and compared at three months after initial surgery.

Results

The incidences of postoperative leg pain and dysesthesia were 36.9% and 26.1%, respectively. Pain medication and epidural block was performed on 40% and 41.5%, respectively. Revision surgery was recommended in six patients (9.2%) due to persistent leg pain. The incidences of leg pain, dysesthesia, and requirement for epidural block were higher in Class III/IV, compared with Class I/II. The incidence of requirement for analgesic medication was significantly higher in Class III/IV, compared with Class I/II (p=0.02, odds ratio=9.82). All patients who required revision surgery due to persistent leg pain were included in Class III/IV.

Conclusion

Concomitant FLDH seems related to postoperative residual leg pain after microdecompression for EFLDH at the L5-S1 level.     

A randomized double-blind crossover trial of deep brain stimulation of the subcallosal cingulate gyrus in patients with treatment-resistant depression: a pilot study of relapse prevention

Background

To date, antidepressant drugs show limited efficacy, leaving a large number of patients experiencing severe and persistent symptoms of major depression. Previous open-label clinical trials have reported significant sustained improvements with deep brain stimulation (DBS) of the subcallosal cingulate gyrus (SCG) in patients with severe, chronic treatment-resistant depression (TRD). This study aimed to confirm the efficacy and measure the impact of discontinuation of the electrical stimulation.

Methods

We conducted a 6-month double-blind, randomized, sham-controlled crossover study in implanted patients with previous severe TRD who experienced full remission after chronic stimulation. After more than 3 months of stable remission, patients were randomly assigned to 2 treatment arms: the ON–OFF arm, which involved active electrode stimulation for 3 months followed by sham stimulation for 3 months, and the OFF–ON arm, which involved sham stimulation for 3 months followed by active stimulation for 3 months. The primary outcome measure was the difference in the 17-item Hamilton Rating Scale for Depression (HAMD-17) total score between sham and active stimulation.

Results

We enrolled 5 patients in our trial. A Friedman repeated-measures analysis of variance revealed a significant effect of treatment (χ²₁ = 5.0, p = 0.025) in patients with higher depression scores during sham stimulation. At the end of active stimulation, depression was remitted in 4 of 5 patients and none of them had experienced a relapse, whereas at the end of sham stimulation, 2 patients remained in remission, 2 relapsed and 1 showed a progressive worsening without reaching relapse criteria.

Limitations

The small sample size limited the statistical power and external validity.

Conclusion

These preliminary findings indicate that DBS of the SCG is an effective and safe treatment for severe forms of TRD and that continuous electrical stimulation is required to maintain therapeutic effects.     

Use of Cortical Stimulation in Neuropathic Pain,Tinnitus, Depression,and Movement Disorders

Medical treatment must strike a balance between benefit and risk. As the field of neuromodulation develops, decreased invasiveness, in combination with maintenance of efficacy, has become a goal. We provide a review of the history of cortical stimulation from its origins to the current state. The first part discusses neuropathic pain and the nonpharmacological treatment options used. The second part covers transitions to tinnitus, believed by many to be another deafferentation disorder, its classification, and treatment. The third part focuses on major depression. The fourth section concludes with the discussion of the use of cortical stimulation in movement disorders. Each part discusses the development of the field, describes the current care protocols, and suggests future avenues for research needed to advance neuromodulation.

Electronic supplementary material

The online version of this article (doi:10.1007/s13311-014-0283-0) contains supplementary material, which is available to authorized users.Key Words: Cortical stimulation, neuropathic pain, depression, tinnitus, movement disorders     

A Comparison of the Effect of Epidural Patient-Controlled Analgesia with Intravenous Patient-Controlled Analgesia on Pain Control after Posterior Lumbar Instrumented Fusion

Objective

Retrospective analysis to compare the effect and complication of epidural patient-controlled analgesia (epidural PCA) with intravenous patient-controlled analgesia (IV PCA) for the treatment of the post-operative pain after posterior lumbar instrumented fusion.

Methods

Sixty patients who underwent posterior lumbar instrumented fusion for degenerative lumbar disease at our institution from September 2007 to January 2008 were enrolled in this study. Out of sixty patients, thirty patients received IV PCA group and thirty patients received epidural PCA group. The pain scale was measured by the visual analogue scale (VAS) score.

Results

There were no significant difference between IV PCA group and epidural PCA group on the PCA related complications (p=0.7168). Ten patients in IV PCA group and six patients in epidural PCA group showed PCA related complications. Also, there were no significant differences in reduction of VAS score between two groups on postoperative 2 hours (p=0.9618) and 6 hours (p=0.0744). However, postoperative 12 hours, 24 hours and 48 hours showed the significant differences as mean of reduction of VAS score (p=0.0069, 0.0165, 0.0058 respectively).

Conclusion

The epidural PCA is more effective method to control the post-operative pain than IV PCA after 12 hours of spinal fusion operation. However, during the first twelve hours after operation, there were no differences between IV PCA and epidural PCA.     

The Relationship between Neck Pain and Cervical Alignment in Young Female Nursing Staff

Objective

Degenerative changes in the cervical spine are commonly accompanied by cervical kyphosis which can cause neck pain. This study examined the relationship between neck pain and cervical alignment.

Methods

A total of 323 female nursing staff from our hospital were enrolled. Sagittal radiographs of the cervical spine, Body Mass Index (BMI), Visual Analogue Scale (VAS) measures of neck and arm pain, Neck Disability Index (NDI) and the Short Form (36) Health Survey (SF-36 scores) were obtained and reviewed retrospectively. Global lordosis (GL) of the cervical spine was measured on radiograph images. Correlations between GL and questionnaire scores were investigated using the following three methods : 1) correlation between GL and questionnaire scores among the entire sample; 2) subgroup analysis of patients with "kyphosis (KYP) : GL scores<0" vs. those with "lordosis (LOR) : GL scores>0" on questionnaire measures; and 3) subgroup analysis of patients with pain vs. those without pain, on GL and questionnaire measures.

Results

There was no significant correlation between GL and any questionnaire measure. There was a significant difference between the mean GLs of the KYP and LOR groups, but there were no group differences in BMI, age or any questionnaire measures. There was no difference between the pain (n=92) and pain-free (n=231) groups in age, BMI or GL, but there were differences in neck, and arm pain, and physical function and NDI scores.

Conclusions

Our data suggest that kyphotic deformity was not associated with neck pain.     

The Effect of Minocycline on Motor Neuron Recovery and Neuropathic Pain in a Rat Model of Spinal Cord Injury

Objective

Minocycline, a second-generation tetracycline-class antibiotic, has been well established to exert a neuroprotective effect in animal models and neurodegenerative disease through the inhibition of microglia. Here, we investigated the effects of minocycline on motor recovery and neuropathic pain in a rat model of spinal cord injury.

Methods

To simulate spinal cord injury, the rats'' spinal cords were hemisected at the 10th thoracic level (T10). Minocycline was injected intraperitoneally, and was administered 30 minutes prior surgery and every second postoperative day until sacrifice 28 days after surgery. Motor recovery was assessed via the Basso-Beattie-Bresnahan test. Mechanical hyperalgesia was measured throughout the 28-day post-operative course via the von Frey test. Microglial and astrocyte activation was assessed by immunohistochemical staining for ionized calcium binding adaptor molecule 1 (Iba1) and glial fibrillary acidic protein (GFAP) at two sites: at the level of hemisection and at the 5th lumbar level (L5).

Results

In rats, spinal cord hemisection reduced locomotor function and induced a mechanical hyperalgesia of the ipsilateral hind limb. The expression of Iba1 and GFAP was also increased in the dorsal and ventral horns of the spinal cord at the site of hemisection and at the L5 level. Intraperitoneal injection of minocycline facilitated overall motor recovery and attenuated mechanical hyperalgesia. The expression of Iba1 and GFAP in the spinal cord was also reduced in rats treated with minocycline.

Conclusion

By inhibiting microglia and astrocyte activation, minocycline may facilitate motor recovery and attenuate mechanical hyperalgesia in individuals with spinal cord injuries.     

Comparison of the spinal neuropathic pain induced by intraspinal injection of N-methyl-d-aspartate and quisquate in rats

Objective

Excitatory amino acids play important roles in the development of secondary pathology following spinal cord injury (SCI). This study was designed to evaluate morphological changes in the dorsal horn of the spinal cord and assess profiles of pain behaviors following intraspinal injection of N-methyl-D-aspartate (NMDA) or quisqualate (QUIS) in rats.

Methods

Forty male Sprague-Dawley rats were randomized into three groups : a sham, and two experimental groups receiving injections of 125 mM NMDA or QUIS into their spinal dorsal horn. Following injection, hypersensitivity to cold and mechanical stimuli, and excessive grooming behaviors were assessed serially for four weeks. At the end of survival periods, morphological changes in the spinal cord were evaluated.

Results

Cold allodynia was developed in both the NMDA and QUIS groups, which was significantly higher in the QUIS group than in the NMDA group. The mechanical threshold for the ipsilateral hind paw in both QUIS and NMDA groups was significantly lower than that in the control group. The number of groomers was significantly higher in the NMDA group than in the QUIS group. The size of the neck region of the spinal dorsal horn, but not the superficial layer, was significantly smaller in the NMDA and QUIS groups than in the control group.

Conclusion

Intraspinal injection of NMDA or QUIS can be used as an excitotoxic model of SCI for further research on spinal neuropathic pain.     

Double-blind optimization of subcallosal cingulate deep brain stimulation for treatment-resistant depression: a pilot study

Background

Deep brain stimulation (DBS) of the subcallosal cingulate (SCC) is reported to be a safe and effective new treatment for treatment-resistant depression (TRD). However, the optimal electrical stimulation parameters are unknown and generally selected by trial and error. This pilot study investigated the relationship between stimulus parameters and clinical effects in SCC-DBS treatment for TRD.

Methods

Four patients with TRD underwent SCC-DBS surgery. In a double-blind stimulus optimization phase, frequency and pulse widths were randomly altered weekly, and corresponding changes in mood and depression were evaluated using a visual analogue scale (VAS) and the 17-item Hamilton Rating Scale for Depression (HAM-D-17). In the open-label postoptimization phase, depressive symptoms were evaluated biweekly for 6 months to determine long-term clinical outcomes.

Results

Longer pulse widths (270–450 μs) were associated with reductions in HAM-D-17 scores in 3 patients and maximal happy mood VAS responses in all 4 patients. Only 1 patient showed acute clinical or mood effects from changing the stimulation frequency. After 6 months of open-label therapy, 2 patients responded and 1 patient partially responded.

Limitations

Limitations include small sample size, weekly changes in stimulus parameters, and fixed-order and carry-forward effects.

Conclusion

Longer pulse width stimulation may have a role in stimulus optimization for SCC-DBS in TRD. Longer pulse durations produce larger apparent current spread, suggesting that we do not yet know the optimal target or stimulus parameters for this therapy. Investigations using different stimulus parameters are required before embarking on large-scale randomized sham-controlled trials.     

Estimated Number of Korean Adults with Back Pain and Population-Based Associated Factors of Back Pain : Data from the Fourth Korea National Health and Nutrition Examination Survey

Objective

We estimated the number of Korean adults with back pain and evaluated population-based associated factors of back pain from a representative sample data from the Fourth Korea National Health and Nutrition Examination Survey.

Methods

The number of Korean adults who experienced back pain (experienced patients), those who experienced back pain lasting for three or more months during the past year (chronic patients), and those who were currently suffering from back pain (current patients) were estimated by analyzing the data from the fourth Korea National Health and Nutrition Examination Survey conducted in 2007 using surveyfreq procedure of the SAS statistical package. Population-based odds ratios for being experienced, chronic, and current patient according to demographic (age and gender), socioeconomic (education and occupation), and lifestyle factors (smoking, drinking, and exercise) were estimated using surveylogistic procedure.

Results

It was estimated that there were 5,554,256 (proportion, 15.4%; 95% CI, 4,809,466 - 6,299,046) experienced patients, 2,060,829 (5.7%; 1,557,413-2,564,246) chronic patients, and 3,084,188 (8.5%; 2,600,197 - 3,568,179) current patients among 36,107,225 Korean adults aged 20-89 years in 2007. Each of explanatory variables was significantly associated with at least one of the response variables for back pain.

Conclusion

Based on our study results, further efforts to investigate epidemiology of back pain, to evaluate associated factors, and to improve treatment outcomes are needed.     

Clinical and Radiological Findings of Discogenic Low Back Pain Confirmed by Automated Pressure-Controlled Discography

Objective

Few studies on the clinical spectrum of automated pressure-controlled discography (APCD)-defined positive discs have been reported to date. Thus, the present study was undertaken to analyze clinical parameters critical for diagnosis of discogenic pain and to correlate imaging findings with intradiscal pressures and pain responses in patients with APCD-positive discs.

Methods

Twenty-three patients who showed APCD-positive discs were selected for analysis. CT discogram findings and the degrees of nuclear degeneration seen on MRI were analyzed in comparison to changes of intradiscal pressure that provoked pain responses; and clinical pain patterns and dynamic factors were evaluated in relation to pain provocation.

Results

Low back pain (LBP), usually centralized, with diffuse leg pain was the most frequently reported pattern of pain in these patients. Overall, LBP was most commonly induced by sitting posture, however, standing was highly correlated with L5/S1 disc lesions (p < 0.01). MRI abnormalities were statistically correlated with grading of CT discogram results (p < 0.05); with most pain response observed in CT discogram Grades 3 and 4. Pain-provoking pressure was not statistically correlated with MRI grading. However, it was higher in Grade 3 than Grade 4.

Conclusion

APCD-positive discs were demonstrated in patients reporting centralized low back pain with diffuse leg pain, aggravated by sitting and standing. MRI was helpful to assess the degree of nuclear degeneration, yet it could not guarantee exact localization of the painful discs. APCD was considered to be more useful than conventional discography for diagnosis of discogenic pain.     

Pallidal Deep Brain Stimulation in Primary Cervical Dystonia with Phasic Type : Clinical Outcome and Postoperative Course

Objective

The purpose of this study was to analyze in detail the relationship between outcome and time course of effect in medically refractory primary cervical dystonia (CD) with phasic type that was treated by bilateral globus pallidus internus (Gpi) deep brain stimulation (DBS).

Methods

Six patients underwent bilateral implantation of DBS into the Gpi under the guide of microelectrode recording and were followed for 18.7 ± 11.1 months. The mean duration of the CD was 5.8 ± 3.4 years. The mean age at time of surgery was 54.2 ± 10.2 years. Patients were evaluated with the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) and relief scale using patient self-reporting.

Results

The TWSTRS total scores improved by 64.5%, 65.5%, 75.8%, and 76.0% at 3, 6, 12 months, and at the last available follow-up after surgery, respectively. Statistically significant improvements in the TWSTRS scores were observed 3 months after surgery (p = 0.028) with gradual improvement up to 12 months after surgery, thereafter, the improvement was sustained. However, there was no statistically significant difference between the scores at 3 and 12 months. Subjective improvement reported averaged 81.7 ± 6.8% at last follow-up. Mild dysarthria, the most frequent adverse event, occurred in 3 patients.

Conclusions

Our results show that the bilateral Gpi-DBS can offer a significant therapeutic effect from 3 months postoperatively in patients with primary CD with phasic type, without significant side effects.     

Levodopa raises objective pain threshold in Parkinson's disease: a RIII reflex study

Background

Patients suffering from Parkinson''s disease (PD) describe painful sensations that could be related to neuropathic pain. Experimental data have indicated the involvement of basal ganglia and dopaminergic pathways in central nociceptive processing.

Aim

The objective of this study was to assess and compare the effect of levodopa on the objective pain threshold in patients with PD and healthy subjects.

Methods

The objective pain threshold was assessed by the nociceptive flexion reflex (RIII) in 13 PD patients and 10 healthy subjects. Patients and healthy subjects were evaluated under two randomised conditions: with levodopa (ON) and without (OFF).

Results

Levodopa significantly increased the RIII threshold of PD patients (6.9 (1.2) mA in the OFF condition vs 8 (1.1) mA in the ON position; p = 0.02). RIII threshold was significantly lower in PD patients than in healthy subjects in the OFF condition (6.9 (1.2) mA vs 9.7 (3.4) mA; p = 0.02). RIII threshold did not change after levodopa administration in healthy subjects.

Conclusion

These results provide evidence of a dopaminergic modulation of objective pain threshold in PD patients. In addition, the decrease in RIII threshold in PD patients, in the OFF condition, compared with controls, confirms the existence of an objective pain perception disturbance in PD.Pain is recognised as a feature of Parkinson''s disease (PD) and is reported by 40–75% of patients with PD.¹ Painful sensations are various (musculoskeletal, neuropathic pain) and may be present at any stage of the disease.^2,3Several anatomical, electrophysiological and pharmacological arguments are in favour of the involvement of the basal ganglia and dopaminergic pathways in central nociceptive processing.⁴There are only a few controversial studies on pain perception in PD. The pain threshold of patients with PD has been found to be lower than, higher than or equal to that of healthy subjects.^5,6,7 Recently, Djaldetti et al have shown that patients with PD have a lower subjective heat pain threshold than healthy subjects.⁸ To our knowledge, the effect of levodopa has only been assessed on the subjective pain threshold. Using two different experimental thermal stimulations (cold pressor test and thermotest with Peltier effect), we have previously shown that acute administration of levodopa significantly raised the subjective pain threshold of patients with PD.^9,10The nociceptive flexion reflex (RIII), a polysynaptic reflex, has been described as a useful tool for objectively investigating the pain threshold and its pharmacological modulation by analgesic drugs in normal subjects.^11,12The primary aim of the present study was to compare the effects of levodopa on objective pain threshold (RIII reflex) in pain free patients with PD and in healthy subjects. A secondary objective was to compare such parameters between these two groups.     

The Effectiveness of Endoscopic Radiofrequency Denervation of Medial Branch for Treatment of Chronic Low Back Pain

Objective

The aim of this study is to evaluate the clinical results of endoscopic radiofrequency ablation of medial branch in patients with chronic low back pain originating from facet joints.

Methods

Between October 2010 and December 2013, 52 consecutive patients had suffering from chronic low back pain had undergone endoscopic radiofrequency denervation of medial branch of dorsal ramus. The clinical outcomes of these 52 patients were reviewed retrospectively. Preoperative and postoperative Visual Analogue Scale (VAS) and Korean version of Oswestry Disability Index (K-ODI), and patients'' satisfaction with the procedure were assessed.

Results

The pain scores on the VAS for back pain had improved significantly from a preoperative mean of 7.1 to a postoperative mean of 2 at the last follow-up (p<0.001). The clinical outcomes based on the K-ODI had also improved significantly from a preoperative mean of 26.5% to postoperative mean of 7.7% at the last follow-up (p<0.001). 80% of patients were satisfied with the procedure. There were no complications associated with the procedure.

Conclusion

Our preliminary results demonstrate that endoscopic radiofrequency denervation of medial branch could be an effective alternative treatment modality for chronic back pain originating from facet joints that provides long-term pain relief.