Migraine may be a risk factor for the development of complex regional pain syndrome

The aim was to assess the relative frequency of migraine and the headache characteristics of complex regional pain syndrome (CRPS) sufferers. CRPS and migraine are chronic, often disabling pain syndromes. Recent studies suggest that headache is associated with the development of CRPS. Consecutive adults fulfilling International Association for the Study of Pain criteria for CRPS at a pain clinic were included. Demographics, medical history, and pain characteristics were obtained. Headache diagnoses were made using International Classification of Headache Disorders, 2nd edn criteria. Migraine and pain characteristics were compared in those with migraine with those without. anova with Tukey post hoc tests was used to determine the significance of continuous variables and Fisher's exact or χ(2) tests for categorical variables. The expected prevalence of migraine and chronic daily headache (CDH) was calculated based on age- and gender-stratified general population estimates. Standardized morbidity ratios (SMR) were calculated by dividing the observed prevalence of migraine by the expected prevalence from the general population. The sample consisted of 124 CRPS participants. The mean age was 45.5 ± 12.0 years. Age- and gender-adjusted SMRs showed that those with CRPS were 3.6 times more likely to have migraine and nearly twice as likely to have CDH as the general population. Aura was reported in 59.7% (74/124) of participants. Of those CRPS sufferers with migraine, 61.2% (41/67) reported the onset of severe headaches before the onset of CRPS symptoms Mean age of onset of CRPS was earlier in those with migraine (34.9 ± 11.1 years) and CDH (32.5 ± 13.4 years) compared with those with no headaches (46.8 ± 14.9 years) and those with tension-type headache (TTH) (39.9 ± 9.9 years), P < 0.05. More extremities were affected by CRPS in participants with migraine (median of four extremities) compared with the combined group of those CRPS sufferers with no headaches or TTH (median 2.0 extremities), P < 0.05. The presence of static, dynamic and deep joint mechano-allodynia together was reported by more CRPS participants with migraine (72.2%) than those with no headaches or TTH (46.2%), P ≤ 0.05. Migraine may be a risk factor for CRPS and the presence of migraine may be associated with a more severe form of CRPS. Specifically: (i) migraine occurs in a greater percentage of CRPS sufferers than expected in the general population; (ii) the onset of CRPS is reported earlier in those with migraine than in those without; and (iii) CRPS symptoms are present in more extremities in those CRPS sufferers with migraine compared with those without. In addition, as we also found that the presence of aura is reported in a higher percentage of those CRPS sufferers with migraine than reported in migraineurs in the general population, further evaluation of the cardiovascular risk profile of CRPS sufferers is warranted.

Kinesigenic dyskinesia in a case of voltage-gated potassium channel-complex protein antibody encephalitis

OBJECTIVE

To describe the first case (to our knowledge) of voltage-gated potassium channel-complex protein antibody encephalitis with kinesigenic dyskinesia and cramp-fasciculation syndrome.

DESIGN

Case report.

SETTING

Hospitalized care.

PATIENT

A 38-year-old man with a history of bronchial asthma, eczema, vitiligo, and immune complex mesangiopathic glomerulonephritis presented with abnormal movements.

MAIN OUTCOME MEASURES

Clinical examination, magnetic resonance imaging, single-photon emission computed tomography, electromyography and nerve conduction studies, video-electroencephalographic monitoring, plasmapheresis exchange therapy, and intravenous immunoglobulin administration.

RESULTS

Clinical examination revealed paroxysmal kinesigenic dyskinesia and fasciculations. Magnetic resonance imaging of the brain revealed a left caudate and left putamen increased signal lesion on T2-weighted and fluid-attenuated inversion recovery sequences as well as increased flow in the same region on single-photon emission computed tomographic scans. Electromyography and nerve conduction studies revealed significant afterdischarges, cramp potentials, and continuous motor activity. The video-electroencephalographic monitoring revealed no epileptiform discharges. The patient dramatically improved after 5 plasmapheresis exchange treatments and a course of intravenous immunoglobulin at 2 gm/kg over 5 divided doses.

CONCLUSION

To our knowledge, this is the first report of paroxysmal kinesigenic dyskinesia with voltage-gated potassium channel-complex protein antibody encephalitis associated with the cramp fasciculation syndrome.

Enantioselective pharmacokinetics of (R)- and (S)-ketamine after a 5-day infusion in patients with complex regional pain syndrome

INTRODUCTION

This study determined the pharmacokinetics and pharmacodynamics of (R)- and (S)-ketamine and (R)- and (S)-norketamine following a 5-day moderate dose, as a continuous (R,S)-ketamine infusion in complex regional pain syndrome (CRPS) patients.

MATERIALS AND METHODS

Ketamine was titrated to 10-40 mg/h and maintained for 5 days. (R)- and (S)-Ketamine and (R)- and (S)-norketamine pharmacokinetic and pharmacodynamic studies were performed. Blood samples were obtained on Day 1 preinfusion, and at 60-90, 120-150, 180-210, and 240-300 min after the start of the infusion, on Days 2, 3, 4, 5, and on Day 5 at 60 min after the end of infusion. The plasma concentrations of (R)- and (S)-ketamine and (R)- and (S)-norketamine were determined using enantioselective liquid chromatography-mass spectrometry.

RESULTS

Ketamine and norketamine levels stabilized 5 h after the start of the infusion. (R)-Ketamine clearance was significantly lower resulting in higher steady-state plasma concentrations than (S)-ketamine. The first-order elimination for (S)-norketamine was significantly greater than that of (R)-enantiomer. When comparing the pharmacokinetic parameters of the patients who responded to ketamine treatment with those who did not, no differences were observed in ketamine clearance and the first-order elimination of norketamine.

CONCLUSION

The results indicate that (R)- and (S)-ketamine and (R)- and (S)-norketamine plasma concentrations do not explain the antinociceptive activity of the drug in patients suffering from CRPS.

Pharmacodynamic profiles of ketamine (R)- and (S)- with 5-day inpatient infusion for the treatment of complex regional pain syndrome

BACKGROUND

Ketamine might be effective in blocking central sensitization of pain transmission neurons through its effect on NMDA receptors in refractory Complex Regional Pain Syndrome (CRPS) patients. At higher doses, ketamine infusions can be associated with significant risks; outpatient therapy requires return visits for a 10-day period with variable efficacy and duration.

OBJECTIVE

This study determined the efficacy of a 5-day moderate dose, continuous racemic ketamine infusion. The pharmacodynamic responses to racemic ketamine and norketamine were examined.

DESIGN

Observational study

METHODS

In this study, ketamine was titrated from 10-40 mg/hour in 16 CRPS patients, and maintained for 5 days. Pain was assessed daily. Ketamine and norketamine concentrations were obtained on Day 1 before starting the infusion; at 60 to 90 minutes, 120 to 150 minutes, 180 to 210 minutes, and 240 to 300 minutes after the initiation of the infusion on Days 2, 3, 4, and 5; and on Day 5 at 60 minutes after the conclusion of the infusion. The plasma concentrations of (R)-ketamine, (S)-ketamine, (R)-norketamine and (S)-norketamine were determined using an enantioselective liquid chromatography - mass spectrometry method.

RESULTS

Ketamine and norketamine infusion rates stabilized 5 hours after the start of the infusion. The subjects showed no evidence of significant tachycardia, arterial oxygen desaturation, or hallucinatory responses. Subjects generally experienced minimal pain relief on day one followed by significant relief by day 3. Mean pain scores decreased from the 8-9 to 3-5 ranges; however, the analgesic response to ketamine infusion was not uniform. On Day 5, there was little or no change in the pain measure assessed as the worst pain experienced over the last 24 hours in 37% of the subjects. (R)- and (S)-ketamine concentrations peaked at 240-300 min. (R)- and (S)-norketamine concentrations were lower and peaked on Day 2 of the infusion, as opposed to Day 1 for (R)- and (S)-ketamine. Significant pain relief was achieved by the second day of infusion and correlated with the maximum plasma levels of ketamine and norketamine. Pain relief continued to significantly improve over the 5-day infusion at concentrations of 200-225 ng/mL for (R)- and (S)-ketamine, and 90-120 ng/mL for (R)- and (S)-norketamine.

CONCLUSIONS

A 5-day ketamine infusion for the treatment of severe CRPS provided significant (p <0.05) pain relief by Day 3 compared to baseline. The pain relief experienced on Day 2 of the infusion continued to improve over the 5-day infusion period and correlated with the maximum plasma levels of ketamine and norketamine. We speculate that downstream metabolites of ketamine and norketamine might be playing a role in its therapeutic efficacy.

Outpatient intravenous ketamine for the treatment of complex regional pain syndrome: a double-blind placebo controlled study

Complex regional pain syndrome (CRPS) is a severe chronic pain condition that most often develops following trauma. The pathophysiology of CRPS is not known but both clinical and experimental evidence demonstrate the important of the NMDA receptor and glial activation in its induction and maintenance. Ketamine is the most potent clinically available safe NMDA antagonist that has a well established role in the treatment of acute and chronic pain. This randomized double-blind placebo controlled trial was designed to evaluate the effectiveness of intravenous ketamine in the treatment of CRPS. Before treatment, after informed consent was obtained, each subject was randomized into a ketamine or a placebo infusion group. Study subjects were evaluated for at least 2 weeks prior to treatment and for 3 months following treatment. All subjects were infused intravenously with normal saline with or without ketamine for 4h (25ml/h) daily for 10 days. The maximum ketamine infusion rate was 0.35mg/kg/h, not to exceed 25mg/h over a 4h period. Subjects in both the ketamine and placebo groups were administered clonidine and versed. This study showed that intravenous ketamine administered in an outpatient setting resulted in statistically significant (p<0.05) reductions in many pain parameters. It also showed that subjects in our placebo group demonstrated no treatment effect in any parameter. The results of this study warrant a larger randomized placebo controlled trial using higher doses of ketamine and a longer follow-up period.

Atypical chest pain: evidence of intercostobrachial nerve sensitization in Complex Regional Pain Syndrome

BACKGROUND

Atypical chest pain is a common complaint among Complex Regional Pain Syndrome (CRPS) patients with brachial plexus involvement. Anatomically, the intercostobrachial nerve (ICBN) is connected to the brachial plexus and innervates the axilla, medial arm and anterior chest wall. By connecting to the brachial plexus, the ICBN could become sensitized by CRPS spread and become a source of atypical chest pain.

OBJECTIVE

To evaluate the sensitivity of chest areas in CRPS patients and normal controls.

DESIGN

Prospective investigation of pressure algometry in chest areas to determine chest wall sensitivity.

METHODS

CRPS patients and normal controls volunteered to participate in our study. Each individual was examined to meet inclusion criteria. Patients' report of chest pain history was collected from every participant. Pressure algometry was used to measure pressure sensitivity in the axilla, anterior axillary line second intercostal space, mid-clavicular third rib, mid-clavicular tenth rib, and midsternal. Each of these measurements were compared to an intra-participant abdominal measure to control for an individuals generalized sensitivity. The ratios of chest wall sensitivities were compared between CRPS patients and normal controls.

RESULTS

A history of chest pain was reported by a majority (94%) of CRPS patients and a minority (19%) of normal controls. CRPS patients reported lifting their arm as a major initiating factor for chest pain. To pressure algometry, the ratios of CRPS patients were significantly greater than control subjects (p< 0.02 throughout), indicating increased chest wall sensitivity.

LIMITATIONS

This study is limited by the relatively small number of patients (n=35) and controls (n=21) used.

CONCLUSION

The results of this study support the idea that chest pain is greater in CRPS patients than normal controls. The ICBN could be the source of this sensitization by CRPS spread from the brachial plexus.

Spinal cord histopathological alterations in a patient with longstanding complex regional pain syndrome

Complex regional pain syndrome (CRPS) is a chronic pain condition that usually arises from an injury or as a complication from a surgical procedure. CRPS can result from multiple mechanisms including active processes involving both the peripheral and the central nervous system and sickness like responses involving interactions between the immune and nervous systems. In animal models both peripheral and central sensitization as well as loss of inhibition has been implicated in neuropathic pain states. Glial cells, in particular microglia and astrocytes, are the immunocompetent cells in the central nervous system and are activated following tissue injury or inflammation. In animal studies, activated glia have been shown to be both necessary and sufficient for enhanced nociception. Using immunohistochemical techniques, this study evaluated the degree of astrocytic and microglial activation as well as neuronal loss in autopsy tissue from the cervical, thoracic and lumbar spinal cord of a patient afflicted with CRPS as compared to four control individuals. The major findings of this study are that in long standing CRPS there was significant posterior horn cell loss and activation of both microglia and astrocytes most prominently at the level of the original injury but extending throughout the entire length of the spinal cord. Our hope is that the data obtained from this and other studies of autopsy material may aid in elucidating the mechanisms involved in the pathophysiology of CRPS, which may lead to the refinement of current therapies as well as novel treatments.

Deep cervical plexus block for the treatment of cervicogenic headache

BACKGROUND

Cervicogenic headache descriptors include its unilateral nature, "signs and symptoms linking it to the neck," and trauma of the neck. Since the pain often occurs over the C2 or C3 nerve root, we used a modification of the deep cervical block technique for treatment of this refractory type headache.

OBJECTIVE

To determine the efficacy of a modified deep cervical block for treatment of cervicogenic headache.

DESIGN

Prospective case study.

METHODS

Thirty-nine patients referred to our pain clinic participated in this study. All patients had undergone extensive screening/diagnostic testing. The blocks were performed unilaterally, without inducing a risk of invading the neural foramen, and repeat injection of the contra-lateral side occurred at >1 week after initial injection. Patients were followed for a 6-month period using a pain diary and questionnaire. Pain was assessed pre- and post-injection and 3 and 6 months post treatments.

RESULTS

The mean treatment period was 59 +/- 61 days. The mean values for pre- and post-injection series pain scores (0-10 pain scale) were 9.54 +/- 1.53 and 6.75 +/- 3.23 respectively (p <0.001). Thirty-three percent (33%) of the patients reported pain scores of < or = 4 on the 0-10 pain scale after their last treatment. Effectiveness of the therapy following the injection procedure was rated to be 42% effective for all first injections and 40% effective for last injections (p =NS). Six months evaluations showed that return of moderate to severe pain took 6.62 +/- 8.1 weeks. At the 3 and 6 months follow up evaluations, mean pain scores had returned to 8.41 +/- 2.96 and 8.83 +/- 2.78, respectively. Ten patients (24%) had pain scores < or = 4 at the 3-month evaluation while 7 of the patients (18%) had pain scores < or = 4 at the 6-month evaluation.

CONCLUSIONS

These results showed that for some patients this series of blocks provided effective pain relief for 3 months post treatment but by 6 months the pain had returned to pre-treatment levels. This block technique significantly diminished pain after the initial as well as the last treatment. These clinically significant changes in pain relief suggest that more aggressive selective therapy targeting these nerve routes might provide longer lasting relief.

A pilot open-label study of the efficacy of subanesthetic isomeric S(+)-ketamine in refractory CRPS patients

OBJECTIVE

Complex regional pain syndrome (CRPS) is a severe neuropathic pain state that is often disproportionate to the initial trauma. Associated features are autonomic dysregulation, swelling, motor dysfunction, and trophic changes to varying degrees. Despite a multitude of treatment modalities, a subgroup of CRPS patients remain refractory to all standard therapies. In these patients, the disease may spread extraterritorially, which results in severe disability. A critical involvement of N-methyl-D-aspartate receptors (NMDARs) has been demonstrated both clinically and by animal experimentation. NMDA antagonists may be effective in many neuropathic pain states. In long-standing, generalized CRPS, we investigated the effects of S(+)-ketamine on pain relief and somatosensory features, assessed by quantitative sensory testing (QST).

METHODS

Four refractory CRPS patients received continous S(+)-ketamine-infusions, gradually titrated (50 mg/day-500 mg/day) over a 10-day period. Pain intensities (average, peak, and least pain) and side effects were rated on visual analogue scales, during a 4-day baseline, over 10 treatment days, and 2 days following treatment. QST (thermo-, mechanical detection, and pain thresholds) was analyzed at baseline and following treatment.

RESULTS

Subanesthetic S(+)-ketamine showed no reduction of pain and effected no change in thermo- and mechanical detection or pain thresholds. This procedure caused no relevant side effects. The lack of therapeutic response in the first four patients led to termination of this pilot study.

CONCLUSION

S(+)-ketamine can be gradually titrated to large doses (500 mg/day) without clinically relevant side effects. There was no pain relief or change in QST measurements in this series of long-standing severe CRPS patients.

Prevalence of complex regional pain syndrome in a cohort of multiple sclerosis patients

BACKGROUND

More than 50% of multiple sclerosis patients experience chronic pain syndrome. We set out to determine the specific type of chronic pain that was seen in our multiple sclerosis patients.

METHODS

Patients with multiple sclerosis were catalogued between January 2002 and April 2006 and identified by a search of the database. Only MS patients that met the 2005 revised McDonald criteria were included.

RESULTS

We determined the prevalence rate of complex regional pain syndrome in a cohort of multiple sclerosis patients. In our sample of 205 multiple sclerosis patients, the prevalence of complex regional pain syndrome was 4 cases per 205 compared to an expected age and sex-adjusted total prevalence of 0.078 cases per 205 (p < 0.0001).

CONCLUSION

This study suggests that multiple sclerosis patients are at a higher risk of developing complex regional pain syndrome than the general population.

Validating an Ataxia Functional Composite Scale in spinocerebellar ataxia

The Ataxia Functional Composite Scale (AFCS) may provide a sensitive and reproducible assessment of treatment responses in studies of the spinocerebellar ataxias (SCA). We previously assessed the effects of buspirone in a cohort of patients with SCA via the International Cooperative Ataxia Rating Scale (ICARS). At each assessment period, AFCS scores were also obtained. A strong correlation of AFCS with ICARS scores was demonstrated at all assessment periods. This study supports the validity of the AFCS as a useful assessment of ataxia in this population.

Treatment of spinocerebellar ataxia with buspirone

Preliminary data suggest potential benefit of 5-HT receptor agonists in the treatment of ataxias. We studied the effects of buspirone in a cohort of twenty patients with spinocerebellar ataxia (SCA). Twenty patients were treated in this double-blind, placebo controlled, cross-over trial with either buspirone HCl 30 mg twice daily or placebo for 3 months. Buspirone was not shown to be superior to placebo in the treatment of patients with SCA.

The neurocognitive effects of 5 day anesthetic ketamine for the treatment of refractory complex regional pain syndrome

BACKGROUND

Complex regional pain syndrome I (CRPS) is characterized by severe neuropathic pain that exceeds the severity of an injury and is refractory to traditional treatments. Recent experimental interventions include ketamine infusion therapy.

OBJECTIVE

We sought to evaluate the physical, neurocognitive, and emotional effects of extended treatment with anesthetic doses of ketamine in refractory CRPS I patients.

METHODS

Nine patients (eight females) received a neuropsychological evaluation pre- and 6 weeks post-treatment that evaluated intellectual and academic abilities, executive functioning/processing speed, attention, learning and memory, and motor functioning. Mood/affect and personality were also evaluated and patients completed an extensive pain questionnaire.

RESULTS

There was a marked reduction in the report of both acute and overall pain after treatment. Brief attention and processing speed improved significantly post-treatment, whereas all other cognitive domains remained stable, with the exception of a mild decline in motor strength.

CONCLUSIONS

Findings suggest that, at least at a 6-week follow up: (1) deep ketamine therapy is effective for relief of pain CRPS I and (2) there were no adverse cognitive effects of extended treatment with deep ketamine infusion. No definitive conclusions could be drawn about the relationship between mood and personality factors and the presence of CRPS I.

Treatment of CRPS with ECT

Background: Electroconvulsive therapy (ECT) is a well-established treatment method for medically refractory depression. ECT has also been used in the treatment of pain for over 50 years. The mechanism of action of ECT is still unknown, although several observations have been made regarding the effect of ECT on pain processes. It has been reported that several patients with medically refractory depression and Complex Regional Pain Syndrome who were treated with ECT for their depression were also cured of their CRPS symptoms. Objective: We report a case of CRPS in a patient who also suffered from medically refractory depression. She was treated with ECT for her depression and subsequently was relieved of all her CRPS symptoms. Case Report: A 42 year-old female patient underwent a series of 12 standard bitemporal electroconvulsive therapy treatments for medically refractory depression. Physical examination and Quantitative Sensory Testing was done before and after the patient’s treatment with ECT. This standard treatment procedure for refractory depression completely resolved the patient’s depressive symptoms. In addition, the patient’s CRPS symptoms were also reversed. Physical examination as well as Quantitative Sensory Testing done before and after the ECT treatment correlated with her CRPS symptom improvement. Conclusion: ECT was effective in the treatment of severe refractory CRPS in this patient. Key words: Iimpedance, posture change, spinal cord stimulation

Treatment of CRPS with ECT

BACKGROUND

Electroconvulsive therapy (ECT) is a well-established treatment method for medically refractory depression. ECT has also been used in the treatment of pain for over 50 years. The mechanism of action of ECT is still unknown, although several observations have been made regarding the effect of ECT on pain processes. It has been reported that several patients with medically refractory depression and Complex Regional Pain Syndrome who were treated with ECT for their depression were also cured of their CRPS symptoms.

OBJECTIVE

We report a case of CRPS in a patient who also suffered from medically refractory depression. She was treated with ECT for her depression and subsequently was relieved of all her CRPS symptoms.

CASE REPORT

A 42 year-old female patient underwent a series of 12 standard bitemporal electroconvulsive therapy treatments for medically refractory depression. Physical examination and Quantitative Sensory Testing was done before and after the patient's treatment with ECT. This standard treatment procedure for refractory depression completely resolved the patient's depressive symptoms. In addition, the patient's CRPS symptoms were also reversed. Physical examination as well as Quantitative Sensory Testing done before and after the ECT treatment correlated with her CRPS symptom improvement.

CONCLUSION

ECT was effective in the treatment of severe refractory CRPS in this patient.

Changes in immune and glial markers in the CSF of patients with Complex Regional Pain Syndrome

Complex Regional Pain Syndrome is a severe chronic pain condition characterized by sensory, autonomic, motor and dystrophic signs and symptoms. The pain in CRPS is continuous, it worsens over time, and it is usually disproportionate to the severity and duration of the inciting event. This study compares cerebrospinal fluid (CSF) levels of pro- and anti-inflammatory cytokines, chemokines and several biochemical factors (glial fibrillary acidic protein (GFAP), the nitric oxide metabolites (nitrate plus nitrite), the excitatory amino acid neurotransmitter glutamate, calcium, total protein and glucose) in patients afflicted with CRPS to levels found in patients suffering with other non-painful or painful conditions. The aim of the study is to determine the degree of involvement of glial cells and immune system mediators in the pathophysiology of CRPS. There was no elevation or reduction of a CSF marker that was specific for CRPS patients. However, there were several patterns of markers that could be helpful in both elucidating the mechanisms involved in the disease process and supporting the diagnosis of CRPS. The most common pattern was found in 50% (11 out of 22) of the CRPS patients and consisted of; elevated IL-6, low levels of IL-4 or IL-10, increased GFAP or MCP1 and increases in at least two of the following markers NO metabolites, calcium or glutamate. The results from this and other similar studies may aid in elucidating the mechanisms involved in the pathophysiology of CRPS. A better understanding of these mechanisms may lead to novel treatments for this very severe, life-altering illness.

Application of voxelwise analysis in the detection of regions of reduced fractional anisotropy in multiple sclerosis patients

PURPOSE

To investigate the utility of voxelwise analysis in the detection of lesions in the normal appearing white matter (NAWM) of individual multiple sclerosis (MS) patients.

MATERIALS AND METHODS

Diffusion tensor imaging (DTI) was performed on 10 normal controls and six patients with MS lesions. The fractional anisotropy (FA) maps derived from the diffusion-weighted images were then spatially normalized (via an affine transformation) into Montreal Neurological Institute (MNI) space, and the normalized FA map of each of the patients was compared voxelwise with the normalized FA maps of the group of normals in a one-sample t-test (P = 0.0001). Two independent board-certified neuroradiologists reviewed the data.

RESULTS

In the patient data for all six cases, the two reviewers determined detection sensitivities of 72% and 96% for the voxelwise technique based on known fluid-attenuated inversion-recovery (FLAIR) lesions. In addition, between the two reviewers, nine NAWM regions exhibiting FA reductions were identified in the six patients. However, numerous regions of abnormal FA were detected that were attributed to poor intersubject image registration.

CONCLUSION

Voxelwise analysis of spatially normalized FA maps has the potential to identify regions of FA reduction in lesions and in the NAWM of individual MS patients in a rapid and reproducible fashion. J. Magn. Reson. Imaging 2007;26:552-556. (c) 2007 Wiley-Liss, Inc.

Pathophysiology of complex regional pain syndrome

Complex regional pain syndrome (CRPS) most often follows injury to peripheral nerves or their endings in soft tissue. A combination of prostanoids, kinins and cytokines cause peripheral nociceptive sensitization. In time, the Mg(2+) block of the N-methyl-D-aspartate receptor is removed, pain transmission neurons (PTN) are altered by an influx of Ca(2+) that activates kinases for excitation and phosphatases for depression, activity-dependent plasticity that alters the firing of PTN. In time, these neurons undergo central sensitization that lead to a major physiological change of the autonomic, pain and motor systems. The role of the immune system and the sickness response is becoming clearer as microglia are activated following injury and can induce central sensitization while astrocytes may maintain the process.

The syndrome of irreversible acidosis after prolonged propofol infusion

INTRODUCTION

Propofol infusion syndrome is described in the pediatric literature as metabolic acidosis, rhabdomyolysis, and bradycardia that results in death. The pathogenesis of this syndrome is thought to be activation of the systemic inflammatory response, which culminates in acidosis and muscle necrosis.

MATERIALS AND METHODS

Retrospective chart review of three patients in the Neurological Critical Care Units at Hahnemann and Massachusetts General Hospitals between October 2001 and September 2004.

RESULTS

Patient 1: A 27-year-old woman had seizures secondary to hemorrhage from an arteriovenous malformation. Propofol coma was induced for sedation. After initiation of propofol, she developed a metabolic acidosis, hypotension, and bradycardia and expired. Patient 2: A 64-year-old man presented in status epilepticus. After prolonged propofol administration, he developed metabolic acidosis, hypotension, and rhabdomyolysis and expired. Patient 3: A 24-year-old woman presented in status epilepticus secondary to encephalitis. Propofol was added for seizure control. She developed hypotension, metabolic acidosis, and bradyarrhythmias. Despite transvenous pacing, she expired.

CONCLUSION

These data show an association between extended propofol use and metabolic acidosis, rhabdomyolysis, and death in adults, as well as children. Risk factors for propofol infusion syndrome in adults include lean body mass index, high dose, and administration of more than 24-hour duration. Creatine phosphokinase, lactic acid levels, electrolytes, and arterial blood gases should be monitored frequently. Both bacterial and fungal cultures should be obtained. If this syndrome is suspected, hemodialysis should be considered. In fatal cases, autopsy should include electron microscopy of cardiac and skeletal muscle to look for mitochondrial dysfunction. Further study is warranted.

Changes in cerebrospinal fluid levels of pro-inflammatory cytokines in CRPS

Complex Regional Pain Syndrome (CRPS) Types I and II are characterized by various combinations of sensory, autonomic and motor abnormalities. Pain disproportionate to the severity and duration of the inciting event is the most devastating symptom. In animal studies, conditions resulting in exaggerated pain states demonstrate elevated pro-inflammatory cytokines. In addition, pro-inflammatory cytokines have been shown to induce or increase neuropathic and inflammatory pain. Utilizing high sensitivity enzyme linked immunosorbent assay (ELISA), we compared the levels of the pro-inflammatory cytokines interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and Tumor Necrosis Factor-alpha (TNF-alpha) in the cerebrospinal fluid (CSF) of patients afflicted with CRPS to CSF levels found in other patients with and without painful conditions. The results from this study demonstrated significant increases in IL-1beta and IL-6, but not TNF-alpha in the CSF of individuals afflicted with CRPS as compared to controls. CSF cytokine levels in controls with painful conditions did not differ from levels in controls without pain. These increases showed no correlation with the patient's gender or weight. These results are consistent with studies that suggest that the pathogenesis of CRPS is due in part to central neuroimmune activation.

Multi-day low dose ketamine infusion for the treatment of complex regional pain syndrome

BACKGROUND

Complex regional pain syndrome (CRPS) is characterized by pain that is out of proportion to the injury and is regional in distribution. A large body of literature supports a dynamic change in the physiology and structure of central pain projecting neurons mediated through the N-methyl-D-aspartate (NMDA) receptor. A critical factor in central sensitization seems to be the release of the magnesium block on the NMDA receptor with influx of calcium and initiation of intracellular cascades. Current literature supports the effectiveness of ketamine in blocking central sensitization through its effects on the NMDA receptor. Recent treatment with anesthetic doses of ketamine in severely ill patients with generalized CRPS prompted our interest in a lower dose therapy.

OBJECTIVE

To report on the efficacy of low dose outpatient ketamine infusion for the treatment of CRPS diagnosed by International Association for the Study of Pain (IASP) criteria in patients who have failed conservative treatment.

DESIGN

Open label, prospective, pain journal evaluation of a 10-day infusion of intravenous ketamine in the CRPS patient.

METHODS

Patients diagnosed with CRPS by a single neurologist were assigned to receive a 10-day outpatient infusion of ketamine supervised by an Anesthesiologist/Pain Management Specialist. The infusion was administered in a short procedure unit after each patient had been instructed on how to complete a pain questionnaire. Monitoring consisted of continuous ECG, pulse oximetry, and non-invasive blood pressure every 15 minutes. Patients made journal entries each day prior to the infusion of 40-80 mg of ketamine. The subjects were also asked to rate their pain intensity using a verbal analog pain scale of 0-10 and the affective component using a verbal scale of 0-4.

RESULTS

There was a significant reduction in pain intensity from initiation of infusion (Day 1) to the 10th day, with a significant reduction in the percentage of patients experiencing pain by Day 10 as well as a reduction in the level of their "worst" pain. The nadirs of pain were lower by Day 10 with a significant reduction in the incidence of "punishing pain." Moreover, there was a significant improvement in the ability to initiate movement by the 10th day.

CONCLUSION

A four-hour ketamine infusion escalated from 40-80 mg over a 10-day period can result in a significant reduction of pain with increased mobility and a tendency to decreased autonomic dysregulation.