Intravenous Subhypnotic Propofol in Central Pain

Spontaneous pain as a challenge of research and management in chronic pain

Spontaneous pain occurring without apparent external stimuli, is a significant complaint of individuals with chronic pain whose mechanisms, somewhat surprisingly, remain poorly understood. Over the past decades, neuroimaging studies start to reveal brain activities accompanying spontaneous pain. Meanwhile, a variety of animal models and behavioral tests have been established, including non-reflexive tests and free-choice tests, which have been shown to be effective in assessing spontaneous pain. For the spontaneous pain mechanisms, multiple lines of research mainly focus on three aspects: (1) sensitization of peripheral nociceptor receptors and ion channels, (2) spontaneous neuronal firing and abnormal activity patterns at the dorsal root ganglion and spinal cord level, (3) functional and structural alterations in the brain, particularly the limbic system and the medial pain pathway. Despite accumulating evidence revealing distinct neuronal mechanisms from evoked pain, we are still far from full understanding of spontaneous pain, leaving a big gap between bench and bedside for chronic pain treatment. A better understanding of the neural processes in chronic pain, with specific linkage as to which anatomical structures and molecules related to spontaneous pain perception and comorbidities, will greatly improve our ability to develop novel therapeutics.

Pharmacotherapy to Manage Central Post-Stroke Pain

Central post-stroke pain is a chronic neuropathic pain syndrome following a cerebrovascular accident. The development of central post-stroke pain is estimated to occur in 8 to 55% of stroke patients and is described as constant or intermittent neuropathic pain accompanied by dysesthesia of temperature and/or pressure sensations. These pain and sensory deficits are within the area of the body corresponding to the stroke lesion. The onset of pain is usually gradual, though it can develop either immediately after stroke or years after. Given the diversity in its clinical presentation, central post-stroke pain is a challenging diagnosis of exclusion. Furthermore, central post-stroke pain is often resistant to pharmacological treatment options and a clear therapeutic algorithm has not been established. Based on current evidence, amitriptyline, lamotrigine, and gabapentinoids should be used as first-line pharmacotherapy options when central post-stroke pain is suspected. Other drugs, such as fluvoxamine, steroids, and Intravenous infusions of lidocaine, ketamine, or even propofol, can be considered in intractable cases. In addition, interventional therapies such as motor cortex stimulation or transcranial magnetic stimulation have been shown to provide relief in difficult-to-treat patients.

Poststroke Pain

Pain is common but often underrecognized after stroke. Poststroke pain (PSP) hinders recovery, impairs quality of life, and is associated with the psychological state of patients with stroke. The most common subtypes of PSP include central PSP, complex regional pain syndrome, shoulder pain, spasticity-related pain, and headache. The pathophysiologies of these PSP subtypes are not yet clearly understood, and PSP is refractory to conventional treatment in many patients. However, recent studies have proposed potential pathophysiologies of PSP subtypes, which may help prioritize therapies that target specific mechanisms.

Pregabalin and lamotrigine in central poststroke pain: A pilot study

BACKGROUND

Comparative study of Class I drugs in central poststroke pain (CPSP) is lacking.

OBJECTIVE

To evaluate the safety and efficacy of pregabalin and lamotrigine in patients with CPSP.

SETTING

Tertiary care teaching referral hospital.

METHODS

We included consecutive patients with CPSP having ≥50 mm score on Visual Analog Scale (VAS) and randomized them to receive either oral pregabalin or oral lamotrigine. Their clinical findings, serum chemistry, and cranial magnetic resonance imaging findings were noted. The severity of CPSP was assessed by VAS while the allodynia was assessed on a 0-10 scale. The hospital anxiety and depression (HAD) score was also recorded. The primary outcome was> 50% reduction in the VAS score while the secondary outcome was> 50% reduction in the severity of allodynia and improvement in HAD score at 3 months. Adverse reactions were noted in both the groups.

RESULTS

There were 30 patients with CPSP with a median age of 54.5 years (Male:Female = 36:4). While both pregabalin (P < 0.0001) and lamotrigine (P < 0.0001) resulted in significant improvement in the VAS score (63.3% vs. 53.3%), allodynia (66.7% vs. 75%), and HAD score (80% vs. 81.8%) compared to the baseline, the was no significant intergroup difference. Lamotrigine had to be withdrawn in three patients due to skin rash.

CONCLUSIONS

Both pregabalin and lamotrigine are equally effective in CPSP, but significant side effects leading to drug withdrawal occured with lamotrigine administration.

The role of NLRP3 inflammasome in stroke and central poststroke pain

BACKGROUND

NLRP3 inflammasome plays a prominent role in the pathogenesis and progression of many diseases, such as type 2 diabetes mellitus, obesity, atherosclerosis, and Alzheimer's disease. However, little knowledge is known about the role of NLRP3 inflammasome in central post-stroke pain (CPSP).

METHODS

We selected relevant studies by searching PubMed, Embase, and Medline from inception through February, 2018. We systematically reviewed available publications according to the terms "NLRP3 inflammasome" and "stroke" or "central post-stroke pain" in the title/abstract field.

RESULTS

We reviewed the articles and put forward two possible ways for NLRP3 inflammasome in CPSP. One way is that NLRP3 activation causes cerebral cortex injure, decreasing descending projection fiber to thalamus. Such condition may let GABAergic releases reduce, making the ventral basal (VB) neurons excitability increased. Finally, CPSP occur. Another way is that NLRP3 inflammasome leads to thalamic lesion and strengthens inflammatory response of microglia at the same time. Persistent inflammation causes GABAergic alteration in thalamus reticular neurons (TRN) to restrain VB interneurons functions, contributing to CPSP.

CONCLUSIONS

These possible mechanisms will help become knowledgeable about the occurrence CPSP and provide potential therapy for CPSP.

Neuropathic pain and spasticity: intricate consequences of spinal cord injury

STUDY DESIGN

The 2016 International Spinal Cord Society Sir Ludwig Guttmann Lecture.

OBJECTIVES

The aim of this review is to identify different symptoms and signs of neuropathic pain and spasticity after spinal cord injury (SCI) and to present different methods of assessing them. The objective is to discuss how a careful characterization of different symptoms and signs, and a better translation of preclinical findings may improve our understanding of the complex and entangled mechanisms of neuropathic pain and spasticity.

METHODS

A MEDLINE search was performed using the following terms: 'pain', 'neuropathic', 'spasticity', 'spasms' and 'spinal cord injury'.

RESULTS

This review identified different domains of neuropathic pain and spasticity after SCI and methods to assess them in preclinical and clinical research. Different factors important for pain description include location, onset, pain descriptors and somatosensory function, while muscle tone, spasms, reflexes and clonus are important aspects of spasticity. Similarities and differences between neuropathic pain and spasticity are discussed.

CONCLUSIONS

Understanding that neuropathic pain and spasticity are multidimensional consequences of SCI, and a careful examination and characterization of the symptoms and signs, are a prerequisite for understanding the relationship between neuropathic pain and spasticity and the intricate underlying mechanisms.

Brain Stimulation Therapy for Central Post-Stroke Pain from a Perspective of Interhemispheric Neural Network Remodeling

Central post-stroke pain (CPSP) is a debilitating, severe disorder affecting patient quality of life. Since CPSP is refractory to medication, various treatment modalities have been tried with marginal results. Following the first report of epidural motor cortex (M1) stimulation (MCS) for CPSP, many researchers have investigated the mechanisms of electrical stimulation of the M1. CPSP is currently considered to be a maladapted network reorganization problem following stroke, and recent studies have revealed that the activities of the impaired hemisphere after stroke may be inhibited by the contralesional hemisphere. Even though this interhemispheric inhibition (IHI) theory was originally proposed to explain the motor recovery process in stroke patients, we considered that IHI may also contribute to the CPSP mechanism. Based on the IHI theory and the fact that electrical stimulation of the M1 suppresses CPSP, we hypothesized that the inhibitory signals from the contralesional hemisphere may suppress the activities of the M1 in the ipsilesional hemisphere, and therefore pain suppression mechanisms may be malfunctioning in CPSP patients. In this context, transcranial direct current stimulation (tDCS) was considered to be a reasonable procedure to address the interhemispheric imbalance, as the bilateral M1 can be simultaneously stimulated using an anode (excitatory) and cathode (inhibitory). In this article, we review the potential mechanisms and propose a new model of CPSP. We also report two cases where CPSP was addressed with tDCS, discuss the potential roles of tDCS in the treatment of CPSP, and make recommendations for future studies.

Thalamic Pain Misdiagnosed as Cervical Disc Herniation

Thalamic pain is a primary cause of central post-stroke pain (CPSP). Clinical symptoms vary depending on the location of the infarction and frequently accompany several pain symptoms. Therefore, correct diagnosis and proper examination are not easy. We report a case of CPSP due to a left acute thalamic infarction with central disc protrusion at C5-6. A 45-year-old-male patient experiencing a tingling sensation in his right arm was referred to our pain clinic under the diagnosis of cervical disc herniation. This patient also complained of right cramp-like abdominal pain. After further evaluations, he was diagnosed with an acute thalamic infarction. Therefore detailed history taking should be performed and examiners should always be aware of other symptoms that could suggest a more dangerous disease.

Spinal cord injury-induced pain: mechanisms and treatments

Pain is a common consequence of a spinal cord injury (SCI) and has a major impact on quality of life through its impact on physical function, mood and participation in work, recreational and social activities. Several types of pain typically present following SCI with central neuropathic pain being a frequent and difficult to manage occurrence. Despite advances in our understanding of the mechanisms contributing to this type of pain and an increasing number of trials examining treatment efficacy, our ability to relieve neuropathic SCI pain is still very limited. Optimal management relies upon an integrated approach that uses a combination of pharmacological and nonpharmacological options.

Optimal Strategies for Reporting Pain in Clinical Trials and Systematic Reviews: Recommendations from an OMERACT 12 Workshop

OBJECTIVE

Pain is a patient-important outcome, but current reporting in randomized controlled trials and systematic reviews is often suboptimal, impeding clinical interpretation and decision making.

METHODS

A working group at the 2014 Outcome Measures in Rheumatology (OMERACT 12) was convened to provide guidance for reporting treatment effects regarding pain for individual studies and systematic reviews.

RESULTS

For individual trials, authors should report, in addition to mean change, the proportion of patients achieving 1 or more thresholds of improvement from baseline pain (e.g., ≥ 20%, ≥ 30%, ≥ 50%), achievement of a desirable pain state (e.g., no worse than mild pain), and/or a combination of change and state. Effects on pain should be accompanied by other patient-important outcomes to facilitate interpretation. When pooling data for metaanalysis, authors should consider converting all continuous measures for pain to a 100 mm visual analog scale (VAS) for pain and use the established, minimally important difference (MID) of 10 mm, and the conventionally used, appreciably important differences of 20 mm, 30 mm, and 50 mm, to facilitate interpretation. Effects ≤ 0.5 units suggest a small or very small effect. To further increase interpretability, the pooled estimate on the VAS should also be transformed to a binary outcome and expressed as a relative risk and risk difference. This transformation can be achieved by calculating the probability of experiencing a treatment effect greater than the MID and the thresholds for appreciably important differences in pain reduction in the control and intervention groups.

CONCLUSION

Presentation of relative effects regarding pain will facilitate interpretation of treatment effects.

A Comprehensive Review of Central Post-Stroke Pain

Although central post-stroke pain is widely recognized as a severe chronic neuropathic pain condition, its consolidated definition, clinical characteristics, and diagnostic criteria have not been defined due to its clinically diverse features. The present study was undertaken to comprehensively review current literature and provide a more complete picture of central post-stroke pain with respect to its definition, prevalence, pathophysiology, clinical characteristics, and diagnostic problems, and to describe the range of therapies currently available. In particular, nursing care perspectives are addressed. It is hoped that this review will help nurses become knowledgeable about central post-stroke pain and provide valuable information for the drafting of effective nursing care plans that improve outcomes and quality of life for patients with central post-stroke pain.

Allodynia and hyperalgesia in neuropathic pain: clinical manifestations and mechanisms

Allodynia (pain due to a stimulus that does not usually provoke pain) and hyperalgesia (increased pain from a stimulus that usually provokes pain) are prominent symptoms in patients with neuropathic pain. Both are seen in various peripheral neuropathies and central pain disorders, and affect 15-50% of patients with neuropathic pain. Allodynia and hyperalgesia are classified according to the sensory modality (touch, pressure, pinprick, cold, and heat) that is used to elicit the sensation. Peripheral sensitisation and maladaptive central changes contribute to the generation and maintenance of these reactions, with separate mechanisms in different subtypes of allodynia and hyperalgesia. Pain intensity and relief are important measures in clinical pain studies, but might be insufficient to capture the complexity of the pain experience. Better understanding of allodynia and hyperalgesia might provide clues to the underlying pathophysiology of neuropathic pain and, as such, they represent new or additional endpoints in pain trials.

Pharmacological management of neuropathic pain following spinal cord injury

Spinal cord injury (SCI) has a number of severe and disabling consequences, including chronic pain, and around 40% of patients develop persistent neuropathic pain. Pain following SCI has a detrimental impact on the patient's quality of life and is a major specific healthcare problem in its own right. Thus far, there is no cure for the pain and oral pharmaceutical intervention is often inadequate, commonly resulting in a reduction of only 20-30% in pain intensity. Neuropathic pain sensations are characterized by spontaneous persistent pain and a range of abnormally evoked responses, e.g. allodynia (pain evoked by normally non-noxious stimuli) and hyperalgesia (an increased response to noxious stimuli). Neuropathic pain following SCI may be present at or below the level of injury. Oral pharmacological agents used in the treatment of neuropathic pain act either by depressing neuronal activity, by blocking sodium channels or inhibiting calcium channels, by increasing inhibition via GABA agonists, by serotonergic and noradrenergic reuptake inhibition, or by decreasing activation via glutamate receptor inhibition, especially by blocking the NMDA receptor. At present, only ten randomized, double-blind, controlled trials have been performed on oral drug treatment of pain after SCI, the results of most of which were negative. The studies included antidepressants (amitriptyline and trazodone), antiepileptics (gabapentin, pregabalin, lamotrigine and valproate) and mexiletine. Gabapentin, pregabalin and amitriptyline showed a significant reduction in neuropathic pain following SCI. Cannabinoids have been found to relieve other types of central pain, and serotonin noradrenaline reuptake inhibitors as well as opioids relieve peripheral neuropathic pain and may be used to treat patients with SCI pain.

Pain following spinal cord injury

Pain is one of the most common, severe, and treatment-resistant complications that follows SCI. Recent years have seen a surge of research on methods for assessing and treating spinal cord injury pain. In this article, pain after SCI is reviewed in terms of nature, scope, assessment techniques, and treatment strategies.

Sustained intravascular exposure to propofol does not prolong pain at the site of injection

BACKGROUND

Pain at the site of intravenous injection of propofol is a common clinical finding. This double-blind, randomized cross-over study was designed to evaluate whether venous occlusion applied during injection of a low dose of propofol reduces the intensity of pain at the site of injection compared with no occlusion.

METHODS

Bilateral 0.5-ml injections of an emulsion containing 10 mg/ml of propofol were given over 30 s in 75 adult surgical patients. Each patient was given one injection with and one without 60-s occlusion of the cannulated vein with a 10-min interval, and asked to score the maximal pain intensity on a visual analogue scale (VAS).

RESULTS

The maximal pain intensity [median (25th percentile; 75th percentile), range] at the site of injection was 0.5 (0; 3.5), 0-8.0 VAS units with venous occlusion and 0.5 (0; 1.4), 0-6.0 VAS units without occlusion (P= 0.042). Pain was first reported within 20 s regardless of the study regimen and was not prolonged by local venous occlusion.

CONCLUSION

Venous occlusion augments pain intensity at the site of propofol injection without prolonging pain, implying that propofol-induced pain is determined more by the blood concentration than by the duration of intravascular exposure. The low intensity of pain induced by low-dose propofol and the fading of pain despite sustained exposure suggest that initial low-dose administration of propofol should be evaluated for the attenuation of local pain induced by higher intravenous doses of propofol.

Pain after spinal cord injury: an evidence-based review for clinical practice and research. Report of the National Institute on Disability and Rehabilitation Research Spinal Cord Injury Measures meeting

BACKGROUND/OBJECTIVES

To examine the reliability, validity, sensitivity, and practicality of various outcome measures for pain after spinal cord injury (SCI), and to provide recommendations for specific measures for use in clinical trials.

DATA SOURCES

Relevant articles were obtained through a search of MEDLINE, EMBASE, CINAHL, and PubMed databases from inception through 2006.

STUDY SELECTION

The authors performed literature searches to find articles containing data relevant to the reliability and validity of each pain outcome measure in SCI and selected non-SCI populations.

DATA EXTRACTION

After reviewing the articles, an investigator extracted information utilizing a standard template. A second investigator reviewed the chosen articles and the extracted pertinent information to confirm the findings of the first investigator.

DATA SYNTHESIS

Taking into consideration both the quantity and quality of the studies analyzed, judgments on reliability and validity of the measures were made by the two investigators. Based upon these judgments, recommendations were formulated for use of specific measures in future clinical trials. In addition, for a subset of measures a voting process by a larger group of SCI experts allowed formulation of recommendations including determining which measures should be incorporated into a minimal dataset of measures for clinical trials and which ones need revision and further validity and reliability testing before use.

CONCLUSIONS

A 0-10 Point Numerical Rating Scale (NRS) is recommended as the outcome measure for pain intensity after SCI, while the 7-Point Guy/Farrar Patient Global Impression of Change (PGIC) scale is recommended as the outcome measure for global improvement in pain. The SF-36 single pain interference question and the Multidimensional Pain Inventory (MPI) or Brief Pain Inventory (BPI) pain interference items are recommended as the outcome measures for pain interference after SCI. Brush or cotton wool and at least one high-threshold von Frey filament are recommended to test mechanical allodynia/hyperalgesia while a Peltier-type thermotester is recommended to test thermal allodynia/hyperalgesia. The International Association for the Study of Pain (IASP) or Bryce-Ragnarsson pain taxonomies are recommended for classification of pain after SCI, while the Neuropathic Pain Scale (NPS) is recommended for measuring change in neuropathic pain and the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) for quantitating neuropathic and nociceptive pain discrimination.

Extradural cortical stimulation for central pain

Central pain results from a central nervous system injury and represents a challenge for the pain therapist. Human studies have shown that motor cortex stimulation (MCS), i.e. the placement of a stimulating plate on the dura overlying the motor cortex can relieve brain central pain. Studies suggest that MCS directly affects activity in the first and second order somatosensory areas, thalamic nuclei and also inhibits spinal primary afferents and spinothalamic tract neurons. The following factors have been found to predict analgesia by MCS: intact or almost intact corticospinal motor function, mild or negligible sensory loss, absence of thermal sensory threshold alteration within the painful area, positive response to the barbiturate and/or ketamine test, positive response to the propofol test, positive response to transcranial magnetic stimulation (TMS). The targeting of the cortical area is made by anatomical localization by computed tomography (CT), magnetic resonance imaging (MRI), neuronavigation, intraoperative neurophysiological recordings, functional MRI (fMRI), and intraoperative clinical assessment. We perform the procedure under local anaesthesia. We describe in detail our surgical technique and stimulation protocol. Furthermore, we review the most important studies with respect to their results, the observed side effects and complications. The future prospects and likely developments of MCS for central pain are also discussed.

Drug therapy of trigeminal neuralgia

Trigeminal neuralgia is a chronic pain syndrome of still unestablished origin. Its diagnosis depends on clinical grounds. Drug therapy initially helps a great majority of patients. The choice of drugs is quite large, but truly effective compounds with a tolerable side effect profile remain few. Carbamazepine (or oxcarbazepine) and lamotrigine appear to be the most effective, followed by baclofen. Several patients require further nonpharmacological treatment for which no evidence-based recommendation is possible. In the future, neuromodulation may be brought to bear, as in other chronic pain syndromes.

[A case of a second cancer of metachronous multiple primary non-small cell lung cancer successfully treated with TS-1 and CDDP chemotherapy]

The patient was a 66-year-old man who had undergone right upper lobectomy and ND 2a systematic lymph node dissection for lung cancer (M/D adenocarcinoma, p-stage IB) in March of 1999 . On November 2003, postoperative routine chest computed tomography(CT) demonstrated a mass in left S6, and pathological diagnosis revealed P/D squamous cell carcinoma (cT1N2M0, stage IIIA) by CT-guided needle biopsy and mediastinoscopy. At first, we tried two courses of a combination chemotherapy consisting of carboplatin (CBDCA) and paclitaxel every 3 weeks. After 2 courses, the regimen was stopped because of grade 3 arthritis. Then, two courses of CBDCA and gemcitabine were performed. The evaluation of the response was SD by the guidelines of Response Evaluation Criteria in Solid Tumor Groups. Next, gefitinib was orally administered for 6 months but the tumor and mediastinal lymph nodes were growing. In January 2005, oral administration of TS-1 (60 mg/1, 2 courses, 75 mg/3-6 courses) was begun twice a day for 21 consecutive days while cisplatin (60 mg/m(2)) was administered intravenously on day 8. The response was PR (the tumor decreased by 46%), no serious adverse effect was observed, and the patient maintained good quality of life throughout the chemotherapy. This case suggests that TS-1+CDDP chemotherapy may be an effective treatment in patients with advanced lung cancer even after many protocols of chemotherapy.

Mechanisms of Disease: mechanism-based classification of neuropathic pain—a critical analysis

Classification of neuropathic pain according to etiology or localization has clear limitations. The discovery of specific molecular and cellular events following experimental nerve injury has raised the possibility of classifying neuropathic pain on the basis of the underlying neurobiological mechanisms. Application of this approach in the clinic is problematic, however, owing to a lack of precise tools to assess symptoms and signs, and difficulties in correlating symptoms and signs with mechanisms. Development and validation of diagnostic methods to identify mechanisms, together with pharmacological agents that specifically target these mechanisms, seems to be the most logical and rational way of improving neuropathic pain treatment.

A proposed algorithm for the management of pain following spinal cord injury

STUDY DESIGN

Review.

OBJECTIVES

To review published articles on the assessment, diagnosis and treatment of pain following spinal cord injury (SCI) and to synthesise evidence from these materials to formulate and propose a systematic approach to management.

METHODS

Relevant articles regarding the treatment of pain were identified from electronic databases using the search terms (('spinal cord injury' or 'spinal cord injuries') and 'pain') and both ('treatment') and ('randomised controlled trials'). Relevant articles were also identified through citations in indexed journal publications and book chapters on this topic.

RESULTS

Review of the literature indicates that there are a large variety of treatments used in the management of pain following SCI with a small number supported by strong evidence for effectiveness. A treatment algorithm is proposed based on identification of underlying pain contributors and application of appropriate treatment.

CONCLUSION

Although there are relatively few studies clearly indicating efficacy in this population, an algorithm for the management of pain following SCI might assist to maximise our effectiveness in the treatment of this condition. It is recognised that choice of treatment is also determined by factors such as medication availability, cost and side effects as well as the preferences and characteristics of the person being treated. Nevertheless, an algorithm is proposed as a way to synthesise our current level of knowledge, identify gaps for further study and aid in the management of this difficult problem.

Transcranial magnetic stimulation for central pain

Transcranial magnetic stimulation recently has emerged as a therapeutic tool in neurology and psychiatry, with contradictory results. Central pain, a major chronic pain syndrome affecting millions of people worldwide, has been the focus of a few studies. Although transcranial magnetic stimulation has no role in the chronic management of such pain, it has potential as a screening procedure for the much more effective extradural cortical stimulation, a minimally invasive neurosurgical procedure that has emerged as the technique of choice in treating these patients.