The functional organization of the brain in chronic pain

Manual Therapy versus Localisation (Tactile, Sensory Training) in Patients with Non-Specific Neck Pain: A Randomised Clinical Pilot Trial

Manual therapy (MT) techniques typically incorporate localised touch on the skin with the application of specific kinetic forces. The contribution of localised touch to the effectiveness of MT techniques has not been evaluated. This study investigated the immediate effects of MT versus localisation training (LT) on pain intensity and range of movement (ROM) for neck pain. In this single-blind randomised controlled trial thirty eligible neck pain volunteers (23 females and 7 males), aged 28.63 ± 12.49 years, were randomly allocated to MT or to a motionless (LT) group. A single three-minute treatment session was delivered to each group's cervico-thoracic area. The LT involved tactile sensory stimulation applied randomly to one out of a nine-block grid. Subjects were asked to identify the number of the square being touched, reflecting a different location on the region of skin. MT involved three-minute anteroposterior (AP) glides and sustained natural apophyseal glides (SNAG) techniques. Pre- and post-intervention pain intensity were assessed using a pressure pain threshold (PPT) algometer and the numeric pain rating scale (NPRS). Neck ROM was recorded with a bubble inclinometer. Improvements in ROM and self-reported pain were recorded in both groups (p < 0.001) without differences in NPRS, ROM or PPT scores between groups (p > 0.05). Tactile sensory training (localisation) was as effective as MT in reducing neck pain, suggesting a component of MT's analgesic effect to be related with the element of localised touch rather than the forces induced during passive movements.

Virtual McKenzie extension exercises for low back and leg pain: a prospective pilot exploratory case series

INTRODUCTION

Current evidence supports the inclusion of directional preference exercises for a subgroup of patients with low back (LBP) and leg pain. Recent pain neuroscience strategies have suggested that cortical restructuring associated with movement activating the body map representation in the brain might account for the observed improvement with the directional preference approach.

OBJECTIVES

To explore whether or not a motor imagery directional preference approach would result in any changes in patients with LBP and leg pain.

METHODS

A consecutive convenience sample of patients with LBP and leg pain were recruited at two outpatient physical therapy clinics. Measurements of LBP, leg pain, fear-avoidance beliefs (FABQ), pain catastrophizing (PCS), active lumbar flexion, and straight leg raise (SLR) were compared before and immediately after a virtual (motor imagery) directional preference exercise.

RESULTS

Statistically significant differences for LBP, FABQ, PCS, active lumbar flexion, and SLR were observed, but only SLR changes met or exceeded the minimally clinically important difference (MCID).

CONCLUSIONS

A brief virtual motor imagery extension treatment yielded some immediate positive shifts in patients presenting to physical therapy with LBP and leg pain. Our results indicate that randomized comparison trials are needed to determine the effect of this intervention on the short- and longer-term outcomes in patients with LBP and leg pain.

Immersive interactive virtual walking reduces neuropathic pain in spinal cord injury: findings from a preliminary investigation of feasibility and clinical efficacy

ABSTRACT

Chronic neuropathic pain (NP) is a common and often debilitating secondary condition for persons with spinal cord injury (SCI) and is minimally responsive to existing pharmacological and nonpharmacological treatments. The current preliminary investigation describes the feasibility and initial comparative efficacy of an interactive virtual reality walking intervention, which is a novel extension of visual feedback/illusory walking therapies shown to reduce SCI NP. Virtual reality walking intervention builds on previous research by, for the first time, allowing individuals with SCI NP to volitionally control virtual gait to interact with a fully immersive virtual environment. The current pilot study compared this interactive, virtual walking intervention to a passive, noninteractive virtual walking condition (analogous to previous illusory walking interventions) in 27 individuals with complete paraplegia (interactive condition, n = 17; passive condition, n = 10; nonrandomized design). The intervention was delivered over 2 weeks in individuals' homes. Participants in the interactive condition endorsed significantly greater reductions in NP intensity and NP-related activity interference preintervention to postintervention. Notable improvements in mood and affect were also observed both within individual sessions and in response to the full intervention. These results, although preliminary, highlight the potentially potent effects of an interactive virtual walking intervention for SCI NP. The current study results require replication in a larger, randomized clinical trial and may form a valuable basis for future inquiry regarding the mechanisms and clinical applications of virtual walking therapies.

Electroencephalography During Nociceptive Stimulation in Chronic Pain Patients: A Systematic Review

BACKGROUND

With its high temporal resolution, electroencephalography (EEG), a technique that records electrical activity of cortical neuronal cells, is a potentially suitable technique to investigate human somatosensory processing. By using EEG, the processing of (nociceptive) stimuli can be investigated, along with the functionality of the nociceptive pathway. Therefore, it can be applied in chronic pain patients to objectify whether changes have occurred in nociceptive processing. Typically, so-called event-related potential (ERP) recordings are used, where EEG signals are recorded in response to specific stimuli and characterized by latency and amplitude.

OBJECTIVE

To summarize whether differences in somatosensory processing occur between chronic pain patients and healthy controls, measured with ERPs, and determine whether this response is related to the subjective pain intensity.

DESIGN

Systematic review.

SETTING AND METHODS

PubMed, Web of Science, and Embase were consulted, and 18 case-control studies were finally included.

SUBJECTS

The chronic pain patients suffered from tension-type headache, back pain, migraine, fibromyalgia, carpal tunnel syndrome, prostatitis, or complex regional pain syndrome.

RESULTS

Chronic neuropathic pain patients showed increased latencies of the N2 and P2 components, along with a decreased amplitude of the N2-P2 complex, which was also obtained in FM patients with small fiber dysfunction. The latter also showed a decreased amplitude of the N2-P3 and N1-P1 complex. For the other chronic pain patients, the latencies and the amplitudes of the ERP components did not seem to differ from healthy controls. One paper indicated that the N2-P3 peak-to-peak amplitude correlates with the subjective experience of the stimulus.

CONCLUSIONS

Differences in ERPs with healthy controls can mostly be found in chronic pain populations that suffer from neuropathic pain or where fiber dysfunction is present. In chronic pain populations with other etiological mechanisms, limited differences were found or agreed upon across studies.

Neuroimaging investigation of memory changes in migraine: a systematic review

BACKGROUND

Individuals with migraine usually complain about lower memory performance. Diagnostic methods such as neuroimaging may help in the understanding of possible morphologic and functional changes related to the memory of those individuals. Therefore, the aim of this review is to analyze the available literature on neuroimaging changes related to memory processing in migraine.

METHODS

We searched the following databases: Pubmed/Medline, Psycinfo, Science Direct, Cochrane and Web of Science. We used articles without restriction of year of publication. The combination of descriptors used for this systematic review of literature were Neuroimaging OR Imaging OR Brain AND Migraine OR Chronic Migraine AND Memory.

RESULTS

Of the 306 articles found, nine were selected and all used magnetic resonance imaging (MRI). The studies used structural and functional MRI techniques with a predominance of 3 Tesla equipment and T1-weighted images. According to the results obtained reported by these studies, migraine would alter the activity of memory-related structures, such as the hippocampus, insula and frontal, parietal and temporal cortices, thereby suggesting a possible mechanism by which migraine would influence memory, especially in relation to the memory of pain.

CONCLUSIONS

Migraine is associated to global dysfunction of multisensory integration and memory processing. This condition changes the activity of structures in various regions related to memory of pain, prospective memory, as well as in short- and long-term verbal and visuospatial memories. However, it is necessary to perform studies with larger samples in association with cognitive tests, and without the interference of medications to verify possible alterations and to draw more concrete conclusions.

The medial temporal lobe in nociception: a meta-analytic and functional connectivity study

Recent neuroimaging studies implicate the medial temporal lobe (MTL) in nociception and pain modulation. Here, we aim to identify which subregions of the MTL are involved in human pain and to test its connectivity in a cohort of chronic low-back pain patients (CBP). We conducted 2 coordinate-based meta-analyses to determine which regions within the MTL showed consistent spatial patterns of functional activation (1) in response to experimental pain in healthy participants and (2) in chronic pain compared with healthy participants. We followed PRISMA guidelines and performed activation likelihood estimate (ALE) meta-analyses. The first meta-analysis revealed consistent activation in the right anterior hippocampus (right antHC), parahippocampal gyrus, and amygdala. The second meta-analysis revealed consistently less activation in patients' right antHC, compared with healthy participants. We then conducted a seed-to-voxel resting state functional connectivity of the right antHC seed with the rest of the brain in 77 CBP and 79 age-matched healthy participants. We found that CBP had significantly weaker antHC functional connectivity to the medial prefrontal cortex compared with healthy participants. Taken together, these data indicate that the antHC has abnormally lower activity in chronic pain and reduced connectivity to the medial prefrontal cortex in CBP. Future studies should investigate the specific role of the antHC in the development and management of chronic pain.

[Two-point discrimination through electrical stimulation of receptive fields]

The effect of two-point discrimination described in this case report indicates a cortical reorganization through electrical stimulation of receptive fields. The "intervention units" compared to the "baseline" show clear effects. The pain behavior in both "intervention units" showed a clear change in the phantom phenomena, which in both "wash out" phases moved back towards "baseline". Thus, electrical stimulation of receptive fields could be another therapy for the treatment of phantom pain, given the change in two-point discrimination.

Child Abuse and Neglect as Risk Factors for Comorbidity Between Depression and Chronic Pain in Adulthood

It is estimated that comorbidity between depression and chronic pain reaches more than half of the depressed adult patients around the world. Evidence indicates that some stressors, such as early-life stress (ELS), mediate the co-occurrence of depression and chronic pain. This study aimed to assess whether ELS or any of its subtypes could be considered as risk factors for comorbidity between depression and chronic pain. For this purpose, 44 patients in depressive episode were evaluated, in which 22 were diagnosed with depression and chronic pain, and the other 22 patients were diagnosed with depression but without chronic pain. Results had shown that ELS occurrence is more significant among depressive patients with chronic pain compared with those without pain. When subtypes of ELS were evaluated, the group of depressive patients with pain showed significantly higher prevalence of emotional neglect than those depressive participants without pain. Data analysis has shown that severity of the depressive symptoms has a significant impact on the total score of childhood trauma, emotional abuse, physical abuse, emotional neglect, and physical neglect, and that emotional abuse, sexual abuse, and physical neglect have significant impact on the severity of depression. In conclusion, our findings indicate that ELS can be considered as a risk factor for the comorbidity between depression and chronic pain.

Clinical assessments can discriminate altered body perception in patients with unilateral chronic low back pain, but not differences between affected and unaffected side

Chronic pain disorders appear to be associated with altered body perception. The clinical tools of two-point discrimination (TPD), left/right judgment task (LRJ) and body image drawing (BID) can all be used to assess altered body perception in people with chronic low back pain (CLBP). The aim of this observational study was to examine whether values from TPD, LRJ and BID can determine altered body perception between unilateral CLBP patients' painful and pain-free trunk sides, through the evaluation of some of the underlying mechanisms of body perception. Twenty-seven eligible participants completed all tasks. Inclusion criteria were: unilateral CLBP with duration of over 12 weeks; pain level higher than two out of ten on the numeric rating scale; a minimum score of four points on the Roland Morris Disability Questionnaire (RMDQ). Findings from TPD and BID tests showed an alteration in body awareness. However, no significant interaction effects were found between the affected sides and their measurements (TPD p = 0.310, LRJ response time p = 0.571, LRJ accuracy p = 0.190, BID p = 0.751). The profiling of people with high levels of distorted body perception for other factors known to contribute to CLBP may be a useful direction for further investigation.

Immediate Effects of Mirror Therapy in Patients With Shoulder Pain and Decreased Range of Motion

OBJECTIVE

To determine the effects of a brief single component of the graded motor imagery (GMI) sequence (mirror therapy) on active range of motion (AROM), pain, fear avoidance, and pain catastrophization in patients with shoulder pain.

DESIGN

Single-blind case series.

SETTING

Three outpatient physical therapy clinics.

PARTICIPANTS

Patients with shoulder pain and limited AROM (N=69).

INTERVENTION

Patients moved their unaffected shoulder through comfortable AROM in front of a mirror so that it appeared that they were moving their affected shoulder.

MAIN OUTCOME MEASURES

We measured pain, pain catastrophization, fear avoidance, and AROM in 69 consecutive patients with shoulder pain and limited AROM before and immediately after mirror therapy.

RESULTS

There were significant differences in self-reported pain (P=.014), pain catastrophization (P<.001), and the Tampa Scale of Kinesiophobia (P=.012) immediately after mirror therapy; however, the means did not meet or exceed the minimal detectable change (MDC) for each outcome measure. There was a significant increase (mean, 14.5°) in affected shoulder flexion AROM immediately postmirror therapy (P<.001), which exceeded the MDC of 8°.

CONCLUSIONS

A brief mirror therapy intervention can result in statistically significant improvements in pain, pain catastrophization, fear avoidance, and shoulder flexion AROM in patients presenting with shoulder pain with limited AROM. The immediate changes may allow a quicker transition to multimodal treatment, including manual therapy and exercise in these patients. Further studies, including randomized controlled trials, are needed to investigate these findings and determine longer-term effects.

[Automated two-point discrimination (TPD) for phantom pain : Effect of a 3‑week automated therapy based on TPD for a transtibial amputee with phantom pain]

There is preliminary evidence that phantom pain is associated with disturbed organization of the sensory cortex and that this organization can be normalized with two-point discrimination (TPD) training. In this case study, a reduction in phantom pain and painful phantom sensation during a test period of 19 days, was achieved using an automated TPD procedure. In a patient with a transtibial amputation, pain levels decreased from a mean of 2.3/10 on the visual analog scale (VAS) to 1.3/10 (VAS) and the painful phantom sensation level decreased from a mean 3.7/10 (VAS) to 2.0/10 (VAS). These results show a positive trend, but are (except of the nocturnal pain attacks) rather of limited clinical relevance.

The effect of manual therapy and neuroplasticity education on chronic low back pain: a randomized clinical trial

Objective

To determine if a neuroplasticity educational explanation for a manual therapy technique will produce a different outcome compared to a traditional mechanical explanation.

Methods

Sixty-two patients with chronic low back pain (CLBP) were recruited for the study. Following consent, demographic data were obtained as well as pain ratings for low back pain (LBP) and leg pain (Numeric Pain Rating Scale), disability (Oswestry Disability Index), fear-avoidance (Fear-Avoidance-Beliefs Questionnaire), forward flexion (fingertips-to-floor), and straight leg raise (SLR) (inclinometer). Patients were then randomly allocated to receive one of two explanations (neuroplasticity or mechanical), a manual therapy technique to their lumbar spine, followed by post-intervention measurements of LBP, leg pain, forward flexion, and SLR.

Results

Sixty-two patients (female 35 [56.5%]), with a mean age of 60.1 years and mean duration of 9.26 years of CLBP participated in the study. There were no statistically significant interactions for LBP (p = .325), leg pain (p = .172), and trunk flexion (p = .818) between the groups, but SLR showed a significant difference in favor of the neuroplasticity explanation (p = .041). Additionally, the neuroplasticity group were 7.2 times (95% confidence interval = 1.8-28.6) more likely to improve beyond the MDC on the SLR than participants in the mechanical group.

Discussion

The results of this study show that a neuroplasticity explanation, compared to a traditional biomechanical explanation, resulted in a measureable difference in SLR in patients with CLBP when receiving manual therapy. Future studies need to explore if the increase in SLR correlated to changes in cortical maps of the low back.

Detection of central circuits implicated in the formation of novel pain memories

Being able to remember physically and emotionally painful events in one's own past may shape behavior, and can create an aversion to a variety of situations. Pain imagination is a related process that may include recall of past experiences, in addition to production of sensory and emotional percepts without external stimuli. This study aimed to understand 1) the central nervous system processes that underlie pain imagination, 2) the retrieval of pain memories, and 3) to compare the latter with visual object memory. These goals were achieved by longitudinally investigating brain function with functional magnetic resonance imaging in a unique group of healthy volunteers who had never experienced tooth pain. In these subjects, we compared brain responses elicited during three experimental conditions in the following order: imagination of tooth pain (pain imagination), remembering one's own house (object memory), and remembrance of tooth pain following an episode of induced acute tooth pain (pain memory). Key observations stemming from group-level conjunction analyses revealed common activation in the posterior parietal cortex for both pain imagination and pain memory, while object and pain memory each had strong activation predominantly within the middle frontal gyrus. When contrasting pain imagination and memory, significant activation differences were observed in subcortical structures (ie, parahippocampus - pain imagination > pain memory; midbrain - pain memory > pain imagination). Importantly, these findings were observed in the presence of consistent and reproducible psychophysical and behavioral measures that informed on the subjects' ability to imagine novel and familiar thoughts, as well as the subjects' pain perception.

Moving without moving: immediate management following lumbar spine surgery using a graded motor imagery approach: a case report

Representational body maps are dynamically maintained in the brain and negatively influenced by neglect, decreased movement and pain. Graded motor imagery (GMI) utilizing various tactile and cognitive processes has shown efficacy in decreasing pain, disability and movement restrictions in musculoskeletal pain. Limited information is known about the cortical changes patients undergo during lumbar surgery (LS), let alone the therapeutic effect of GMI for LS. A 56-year-old patient underwent LS for low back pain, leg pain and progressive neurological deficit. Twenty-four hours prior to and 48 h after LS various psychometric, physical movement and tactile acuity measurements were recorded. Apart from predictable postoperative increases in pain, fear-avoidance, disability and movement-restrictions, pressure pain thresholds (PPT), two-point discrimination (TPD) and tactile acuity was greatly reduced. The patient underwent six physiotherapy (PT) treatments receiving a GMI program aimed at restoring the PPT, TPD and tactile acuity. The results revealed that GMI techniques applied to a patient immediately after LS caused marked improvements in movement (flexion average improvement/session 3.3 cm; straight leg raise average 8.3°/session) and an immediate hypoalgesic effect. GMI may provide PT with a non-threatening therapeutic treatment for the acute LS patient and establish a new role for PT in acute LS patients.

Listening is therapy: Patient interviewing from a pain science perspective

The interview of a patient attending physical therapy is the cornerstone of the physical examination, diagnosis, plan of care, prognosis, and overall efficacy of the therapeutic experience. A thorough, skilled interview drives the objective tests and measures chosen, as well as provides context for the interpretation of those tests and measures, during the physical examination. Information from the interview powerfully influences the treatment modalities chosen by the physical therapist (PT) and thus also impacts the overall outcome and prognosis of the therapy sessions. Traditional physical therapy focuses heavily on biomedical information to educate people about their pain, and this predominant model focusing on anatomy, biomechanics, and pathoanatomy permeates the interview and physical examination. Although this model may have a significant effect on people with acute, sub-acute or postoperative pain, this type of examination may not only gather insufficient information regarding the pain experience and suffering, but negatively impact a patient's pain experience. In recent years, physical therapy treatment for pain has increasingly focused on pain science education, with increasing evidence of pain science education positively affecting pain, disability, pain catastrophization, movement limitations, and overall healthcare cost. In line with the ever-increasing focus of pain science in physical therapy, it is time for the examination, both subjective and objective, to embrace a biopsychosocial approach beyond the realm of only a biomedical approach. A patient interview is far more than "just" collecting information. It also is a critical component to establishing an alliance with a patient and a fundamental first step in therapeutic neuroscience education (TNE) for patients in pain. This article highlights the interview process focusing on a pain science perspective as it relates to screening patients, establishing psychosocial barriers to improvement, and pain mechanism assessment.

Motor Imagery and Its Effect on Complex Regional Pain Syndrome: An Integrative Review

The motor imagery (MI) has been proposed as a treatment in the complex regional pain syndrome type 1 (CRPS-1), since it seems to promote a brain reorganization effect on sensory-motor areas of pain perception. The aim of this paper is to investigate, through an integrative critical review, the influence of MI on the CRPS-1, correlating their evidence to clinical practice. Research in PEDro, Medline, Bireme and Google Scholar databases was conducted. Nine randomized controlled trials (level 2), 1 non-controlled clinical study (level 3), 1 case study (level 4), 1 systematic review (level 1), 2 review articles and 1 comment (level 5) were found. We can conclude that MI has shown effect in reducing pain and functionality that remains after 6 months of treatment. However, the difference between the MI strategies for CRPS-1 is unknown as well as the intensity of mental stress influences the painful response or effect of MI or other peripheral neuropathies.

Chronic pain and the thoracic spine

In recent years there has been an increased interest in pain neuroscience in physical therapy.1,2 Emerging pain neuroscience research has challenged prevailing models used to understand and treat pain, including the Cartesian model of pain and the pain gate.2-4 Focus has shifted to the brain's processing of a pain experience, the pain neuromatrix and more recently, cortical reorganisation of body maps.2,3,5,6 In turn, these emerging theories have catapulted new treatments, such as therapeutic neuroscience education (TNE)7-10 and graded motor imagery (GMI),11,12 to the forefront of treating people suffering from persistent spinal pain. In line with their increased use, both of these approaches have exponentially gathered increasing evidence to support their use.4,10 For example, various randomised controlled trials and systematic reviews have shown that teaching patients more about the biology and physiology of their pain experience leads to positive changes in pain, pain catastrophization, function, physical movement and healthcare utilisation.7-10 Graded motor imagery, in turn, has shown increasing evidence to help pain and disability in complex pain states such as complex regional pain syndrome (CRPS).11,12 Most research using TNE and GMI has focussed on chronic low back pain (CLBP) and CRPS and none of these advanced pain treatments have been trialled on the thoracic spine. This lack of research and writings in regards to the thoracic spine is not unique to pain science, but also in manual therapy. There are, however, very unique pain neuroscience issues that skilled manual therapists may find clinically meaningful when treating a patient struggling with persistent thoracic pain. Utilising the latest understanding of pain neuroscience, three key clinical chronic thoracic issues will be discussed - hypersensitisation of intercostal nerves, posterior primary rami nerves mimicking Cloward areas and mechanical and sensitisation issues of the spinal dura in the thoracic spine.

Classical conditioning and pain: conditioned analgesia and hyperalgesia

This article reviews situations in which stimuli produce an increase or a decrease in nociceptive responses through basic associative processes and provides an associative account of such changes. Specifically, the literature suggests that cues associated with stress can produce conditioned analgesia or conditioned hyperalgesia, depending on the properties of the conditioned stimulus (e.g., contextual cues and audiovisual cues vs. gustatory and olfactory cues, respectively) and the proprieties of the unconditioned stimulus (e.g., appetitive, aversive, or analgesic, respectively). When such cues are associated with reducers of exogenous pain (e.g., opiates), they typically increase sensitivity to pain. Overall, the evidence concerning conditioned stress-induced analgesia, conditioned hyperalagesia, conditioned tolerance to morphine, and conditioned reduction of morphine analgesia suggests that selective associations between stimuli underlie changes in pain sensitivity.

Functional blockage of the cannabinoid receptor type 1 evokes a kappa-opiate-dependent analgesia

Progress in the control and treatment of pain may be facilitated by a better understanding of mechanisms underlying nociceptive processing. Cannabinoids and opioids are endogenous modulator of pain sensation, but therapies based in these compounds are not completely exploited because of their side effects. To test the role of cannabinoid receptor type 1 (CB1-R) inhibition in nociception, we performed a subchronic administration of the CB1-R antagonist N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM281) in mice. This treatment provoked analgesia in peripheral thermal and visceral models of pain. Analysis of genes encoded for the opioid system in the spinal cord showed an increase in the expression of genes encoded for the κ-opioid system in AM281-injected mice compared with vehicle-injected ones. Furthermore, systemic administration of nor-binaltorphimine, a κ-opioid receptor antagonist, blocked AM281-induced analgesia. Finally, c-fos expression in the dorsal spinal cord and higher centers of pain processing after noxious stimulation were significantly lower in AM281-injected mice than in vehicle-injected animals, indicating that dynorphin could block nociceptive information transmission at the spinal cord level. These results indicate the existence of a cross-talk between opioid and cannabinoid systems in nociception. Furthermore, the results suggest that CB1-R antagonists could be useful as a new therapeutic approach for pain relief.

Alteration of delay and trace eyeblink conditioning in fibromyalgia patients

OBJECTIVE

Classical conditioning processes are important for the generation and persistence of symptoms in psychosomatic disorders, such as the fibromyalgia syndrome (FMS). Pharmacologically induced hyper- and hypocortisolism were shown to affect trace but not delay classical eyeblink conditioning. As previous studies revealed a relative hypocortisolism in FMS patients, we hypothesized that FMS patients also show altered eyeblink conditioning.

METHODS

FMS patients (n = 30) and healthy control subjects (n = 20) matched for gender and age were randomly assigned to a delay or trace eyeblink conditioning protocol, where conditioned eyeblink response probability was assessed by electromyogram. Morning cortisol levels, ratings of depression, anxiety as well as psychosomatic complaints, general symptomatology, and psychological distress were assessed.

RESULTS

As compared with healthy controls, FMS patients showed lower morning cortisol levels, corroborating previously described disturbances in neuroendocrine regulation of the hypothalamus-pituitary-adrenal axis in these patients. Trace eyeblink conditioning was facilitated in FMS patients, whereas delay eyeblink conditioning was reduced, and cortisol measures correlated significantly only with trace eyeblink conditioning.

CONCLUSION

We conclude that FMS patients characterized by decreased cortisol levels differ in classical trace eyeblink conditioning from healthy controls, suggesting that endocrine mechanisms affecting hippocampus-mediated forms of associative learning may play a role in the generation of symptoms in these patients.

Explicit episodic memory for sensory-discriminative components of capsaicin-induced pain: immediate and delayed ratings

Pain memory is thought to affect future pain sensitivity and thus contribute to clinical pain conditions. Systematic investigations of the human capacity to remember sensory features of experimental pain are sparse. In order to address long-term pain memory, nine healthy male volunteers received intradermal injections of three doses of capsaicin (0.05, 1 and 20 microg, separated by 15 min breaks), each given three times in a balanced design across three sessions at one week intervals. Pain rating was performed using a computerized visual analogue scale (0-100) digitized at 1/s, either immediately online or one hour or one day after injection. Subjects also recalled their pains one week later. Capsaicin injection reliably induced a dose-dependent flare (p<0.001) without any difference within or across sessions. The strong burning pain decayed exponentially within a few minutes. Subjects were able to reliably discriminate pain magnitude and duration across capsaicin doses (both p<0.001), regardless of whether first-time ratings were requested immediately, after one hour or after one day. Pain recall after one week was similarly precise (magnitude: p<0.01, duration: p<0.05). Correlation with rating recall after one week was best when first-time ratings were requested as late as one day after injection (R(2)=0.79) indicating that both rating retrievals utilized similar memory traces. These results indicate a reliable memory for magnitude and duration of experimentally induced pain. The data further suggest that the consolidation of this memory is an important interim stage, and may take up to one day.

Noxious counterirritation in patients with advanced osteoarthritis of the knee reduces MCC but not SII pain generators: A combined use of MEG and EEG

Chronic pain is mainly a result of two processes: peripheral and central sensitization, which can result in neuroplastic changes. Previous psychophysical studies suggested a decrease of the so-called pain-inhibiting-pain effect (DNIC) in chronic pain patients. We aimed to study the DNIC effect on the neuronal level using magnetoencephalography and electroencephalography in 12 patients suffering from advanced unilateral knee osteoarthritis (OA). DNIC was induced in patients by provoking the typical OA pain by a slightly hyperextended joint position, while they received short electrical pain stimuli. Although the patients did not report a reduction of electrical pain perception, the cingulate gyrus showed a decrease of activation during provoked OA pain, while activity in the secondary somatosensory cortex did not change. Based on much stronger DNIC induction at comparable intensities of an acute counterirritant pain in healthy subjects this result suggests a deficit of DNIC in OA patients. We suggest that the strength of DNIC is subject to neuronal plasticity of descending inhibitory pain systems and diminishes during the development of a chronic pain condition.

Inhibition of cortisol production by metyrapone enhances trace, but not delay, eyeblink conditioning

RATIONALE

Hypercortisolism [ corrected] impairs trace classical conditioning of the eyeblink response to an air puff but does not affect delay conditioning.

OBJECTIVES

The opposite neurohormonal condition, hypocortisolism, may facilitate trace classical conditioning, which might be informative in understanding the role of classical conditioning in stress-sensitive syndromes such as fibromyalgia.

MATERIALS AND METHODS

Volunteers (n = 82) were randomized to receive either an inhibitor of cortisol production (metyrapone, 1500 mg) or placebo and to complete a delay or a trace eyeblink conditioning protocol (unconditioned stimulus: corneal air puff, 10 psi, 50 ms; conditioned stimulus: binaural pure tone, 75 dB, 1000 Hz, 400 ms; empty interval in trace conditioning: 600 ms), where conditioned eyeblink response probability was assessed electromyographically.

RESULTS

Metyrapone induced hypocortisolism, reflected by a 30% decrease of salivary cortisol levels (p < 0.01), and facilitated trace eyeblink conditioning (p < 0.001), while delay eyeblink conditioning remained unaffected. Moreover, extinction of delay-conditioned eyeblink responses was impaired (p = 0.023), but extinction of trace-conditioned responses remained unaffected.

CONCLUSIONS

We conclude that acute mild metyrapone-induced hypocortisolism facilitates hippocampus-mediated classical trace eyeblink conditioning but suppresses the extinction of cerebellum-based delay-conditioned responses. Both results may be of theoretical and clinical significance for the generation and persistence of psychosomatic symptoms in patient groups characterized by relative hypocortisolism (e.g., fibromyalgia and chronic fatigue).

Chronic non-specific low back pain - sub-groups or a single mechanism?

BACKGROUND

Low back pain is a substantial health problem and has subsequently attracted a considerable amount of research. Clinical trials evaluating the efficacy of a variety of interventions for chronic non-specific low back pain indicate limited effectiveness for most commonly applied interventions and approaches.

DISCUSSION

Many clinicians challenge the results of clinical trials as they feel that this lack of effectiveness is at odds with their clinical experience of managing patients with back pain. A common explanation for this discrepancy is the perceived heterogeneity of patients with chronic non-specific low back pain. It is felt that the effects of treatment may be diluted by the application of a single intervention to a complex, heterogeneous group with diverse treatment needs. This argument presupposes that current treatment is effective when applied to the correct patient. An alternative perspective is that the clinical trials are correct and current treatments have limited efficacy. Preoccupation with sub-grouping may stifle engagement with this view and it is important that the sub-grouping paradigm is closely examined. This paper argues that there are numerous problems with the sub-grouping approach and that it may not be an important reason for the disappointing results of clinical trials. We propose instead that current treatment may be ineffective because it has been misdirected. Recent evidence that demonstrates changes within the brain in chronic low back pain sufferers raises the possibility that persistent back pain may be a problem of cortical reorganisation and degeneration. This perspective offers interesting insights into the chronic low back pain experience and suggests alternative models of intervention.

SUMMARY

The disappointing results of clinical research are commonly explained by the failure of researchers to adequately attend to sub-grouping of the chronic non-specific low back pain population. Alternatively, current approaches may be ineffective and clinicians and researchers may need to radically rethink the nature of the problem and how it should best be managed.

Alteration in the response properties of primary somatosensory cortex related to differential aversive Pavlovian conditioning

The effects of differential aversive Pavlovian conditioning on the functional organization of primary somatosensory cortex (SI) were examined in 17 healthy participants. Neuroelectric source imaging from 60 electrodes was employed while nine subjects received an innocuous electric stimulus (conditioned stimulus, CS) to one finger (left or right) that was followed by painful electric shock to the lower back (unconditioned stimulus, US) and an innocuous stimulus to the other finger that was never followed by pain. Eight subjects received a presentation of the innocuous and painful stimuli with equal probability to both fingers (control group). The data included the electromyogram (EMG) from the left m. corrugator, and judgments of intensity, aversiveness, and CS-US contingency. Only the experimental group displayed EMG conditioning, differential contingency judgments, as well as a change of dipole orientation for the CS and an enhanced dipole moment for the US in the electroencephalogram. Intensity and unpleasantness ratings were altered in a more unspecific manner and did not differ between groups and stimulus conditions. The data suggest that SI contributes to memory processes in associative learning. Pavlovian conditioning of tactile responses might be important in the altered processing of painful stimuli in chronic pain patients where enhanced conditioning has been demonstrated.

Using visual illusion to reduce at-level neuropathic pain in paraplegia

Neuropathic pain after spinal cord injury is not well understood and is difficult to treat. One possible cause is mismatch between motor commands and sensory feedback. This two-part study in five paraplegic patients investigated whether a visual illusion aimed to correct this mismatch reduces pain. In study 1, patients undertook three conditions: (i) virtual walking: with a mirror placed in front of a screen, patients aligned their own upper body with a film of a lower body walking. Patients imagined walking and 'watched themselves' walk; (ii) guided imagery; (iii) watching a film. One patient withdrew from virtual walking because of distress. For all patients, the mean (95% CI) decrease in pain (100 mm VAS) was 42 mm (approximately 65%) (11-73 mm) for virtual walking, 18 mm (4-31 mm) for guided imagery and 4mm (-3 to 11 mm) for watching the film. Mean (95% CI) time to return to pre-task pain was 34.9 min (20.1-49.8 min) for virtual walking; 13.9 min (-0.9 to 28.8 min) for the guided imagery and 16.3 min (1.5-31.2 min) for the film. To investigate its clinical utility, four patients underwent virtual walking every weekday for 3 weeks. Mean (95% CI) decrease in pain was 53 mm (45-61 mm) at post training and 43 mm (27-58 mm) at 3-month follow-up. Virtual walking may be a viable treatment for pain after spinal cord injury. A clinical trial seems warranted.

Cortical Dynamics As A Therapeutic Mechanism for Touch Healing

Touch Healing (TH) therapies, defined here as treatments whose primary route of administration is tactile contact and/or active guiding of somatic attention, are ubiquitous across cultures. Despite increasing integration of TH into mainstream medicine through therapies such as Reiki, Therapeutic Touch,(TM) and somatically focused meditation practices such as Mindfulness-Based Stress Reduction, relatively little is known about potential underlying mechanisms. Here, we present a neuroscientific explanation for the prevalence and effectiveness of TH therapies for relieving chronic pain. We begin with a cross-cultural review of several different types of TH treatments and identify common characteristics, including: light tactile contact and/or a somatosensory attention directed toward the body, a behaviorally relevant context, a relaxed context and repeated treatment sessions. These cardinal features are also key elements of established mechanisms of neural plasticity in somatosensory cortical maps, suggesting that sensory reorganization is a mechanism for the healing observed. Consideration of the potential health benefits of meditation practice specifically suggests that these practices provide training in the regulation of neural and perceptual dynamics that provide ongoing resistance to the development of maladaptive somatic representations. This model provides several direct predictions for investigating ways that TH may induce cortical plasticity and dynamics in pain remediation.

Phantom limb pain: a case of maladaptive CNS plasticity?

Phantom pain refers to pain in a body part that has been amputated or deafferented. It has often been viewed as a type of mental disorder or has been assumed to stem from pathological alterations in the region of the amputation stump. In the past decade, evidence has accumulated that phantom pain might be a phenomenon of the CNS that is related to plastic changes at several levels of the neuraxis and especially the cortex. Here, we discuss the evidence for putative pathophysiological mechanisms with an emphasis on central, and in particular cortical, changes. We cite both animal and human studies and derive suggestions for innovative interventions aimed at alleviating phantom pain.

Reward-aversion circuitry in analgesia and pain: implications for psychiatric disorders

Sensory and emotional systems normally interact in a manner that optimizes an organism's ability to survive using conscious and unconscious processing. Pain and analgesia are interpreted by the nervous system as aversive and rewarding processes that trigger specific behavioral responses. Under normal physiological conditions these processes are adaptive. However, under chronic pain conditions, functional alterations of the central nervous system frequently result in maladaptive behaviors. In this review, we examine: (a) the interactions between sensory and emotional systems involved in processing pain and analgesia in the physiological state; (b) the role of reward/aversion circuitry in pain and analgesia; and (c) the role of alterations in reward/aversion circuitry in the development of chronic pain and co-morbid psychiatric disorders. These underlying features have implications for understanding the neurobiology of functional illnesses such as depression and anxiety and for the development and evaluation of novel therapeutic interventions.

Biopsychosocial pain medicine and mind-brain-body science

This article reviews how emotions, behavior, and psychiatric comorbidity influence the course and outcome of chronic pain disorders and addresses methods of identifying and managing these problems in clinical practice. Successful medical rehabilitation for patients with chronic pain requires (1) appreciating the effects of biopsychosocial factors in the onset, course, and outcomes of pain disorders; (2) understanding neurobiologic mechanisms linking mind, brain, and body in the functions of pain perception and modulation; and (3) being able to review critically and use selectively the plethora of new medications and interventional technologies that are proposed in the literature. Deficits in these skills now are recognized as hazardous to the public health so that medical school education and post residency training in pain medicine is now mandatory in some states.

Pavlovian conditioning of muscular responses in chronic pain patients: central and peripheral correlates

A differential conditioning design using an aversive slide as conditioned stimulus (CS(+)) that was followed by an intracutaneous electric stimulus to the left index finger as unconditioned stimulus (US) and a pleasant slide that was not followed by shock (CS(-)) were used to test the hypothesis of enhanced aversive conditioning of muscular responses in chronic back pain patients (CBP). Heart rate, skin conductance levels, and integrated surface electromyograms (EMG) from the left and right m. flexor digitorum, the right m. trapezius, and bilaterally from the m. orbicularis oculi were recorded. The electroencephalogram (EEG) was measured from nine electrode positions. The CBP patients showed an enhanced muscular response of the left forearm (where the US was applied) to the CS(+) already in the preconditioning phase. During acquisition both the left forearm and the right trapezius of the patients but not the controls displayed enhanced muscular responding to the CS(+). During extinction the CBP patients' muscular responses to both CS(+) and CS(-) were elevated. The contingent negative variation of the EEG differentiated between CS(+) and CS(-) in the healthy controls but not the chronic pain patients. These data confirm the hypothesis of enhanced muscular responding in chronic pain patients and suggest a dissociation of muscular and central processes during aversive conditioning in the patients that might contribute to the chronicity problem.

The AMPA Receptor Subunits GluR-A and GluR-B Reciprocally Modulate Spinal Synaptic Plasticity and Inflammatory Pain

Ca(2+)-permeable AMPA receptors are densely expressed in the spinal dorsal horn, but their functional significance in pain processing is not understood. By disrupting the genes encoding GluR-A or GluR-B, we generated mice exhibiting increased or decreased numbers of Ca(2+)-permeable AMPA receptors, respectively. Here, we demonstrate that AMPA receptors are critical determinants of nociceptive plasticity and inflammatory pain. A reduction in the number of Ca(2+)-permeable AMPA receptors and density of AMPA channel currents in spinal neurons of GluR-A-deficient mice is accompanied by a loss of nociceptive plasticity in vitro and a reduction in acute inflammatory hyperalgesia in vivo. In contrast, an increase in spinal Ca(2+)-permeable AMPA receptors in GluR-B-deficient mice facilitated nociceptive plasticity and enhanced long-lasting inflammatory hyperalgesia. Thus, AMPA receptors are not mere determinants of fast synaptic transmission underlying basal pain sensitivity as previously thought, but are critically involved in activity-dependent changes in synaptic processing of nociceptive inputs.

Functional imaging of the human trigeminal system: Opportunities for new insights into pain processing in health and disease

Peripheral inflammation or nerve damage result in changes in nervous system function, and may be a source of chronic pain. A number of animal studies have indicated that central neural plasticity, including sensitization of neurons within the spinal cord and brain, is part of the response to nervous system insult, and can result in the appearance of altered sensation, including pain. It cannot be assumed, however, that data obtained from animal models unambiguously reflects CNS changes that occur in humans. Currently, the only noninvasive approach to determining objective changes in neural processing and responsiveness within the CNS in humans is the use of functional imaging techniques. It is now possible to use functional magnetic resonance imaging (fMRI) to measure CNS activation in the trigeminal ganglion, spinal trigeminal nucleus, the thalamus, and the somatosensory cortex in healthy volunteers, in a surrogate model of hyperalgesia, and in patients with trigeminal pain. By offering a window into the temporal and functional changes that occur in the damaged nervous system in humans, fMRI can provide both insight into the mechanisms of normal and pathological pain and, potentially, an objective method for measuring altered sensation. These advances are likely to contribute greatly to the diagnosis and treatment of clinical pain conditions affecting the trigeminal system (e.g., neuropathic pain, migraine).

Pain imaging: future applications to integrative clinical and basic neurobiology

We have entered a new era in understanding CNS circuitry involved in acute and chronic pain. The ability to objectively measure a pain or analgesic state of the brain using non-invasive methods that define neural activation provides the possibility for top-down approaches to drug discovery. These brain maps represent the specific brain state. In the future, correlations with such states and behavioral, genetic, epigenetic or other chemical markers may help define specific diagnostic tools and novel approaches to drug discovery.

The management of persistent pain

Persistent pain is a complex mix of physical and psychological symptoms and is ideally managed by a biopsychosocial approach. Often the relative contributions of family and personal relationships, finances, work, past pain experiences and personality outweigh those of the nociceptive or neuropathic processes from which most pain originates. Recent advances in our understanding of the pathophysiology of pain may lead to improved drug treatments; however, non-drug treatments--education, lifestyle modification, exercise and reassurance--should be used routinely to improve patients' quality of life. Patients with persistent pain that is difficult to control or has complex psychosocial influences, or who have a history of medication misuse, should be referred to a multidisciplinary pain centre. Selected patients may be offered invasive options such as nerve blocks or spinal-cord stimulation. The best outcomes are achieved in patients treated in group-based pain-management programs using cognitive-behavioural therapy to improve physical function, change unhelpful thinking and improve patients' understanding of their situation.

Nonopioid and neuropathy-specific analgesic action of the nootropic drug nefiracetam in mice

Nootropic drug nefiracetam and related compounds are used in diseases with learning and memory deficits. Recent studies have implicated relationships between learning, memory, and chronic pain. Thus, in the present report, we have studied the effects of nootropic drug nefiracetam on the thermal and mechanical hyperalgesia induced by partial sciatic nerve ligation or streptozotocin treatment in mice. In the thermal paw withdrawal test, p.o., s.c., i.t., and i.c.v. administration of nefiracetam dose dependently reversed the thermal hyperalgesia observed in nerve-injured mice. Nefiracetam (p.o. and i.t.) also significantly reversed the thermal hyperalgesia observed in streptozotocin-induced diabetic mice. In the paw pressure test, p.o. and i.t. administration of nefiracetam dose dependently reversed the mechanical hyperalgesia observed in both nerve-injured and diabetic mice. In contrast, nefiracetam had no effect in sham-operated or control nondiabetic mice in all paradigms. Among other pyrrolidine nootropics (p.o.), aniracetam produced significant analgesic effects. Other analogs also had some, but not significant, analgesic effects. Finally, nefiracetam (p.o.)-induced analgesia in injured mice was not affected by opioid antagonist naloxone (s.c., i.t., and i.c.v.) but was dose dependently inhibited by nicotinic antagonist mecamylamine (i.t. and i.c.v.). The analgesic effect of i.t. nefiracetam was also blocked by i.t. mecamylamine pretreatment. Together, these findings suggest that nefiracetam, a new member of the piracetam group of cognition enhancers, could be a good therapeutic tool against neuropathic pain. We also demonstrate that nefiracetam-induced analgesic action was nonopioid in nature and was due to stimulation of nicotinic cholinergic system at spinal and supraspinal levels.

Human brain plasticity: an emerging view of the multiple substrates and mechanisms that cause cortical changes and related sensory dysfunctions after injuries of sensory inputs from the body

Injuries of peripheral inputs from the body cause sensory dysfunctions that are thought to be attributable to functional changes in cerebral cortical maps of the body. Prevalent theories propose that these cortical changes are explained by mechanisms that preeminently operate within cortex. This paper reviews findings from humans and other primates that point to a very different explanation, i.e. that injury triggers an immediately initiated, and subsequently continuing, progression of mechanisms that alter substrates at multiple subcortical as well as cortical locations. As part of this progression, peripheral injuries cause surprisingly rapid neurochemical/molecular, functional, and structural changes in peripheral, spinal, and brainstem substrates. Moreover, recent comparisons of extents of subcortical and cortical map changes indicate that initial subcortical changes can be more extensive than cortical changes, and that over time cortical and subcortical extents of change reach new balances. Mechanisms for these changes are ubiquitous in subcortical and cortical substrates and include neurochemical/molecular changes that cause functional alterations of normal excitation and inhibition, atrophy and degeneration of normal substrates, and sprouting of new connections. The result is that injuries that begin in the body become rapidly further embodied in reorganizational make-overs of the entire core of the somatosensory brain, from peripheral sensory neurons to cortex. We suggest that sensory dysfunctions after nerve, root, dorsal column (spinal), and amputation injuries can be viewed as diseases of reorganization in this core.

The relationship of perceptual phenomena and cortical reorganization in upper extremity amputees

In this study 16 unilateral upper extremity amputees participated in a comprehensive psychophysiological examination that included the assessment of painful and non-painful phantom and stump sensations, thermal and electric perception as well as two-point discrimination thresholds, the detailed analysis of referred sensation and the measurement of reorganizational changes in primary somatosensory cortex using neuroelectric source imaging. Reorganization of the primary somatosensory cortex was associated with increased habitual phantom limb pain, telescoping, non-painful stump sensations and painful referred sensation induced by painful stimulation. It was unrelated to non-painful phantom sensations, non-painful referred sensation elicited by painful or non-painful stimulation, painful referred sensation elicited by non-painful stimulation, perception thresholds and stump pain. These data substantiate the hypothesis that painful and non-painful phantom phenomena are mediated by different neural substrates.