Elevated [11C]-D-deprenyl uptake in chronic Whiplash Associated Disorder suggests persistent musculoskeletal inflammation

Recent developments and challenges in positron emission tomography imaging of gliosis in chronic neuropathic pain

ABSTRACT

Understanding the mechanisms that underpin the transition from acute to chronic pain is critical for the development of more effective and targeted treatments. There is growing interest in the contribution of glial cells to this process, with cross-sectional preclinical studies demonstrating specific changes in these cell types capturing targeted timepoints from the acute phase and the chronic phase. In vivo longitudinal assessment of the development and evolution of these changes in experimental animals and humans has presented a significant challenge. Recent technological advances in preclinical and clinical positron emission tomography, including the development of specific radiotracers for gliosis, offer great promise for the field. These advances now permit tracking of glial changes over time and provide the ability to relate these changes to pain-relevant symptomology, comorbid psychiatric conditions, and treatment outcomes at both a group and an individual level. In this article, we summarize evidence for gliosis in the transition from acute to chronic pain and provide an overview of the specific radiotracers available to measure this process, highlighting their potential, particularly when combined with ex vivo / in vitro techniques, to understand the pathophysiology of chronic neuropathic pain. These complementary investigations can be used to bridge the existing gap in the field concerning the contribution of gliosis to neuropathic pain and identify potential targets for interventions.

Nerve pathology and neuropathic pain after whiplash injury: a systematic review and meta-analysis

ABSTRACT

There is no clear understanding of the mechanisms causing persistent pain in patients with whiplash-associated disorder (WAD). The aim of this systematic review was to assess the evidence for nerve pathology and neuropathic pain in patients with WAD. EMBASE, PubMed, CINAHL (EBSCO), and MEDLINE were searched from inception to September 1, 2020. Study quality and risk of bias were assessed using the Newcastle-Ottawa Quality Assessment Scales. Fifty-four studies reporting on 390,644 patients and 918 controls were included. Clinical questionnaires suggested symptoms of predominant neuropathic characteristic in 34% of patients (range 25%-75%). The mean prevalence of nerve pathology detected with neurological examination was 13% (0%-100%) and 32% (10%-100%) with electrodiagnostic testing. Patients independent of WAD severity (Quebec Task Force grades I-IV) demonstrated significantly impaired sensory detection thresholds of the index finger compared with controls, including mechanical (SMD 0.65 [0.30; 1.00] P < 0.005), current (SMD 0.82 [0.25; 1.39] P = 0.0165), cold (SMD -0.43 [-0.73; -0.13] P = 0.0204), and warm detection (SMD 0.84 [0.25; 1.42] P = 0.0200). Patients with WAD had significantly heightened nerve mechanosensitivity compared with controls on median nerve pressure pain thresholds (SMD -1.10 [-1.50; -0.70], P < 0.0001) and neurodynamic tests (SMD 1.68 [0.92; 2.44], P = 0.0004). Similar sensory dysfunction and nerve mechanosensitivity was seen in WAD grade II, which contradicts its traditional definition of absent nerve involvement. Our findings strongly suggest a subset of patients with WAD demonstrate signs of peripheral nerve pathology and neuropathic pain. Although there was heterogeneity among some studies, typical WAD classifications may need to be reconsidered and include detailed clinical assessments for nerve integrity.

Whiplash injuries associated with experienced pain and disability can be visualized with [11C]-D-deprenyl positron emission tomography and computed tomography

ABSTRACT

Knowledge of etiological mechanisms underlying whiplash-associated disorders is incomplete. Localisation and quantification of peripheral musculoskeletal injury and inflammation in whiplash-associated disorders would facilitate diagnosis, strengthen patients' subjective pain reports, and aid clinical decisions, all of which could lead to improved treatment. In this longitudinal observational study, we evaluated combined [11C]-D-deprenyl positron emission tomography and computed tomography after acute whiplash injury and at 6-month follow-up. Sixteen adult patients (mean age 33 years) with whiplash injury grade II were recruited at the emergency department. [11C]-D-deprenyl positron emission tomography and computed tomography, subjective pain levels, self-rated neck disability, and active cervical range of motion were recorded within 7 days after injury and again at 6-month follow-up. Imaging results showed possible tissue injuries after acute whiplash with an altered [11C]-D-deprenyl uptake in the cervical bone structures and facet joints, associated with subjective pain locale and levels, as well as self-rated disability. At follow-up, some patients had recovered and some showed persistent symptoms and reductions in [11C]-D-deprenyl uptake correlated to reductions in pain levels. These findings help identify affected peripheral structures in whiplash injury and strengthen the idea that positron emission tomography and computed tomography detectable organic lesions in peripheral tissue are relevant for the development of persistent pain and disability in whiplash injury.

Monoamine Oxidase Inhibitors: A Review of Their Anti-Inflammatory Therapeutic Potential and Mechanisms of Action

Chronic inflammatory diseases are debilitating, affect patients' quality of life, and are a significant financial burden on health care. Inflammation is regulated by pro-inflammatory cytokines and chemokines that are expressed by immune and non-immune cells, and their expression is highly controlled, both spatially and temporally. Their dysregulation is a hallmark of chronic inflammatory and autoimmune diseases. Significant evidence supports that monoamine oxidase (MAO) inhibitor drugs have anti-inflammatory effects. MAO inhibitors are principally prescribed for the management of a variety of central nervous system (CNS)-associated diseases such as depression, Alzheimer's, and Parkinson's; however, they also have anti-inflammatory effects in the CNS and a variety of non-CNS tissues. To bolster support for their development as anti-inflammatories, it is critical to elucidate their mechanism(s) of action. MAO inhibitors decrease the generation of end products such as hydrogen peroxide, aldehyde, and ammonium. They also inhibit biogenic amine degradation, and this increases cellular and pericellular catecholamines in a variety of immune and some non-immune cells. This decrease in end product metabolites and increase in catecholamines can play a significant role in the anti-inflammatory effects of MAO inhibitors. This review examines MAO inhibitor effects on inflammation in a variety of in vitro and in vivo CNS and non-CNS disease models, as well as their anti-inflammatory mechanism(s) of action.

A population-based study of inflammatory mechanisms and pain sensitivity

Two recent studies suggest that experimental pain sensitivity is associated with low-grade systemic inflammation. However, only 2 biomarkers have been identified, and the studies were conducted in adult individuals where confounding effects of comorbid diseases cannot be excluded. We therefore tested associations between pain sensitivity and 119 inflammation-related serum biomarkers in 827 healthy adolescents (15-19 years) in the population-based Tromsø Study: Fit Futures. The main outcome measure was cold-pressor pain tolerance (CPT), tested by placing the dominant hand in circulating cold (3°C) water for a maximum of 105 seconds. Secondary outcomes were heat and pressure pain threshold and tolerance. Twelve proteins and 6 fatty acids were significantly associated with CPT after adjustment for possible confounding factors and correction for multiple comparisons. Of these, all fatty acids and 10 proteins were protective, ie, higher biomarkers levels were associated with increased CPT, whereas 2 biomarkers were associated with lower tolerance. Taken together, these biomarkers predicted completion of the tolerance test with a C-statistic of 0.65. Results for heat and pressure pain tolerance were remarkably similar, strengthening the generalizability of our findings. In this cohort of young healthy individuals, we found a relationship between inflammation-related biomarkers and pain tolerance and thresholds. Biomarkers with anti-inflammatory and analgesic effects predominated, suggesting that the development of prophylactic dietary or pharmaceutical treatments may be possible.

Potential Applications of PET/CT/MR Imaging in Inflammatory Diseases: Part I: Musculoskeletal and Gastrointestinal Systems

During the past decades, the role of fludeoxyglucose (FDG)-PET and hybrid PET/computed tomography (CT) has been established clinically in the diagnostic workup of a multitude of infectious and inflammatory disorders. In recent years, the fusion of MR imaging to PET has also been increasingly explored, and this may be especially useful in musculoskeletal and gastrointestinal inflammatory diseases due to exceptional soft tissue contrast and reduced radiation dose. This article outlines the current potential for hybrid molecular imaging in the musculoskeletal system and the gastrointestinal tract with special focus on the potential for fused PET/CT/MR imaging.

Intramuscular fat is present in cervical multifidus but not soleus in patients with chronic whiplash associated disorders

The presence of intramuscular fat (IMF) in the cervical spine muscles of patients with whiplash associated disorders (WAD) has been consistently found. The mechanisms underlying IMF are not clear but preliminary evidence implicates a relationship with stress system responses. We hypothesised that if systemic stress system responses do play a role then IMF would be present in muscles remote to the cervical spine. We aimed to investigate if IMF are present in muscle tissue remote (soleus) to the cervical spine in people with chronic WAD. A secondary aim was to investigate associations between IMF and posttraumatic stress symptom levels. Forty-three people with chronic WAD (25 female) and 16 asymptomatic control participants (11 female) participated. Measures of pain, disability and posttraumatic stress symptoms were collected from the WAD participants. Both groups underwent MRI measures of IMF in cervical multifidus and the right soleus muscle. There was significantly greater IMF in cervical multifidus in patients with WAD and moderate/severe disability compared to controls (p = 0.009). There was no difference in multifidus IMF between the mild and moderate/severe disability WAD groups (p = 0.64), or the control and mild WAD groups (p = 0.21). IMF in the right soleus was not different between the groups (p = 0.47). In the WAD group, we found no correlation between PDS symptoms and cervical multifidus IMF or between PDS symptoms and soleus IMF. Global differences in IMF are not a feature of chronic WAD, with differences in IMF limited to the cervical spine musculature. While the mechanisms for the development of IMF in the cervical spine following whiplash injury remain unclear, our data indicate that local factors more likely contribute to these differences.

New SPECT and PET Radiopharmaceuticals for Imaging Inflammatory Diseases: A Meta-analysis of the Last 10 Years

Modern molecular nuclear medicine is rapidly developing in the field of imaging of chronic inflammatory diseases, and many new radiopharmaceuticals have been recently described and tested in animals and man. These can detect early pathophysiological changes before the development of anatomical changes and, often, before clinical onset of symptoms. This field includes new radiopharmaceuticals for SPECT and PET use to define new strategies for imaging immune cells as well as tissue modifications induced by the inflammatory process. In this review, we present the results of a meta-analysis based on radiopharmaceuticals (for SPECT or PET) that are not commercially available and that have been used, at least once, in humans in the last 10 years.

Neck-specific exercises with internet-based support compared to neck-specific exercises at a physiotherapy clinic for chronic whiplash-associated disorders: study protocol of a randomized controlled multicentre trial

Background

Globally, neck pain is the fourth most common condition associated with longer periods of living with disability. Annually, approximately 0.3% of the population of Western countries undergo whiplash trauma, and half of those individuals will develop chronic problems with high costs for the individual and society. Evidence for chronic whiplash-associated disorders (WAD) treatment is scarce, though neck-specific training at a physiotherapy clinic twice a week for 12 weeks has demonstrated good results. More efficient, flexible rehabilitation with reduced waiting times and lower costs is needed, ideally replacing lengthy on-site treatment series by healthcare providers. Internet-based care has been shown to be a viable alternative for a variety of diseases and interventions, but studies are lacking on Internet-based interventions for individuals with chronic neck problems. The aim of the trial described here is to compare the effects of an Internet-based neck-specific exercise programme to the same exercises performed at a physiotherapy clinic in regards to self-reported and clinical measures, as well as cost-effectiveness.

Methods

This prospective, randomized controlled trial will involve 140 participants. Measurements will be made at baseline, 3 months (end of treatment), and 15 months (12 months after end of intervention) and will include ratings of pain, disability, satisfaction with care, work ability, quality of life, and cost-effectiveness.

Discussion

The study results may contribute to the development of a more effective rehabilitation, flexible and equal care, shorter waiting times, increased availability, and lower costs for healthcare and society.

Trial registration

ClinicalTrials.gov Protocol ID: NCT03022812, initial release 12/20/2016.

Characterization of the binding site for d-deprenyl in human inflamed synovial membrane

AIMS

d-Deprenyl when used as a positron emission tomography tracer visualizes peripheral inflammation. The major aim of the current study was to identify and investigate the properties of the binding target for d-deprenyl in synovial membrane explants from arthritic patients.

MAIN METHODS

Thirty patients diagnosed with arthritis or osteoarthritis were enrolled into the study. Homologous and competitive radioligand binding assays utilizing [³H]d-deprenyl were performed to investigate the biochemical characteristics of the binding site and assess differences in the binding profile in synovial membranes exhibiting varying levels of inflammation.

KEY FINDINGS

The [³H]d-deprenyl binding assay confirmed the existence of a single, saturable population of membrane-bound protein binding sites in synovial membrane homogenates. The macroscopically determined level of inflammation correlated with an increase in [³H]d-deprenyl binding affinity, without significant alterations in binding site density. Selective monoamine oxidase B inhibitor, selegiline competed for the same site as [³H]d-deprenyl, but failed to differentiate the samples with regard to their inflammation grade. A monoamine oxidase A inhibitor, pirlindole mesylate showed only weak displacement of [³H]d-deprenyl binding. No significant alterations in monoamine oxidase B expression was detected, thus it was not confirmed whether it could serve as a marker for ongoing inflammation.

SIGNIFICANCE

Our study was the first to show the biochemical characteristics of the [³H]d-deprenyl binding site in inflamed human synovium. We confirmed that d-deprenyl could differentiate between patients with varying severity of synovitis in the knee joint by binding to a protein target distinct from monoamine oxidase B.

The Role of the Trigemino Cervical Complex in Chronic Whiplash Associated Headache: A Cross Sectional Study

OBJECTIVE

To investigate signs of central sensitization in a cohort of patients with chronic whiplash associated headache (CWAH).

BACKGROUND

Central sensitization is one of the mechanisms leading to chronicity of primary headache, and thus might contribute to CWAH. However, the pathophysiological mechanism of CWAH is poorly understood and whether it is simply an expression of the primary headache or has a distinct pathogenesis remains unclear. Thus, the factors involved in the genesis of CWAH require further investigation.

METHODS

Twenty-two patients with CWAH (20 females, 2 males; age 25-50 years, mean age 36.3 years) and 25 asymptomatic participants (13 females, 12 males; age 18-50 years, mean age 35.6 years) rated glare and light-induced discomfort in response to light from an ophthalmoscope. Hyperalgesia evoked by a pressure algometer was assessed bilaterally on the forehead, temples, occipital base, and the middle phalanx of the third finger. The number, latency, area under the curve, and recovery cycle of nociceptive blink reflexes elicited by a supraorbital electrical stimulus were also recorded.

RESULTS

Eight and 6 CWAH patients had migrainous and tension-type headache (TTH) profiles, respectively; the remainder had features attributable to both migraine and TTH. Patients in the whiplash group reported significantly greater light-induced pain than controls (8.48 ± .35 vs 6.66 ± .43 on a 0-10 scale; P = .001). The CWAH patients reported significantly lower pressure pain thresholds at all sites. For stimuli delivered at 20 second intervals, whiplash patients were more responsive than controls (4.8 ± .6 blinks vs 3.0 ± .6 blinks in a block of 10 stimuli; P = .036). While R2 latencies and the area under the curve for the 20 second interval trials were comparable in both groups, there was a significant reduction of the area under the curve from the first to the second of the 2-second interval trials only in controls (99 ± 8% of baseline in whiplash patients vs 68 ± 7% in controls; P = .009). The recovery cycle was comparable for both groups.

CONCLUSIONS

Our results corroborate previous findings of mechanical hypersensitivity and photophobia in CWAH patients. The neurophysiological data provide further evidence for hyperexcitability in central nociceptive pathways, and endorse the hypothesis that CWAH may be driven by central sensitization.

In Vivo Imaging of Human Neuroinflammation

Neuroinflammation is implicated in the pathophysiology of a growing number of human disorders, including multiple sclerosis, chronic pain, traumatic brain injury, and amyotrophic lateral sclerosis. As a result, interest in the development of novel methods to investigate neuroinflammatory processes, for the purpose of diagnosis, development of new therapies, and treatment monitoring, has surged over the past 15 years. Neuroimaging offers a wide array of non- or minimally invasive techniques to characterize neuroinflammatory processes. The intent of this Review is to provide brief descriptions of currently available neuroimaging methods to image neuroinflammation in the human central nervous system (CNS) in vivo. Specifically, because of the relatively widespread accessibility of equipment for nuclear imaging (positron emission tomography [PET]; single photon emission computed tomography [SPECT]) and magnetic resonance imaging (MRI), we will focus on strategies utilizing these technologies. We first provide a working definition of "neuroinflammation" and then discuss available neuroimaging methods to study human neuroinflammatory processes. Specifically, we will focus on neuroimaging methods that target (1) the activation of CNS immunocompetent cells (e.g. imaging of glial activation with TSPO tracer [(11)C]PBR28), (2) compromised BBB (e.g. identification of MS lesions with gadolinium-enhanced MRI), (3) CNS-infiltration of circulating immune cells (e.g. tracking monocyte infiltration into brain parenchyma with iron oxide nanoparticles and MRI), and (4) pathological consequences of neuroinflammation (e.g. imaging apoptosis with [(99m)Tc]Annexin V or iron accumulation with T2* relaxometry). This Review provides an overview of state-of-the-art techniques for imaging human neuroinflammation which have potential to impact patient care in the foreseeable future.

High-throughput screening and radioligand binding studies reveal monoamine oxidase-B as the primary binding target for d-deprenyl

AIMS

d-deprenyl is a useful positron emission tomography tracer for visualization of inflammatory processes. Studies with [(11)C]-d-deprenyl showed robust uptake in peripheral painful sites of patients with rheumatoid arthritis or chronic whiplash injury. The mechanism of preferential d-deprenyl uptake is not yet known, but the existence of a specific binding site was proposed. Thus, in the present study, we sought to identify the binding site for d-deprenyl and verify the hypothesis about the possibility of monoamine oxidase enzymes as major targets for this molecule.

MAIN METHODS

A high-throughput analysis of d-deprenyl activity towards 165G-protein coupled receptors and 84 enzyme targets was performed. Additionally, binding studies were used to verify the competition of [(3)H]d-deprenyl with ligands specific for targets identified in the high-throughput screen.

KEY FINDINGS

Our high-throughput investigation identified monoamine oxidase-B, monoamine oxidase-A and angiotensin converting enzyme as potential targets for d-deprenyl. Further competitive [(3)H]d-deprenyl binding studies with specific inhibitors identified monoamine oxidase-B as the major binding site. No evident high-affinity hits were identified among G-protein coupled receptors.

SIGNIFICANCE

Our study was the first to utilize a high-throughput screening approach to identify putative d-deprenyl targets. It verified 249 candidate proteins and confirmed the role of monoamine oxidase - B in d-deprenyl binding. Our results add knowledge about the possible mechanism of d-deprenyl binding, which might aid in explaining the increased uptake of this compound in peripheral inflammation. Monoamine oxidase-B will be further investigated in future studies utilizing human inflamed synovium.

Serum C-reactive protein levels predict regional brain responses to noxious cold stimulation of the hand in chronic whiplash associated disorders

BACKGROUND AND AIMS

Whiplash Associated Disorders (WAD) are a costly health burden. The condition is characterised by sensory disturbances such as widespread hyperalgesia likely indicative of central hyperexcitability. Recently elevated levels of pro-inflammatory biomarkers have also found in acute and chronic WAD. The aim of this cross-sectional study was to investigate the relationship between inflammatory biomarkers and pain processing in people with persistent whiplash associated disorders (WAD).

METHODS

Twenty one participants with chronic whiplash (>3 months) were recruited. Venous blood samples were collected and assays performed for C-reactive protein (CRP) and TNF-α. Blood oxygen level-dependent (BOLD) contrast images of the brain were acquired with a Siemens 1.5T MRI scanner during repeated 24s stimulus blocks of innocuous or painful stimuli (thumbnail pressure and cold stimulation of dorsum of hand) separated by 36s inter-stimulus intervals. Stimulus intensities used during scanning were at the level of participants' thresholds for moderate pain. Parameter estimates representing BOLD signal increases during painful events from each participant were tested for associations with inflammatory biomarkers.

RESULTS

Clinically relevant levels of CRP and TNF-α were found in 33% and 38% of participants. Levels of CRP showed a positive correlation with levels of cold pain activation in brain regions including the anterior insula, posterior parietal cortex, caudate and thalamus (p_corrected<0.05). Levels of TNF-α were not related to activation levels during either noxious pressure or cold. Pressure pain activations also did not show a relationship with CRP levels.

CONCLUSIONS

Shared variance between inflammation and increased levels of regional pain-related activation in people with persistent whiplash symptoms is apparent for cold, but not pressure stimuli.

IMPLICATIONS

The results highlight cold pain processing as an important aspect of whiplash chronicity, although the implications of this modality-specific effect are not readily apparent.

Signal changes of the alar ligament in a healthy population: a dispositional or degenerative consequence?

OBJECT The alar ligaments (ALs) are vital for stabilizing the craniocervical junction. In terms of morphology, their appearance varies and is visible on MRI. Dark signal of the AL on proton-density (PD)-weighted images is generally considered the norm, but the etiology of frequently observed signal hyperintensities is poorly understood. Using spectral fat suppression, signal hyperintensities can be differentiated into fat- and nonfat-related hyperintensities (NFH). Although signal hyperintensities have no evident association with whiplash-associated disorder, age-related degeneration has often been theorized. Therefore, this study investigates the signal intensities of the ALs on 3.0-T MRI with special reference to age. Expanding thereon, the authors investigated the relationship between signal hyperintensities and patient characteristics, such as height, weight, and sex. METHODS Sixty-six healthy volunteers were scanned using 3.0-T PD-weighted MRI, including spectral fat suppression of the craniocervical junction. The study population was separated into 2 groups (old vs young) using 2 approaches: dichotomization at the median age (40.0 years) and the calculated threshold (28.5 years) using receiver operating characteristics (ROC). The AL was independently characterized with respect to continuity, course, shape, signal intensity, and graduation of homogeneity by 2 experienced neuroradiologists. Signal intensity was differentiated into fat-related hyperintensity and NFH. Univariate and multivariate logistic regression models were employed to investigate the relationship between patient characteristics and signal intensities. RESULTS Two different AL patterns were observed: inhomogeneous (33.3%) and homogeneous (66.7%). The latter pattern was mostly surrounded by a small dark rim (56.8%). Fat could be identified in 15.9% of all ALs (21 of 132 patients), and NFH was identified in 17.4% of all ALs (23 of 132 patients). Here, 28.5 years was the preferred threshold, demonstrating a relatively high sensitivity for dichotomizing the population based on the ROC of NFH. The most relevant factor for having NFH was being older than the calculated threshold (odds ratio [OR] 3.420, p = 0.051). Fat-related hyperintensities occurred significantly more frequently in men than women (OR 0.110 and p = 0.007 for women; OR 9.075 and p = 0.007 for men). Height was the second most significant factor: for every 1-cm increase, the odds of having fat lesions increased by approximately 10% (OR 1.102; p = 0.017). CONCLUSIONS This study shows that AL signal hyperintensities are substantially influenced by age, sex, and height in healthy individuals. Regarding fat-related hyperintensities, the most relevant factors proved to be sex and height. The odds of detecting NFH increased almost significantly after a relatively young age (> 28.5 years) and were remarkably more frequent in individuals older than 28.5 years. The authors caution presumptions equating signal alterations with age-related deterioration. Instead, they suggest that dispositional factors such as sex and height are more relevant in the AL constitution. Signal alterations in ALs naturally occur in healthy symptom-free individuals, underscoring the importance of cautiously interpreting such lesions on posttraumatic MRI scans.

High-throughput screening reveals enzyme and GPCR targets as putative binding sites for D-deprenyl

Aims

In PET studies of patients suffering from chronic pain following whip lash trauma, d-deprenyl was shown to bind to painful sites in the neck [1]. High uptake points towards an existence of an inflammation-specific binding site. Thus, the aim of this study was to identify the binding site for d-deprenyl employing radioligand receptor binding and high-throughput analysis of its activity towards 165 G-protein coupled receptors and 84 enzyme targets commonly used in drug discovery and development.

Methods

D-Deprenyl activity towards GPCR targets was assessed by DiscoverX in CHO-K1 EDG1 β-arrest in EFC cell line utilizing the PathHunter™ technique. Enzyme inhibition by D-deprenyl was identified in the EnzymeProfiling™ screening panel provided by Eurofins Cerep Panlabs. [H3]D-deprenyl binding studies with specific GPCR agonists and enzyme inhibitors at newly identified targets were also performed.

Results

Our investigation revealed that a 10μM concentration of d-deprenyl inhibited MAO-B and MAO-A activity by 99% and 55%, respectively. In addition, a 70% inhibition of angiotens in converting enzyme (ACE) activity in rabbit lung preparations was found. Furthermore, binding studies in rat mitochondrial membrane homogenates confirmed a submicromolar [H3]D-deprenyl competition with a selective MAO-B inhibitor seligiline, but not with the selective MAO-A inhibitor pirlindole mesylate. No evident hits among GPCR targets were identified. However, attention was drawn towards the histamine HRH1 and HRH3 receptors to which d-deprenyl showed a 20% and 42% antagonistic activity.

Conclusions

MAO-B might be a candidate target for D-deprenyl, as many other studies documented higher d-deprenyl uptake in activated astrocytes, non-secreting pituitary adenomas and brown adipose tissue, where MAO-B is over expressed. Moreover, ACE inhibition was shown to hamper down-regulation of transcription factors preventing ROS-mediated cartilage damage.

Modulation of Cervical Facet Joint Nociception and Pain Attenuates Physical and Psychological Features of Chronic Whiplash: A Prospective Study

OBJECTIVE

To investigate changes in clinical (physical and psychological) features of individuals with chronic whiplash-associated disorder who had previously undergone cervical radiofrequency neurotomy at the time point when the effects of radiofrequency neurotomy had dissipated and pain returned.

DESIGN

Prospective cohort observational trial of consecutive patients.

SETTING

Tertiary spinal intervention centre in Calgary, Alberta, Canada.

PATIENTS

A total of 53 consecutive individuals with chronic whiplash-associated disorder.

METHODS

Individuals underwent radiofrequency neurotomy and were assessed before radiofrequency neurotomy, at 1 and 3 months postprocedure, and then after the return of pain (approximately 10 months postprocedure).

MAIN OUTCOME MEASUREMENTS

Quantitative sensory tests (pressure; thermal pain thresholds; brachial plexus provocation test), nociceptive flexion reflex, and motor function (cervical range of movement; craniocervical flexion test) were measured. Self-reported disability, psychological distress, pain catastrophization, and posttraumatic stress disorder symptoms also were measured.

RESULTS

Upon the return of pain after radiofrequency neurotomy, levels of disability increased (P < .0001), and were no different to those before radiofrequency neurotomy (P = .99). There also was a significant deterioration in quantitative sensory testing measures and reduced cervical range of motion after the return of pain (all P < .05); all approaching values were recorded before radiofrequency neurotomy (P > .22). There were no significant changes in pressure hyperalgesia (P > .054) or craniocervical flexion test performance (P > .07) after the return of pain. Psychological distress and pain catastrophizing increased significantly after the return of pain (P < .01), and again were no different than measures taken prior to radiofrequency neurotomy (P > .13). However, there was no difference in number or severity of posttraumatic stress symptoms after the return of pain (P > .30).

CONCLUSIONS

Physical and psychological features of chronic whiplash-associated disorder are modulated dynamically with cervical radiofrequency neurotomy. These findings indicate that peripheral nociception is involved in the manifestations of chronic whiplash-associated disorder in this cohort of individuals.

Symptoms, disabilities, and life satisfaction five years after whiplash injuries

Background Chronic whiplash-associated disorders (WADs) are often associated with social functioning problems and decreased ability to perform previous activities. This may lead to decreased life satisfaction, which is insufficiently studied in the context of whiplash injuries. Symptoms included in chronic WAD are similar to symptoms frequently reported by persons who have sustained mild traumatic brain injury (MTBI)/concussion. In cases of MTBI, the severity and number of symptoms have been suggested to have a diagnostic value. The corresponding importance of symptoms in chronic WAD has not been documented. Most studies of whiplash injuries have focused on neck pain because this is the dominant complaint, while other symptoms are less studied. The frequency of long-term symptoms after whiplash injuries seems to vary. It is difficult to compare the long-term outcome since the follow-up after whiplash injury in most studies has been rather short. Therefore, the primary aim of this investigation was to study neck pain and other symptoms, disability, and life satisfaction five years after whiplash injury in a defined population and geographical area. Methods The study was carried out at a public hospital in northern Sweden and was a cross-sectional survey of patients five years after the injury event in a cohort of whiplash-injured patients. Five years after the emergency department visit, 186 persons aged 18-64 answered questionnaires on symptoms (Rivermead Post-Concussion Symptoms Questionnaire, RPQ), disabilities (Rivermead Head Injury Follow Up Questionnaire, RHFUQ), and life satisfaction (LiSat-11). The answers were compared to those of a comparison cohort. Results The most common symptoms five years after whiplash injury were fatigue (41%), poor memory (39%), and headache (37%). Inability to sustain previous workload (44%) and fatigue at work (43%) were frequently reported disabilities. Only 39% were satisfied with their somatic health and 60% with their psychological health. Compared with healthy controls, the whiplash injured exhibited more symptoms and had lower life satisfaction. Women reported significantly higher pain intensity than men. Few significant differences between women and men regarding the other parameters were found. Conclusions This study shows that five years after a whiplash injury, patients reported symptoms that are typical of mild traumatic brain injury. Further, this study emphasizes the possibility of screening patients with chronic WAD for these symptoms as a complement to the assessment. Implications Untreated symptoms may negatively affect the outcome of pain rehabilitation. This implies that it might be clinically meaningful to quantify symptoms earlier in the rehabilitation process.

Autoradiography screening of potential positron emission tomography tracers for asymptomatic abdominal aortic aneurysms

OBJECTIVE

The aetiology and early pathophysiological mechanisms of aortic aneurysm formation are still unknown and challenging to study in vivo. Positron emission tomography (PET) is a potentially valuable instrument for non-invasive in vivo pathophysiological studies. No specific tracer to identify the pathophysiological process of aneurysmal dilatation is yet available, however. The aim of this study was to explore if different PET tracers could be useful to image aneurysmal disease.

METHODS AND RESULTS

Human aneurysmal aortic tissue, collected during elective resection of abdominal aortic aneurysm (AAA) of asymptomatic patients, was investigated in vitro by means of autoradiography with [(68)Ga]CRP-binder targeting C-reactive protein, [(11)C]DAA1106 targeting translocator protein (18 kDa), [(11)C]D-deprenyl with unknown target receptor, [(11)C]deuterium-L-deprenyl targeting astrocytes, [(18)F]fluciclatide targeting integrin αVβ3, [(68)Ga]IMP461 and bi-specific antibody TF2 052107 targeting carcinoembryonic antigen, [(18)F]F-metomidate targeting mitochondrial cytochrome P-450 species in the adrenal cortex, and [(18)F]vorozole targeting aromatase. Of the investigated tracers, only [(18)F]fluciclatide exhibited specific binding, whereas the other PET tracers failed to show specific uptake in the investigated tissue and are probably not useful for the intended purpose.

CONCLUSION

It seems likely that αVβ3 integrin expression in AAA can be visualized with PET and that the αVβ3 selective tracer, [(18)F]fluciclatide, may be suitable for in vivo molecular imaging of asymptomatic AAA. Additional evaluation of [(18)F]fluciclatide and αVβ3 integrin expression in AAA will be performed in vitro as well as in vivo.

A 15-year follow-up of temporomandibular joint symptoms and magnetic resonance imaging findings in whiplash patients: a prospective, controlled study

OBJECTIVE

This study aimed to determine the incidence, prevalence, and progression of temporomandibular joint (TMJ) magnetic resonance (MR) imaging findings and symptoms in patients over a 15-year period after whiplash trauma, compared with control participants.

STUDY DESIGN

Sixty consecutive patients were enrolled directly after whiplash trauma. The study protocol included TMJ MR imaging at inception and 15 years later, as well as a questionnaire and interview at inception, at 1-year follow-up, and at 15-year follow-up. Fifty-seven patients (95%) participated in all three examinations (85% for MR imaging). Fifty matched control participants were examined.

RESULTS

The prevalence of TMJ symptoms was significantly higher in patients compared with control participants at inception (44% vs 20%, P = .0055) and remained significantly higher throughout the study period. The prevalence of disk displacement did not differ significantly between groups either at inception (63% vs 53%) or at 15-year follow-up (63% vs 55%).

CONCLUSIONS

This prospective 15-year follow-up suggests that the development of TMJ symptoms, both immediate and delayed, is common in whiplash patients.

Completing the Pain Circuit: Recent Advances in Imaging Pain and Inflammation beyond the Central Nervous System

This review describes some of the recent developments in imaging aspects of pain in the periphery. It is now possible to image nerves in the cornea non-invasively, to image receptor level expression and inflammatory processes in injured tissue, to image nerves and alterations in nerve properties, to image astrocyte and glial roles in neuroinflammatory processes, and to image pain conduction functionally in the trigeminal ganglion. These advances will ultimately allow us to describe the pain pathway, from injury site to behavioral consequence, in a quantitative manner. Such a development could lead to diagnostics determining the source of pain (peripheral or central), objective monitoring of treatment progression, and, hopefully, objective biomarkers of pain.

PET-scan shows peripherally increased neurokinin 1 receptor availability in chronic tennis elbow: visualizing neurogenic inflammation?

In response to pain, neurokinin 1 (NK1) receptor availability is altered in the central nervous system. The NK1 receptor and its primary agonist, substance P, also play a crucial role in peripheral tissue in response to pain, as part of neurogenic inflammation. However, little is known about alterations in NK1 receptor availability in peripheral tissue in chronic pain conditions and very few studies have been performed on human beings. Ten subjects with chronic tennis elbow were therefore examined by positron emission tomography (PET) with the NK1 specific radioligand [(11)C]GR205171 before and after treatment with graded exercise. The radioligand signal intensity was higher in the affected arm as compared with the unaffected arm, measured as differences between the arms in volume of voxels and signal intensity of this volume above a reference threshold set as 2.5 SD above mean signal intensity of the unaffected arm before treatment. In the eight subjects examined after treatment, pain ratings decreased in all subjects but signal intensity decreased in five and increased in three. In conclusion, NK1 receptors may be activated, or up-regulated in the peripheral, painful tissue of a chronic pain condition. This up-regulation does, however, have moderate correlation to pain ratings. The increased NK1 receptor availability is interpreted as part of ongoing neurogenic inflammation and may have correlation to the pathogenesis of chronic tennis elbow.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00888225 http://clinicaltrials.gov/

New objective findings after whiplash injuries: High blood flow in painful cervical soft tissue: An ultrasound pilot study

Background

The presence of high blood flow in the structurally abnormal and painful regions of tendinosis, but not in the normal pain-free tendons, was recently confirmed by colour Doppler (CD) ultrasound (US). Biopsies from the regions with high blood flow demonstrated the presence of sympathetic and sensitive nerve fibres juxtapositioned to neovessels. Grey-scale US and CD are reliable methods used to evaluate structural homogeneity, thickness, and blood flow in the peripheral tendons. The aim of this study was to utilize CD to qualitatively evaluate for the presence of abnormal high blood flow in paravertebral tissues after whiplash injuries in patients with chronic neck pain.

Methods

Twenty patients with chronic neck pain after whiplash-associated disorder (WAD) and 20 pain-free control subjects were included in the study. The same experienced radiologist performed all grey-scale US and CD examinations.

Results

More regions with high blood flow were observed in the patient group than in the control group. At all levels, the high blood flow pattern was detected at the enthesis of the spinous processes and bilaterally juxtapositioned to the facet joints.

Conclusion

All regions identified by the patients as painful and tender corresponded to the positive high blood flow found during the CD examination.

Implications

These findings document increased blood-flow/neovascularisation at insertions of neck muscles which may indicate that there are pathological neovascularisation with accomanying pain-and sympathetic nerves, similar to what has been found in Achilles-tendinosis. These findings promise that similar treatments that now is successful with Achilles tendinosis, may be effective in the WAD-painful muscle insertions of the neck.

Subgroups based on thermal and pressure pain thresholds in women with chronic whiplash display differences in clinical presentation - an explorative study

PURPOSE

To investigate the presence of subgroups in chronic whiplash-associated disorders (WAD) based on pain thresholds for pressure (PPT), cold (CPT), and heat (HPT) and to compare these subgroups with respect to symptomatology, disability, and health aspects.

METHODS

Two groups of female subjects - patients with chronic WAD (n = 28) and healthy controls (CON; n = 29) - were investigated. Quantitative sensory testing (QST) for thermal thresholds and algometry for PPT at four sites in the body (over the trapezius and tibialis anterior bilaterally) were determined. Habitual pain intensities, psychological strain, disability, and health aspects were registered using a questionnaire.

RESULTS

A CLUSTER ANALYSIS BASED ON PPT, CPT, AND HPT IDENTIFIED TWO SUBGROUPS OF CHRONIC WAD: one sensitive subgroup (s-WAD; n = 21), and one less sensitive subgroup (ls-WAD; n = 6). S-WAD displayed widespread hyperalgesia, whereas ls-WAD had localized hyperalgesia in the neck area, with tendencies to supernormal values in remote areas of the body. Generally, s-WAD had a significantly worse situation than the CON with respect to symptomatology, disability, and health aspects. The ls-WAD group was intermediary between s-WAD and CON in these aspects.

CONCLUSION

Different explanations, eg, severity of the pain condition per se, etiological factors, and pre-trauma differences in pain sensitivity, may exist for the differences in pain thresholds between the two subgroups. Future research should investigate the role of pain thresholds in the chronic stage to determine the efficacy of treatment interventions.

The risk assessment score in acute whiplash injury predicts outcome and reflects biopsychosocial factors

STUDY DESIGN

One-year prospective study of 141 acute whiplash patients (WLP) and 40 acute ankle-injured controls.

OBJECTIVE

This study investigates a priori determined potential risk factors to develop a risk assessment tool, for which the expediency was examined.

SUMMARY OF BACKGROUND DATA

The whiplash-associated disorders (WAD) grading system that emerged from The Quebec Task-Force-on-Whiplash has been of limited value for predicting work-related recovery and for explaining biopsychosocial disability after whiplash and new predictive factors, for example, risk criteria that comprehensively differentiate acute WLP in a biopsychosocial manner are needed.

METHODS

Consecutively, 141 acute WLP and 40 ankle-injured recruited from emergency units were examined after 1 week, 1, 3, 6, and 12 months obtaining neck/head visual analog scale score, number of nonpainful complaints, epidemiological, social, psychological data and neurological examination, active neck mobility, and furthermore muscle tenderness and pain response, and strength and duration of neck muscles. Risk factors derived (reduced cervical range of motion, intense neck pain/headache, multiple nonpain complaints) were applied in a risk assessment score and divided into seven risk strata.

RESULTS

A receiver operating characteristics curve for the Risk Assessment Score and 1-year work disability showed an area of 0.90. Risk strata and number of sick days showed a log-linear relationship. In stratum 1 full recovery was encountered, but for high-risk patients in stratum 6 only 50% and 7 only 20% had returned to work after 1 year (P < 5.4 × 10). Strength measures, psychophysical pain measurements, and psychological and social data (reported elsewhere) showed significant relation to risk strata.

CONCLUSION

The Risk Assessment score is suggested as a valuable tool for grading WLP early after injury. It has reasonable screening power for encountering work disability and reflects the biopsychosocial nature of whiplash injuries.

Does the region of pain influence the presence of sensorimotor disturbances in neck pain disorders?

Impairments in sensorimotor control have been demonstrated in neck pain disorders. However, there are more anatomical and neurophysiological connections between the sensorimotor control system and the upper cervical region and thus potential for greater disturbances in those with upper region pain. This study investigated whether sensorimotor impairment was greater in those suffering pain from the upper rather than lower cervical spine region, taking the onset of pain into account. Sixty-four subjects with persistent neck pain were divided into 4 groups -upper and lower region non-traumatic and upper and lower region traumatic. Cervical Joint Position Error (JPE), smooth pursuit neck torsion (SPNT) and standing balance tests were compared between groups. The lower non-traumatic group demonstrated significantly less (p < 0.03) deficit in SPNT compared to all other groups as well as less total energy of sway on the eyes open balance tests (p < 0.05) compared to both traumatic neck pain groups. The upper traumatic group demonstrated significantly greater JPE following rotation to the right (p < 0.04) when compared to both lower groups. Less sensorimotor dysfunction appears to occur in those with lower compared to upper cervical region pain, although this depends on whether trauma is involved in the onset of pain.