Functional pain disorders - more than nociplastic pain

Repetitive Transcranial Magnetic Stimulation in Fibromyalgia: Exploring the Necessity of Neuronavigation for Targeting New Brain Regions

Fibromyalgia and osteoarthritis are among the most prevalent rheumatic conditions worldwide. Nonpharmacological interventions have gained scientific endorsements as the preferred initial treatments before resorting to pharmacological modalities. Repetitive transcranial magnetic stimulation (rTMS) is among the most widely researched neuromodulation techniques, though it has not yet been officially recommended for fibromyalgia. This review aims to summarize the current evidence supporting rTMS for treating various fibromyalgia symptoms. Recent findings: High-frequency rTMS directed at the primary motor cortex (M1) has the strongest support in the literature for reducing pain intensity, with new research examining its long-term effectiveness. Nonetheless, some individuals may not respond to M1-targeted rTMS, and symptoms beyond pain can be prominent. Ongoing research aims to improve the efficacy of rTMS by exploring new brain targets, using innovative stimulation parameters, incorporating neuronavigation, and better identifying patients likely to benefit from this treatment. Summary: Noninvasive brain stimulation with rTMS over M1 is a well-tolerated treatment that can improve chronic pain and overall quality of life in fibromyalgia patients. However, the data are highly heterogeneous, with a limited level of evidence, posing a significant challenge to the inclusion of rTMS in official treatment guidelines. Research is ongoing to enhance its effectiveness, with future perspectives exploring its impact by targeting additional areas of the brain such as the medial prefrontal cortex, anterior cingulate cortex, and inferior parietal lobe, as well as selecting the right patients who could benefit from this treatment.

[Understanding and explaining functional movement disorders]

Functional movement disorders are not uncommon in neurological consultations, hospitals and emergency departments. Although the disorder can usually be recognized clinically, the communication of the diagnosis is often unsatisfactory. Those affected are indirectly accused of a lack of insight or openness but it is often the doctors who fail to formulate a coherent and comprehensible explanation of the underlying disorder. In this review an integrative model for the development of functional movement disorders is presented, which places the motor (and nonmotor) symptoms in a neuroscientific light. In addition, explanations and metaphors are presented that have proven helpful in conveying an understanding of the disorder.

Abnormalities of the Descending Inhibitory Nociceptive Pathway in Functional Motor Disorders

BACKGROUND

Pain is a common disabling non-motor symptom affecting patients with functional motor disorders (FMD).

OBJECTIVE

We aimed to explore ascending and descending nociceptive pathways with laser evoked potentials (LEPs) in FMD.

METHODS

We studied a "bottom-up and top-down" noxious paradigm applying a conditioned pain modulation (CPM) protocol and recorded N2/P2 amplitude in 21 FMD and 20 controls following stimulation of both right arm and leg at baseline (BS) (bottom-up), during heterotopic noxious conditioning stimulation (HNCS) with ice test (top-down) and post-HNCS.

RESULTS

We found a normal ascending pathway, but reduced CPM response (lower reduction of the N2/P2 amplitude) in FMD patients, by stimulating both upper and lower limbs. The N2/P2 amplitude ratio*100 (between the HNCS and BS) was significantly higher in patients with FMD than HC.

CONCLUSIONS

Our results suggest that pain in FMD possibly reflects a descending pain inhibitory control impairment, therefore, providing a novel venue to explore the pathophysiology of pain in FMD. © 2024 International Parkinson and Movement Disorder Society.

Sensory profiles and their role in the persistence of central sensitization symptoms in low back pain. A prospective cohort study

INTRODUCTION

Acute lower back pain can lead to neuroplastic changes in the central nervous system, and symptoms of central sensitization after 12 weeks. While sensory sensitivity has been shown to predict symptoms of central sensitization, trait sensory profiles may be prognostic in the persistence of central sensitization symptoms in low back pain over time.

OBJECTIVE

To examine sensory profiles as prognostic symptoms of central sensitization in people with acute low back pain.

METHODS

A longitudinal type 2 prognostic factor research study was performed according to the PROGRESS framework. Baseline and 12-week follow-up measures were taken using the Adolescent/Adult Sensory Profile and the Central Sensitization Inventory measures. Study participants were consecutively included from primary care physiotherapy practices. Univariable, and multivariable regression analyses were performed to adjust sensory profiles based on previous history of low back pain, baseline Central Sensitization Inventory scores, level of pain, disability, age, and duration of low back pain.

RESULTS

After adjustment, the sensory profiles of Low Registration B = 0.44, 95%CI (0.18, 0.70), Sensation Seeking B = 0.38, 95%CI (0.19, 0.57), Sensory Sensitive B = 0.49, 95%CI (0.25, 0.74), Sensation Avoiding B = 0.40, 95% CI (0.15, 0.65) was significantly associated with the persistence of central sensitization symptoms (N = 103).

CONCLUSION

Sensory profiles may predict symptoms of central sensitization after 12 weeks in people with acute low back pain.

Occupational orthopedic problems and its relation to personal radiation protection in interventional radiology

PURPOSE

Several studies report occupational orthopedic problems among interventional cardiologists. These health problems are usually multifactorial. However, the personal protective equipment used should play a major role. An online survey was conducted to determine the frequency of such health problems among interventional radiologists and to correlate them with the use of personal radiation protective clothing.

MATERIAL AND METHODS

An anonymous online survey that comprised of 17 questions was sent via e-mail to 1427 members of the German Society for Interventional Radiology (DeGIR) in Germany, Austria and Switzerland. The questions were focused on interventional workload, the use of personal radiation protection apparel and orthopedic problems. Given the different scale levels, the associations between the variables were analyzed using different statistical methods. A significance level of p < 0.05 was chosen.

RESULTS

There were 221 survey responders (15.5% response rate). About half of responders (47.7%) suffered from more than five episodes of orthopedic problems during their interventional career. Lumbar spine was involved in 81.7% of these cases, cervical spine in 32.8%, shoulder in 28.5% and knee in 24.7%. Because of orthopedic problems, 16.1% of the responders had to reduce and 2.7% had to stop their interventional practice. The number of affected body regions correlates with the fit of the radiation protection means (p < 0.05, r = 0.135) and the reduction of activity as an interventional radiologist (p < 0.05, r = -0.148).

CONCLUSION

Overall, the survey reveals widespread orthopedic problems at several body regions among interventional radiologists, associated with the fit of radiation protection systems, among other factors. A connection between the orthopaedic complaints and the radiation protection system used could not be established.

Pain and functional neurological disorder: a systematic review and meta-analysis

BACKGROUND

Functional neurological disorder (FND) is characterised by neurological symptoms, such as seizures and abnormal movements. Despite its significance to patients, the clinical features of chronic pain in people with FND, and of FND in people with chronic pain, have not been comprehensively studied.

METHODS

We systematically reviewed PubMed, Embase and PsycINFO for studies of chronic pain in adults with FND and FND in patients with chronic pain. We described the proportions of patients reporting pain, pain rating and timing, pain-related diagnoses and responsiveness to treatment. We performed random effects meta-analyses of the proportions of patients with FND who reported pain or were diagnosed with pain-related disorders.

RESULTS

Seven hundred and fifteen articles were screened and 64 were included in the analysis. Eight case-control studies of 3476 patients described pain symptoms in a higher proportion of patients with FND than controls with other neurological disorders. A random effects model of 30 cohorts found that an estimated 55% (95% CI 46% to 64%) of 4272 patients with FND reported pain. Random effects models estimated diagnoses of complex regional pain syndrome in 22% (95% CI 6% to 39%) of patients, irritable bowel syndrome in 16% (95% CI 9% to 24%) and fibromyalgia in 10% (95% CI 8% to 13%). Five studies of FND diagnoses among 361 patients with chronic pain were identified. Most interventions for FND did not ameliorate pain, even when other symptoms improved.

CONCLUSIONS

Pain symptoms and pain-related diagnoses are common in FND. Classification systems and treatments should routinely consider pain as a comorbidity in patients with FND.

Is fibromyalgia an autoimmune disorder?

Fibromyalgia (FM) is a multifactorial syndrome which includes not only widespread pain and stiffness, now recognized as major symptoms, but also numerous other somatic, emotional, and neuropsychic manifestation. The lack of specific validated biological and instrumental biomarkers has made FM a condition of unexplained medical significance, and its pathophysiology remains controversial and subject to debate. The current hypothesis regarding the pathogenesis of FM proposes that its development is influenced by various mechanism, including genetic predisposition, stressful life events, inflammatory processes, and cognitive-emotional factors. However, despite the extensive research conducted to date, the available data do not provide a clear understanding of the pathogenesis of FM. In this article, we report the opposing viewpoints of two leading experts who debate the question of whether FM is an autoimmune disease, based on scientific data regarding this condition. Both perspectives are discussed and the latest evidence on the pathophysiology of FM is reported to provide a comprehensive understanding of this complex syndrome.

Not a general, symptom-unspecific, transdiagnostic marker for functional symptoms: sensorimotor processing of head control is intact in chronic pain

Introduction

Functional disorders are prevalent in all medical fields and pose a tremendous public health problem, with pain being one of the most common functional symptoms. Understanding the underlying, potentially unifying mechanism in functional (pain) disorders is instrumental in facilitating timely diagnosis, stigma reduction, and adequate treatment options. Neuroscientific models of perception suggest that functional symptoms arise due to dysregulated sensorimotor processing in the central nervous system, with brain-based predictions dominating the eventual percept. Experimental evidence for this transdiagnostic mechanism has been established in various functional symptoms. The goal of the current study was to investigate whether erroneous sensorimotor processing is an underlying transdiagnostic mechanism in chronic (functional) pain.

Method

A total of 13 patients with chronic (functional) pain [three patients with chronic (functional) pain disorder, F45.40, ICD-10; 10 patients with chronic pain disorder with somatic and psychological factors, F45.41, ICD-10]; and 15 healthy controls performed large combined eye-head gaze shifts toward visual targets, naturally and with increased head moment of inertia. We simultaneously measured participants' eye and head movements to assess head oscillations at the end of the gaze shift, which are an established indicator of (transdiagnostic) sensorimotor processing deficits of head control.

Results

Using a Bayesian analysis protocol, we found that patients with chronic (functional) pain and control participants stabilized their heads equally well (Bayes Factor 01 = 3.7, Bayes Factor exclusion = 5.23; corresponding to substantial evidence) during all sessions of the experiment.

Conclusion

Our results suggest that patients with chronic (functional) pain do not show measurable symptom-unspecific sensorimotor processing deficits. We discuss outcome parameter choice, organ system specificity, and selection of patient diagnoses as possible reasons for this result and recommend future avenues for research.

Relationship between latent trigger points, lower limb asymmetry and muscle fatigue in elite short-track athletes

BACKGROUND

Short-track speed skating movement involves asymmetric overloading of the lower left side of the body. The gluteus maximus fatigue limits the physical and mental athletic capacity to perform set tasks. A possible link between the presence of latent trigger points (LTrPs) and muscle fatigue development/persistence has been posited. The aim of the study was to determine whether elite short-track speed skating can result in the impairment of the musculoskeletal system of the lower limbs.

METHODS

Elite short-track athletes as the experimental group (EXP) = 9, 19.5 ± 1.8 years, and healthy subjects as the control group (CON) = 18, 20.8 ± 1.2 years, were tested for: (i) lower limb loading asymmetry using ground reaction force (GRF) measurements during quiet standing, (ii) gluteus maximus fatigue measured with surface electromyography (sEMG) during the Biering-Sorensen test, and (iii) LTrPs presence in the 14 examined muscles of the pelvic girdle and lower limbs.

RESULTS

There were between-group differences in the number of LTrPs, with the EXP group (left lower limb (LLL) n = 18, right lower limb (RLL) n = 9) showing more LTrPs compared to the CON group (LLL n = 2, RLL n = 1), (p < 0.001), and within-group differences in the EXP group only (p < 0.001). There were also significant differences in muscle fatigue for the left side (p < 0.001) both between the groups and within the EXP group (p ≤ 0.001). The vertical ground reaction force (GRF) measurement showed a loading rate of 2% (p = 0.013) in the athletes' LLL exclusively.

CONCLUSIONS

The study confirmed an increased prevalence of LTrPs, increased muscle fatigue and left-sided limb load asymmetry in elite short-track athletes.

TRIAL REGISTRATION

The study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of the Poznan University of Medical Sciences (Resolution No 110/22 of 10 March 2022).

TRIAL REGISTRATION

20/07/2022, Trial Id: ACTRN12622001016729.

What Do We Know about Nociplastic Pain?

Nociplastic pain is a recently distinguished type of pain, distinct from neuropathic and nociceptive pain, and is well described in the literature. It is often mistaken for central sensitization. Pathophysiology has not been clearly established with regard to alteration of the concentration of spinal fluid elements, the structure of the white and gray matter of the brain, and psychological aspects. Many different diagnostic tools, i.e., the painDETECT and Douleur Neuropathique 4 questionnaires, have been developed to diagnose neuropathic pain, but they can also be applied for nociplastic pain; however, more standardized instruments are still needed in order to assess its occurrence and clinical presentation. Numerous studies have shown that nociplastic pain is present in many different diseases such as fibromyalgia, complex regional pain syndrome type 1, and irritable bowel syndrome. Current pharmacological and nonpharmacological treatments for nociceptive and neuropathic pain are not entirely suitable for treating nociplastic pain. There is an ongoing effort to establish the most efficient way to manage it. The significance of this field has led to several clinical trials being carried out in a short time. The aim of this narrative review was to discuss the currently available evidence on pathophysiology, associated diseases, treatment possibilities, and clinical trials. It is important that physicians widely discuss and acknowledge this relatively new concept in order to provide optimized pain control for patients.

The Neurophysiological Lesion: A Scoping Review

Objective

The purpose of this study was to examine the extent of the literature on the neurophysiological lesion as referenced in functional neurology.

Methods

A literature search was performed within the period from 2010 to March 2021. Search terms included central sensitization, central sensitivity syndrome, nociplastic pain, cold hyperalgesia, heat hyperalgesia, mechanical hyperalgesia, dynamic mechanical allodynia, temporal summation, spatial summation, and descending inhibition. A qualitative synthesis summarized the research findings, including clinical conditions and effect of spinal manipulation.

Results

There were 30 studies, which included 7 high-level studies (meta-analysis or systematic reviews), 22 randomized controlled studies, and 1 scoping review. The findings suggest the existence of the changes in the central integrated state of a population of neurons with various disorders, experimentally induced stimulation, and treatment. The current literature suggests plasticity of the central integrative state (CIS) with the onset of pathologies and the changes in the CIS with different conservative nonpharmacologic treatments.

Conclusions

This review suggests changes in the resting state of the CIS of a population of neurons that exist in the physiologic lesion may change in response to various therapies, including manipulative therapy. The findings from this review provide support of the hypothesis that nonpharmacologic conservative care may affect the neurophysiological lesion. However, studies were heterogeneous and evidence was lacking in the translation of targeting the therapies to distinct neuronal areas for clinical outcomes to treat specific disease states.

The relationship of centralized pain in fibromyalgia syndrome with sleep, fatigue and quality of life

OBJECTIVES

The aim of this study was to examine the central role of pain in patients' lives by evaluating the relationship between the centralization of pain and clinical and functional parameters.

METHODS

Adult patients aged 18-70 diagnosed with FM were included in the study. The Fibromyalgia Impact Questionnaire (FIQ) was used to assess the severity of FM, and the Centrality of Pain Scale (COPS) was used to assess pain centralization. The European Quality of Life Scale 5 Dimension (EQ-5D) assessed quality of life, the Jenkins Sleep Scale (JSS-TR) sleep, and the Beck Depression Inventory (BDI) depression.Spearman correlation coefficient (rho) was used to examine the relationship between COPS scores and other parameters, and p < .05 was considered significant.

RESULTS

One hundred and sixty-five FM patients (143 female) were included in the study. The mean age of the patients was 43.7 ± 10.1 years, and the mean disease duration was 4.8 ± 7.8 years. Centrality of pain was found to be related to FIQ (rho = 0.59, p = .0005), EQ-5D (rho = -0.53, p = .0005), JSS-TR (rho = 0.43, p = .0005), and BDI (rho = 0.41, p = .0005).

CONCLUSION

Centralization of pain in FM was more common in patients with high disease severity, poor quality of life, and sleep and depression problems.

Functional neurological symptoms are a frequent and relevant comorbidity in patients with multiple sclerosis

Introduction

Functional neurological symptoms (FNS) in multiple sclerosis (MS) have shown to be underinvestigated even though neurological diseases such as MS represent a risk factor for developing FNS. Comorbidity of FNS and MS can produce high personal and social costs since FNS patients have high healthcare utilization costs and a quality of life at least as impaired as in patients with disorders with underlying structural pathology. This study aims to assess comorbid FNS in patients with MS (pwMS) and investigate whether FNS in pwMS are associated with poorer health-related quality of life and work ability.

Methods

Newly admitted patients (234) with MS were studied during their stay at Kliniken Schmieder, a neurological rehabilitation clinic in Konstanz, Germany. The degree to which the overall clinical picture was explained by MS pathology was rated by neurologists and allied health practitioners on a five-point Likert scale. Additionally, neurologists rated each symptom reported by the patients. Health-related quality of life was assessed using a self-report questionnaire and work ability was assessed using the mean number of hours worked per day and information regarding disability pension as reported by patients.

Results

In 55.1% of cases, the clinical picture was completely explained by structural pathology due to MS. 17.1% of pwMS presented an overall clinical picture half or less of which could be explained by underlying structural pathology. PwMS with a higher comorbid FNS burden had a lower health-related quality of life and reported fewer working hours per day than pwMS with symptoms explained by structural pathology. Furthermore, pwMS with a full disability pension had a higher comorbid FNS burden than pwMS with no or partial disability pension.

Discussion

These results show that FNS should be addressed diagnostically and therapeutically since such symptoms are an important comorbidity in MS that is related to poorer health-related quality of life and lower work ability.

Modern Principles of Diagnosis and Treatment in Complex Regional Pain Syndrome

BACKGROUND

Background: Complex regional pain syndrome (CRPS) is a relatively common complication, occurring in 5% of cases after injury or surgery, particularly in the limbs. The incidence of CPRS is around 5-26/100 000. The latest revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-11) now categorizes CRPS as a primary pain condition of multifactorial origin, rather than a disease of the skeletal system or the autonomic nervous system.

METHODS

Method: Based on a selective search of the literature, we summarize current principles for the diagnosis and treatment of CRPS.

RESULTS

Results: Regional findings in CRPS are accompanied by systemic symptoms, especially by neurocognitive disorders of body perception and of symptom processing. The therapeutic focus is shifting from predominantly passive peripheral measures to early active treatments acting both centrally and peripherally. The treatment is centered on physiotherapy and occupational therapy to improve sensory perception, strength, (fine) motor skills, and sensorimotor integration/ body perception. This is supported by stepped psychological interventions to reduce anxiety and avoidance behavior, medication to decrease inflammation and pain, passive physical measures for reduction of edema and of pain, and medical aids to improve functioning in daily life. Interventional procedures should be limited to exceptional cases and only be performed in specialized centers. Spinal cord and dorsal root ganglion stimulation, respectively, are the interventions with the best evidence.

CONCLUSION

Conclusion: The modern principles for the diagnosis and treatment of CRPS consider both, physiological and psychological mechanisms, with the primary goal of restoring function and participation. More research is needed to strengthen the evidence base in this field.

Migraine in the context of chronic primary pain, chronic overlapping pain disorders, and functional somatic disorders: A narrative review

OBJECTIVE

To contextualize migraine as the most common primary headache disorder in relation to other chronic primary pain and non-pain functional somatic and mental conditions.

BACKGROUND

Migraine is increasingly understood as a sensory processing disorder within a broader spectrum of symptom disorders. This has implications for diagnosis and treatment.

METHOD

Narrative review based on a search of the literature of the last 15 years on the overlap of migraine with other symptom disorders.

RESULTS

Migraine as the prototypical primary headache disorder not only comprises many non-headache symptoms in itself, it also shows high comorbidity with other chronic pain and non-pain conditions (e.g., fibromyalgia syndrome, irritable bowel syndrome, functional non-epileptic seizures, depression, anxiety, and posttraumatic stress disorder). Such "symptom disorders" share several etiological factors (e.g., female preponderance, psychological vulnerability) and psychophysiological mechanisms (e.g., altered sensory processing, pain expectancy). These facts are acknowledged by several recent integrative conceptualizations such as chronic primary pain, chronic overlapping pain conditions, or functional somatic disorders. Accordingly, migraine management increasingly addresses the total symptom burden and individual contributors to symptom experience, and thus incorporates centrally acting pharmacological and non-pharmacological, that is, psychological and behavioral, treatment approaches.

CONCLUSIONS

Migraine and also other primary headache disorders should be seen as particular phenotypes within a broader spectrum of symptom perception and processing disorders that require integrative diagnostics and treatment. A harmonization of classifications and better interdisciplinary collaboration are desirable.

A new way of thinking about pains

ABSTRACT

The traditional construct of acute pain vs chronic pain is arbitrary and obscures fundamental differences in clinical pain phenomena. A more powerful dichotomy between peripherally generated pain and centrally maintained pains can facilitate advances in both pain research and clinical care. We should abandon the temporally based pain classification scheme because it does not accurately reflect the underlying principles inherent in the phenomena of pain.

Understanding chronic ocular surface pain: An unmet need for targeted drug therapy

Chronic ocular surface pain (COSP) may be defined as a feeling of pain, perceived as originating from the ocular surface, that persists for >3 months. COSP is a complex multifactorial condition associated with several risk factors that may significantly interfere with an individual's daily activities, resulting in poor quality of life (QoL). COSP is also likely to have a high burden on patients with substantial implications on global healthcare costs. While patients may use varied terminology to describe symptoms of COSP, any ocular surface damage in the ocular sensory apparatus (nociceptive, neuropathic, inflammatory, or combination thereof) resulting in low tear production, chronic inflammation, or nerve abnormalities (functional and/or morphological), is typically associated with COSP. Considering the heterogeneity of this condition, it is highly recommended that advanced multimodal diagnostic tools are utilized to help discern the nociceptive and neuropathic pain pathways in order to provide targeted treatment and effective clinical management. The current article provides an overview of COSP, including its multifactorial pathophysiology, etiology, prevalence, clinical presentation, impact on QoL, diagnosis, current management, and unmet medical needs.

Chronic Pain in Musculoskeletal Diseases: Do You Know Your Enemy?

Musculoskeletal pain is a condition that characterises several diseases and represents a constantly growing issue with enormous socio-economic burdens, highlighting the importance of developing treatment algorithms appropriate to the patient’s needs and effective management strategies. Indeed, the algic condition must be assessed and treated independently of the underlying pathological process since it has an extremely negative impact on the emotional and psychic aspects of the individual, leading to isolation and depression. A full understanding of the pathophysiological mechanisms involved in nociceptive stimulation and central sensitization is an important step in improving approaches to musculoskeletal pain. In this context, the bidirectional relationship between immune cells and neurons involved in nociception could represent a key point in the understanding of these mechanisms. Therefore, we provide an updated overview of the magnitude of the musculoskeletal pain problem, in terms of prevalence and costs, and summarise the role of the most important molecular players involved in the development and maintenance of pain. Finally, based on the pathophysiological mechanisms, we propose a model, called the “musculoskeletal pain cycle”, which could be a useful tool to counteract resignation to the algic condition and provide a starting point for developing a treatment algorithm for the patient with musculoskeletal pain.

Beyond the Raskin Protocol: Ketamine, Lidocaine, and Other Therapies for Refractory Chronic Migraine

PURPOSE OF REVIEW

The purpose of this review is to discuss the available evidence and therapeutic considerations for intravenous drug therapy for refractory chronic migraine.

RECENT FINDINGS

In carefully monitored settings, the inpatient administration of intravenous lidocaine and ketamine can be successful in treating refractory chronic migraine. Many patients with refractory chronic migraine have experienced treatment failure with the Raskin protocol. The use of aggressive inpatient infusion therapy consisting of intravenous lidocaine or ketamine, along with other adjunctive medications, has become increasingly common for these patients when all other treatments have failed. There is a clear need for prospective studies in this population comprised of patients who have largely been excluded from other studies.

Ketamine in the Past, Present, and Future: Mechanisms, Metabolites, and Toxicity

PURPOSE OF REVIEW

While ketamine's analgesia has mostly been attributed to antagonism of N-methyl-D-aspartate receptors, evidence suggests multiple other pathways are involved in its antidepressant and possibly analgesic activity. These mechanisms and ketamine's role in the nociplastic pain paradigm are discussed. Animal studies demonstrating ketamine's neurotoxicity have unclear human translatability and findings from key rodent and human studies are presented.

RECENT FINDINGS

Ketamine's metabolites, and (2R,6R)-hydroxynorketamine in particular, may play a greater role in its clinical activity than previously believed. The activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and the mammalian target of rapamycin by ketamine are mechanisms that are still being elucidated. Ketamine might work best in nociplastic pain, which involves altered pain processing. While much is known about ketamine, new studies will continue to define its role in clinical medicine. Evidence supporting ketamine's neurotoxicity in humans is lacking and should not impede future ketamine clinical trials.

[Endometriosis and chronic overlapping pain conditions]

BACKGROUND

The concept of chronic overlapping pain conditions (COPC) is relatively unknown in German pain medicine.

AIMS

Definition, prevalence, shared etiological and pathophysiological mechanisms of COPC. Summary of recommendations of the interdisciplinary S2k guidelines on diagnostics and treatment of endometriosis relevant for pain physicians.

METHODS

Selective search of literature in PubMed and selection of recommendations of the S2k guidelines on diagnostics and treatment of endometriosis.

RESULTS

According to the US National Institutes of Health, COPCs comprise chronic fatigue syndrome, chronic (unspecific) low back pain, chronic tension headache, endometriosis, fibromyalgia syndrome, migraine, painful bladder syndrome, temporomandibular disorder and vulvodynia. Shared etiological factors are family aggregation, childhood adversities and major or traumatic life events. A major shared pathophysiological mechanism is altered processing of stimuli in the central nervous system. Patients with endometriosis should be screened for other chronic pain conditions and psychological distress. The physical examination should check for local (myofascial trigger points) and generalized signs of hyperalgesia and allodynia indicating central sensitization. In cases of endometriosis with COPCs repeated surgery for pain relief should be avoided. Amitriptyline and duloxetine can be considered as pharmacological treatment options.

DISCUSSION

Pain physicians can play a role in the management of patients with endometriosis and COPCs. A multimodal therapy should include physiotherapy and pain-related psychological treatment and possibly centrally acting pain modulation medication.