Application of a Clinical Approach to Diagnosing Primary Pain: Prevalence and Correlates of Primary Back and Neck Pain in a Community Physiatry Clinic

Chronic back or neck pain (CBNP) can be primary (nociplastic or neuroplastic; without clear peripheral etiology) or secondary (to nociceptive or neuropathic causes). Expanding on available models of nociplastic pain, we developed a clinic-ready approach to diagnose primary/nociplastic pain: first, a standard physical exam and review of imaging to rule out secondary pain; and second, a detailed history of symptom presentation to rule in primary pain. We trained a physician who evaluated 222 patients (73.9% female, age M = 59.6) with CBNP; patients separately completed pain and psychosocial questionnaires. We estimated the prevalence of primary CBNP and explored biomedical, imaging, and psychological correlates of primary CBNP. Although almost all patients (97.7%) had at least 1 spinal anomaly on imaging, the diagnostic approach estimated that 88.3% of patients had primary pain, 5.0% had secondary pain, and 6.8% had mixed pain. Patients with primary pain were more likely than the other 2 groups of patients (combined as "non-primary pain") to report certain functional conditions, central sensitization, and features such as sensitivity to light touch, spreading pain, and pain worsening with stress; however, no difference was detected in depression, anxiety, and pain catastrophizing between those with primary and nonprimary pain. These findings are consistent with prior estimates that 85 to 90% of CBNP is "nonspecific." Further research is needed to validate and perhaps refine this diagnostic approach, which holds the potential for better outcomes if patients are offered treatments targeted to primary pain, such as pain neuroscience education and several emerging psychological therapies. PERSPECTIVE: We developed an approach to diagnose chronic primary pain, which was applied in a physiatry clinic to 222 patients with CBNP. Most patients (88.3%) had primary pain, despite almost universal anomalies on spinal imaging. This diagnostic approach can guide educational and psychological treatments tailored for primary pain.

Low-Frequency Stimulation of Trpv1-Lineage Peripheral Afferents Potentiates the Excitability of Spino-Periaqueductal Gray Projection Neurons

High-threshold dorsal root ganglion (HT DRG) neurons fire at low frequencies during inflammatory injury, and low-frequency stimulation (LFS) of HT DRG neurons selectively potentiates excitatory synapses onto spinal neurons projecting to the periaqueductal gray (spino-PAG). Here, in male and female mice, we have identified an underlying peripheral sensory population driving this plasticity and its effects on the output of spino-PAG neurons. We provide the first evidence that Trpv1-lineage sensory neurons predominantly induce burst firing, a unique mode of neuronal activity, in lamina I spino-PAG projection neurons. We modeled inflammatory injury by optogenetically stimulating Trpv1+ primary afferents at 2 Hz for 2 min (LFS), as peripheral inflammation induces 1-2 Hz firing in high-threshold C fibers. LFS of Trpv1+ afferents enhanced the synaptically evoked and intrinsic excitability of spino-PAG projection neurons, eliciting a stable increase in the number of action potentials (APs) within a Trpv1+ fiber-induced burst, while decreasing the intrinsic AP threshold and increasing the membrane resistance. Further experiments revealed that this plasticity required Trpv1+ afferent input, postsynaptic G protein-coupled signaling, and NMDA receptor activation. Intriguingly, an inflammatory injury and heat exposure in vivo also increased APs per burst, in vitro These results suggest that inflammatory injury-mediated plasticity is driven though Trpv1+ DRG neurons and amplifies the spino-PAG pathway. Spinal inputs to the PAG could play an integral role in its modulation of heat sensation during peripheral inflammation, warranting further exploration of the organization and function of these neural pathways.

A practical guide to recognize, assess, treat and evaluate (RATE) primary care patients with chronic pain

The management of patients with chronic pain is one of the most important issues In medicine and public health. Chronic pain conditions cause substantial suffering for patients, their significant others and society over years and even decades and increases healthcare utilization resources including the cost of medical care, loss of productivity and provision of disability services. Primary care providers are at the frontline in the identification and management of patients with chronic pain, as the majority of patients enter the healthcare system through primary care and are managed by primary care providers. Due to the complexity of chronic pain and the range of issues involved, the accurate diagnosis of the causes of pain and the formulation of effective treatment plans presents significant challenges in the primary care setting. In this review, we use the classification of pain types based on pathophysiology as the template to guide the assessment, treatment, and monitoring of patients with chronic pain conditions. We outline key methods that can be used to efficiently and accurately diagnose the putative pathophysiological mechanisms underlying chronic pain conditions and describe how this information should be used to tailor the treatment plan to meet the patient's needs. We discuss methods to evaluate patients and the impact of treatment plans over a series of consultations, with a particular focus on strategies to improve the patient's ability to self-manage their pain and related symptoms and perform daily functions despite persistent pain. Finally, we introduce the mnemonic RATE (Recognize, Assess, Treat, and Evaluate) as a general strategy that healthcare providers can use to aid their management of patients presenting with chronic pain.

Pain assessment 3 × 3: a clinical reasoning framework for healthcare professionals

OBJECTIVES

To give an overview of central aspects of pain medicine-specific clinical reasoning when assessing a pain patient. Clinical reasoning is the thinking and decision-making processes associated with clinical practice.

METHODS

Three core pain assessment areas that are crucial for clinical reasoning in the field of pain medicine are discussed, each of them consisting of three points.

RESULTS

First, it is important to distinguish acute, chronic non-cancer, and cancer-related pain conditions. This classical and very simple trichotomy still has important implications treatment-wise, e.g., concerning the use of opioids. Second, the pain mechanism needs to be assessed. Is the pain nociceptive, neuropathic, or nociplastic? Simply put, nociceptive pain has to do with injury of non-neural tissue, neuropathic pain is caused by a disease or lesion of the somatosensory nervous system, and nociplastic pain is believed to be related to a sensitized nervous system (c.f. the concept of "central sensitization"). This also has implications concerning treatment. Some chronic pain conditions are nowadays viewed more as diseases rather than the pain being merely a symptom. In the new ICD-11 pain classification, this is conceptualized by the characterization of some chronic pains as "primary". Third, in addition to a conventional biomedical evaluation, psychosocial and behavioral aspects must also be assessed, the pain patient being viewed as an active agent and not merely as the passive recipient of an intervention. Hence, the importance of a dynamic bio-psycho-social perspective. The dynamic interplay of biological, psychological, and social aspects must be taken into account, putative behavioral "vicious circles" thereby being identified. Some core psycho-social concepts in pain medicine are mentioned.

CONCLUSIONS

The clinical applicability and clinical reasoning power of the 3 × 3 framework is illustrated by three short (albeit fictional) case descriptions.

Pain Characteristics in Patients with Inflammatory Bowel Disease: A Monocentric Cross-Sectional Study

BACKGROUND AND AIMS

The abdominal pain common in inflammatory bowel disease [IBD] patients is traditionally associated with inflammation but may persist during clinical remission. Central sensitization [CS] has not previously been explored in these patients. This study aimed to determine the epidemiology of pain in IBD patients and to specify pain characteristics with particular attention to CS.

METHODS

This cross-sectional study included 200 patients; 67% had Crohn's disease [CD]. Pain was assessed using the McGill questionnaire, using the Douleur Neuropathique 4 [DN4] questionnaire and by clinical examination. Its impacts on quality of life, depression and anxiety were also assessed.

RESULTS

Three-quarters of IBD patients complained of pain, including intermittent pain attacks, 62% reported abdominal pain and 17.5% had CS. The prevalence of pain [83.6% vs 59.1%; p < 0.001] and abdominal pain [68.7% vs 48.5%; p = 0.006] was higher in CD patients than in ulcerative colitis [UC] patients. Multivariate analysis confirmed that age [p = 0.02], sex [female] [p = 0.004] and CD [p = 0.005] were independent risk factors for pain. Pain intensity was greater in the case of CS (6 [5-3] vs 3 [1.5-5], p < 0.003) which significantly impaired quality of life [p < 0.003] compared with pain without CS.

CONCLUSIONS

The prevalence of pain was high in IBD patients [≈75%] and higher in CD patients. Significant impacts on quality of life were confirmed. More than 25% of patients with abdominal pain described CS as responsible for more severe pain and worsened quality of life.

TRIAL REGISTRATION REF

NCT04488146.

High Prevalence of Pain Sensitization in Knee Osteoarthritis: A Meta-Analysis with Meta-Regression

OBJECTIVE

The aim of this meta-analysis was to study the evidence on pain sensitization in knee osteoarthritis (OA), providing a quantitative synthesis of its prevalence and impact. Factors associated with pain sensitization were also investigated.

METHODS

Meta-analysis; PubMed (MEDLINE), Cochrane Central Register (CENTRAL), and Web of Science were searched on February 2021. Level I to level IV studies evaluating the presence of pain sensitization in patients with symptomatic knee OA, documented through a validated method (questionnaires or quantitative sensory testing), were included. The primary outcome was the prevalence of pain sensitization. Factors influencing the prevalence were also evaluated, as well as differences in terms of pain thresholds between knee OA patients and healthy controls.

RESULTS

Fifty-three articles including 7,117 patients were included. The meta-analysis of proportion documented a prevalence of pain sensitization of 20% (95% confidence interval [CI] = 16%-26%) with a significant heterogeneity of results (I² = 89%, P < 0.001). The diagnostic tool used was the main factor influencing the documented prevalence of pain sensitization (P = 0.01). Knee OA patients presented higher pain sensitivity compared with healthy controls, both in terms of local pressure pain threshold (standardized mean difference [SMD] = -1.00, 95% CI = -1.67 to -0.32, P = 0.007) and distant pressure pain threshold (SMD = -0.54, 95% CI = -0.76 to -0.31, P < 0.001).

CONCLUSIONS

Knee OA pain presents features that are consistent with a significant degree of pain sensitization. There is a high heterogeneity in the reported results, mainly based on the diagnostic tool used. The identification of the best methods to detect pain sensitization is warranted to correctly evaluate and manage symptoms of patients affected by knee OA.

REGISTRATION

PROSPERO CRD42019123347.

The Parkinson disease pain classification system: results from an international mechanism-based classification approach

ABSTRACT

Pain is a common nonmotor symptom in patients with Parkinson disease (PD) but the correct diagnosis of the respective cause remains difficult because suitable tools are lacking, so far. We developed a framework to differentiate PD- from non-PD-related pain and classify PD-related pain into 3 groups based on validated mechanistic pain descriptors (nociceptive, neuropathic, or nociplastic), which encompass all the previously described PD pain types. Severity of PD-related pain syndromes was scored by ratings of intensity, frequency, and interference with daily living activities. The PD-Pain Classification System (PD-PCS) was compared with classic pain measures (ie, brief pain inventory and McGill pain questionnaire [MPQ], PDQ-8 quality of life score, MDS-UPDRS scores, and nonmotor symptoms). 159 nondemented PD patients (disease duration 10.2 ± 7.6 years) and 37 healthy controls were recruited in 4 centers. PD-related pain was present in 122 patients (77%), with 24 (15%) suffering one or more syndromes at the same time. PD-related nociceptive, neuropathic, or nociplastic pain was diagnosed in 87 (55%), 25 (16%), or 35 (22%), respectively. Pain unrelated to PD was present in 35 (22%) patients. Overall, PD-PCS severity score significantly correlated with pain's Brief Pain Inventory and MPQ ratings, presence of dyskinesia and motor fluctuations, PDQ-8 scores, depression, and anxiety measures. Moderate intrarater and interrater reliability was observed. The PD-PCS is a valid and reliable tool for differentiating PD-related pain from PD-unrelated pain. It detects and scores mechanistic pain subtypes in a pragmatic and treatment-oriented approach, unifying previous classifications of PD-pain.