Chronic pain: Overview

Abstract
Objective: Complex Regional Pain Syndrome (CRPS) presents significant diagnostic challenges due to its diverse clinical presentation. This study aims to describe the diagnostic trajectory of patients labeled with CRPS, focusing on referral patterns, application of the Budapest criteria, and accuracy of CRPS diagnosis.

Methods: A retrospective study was conducted of 53 patients treated for CRPS at a peripheral nerve clinic within a tertiary care center (2020-2024). Patient demographics, referral patterns, events leading to CRPS diagnosis, and diagnostic tests were analyzed. Three clinicians (two plastic surgeons, one pain medicine specialist) retrospectively assessed the validity of CRPS diagnoses using the Budapest criteria. Inter-rater reliability (IRR) for CRPS presence and type was calculated using Cohen's kappa (κ).

Results: Among the 53 patients, the median time from the first mention of CRPS to referral to the nerve clinic was 1.3 years (IQR:0.4-3.6). The Budapest criteria had been assessed in 26% of patients pre-evaluation. In 33% of patients labeled with CRPS type I, an inciting nerve injury was identified. Following retrospective assessment, 42% of patients were determined to have CRPS by all raters, 26% were determined not to have CRPS, and 32% showed inconsistent agreement. The IRR for CRPS diagnosis and type ranged from minimal to moderate (κ=0.32-0.72).

Discussion: Our findings highlight variability in the application of the Budapest criteria for CRPS diagnosis, as well as inconsistencies in its retrospective application. Potentially treatable peripheral nerve injuries should be addressed prior to CRPS diagnosis. These findings may help improve early diagnostic assessment in patients with chronic pain.

Abstract
The aim of this systematic review was to identify and critically analyse the tools available for categorising pain as nociceptive, neuropathic and nociplastic pain in children and adolescents. Studies were included if they (i) included children and adolescents with a mean age of 0-24 years old, (ii) examined assessment tools that categorise pain as nociceptive, neuropathic or nociplastic, and (iii) examined the psychometric properties of the tools. Sensitive searches were conducted in five online databases in March 2024. Eligible studies were assessed for risk of bias and quality by two authors using COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) criteria. The search yielded 26 studies for 11 tools. No assessment tool had evidence for all nine recommended psychometric properties. Quantitative Sensory Testing, a tool used to identify signs and symptoms of nociplastic and neuropathic pain, was the most studied tool and had moderate evidence for construct validity, criterion validity and reliability. Three self-reported questionnaires, the Self-reported Leeds Assessment of Neuropathic Symptoms and Signs (S-LANSS), Central Sensitisation Inventory (CSI) and PainDETECT, had moderate evidence for construct validity and show promise as preliminary tools to identify possible neuropathic or nociplastic pain. However, they had low specificity when used in isolation. All assessment methods would benefit from further psychometric evaluation and validation in children and adolescents. PERSPECTIVE: This systematic review highlights the limited validation of pain assessment tools for children and adolescents. While Quantitative Sensory Testing and self-reported questionnaires show promise in identifying pain mechanisms, their applicability remains uncertain. Further psychometric validation is crucial to improve pain assessment and guide personalized treatment in young populations.

Abstract
Objective: To explore the short-term and long-term lived experiences of patients with chronic pain and angina pectoris with spinal cord stimulation.

Design: An interpretive qualitative study with thematic analysis of one-off, semistructured interviews, following Braun and Clarke (2006).

Setting: A multidisciplinary, publicly funded pain service in Auckland, New Zealand. Patients usually undergo a comprehensive medical, psychological and functional assessment and an in-house pain management programme before proceeding to spinal cord stimulator implantation.

Participants: Participants implanted with a spinal cord stimulator between 1998 and 2019 who had their stimulator for ≥1 year, purposively sampled to increase the range of ethnicities.

Main outcome: The themes identified from the interviews.

Results: 24 participants with chronic pain of varied aetiology and a median (range) of 5.2 (2.4-23.2) years since stimulator implantation participated. 22 participants had the device in situ, and 2 had been explanted. Five main themes were identified: (1) embodiment: stimulator and body as one; (2) technical factors: batteries and type of stimulation; (3) improved well-being; (4) social connection and (5) healthcare system interaction. Most participants reported pain relief, but many had experienced complications and discomfort. They emphasised the importance of ongoing support from the pain service. Acceptance of pain, coping and embodiment emerged as common motifs across these themes. 21 participants were satisfied with their treatment.

Conclusion: Within the context of a multidisciplinary pain clinic, despite some discomfort and various complications, most participants valued the ongoing reduction of pain achieved with spinal cord stimulation. Timely access to support from the pain service influenced their experience and satisfaction with their stimulators. Acceptance of pain and embodiment of the stimulator helped participants adapt to living with their stimulator, often over many years.