Human Studies

C-tactile afferents form a distinct channel that encodes pleasant tactile stimulation. Prevailing views indicate they project, as with other unmyelinated afferents, in lamina I-spinothalamic pathways. However, we found that spinothalamic ablation in humans, whilst profoundly impairing pain, temperature and itch, had no effect on pleasant touch perception. Only discriminative touch deficits were seen. These findings preclude privileged C-tactile-lamina I-spinothalamic projections and imply integrated hedonic and discriminative spinal processing from the body.

Codeine is one of the most common opioid medicines for treating pain. Australia introduced policy changes in February 2018 to up-schedule codeine to prescription-only medicine due to concerns of adverse effects, opioid dependency and overdose-related mortality. This study investigated the frequency and content of messages promoted on Twitter by four Australian peak pain organizations, pre- and post-policy implementation. A time series analysis examined frequency of Twitter posts over a 48-week period. Text analysis via Leximancer examined message content. Results showed that promotion and education of the pending policy change dominated the Twitter feed prior to up-scheduling. However, immediately following policy change, there was a shift in content towards promoting conferences and research, and a significant decrease in the frequency of codeine-related posts, compared to opioid-related non-codeine posts. The findings suggest that pain organizations can provide timely and educational policy dissemination in the online environment. They have implications for individuals with chronic pain who use the Internet for health information and the degree to which they can trust these sources, as well as health professionals. Further research is required to determine if public health campaigns can be targeted to prevent opioid-related harm and improve pain care via this increasingly used medium. Perspective: This study presents a first look at what information is being communicated by influential pain organizations who have an online Twitter presence and how messages were delivered during a major policy change restricting access to codeine medicines. Insights could drive targeted future online health campaigns for improved pain management.

Human twin studies and other studies have indicated that chronic pain has heritability that ranges from 30% to 70%. We aimed to identify potential genetic variants that contribute to the susceptibility to chronic pain and efficacy of administered drugs. We conducted genome-wide association studies (GWASs) using whole-genome genotyping arrays with more than 700,000 markers in 191 chronic pain patients and a subgroup of 89 patients with postherpetic neuralgia (PHN) in addition to 282 healthy control subjects in several genetic models, followed by additional gene-based and gene-set analyses of the same phenotypes. We also performed a GWAS for the efficacy of drugs for the treatment of pain.

Thigh muscle weakness is associated with knee discomfort and osteoarthritis disease progression. Little is known about the efficacy of high-intensity strength training in patients with knee osteoarthritis or whether it may worsen knee symptoms.

Chronic low back pain (CLBP) is often treated with opioid analgesics (OA), a class of medications associated with a significant risk of misuse. However, little is known about how treatment with OA affect the brain in chronic pain patients. Gaining this knowledge is a necessary first step towards understanding OA associated analgesia and elucidating long-term risk of OA misuse. Here we study CLBP patients chronically medicated with opioids without any evidence of misuse and compare them to CLBP patients not on opioids and to healthy controls using structural and functional brain imaging. CLBP patients medicated with OA showed loss of volume in the nucleus accumbens and thalamus, and an overall significant decrease in signal to noise ratio in their sub-cortical areas. Power spectral density analysis (PSD) of frequency content in the accumbens' resting state activity revealed that both medicated and unmedicated patients showed loss of PSD within the slow-5 frequency band (0.01-0.027 Hz) while only CLBP patients on OA showed additional density loss within the slow-4 frequency band (0.027-0.073 Hz). We conclude that chronic treatment with OA is associated with altered brain structure and function within sensory limbic areas.

Critical for the diagnosis and treatment of chronic pain is the anatomical distribution of pain. Several body maps allow patients to indicate pain areas on paper; however, each has its limitations.