Multimodal hypersensitivity derived from quantitative sensory testing predicts pelvic pain outcome: an observational cohort study

Multimodal hypersensitivity and somatic symptoms predict adolescent postmenarchal widespread pain

ABSTRACT

Widespread pain in adolescence is linked with poor mental health, pain, and somatic symptoms in childhood. This prospective study in 207 premenarchal adolescents used quantitative sensory testing (QST) and multimodal hypersensitivity (MMH) measures to assess somatosensory system function and identify predictors for widespread pain (≥3/7 sites). We hypothesized that premenarchal pain, somatic symptoms, psychological factors, and somatosensory system function would predict postmenarchal widespread pain, which would be associated with greater menstrual pain intensity. At premenarchal and postmenarchal study visits, participants completed measures of somatic symptoms, a pain body map, psychosocial questionnaires, QST, and experimental MMH measures including auditory, visual, and visceral stimulation. Electroencephalography (EEG) was collected during auditory and visual tasks to identify neural correlates of MMH. Premenarchal widespread pain was reported by 25% of participants, whereas 29% developed new incident widespread pain postmenarche. Adolescents with postmenarchal widespread pain reported greater menstrual pain intensity (median [interquartile range] 47 [28-61]; 0-100 visual analog scale) than those without (24 [8-50], P = 0.001). Elevated somatic symptoms (P = 0.012), stress (P = 0.015), and sensitivity to visceral (bladder filling) (P = 0.046) and unpleasant visual stimuli (P = 0.043) were significant predictors of postmenarche widespread pain. A multivariable regression model found premenarchal body map score (OR = 1.75, 95% CI [1.20, 2.55]), somatic symptoms (OR = 1.47, 95% CI [1.03, 2.11]), and visual hypersensitivity (OR = 1.62, 95% CI [1.12, 2.33]) predicted postmenarchal widespread pain. No EEG differences in early cortical sensory processing were found. Our results suggest that increased sensitivity to multimodal unpleasant and painful stimuli represents a novel risk factor for postmenarche widespread pain.

Independent effects of transcranial direct current stimulation and social influence on pain

ABSTRACT

Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulatory technique with the potential to provide pain relief. However, tDCS effects on pain are variable across existing studies, possibly related to differences in stimulation protocols and expectancy effects. We investigated the independent and joint effects of contralateral motor cortex tDCS (anodal vs cathodal) and socially induced expectations (analgesia vs hyperalgesia) about tDCS on thermal pain. We employed a double-blind, randomized 2 × 2 factorial cross-over design, with 5 sessions per participant on separate days. After calibration in Session 1, Sessions 2 to 5 crossed anodal or cathodal tDCS (20 minutes 2 mA) with socially induced analgesic or hyperalgesic expectations, with 6 to 7 days between the sessions. The social manipulation involved videos of previous "participants" (confederates) describing tDCS as inducing a low-pain state ("analgesic expectancy") or hypersensitivity to sensation ("hyperalgesic expectancy"). Anodal tDCS reduced pain compared with cathodal stimulation (F(1,19.9) = 19.53, P < 0.001, Cohen d = 0.86) and analgesic expectancy reduced pain compared with hyperalgesic expectancy (F(1,19.8) = 5.62, P = 0.027, Cohen d = 0.56). There was no significant interaction between tDCS and social expectations. Effects of social suggestions were related to expectations, whereas tDCS effects were unrelated to expectancies. The observed additive effects provide novel evidence that tDCS and socially induced expectations operate through independent processes. They extend clinical tDCS studies by showing tDCS effects on controlled nociceptive pain independent of expectancy effects. In addition, they show that social suggestions about neurostimulation effects can elicit potent placebo effects.

Deciphering nociplastic pain: clinical features, risk factors and potential mechanisms

Nociplastic pain is a mechanistic term used to describe pain that arises or is sustained by altered nociception, despite the absence of tissue damage. Although nociplastic pain has distinct pathophysiology from nociceptive and neuropathic pain, these pain mechanisms often coincide within individuals, which contributes to the intractability of chronic pain. Key symptoms of nociplastic pain include pain in multiple body regions, fatigue, sleep disturbances, cognitive dysfunction, depression and anxiety. Individuals with nociplastic pain are often diffusely tender - indicative of hyperalgesia and/or allodynia - and are often more sensitive than others to non-painful sensory stimuli such as lights, odours and noises. This Review summarizes the risk factors, clinical presentation and treatment of nociplastic pain, and describes how alterations in brain function and structure, immune processing and peripheral factors might contribute to the nociplastic pain phenotype. This article concludes with a discussion of two proposed subtypes of nociplastic pain that reflect distinct neurobiological features and treatment responsivity.