Preoperative susceptibility to developing secondary hyperalgesia is associated with post-thoracotomy pain at 2 months.

Background: Identifying the subset of patients at risk for developing persistent pain after surgery is clinically important as they could benefit from targeted prevention measures. In this prospective study, we investigated if the preoperative assessment of the individual susceptibility to developing experimentally induced secondary hyperalgesia is associated with post-thoracotomy pain at 2 months.

Methods: Forty-one patients scheduled to undergo a posterolateral thoracotomy were recruited before surgery and followed prospectively for 2 months.

Assessing signs of central sensitization: A critical review of physiological measures in experimentally induced secondary hyperalgesia.

Background And Objectives: Central sensitization (CS) is believed to play a role in many chronic pain conditions. Direct non-invasive recording from single nociceptive neurons is not feasible in humans, complicating CS establishment. This review discusses how secondary hyperalgesia (SHA), considered a manifestation of CS, affects physiological measures in healthy individuals and if these measures could indicate CS.

Intra-operative electroencephalogram frontal alpha-band spectral analysis and postoperative delirium in cardiac surgery: A prospective cohort study.

Background: Postoperative delirium (POD) remains a frequent complication after cardiac surgery, with pre-operative cognitive status being one of the main predisposing factors. However, performing complete pre-operative neuropsychological testing is challenging. The magnitude of frontal electroencephalographic (EEG) α oscillations during general anaesthesia has been related to pre-operative cognition and could constitute a functional marker for brain vulnerability.

Multichannel transcranial direct current stimulation over the left dorsolateral prefrontal cortex may modulate the induction of secondary hyperalgesia, a double-blinded cross-over study in healthy volunteers.

Background: Central sensitization is thought to play a critical role in the development of chronic pain, and secondary mechanical hyperalgesia is considered one of its hall-mark features. Consequently, interventions capable of modulating its development could have important therapeutic value. Non-invasive neuromodulation of the left dorsolateral prefrontal cortex (DLPFC) has shown potential to reduce pain, both in healthy volunteers and in patients.

The long-term effect of complex regional pain syndrome type 1 on disability and quality of life after foot injury.

Purpose: To study the long-term evolution of patients with lower-limb Complex Regional Pain Syndrome (CRPS), focusing on functional and proprioceptive aspects and quality of life.

Methods: In 20 patients suffering from chronic distal lower-limb CRPS diagnosed using Budapest criteria, we assessed joint position sense and strength of the knee muscles at the CRPS and unaffected leg, functional exercise capacity, pain, CRPS severity score, quality of life and kinesiophobia. Similar assessments were performed in 20 age-matched controls.

Anodal Transcutaneous Spinal Direct Current Stimulation (tsDCS) Selectively Inhibits the Synaptic Efficacy of Nociceptive Transmission at Spinal Cord Level.

Recently studies have aimed at developing transcutaneous spinal direct current stimulation (tsDCS) as a non-invasive technique to modulate spinal function in humans. Independent studies evaluating its after-effects on nociceptive or non-nociceptive somatosensory responses have reported comparable effects suggesting that tsDCS impairs axonal conduction of both the spino-thalamic and the medial lemniscus tracts. The present study aimed to better understand how tsDCS affects, in humans, the spinal transmission of nociceptive and non-nociceptive somatosensory inputs.

Deep continuous theta burst stimulation of the operculo-insular cortex selectively affects Aδ-fibre heat pain.

Key Points: Deep continuous theta burst stimulation (cTBS) of the right operculo-insular cortex delivered with a double cone coil selectively impairs the ability to perceive thermonociceptive input conveyed by Aδ-fibre thermonociceptors without concomitantly affecting the ability to perceive innocuous warm, cold or vibrotactile sensations. Unlike deep cTBS, superficial cTBS of the right operculum delivered with a figure-of-eight coil does not affect the ability to perceive thermonociceptive input conveyed by Aδ-fibre thermonociceptors. The effect of deep operculo-insular cTBS on the perception of Aδ-fibre input was present at both the contralateral and the ipsilateral hand.

Quickly responding C-fibre nociceptors contribute to heat hypersensitivity in the area of secondary hyperalgesia.

Key Points: A recent animal study showed that high frequency electrical stimulation (HFS) of C-fibres induces a gliogenic heterosynaptic long-term potentiation at the spinal cord that is hypothesized to mediate secondary hyperalgesia in humans. Here this hypothesis was tested by predominantly activating C-fibre nociceptors in the area of secondary mechanical hyperalgesia induced by HFS in humans. It is shown that heat perception elicited by stimuli predominantly activating C-fibre nociceptors is greater, as compared to the control site, after HFS in the area of secondary mechanical hyperalgesia.

Human primary somatosensory cortex is differentially involved in vibrotaction and nociception.

The role of the primary somatosensory cortex (S1) in vibrotaction is well established. In contrast, its involvement in nociception is still debated. Here we test whether S1 is similarly involved in the processing of nonnociceptive and nociceptive somatosensory input in humans by comparing the aftereffects of high-definition transcranial direct current stimulation (HD-tDCS) of S1 on the event-related potentials (ERPs) elicited by nonnociceptive and nociceptive somatosensory stimuli delivered to the ipsilateral and contralateral hands.

Secondary hyperalgesia is mediated by heat-insensitive A-fibre nociceptors.

Key Points: It is believed that secondary hyperalgesia (the increased sensitivity to mechanical nociceptive stimuli that develops after cutaneous tissue injury in the surrounding uninjured skin) is mediated by a subclass of nociceptors: the slowly adapting A-fibre mechano-heat nociceptors (AMH-type I). Here we tested this hypothesis. By using intense long-lasting heat stimuli, which are known to activate these slowly adapting AMH-type I nociceptors, we show that the perceived intensity elicited by these stimuli is not increased in the area of secondary hyperalgesia.