Treatment of chronic back pain by sensory discrimination training. A Phase I RCT of a novel device (FairMed) vs. TENS

Background: The causes of chronic low back pain (CLBP) remain obscure and effective treatment of symptoms remains elusive. A mechanism of relieving chronic pain based on the consequences of conflicting unpleasant sensory inputs to the central nervous system has been hypothesised. As a result a device was generated to deliver sensory discrimination training (FairMed), and this randomised controlled trial compared therapeutic effects with a comparable treatment modality, TENS. Methods: 60 patients with CLBP were recruited from physiotherapy referrals to a single-blinded, randomised controlled, non-inferiority trial. They were randomised to receive either FairMed or TENS and asked to use the allocated device for 30 minutes, twice a day, for 3 weeks. The primary outcome variable measured at 0 and 3 weeks was pain intensity measured using a visual analogue scale averaged over 7 days. Secondary outcome measures were Oswestry Disability Index, 3 timed physical tests, 4 questionnaires assessing different aspects of emotional coping and a global measure of patient rating of change. Data were analysed for the difference in change of scores between groups using one-way ANOVA. Results: Baseline characteristics of the two groups were comparable. The primary outcome, change in pain intensity (VAS) at 3 weeks showed a mean difference between groups of -0.1, (non significant p = 0.82). The mean difference in change in ODI scores was 0.4; (non significant p = 0.85). Differences in change of physical functioning showed that no significant difference in change of scores for any of these test (p = 0.58 – 0.90). Changes in scores of aspects of emotional coping also demonstrated no significant difference in change scores between the groups (p = 0.14 – 0.94). Conclusion: FairMed was not inferior to TENS treatment. The findings have implications for further research on current chronic pain theories and treatments. Further work to explore these mechanisms is important to expand our understanding of chronic pain and the role of neuro-modulation

The Relationship between Amygdala Activation and Passive Exposure Time to an Aversive Cue during a Continuous Performance Task

The allocation of attention modulates negative emotional processing in the amygdala. However, the role of passive exposure time to emotional signals in the modulation of amygdala activity during active task performance has not been examined. In two functional Magnetic Resonance Imaging (fMRI) experiments conducted in two different groups of healthy human subjects, we examined activation in the amygdala due to cued anticipation of painful stimuli while subjects performed a simple continuous performance task (CPT) with either a fixed or a parametrically varied trial duration. In the first experiment (N = 16), engagement in the CPT during a task with fixed trial duration produced the expected attenuation of amygdala activation, but close analysis suggested that the attenuation occurred during the period of active engagement in CPT, and that amygdala activity increased proportionately during the remainder of each trial, when subjects were passively exposed to the pain cue. In the second experiment (N = 12), the duration of each trial was parametrically varied, and we found that amygdala activation was linearly related to the time of passive exposure to the anticipatory cue. We suggest that amygdala activation during negative anticipatory processing depends directly on the passive exposure time to the negative cue

Spreading of complex regional pain syndrome: not a random process

Complex regional pain syndrome (CRPS) generally remains restricted to one limb but occasionally may spread to other limbs. Knowledge of the spreading pattern of CRPS may lead to hypotheses about underlying mechanisms but to date little is known about this process. The objective is to study patterns of spread of CRPS from a first to a second limb and the factors associated with this process. One hundred and eighty-five CRPS patients were retrospectively evaluated. Cox’s proportional hazards model was used to evaluate factors that influenced spread of CRPS symptoms. Eighty-nine patients exhibited CRPS in multiple limbs. In 72 patients spread from a first to a second limb occurred showing a contralateral pattern in 49%, ipsilateral pattern in 30% and diagonal pattern in 14%. A trauma preceded the onset in the second limb in 37, 44 and 91%, respectively. The hazard of spread of CRPS increased with the number of limbs affected. Compared to patients with CRPS in one limb, patients with CRPS in multiple limbs were on average 7 years younger and more often had movement disorders. In patients with CRPS in multiple limbs, spontaneous spread of symptoms generally follows a contralateral or ipsilateral pattern whereas diagonal spread is rare and generally preceded by a new trauma. Spread is associated with a younger age at onset and a more severely affected phenotype. We argue that processes in the spinal cord as well as supraspinal changes are responsible for spontaneous spread in CRPS

Brain Imaging of Pain

The brain is the principal processor of internal and external sensory experiences including pain. Pain is a multidimensional experience influenced by complex interactions among multiple processes including nociception (the afferent neural activity transmitting sensory information about noxious stimuli), cognitive appraisals (expectation, attention), and emotional aspects (affect)

5-HT modulation of pain perception in humans

© 2017, The Author(s). Introduction: Although there is clear evidence for the serotonergic regulation of descending control of pain in animals, little direct evidence exists in humans. The majority of our knowledge comes from the use of serotonin (5-HT)-modulating antidepressants as analgesics in the clinical management of chronic pain. Objectives: Here, we have used an acute tryptophan depletion (ATD) to manipulate 5-HT function and examine its effects of ATD on heat pain threshold and tolerance, attentional manipulation of nociceptive processing and mood in human volunteers. Methods: Fifteen healthy participants received both ATD and balanced amino acid (BAL) drinks on two separate sessions in a double-blind cross-over design. Pain threshold and tolerance were determined 4 h post-drink via a heat thermode. Additional attention, distraction and temperature discrimination paradigms were completed using a laser-induced heat pain stimulus. Mood was assessed prior and throughout each session. Results: Our investigation reported that the ATD lowered plasma TRP levels by 65.05 ± 7.29% and significantly reduced pain threshold and tolerance in response to the heat thermode. There was a direct correlation between the reduction in total plasma TRP levels and reduction in thermode temperature. In contrast, ATD showed no effect on laser-induced pain nor significant impact of the distraction-induced analgesia on pain perception but did reduce performance of the painful temperature discrimination task. Importantly, all findings were independent of any effects of ATD on mood. Conclusion: As far as we are aware, it is the first demonstration of 5-HT effects on pain perception which are not confounded by mood changes

Imaging the neural correlates of cutaneous sensation and its modulation by psychological factors

This thesis looks at the central processing of two unpleasant sensations, itch and pain, and how these sensations can be modulated using psychological tools. The initial section focuses on the induction and modulation of thermal noxious stimuli and the way in which this is represented in the brain.It is well known that pain can be modulated by distraction, and also which areas of the brain are frequently activated by noxious stimuli. The research reported here expands upon this knowledge. The first study found that when subjects were engaged in a cognitively demanding task (the Counting Stroop task) their attention was distracted away from thermal painful stimuli. They reported a significantly (p=0.006) lower pain intensity rating for stimuli during the interference (more cognitively demanding) task compared to the neutral (less cognitively demanding) task. The interference task was confirmed to be more difficult than the neutral task by significantly increased reaction times in the former compared to the latter. The reduced perception of painful thermal stimuli applied during the interference task compared with those felt in the neutral task was accompanied by a reduced activation in some key components of the pain matrix (insula, mid-cingulate, thalamus). Some key pain processing regions showed an increase in signal during the interference task compared with the neutral task (perigenual cingulate, orbitofrontal regions). [continued in main text ...]</p

Imaging the neural correlates of cutaneous sensation and its modulation by psychological factors

This thesis looks at the central processing of two unpleasant sensations, itch and pain, and how these sensations can be modulated using psychological tools. The initial section focuses on the induction and modulation of thermal noxious stimuli and the way in which this is represented in the brain.It is well known that pain can be modulated by distraction, and also which areas of the brain are frequently activated by noxious stimuli. The research reported here expands upon this knowledge. The first study found that when subjects were engaged in a cognitively demanding task (the Counting Stroop task) their attention was distracted away from thermal painful stimuli. They reported a significantly (p=0.006) lower pain intensity rating for stimuli during the interference (more cognitively demanding) task compared to the neutral (less cognitively demanding) task. The interference task was confirmed to be more difficult than the neutral task by significantly increased reaction times in the former compared to the latter. The reduced perception of painful thermal stimuli applied during the interference task compared with those felt in the neutral task was accompanied by a reduced activation in some key components of the pain matrix (insula, mid-cingulate, thalamus). Some key pain processing regions showed an increase in signal during the interference task compared with the neutral task (perigenual cingulate, orbitofrontal regions). [continued in main text ...

Imaging the neural correlates of cutaneous sensation and its modulation by psychological factors

This thesis looks at the central processing of two unpleasant sensations, itch and pain, and how these sensations can be modulated using psychological tools. The initial section focuses on the induction and modulation of thermal noxious stimuli and the way in which this is represented in the brain. It is well known that pain can be modulated by distraction, and also which areas of the brain are frequently activated by noxious stimuli. The research reported here expands upon this knowledge. The first study found that when subjects were engaged in a cognitively demanding task (the Counting Stroop task) their attention was distracted away from thermal painful stimuli. They reported a significantly (p=0.006) lower pain intensity rating for stimuli during the interference (more cognitively demanding) task compared to the neutral (less cognitively demanding) task. The interference task was confirmed to be more difficult than the neutral task by significantly increased reaction times in the former compared to the latter. The reduced perception of painful thermal stimuli applied during the interference task compared with those felt in the neutral task was accompanied by a reduced activation in some key components of the pain matrix (insula, mid-cingulate, thalamus). Some key pain processing regions showed an increase in signal during the interference task compared with the neutral task (perigenual cingulate, orbitofrontal regions). [continued in main text ...]EThOS - Electronic Theses Online ServiceGBUnited Kingdo