Lorimer Moseley

The Pain of Tendinopathy: Physiological or Pathophysiological?

Tendon pain remains an enigma. Many clinical features are consistent with tissue disruption—the pain is localised, persistent and specifically associated with tendon loading, whereas others are not—investigations do not always match symptoms and painless tendons can be catastrophically degenerated. As such, the question ‘what causes a tendon to be painful?’ remains unanswered. Without a proper understanding of the mechanism behind tendon pain, it is no surprise that treatments are often ineffective. Tendon pain certainly serves to protect the area—this is a defining characteristic of pain—and there is often a plausible nociceptive contributor. However, the problem of tendon pain is that the relation between pain and evidence of tissue disruption is variable. The investigation into mechanisms for tendon pain should extend beyond local tissue changes and include peripheral and central mechanisms of nociception modulation. This review integrates recent discoveries in diverse fields such as histology, physiology and neuroscience with clinical insight to present a current state of the art in tendon pain. New hypotheses for this condition are proposed, which focus on the potential role of tenocytes, mechanosensitive and chemosensitive receptors, the role of ion channels in nociception and pain and central mechanisms associated with load and threat monitoring.

Are children who play a sport or a musical instrument better at motor imagery than children who do not

Objective Playing a sport or a musical instrument is presumed to improve motor ability. One would therefore predict that children who play a sport or music are better at motor imagery tasks, which rely on an intact cortical proprioceptive representation and precise motor planning, than children who do not. The authors tested this prediction. Methods This study involved an online questionnaire and then a motor imagery task. The task measured the reaction time (RT) and the accuracy for left/right-hand judgements in children aged 5 to 17 years. Forty pictured hands (20 left), held in various positions and rotated zero, 90°, 180° or 270°, were displayed on a screen. Participants indicated whether the displayed hands were left or right by pressing keys on a keyboard. Results Fifty-seven children (30 boys; mean±SD age=10±3.3 years) participated. The mean±SD RT was 3015.4±1330.0 ms and the accuracy was 73.9±16.6%. There was no difference in RT between children who played sport, music, neither or both (four-level one-way analysis of variance, p=0.85). There was no difference in accuracy between groups either (Kruskal–Wallis, p=0.46). In a secondary analysis, participants whose parents rated them as being ‘clumsy’ were no slower (n.s.) but were about 25% less accurate than those rated coordinated or very coordinated (p<0.05). Conclusion The authors conclude against the intuitively sensible and widely held view that participation in a sport or music is associated with better cortical proprioceptive representation and motor planning. Secondary analyses suggest that parent-rated clumsiness is negatively related to motor imagery performance.

The 'survival perceptions': time to put some Bacon on our plates?

The difficulty with changing the way we interpret the world has long been recognised. Changing the way we consciously or subconsciously think about health-related behaviours has underpinned many major public health strategies (such as smoking cessation, immunisation, sexual health, participation in physical activity) and behavioural health interventions (such as eating and anxiety disorders), but it is a relatively recent strategy for managing symptoms commonly associated with chronic health conditions, such as pain (Butler and Moseley 2003), dyspnoea (Parshall et al 2012), urinary urgency, tinnitus, fatigue, and nausea. Symptoms are perceptual experiences that require conscious awareness in order to be described by the individual experiencing them. Sensations (pain, distress with breathing/dyspnoea, urgency, etc) are not single generic experiences but vary within individuals and contexts (Williams et al 2009) with respect to severity of intensity, degree of unpleasantness, and sensory quality (descriptors such as burning, tight, stabbing, suffocating, etc).

Pain while you are out of your body--a new approach to pain relief? Commentary on a paper by Hänsel et al. (2011).

A great deal of attention has been given lately to illusions of body ownership. Experiments that involve the illusory ownership over an artificial body (Blanke et al., 2002), arm (Botvinick and Cohen, 1998) or finger (Walsh et al., 2011) have revealed much about the physiological underpinnings of these illusions, including which brain areas are involved (see Tsakiris, 2010 for review). Bodily illusions occur in a range of clinical conditions, including, but not limited to, chronic pain (Moseley et al., 2008b). For example, people with complex regional pain syndrome of one arm can perceive that their affected arm is bigger than it really is (Moseley, 2005; Lewis et al., 2007), and people with back pain can feel that their back is ‘missing’ (Moseley, 2008a). Indeed, the large body of literature in this area has led to a proposal that a network of homeostatic and multisensory brain areas form a ‘cortical body matrix’ – a dynamic neural representation that integrates sensory data, from across several frames of reference, with physiological regulation of the body, and which subserves our sense of where and who, physically, we are (Moseley et al., 2011). Relevant to this is a recent paper by Hänsel et al. (2011), published in this issue, in which they investigate, in healthy volunteers, pressure pain thresholds during an out of body illusion. Hänsel et al. assessed pressure pain threshold on the index finger under four different conditions. The experimental condition involved an established method to induce an out of body experience. By synchronous stroking on the back of both the mannequin and the participant while the participant watches a rearview of the mannequin through a head mounted display, the participant quickly feels as though they can actually sense the stroking on the mannequin and therefore, they are standing outside of themselves (Lenggenhager et al., 2007). This method of inducing the illusion can be considered a third person approach, whereas others use a first person approach by tapping the mannequin and the participant on the chest, within the first-person field of view (Ehrsson, 2007). In the Hänsel et al. experiment, there were three control conditions – asynchronous stroking of the mannequin and the participant (which does not induce the illusion) and two identical conditions but with a panel or ‘object’ instead of a mannequin. The authors predicted that pressure pain thresholds would be higher during the illusion, or synchronous stroking condition, than they were during the other conditions. That is, they predicted that the illusion would have an analgesic effect. I suspect that, with

Preserved cortical maps of the body in Complex Regional Pain Syndrome

Chronic pain can be associated with functional and morphological changes in the brain. It has long been thought that some severe chronic pain conditions, such as Complex Regional Pain Syndrome (CRPS), are not only associated with, but even maintained by a reorganisation of the somatotopic representation of the affected limb in the primary somatosensory cortex (S1). This notion has driven treatments that aim to restore S1 representations, such as sensory discrimination training and mirror therapy. However, this notion is based on both indirect and incomplete evidence obtained with imaging methods with low spatial resolution. Here, we used functional MRI to characterize the S1 representation of the affected and unaffected hand in patients with unilateral CRPS of one hand. Our study demonstrates that the cortical area, location, and geometry of the S1 representation of the CRPS hand are comparable to those of the healthy hand, as well as to those of controls. Given that S1 representations are largely preserved in CPRS patients, it is compelling to reconsider not only the cortical mechanisms that underlie the disorder, but also the rationale for interventions that aim to restore somatotopic representations.It has long been thought that severe chronic pain conditions, such as Complex Regional Pain Syndrome (CRPS), are not only associated with, but even maintained by a reorganisation of the somatotopic representation of the affected limb in primary somatosensory cortex (S1). This notion has driven treatments that aim to restore S1 representations, such as sensory discrimination training and mirror therapy. However, this notion is based on both indirect and incomplete evidence obtained with imaging methods with low spatial resolution. Here, we used functional MRI to characterize the S1 representation of the affected and unaffected hand in patients with unilateral CRPS. At the group level, the cortical area, location, and geometry of the S1 representation of the CRPS hand were largely comparable to those of the healthy hand and controls. However, the area of the map of the affected hand was modulated by disease duration (the smaller the map, the more chronic the CRPS), but not by pain intensity, pain sensitivity and severity of the physical disability. Thus, if any map reorganization occurs, it does not appear to be directly related to our pain measures. These findings compel us to reconsider the cortical mechanisms underlying CRPS and the rationale for interventions that aim to “restore” somatotopic representations to treat pain. Significance statement This study shows that the spatial map of the fingers in S1 is largely preserved in chronic CRPS. Shrinkage of the area of the affected hand map can occur in the most chronic stages of disease. Map shrinkage is related to CRPS duration rather than diagnosis, and is unrelated to how much pain patients experience or to the severity of the physical disability. These findings challenge the rationale for using sensory interventions to treat pain by restoring somatotopic representations in CRPS patients.

Visually-induced analgesia in a deep tissue experimental pain model: A randomised cross-over experiment

Visualizing ones own painful body part appears to have an effect on reported pain intensity. Furthermore, it seems that manipulating the size of the viewed image can determine the direction and extent of this phenomenon. When visual distortion has been applied to clinical populations, the analgesic effects have been in opposition to those observed in some experimental pain models. To help resolve this problem, we explored the effect of visualisation and magnification of the visual image on reported pain using a delayed onset muscle soreness (DOMS) pain model.