Illusion-enhanced Virtual Reality Exercise for Neck Pain: A Replicated Single Case Series.

OBJECTIVES: Body illusions have shown promise in treating some chronic pain conditions. We hypothesized that neck exercises performed in virtual reality (VR) with visual feedback of rotation amplified would reduce persistent neck pain. METHODS: In a multiple-baseline replicated single case series, 8 blinded individuals with persistent neck pain completed a 4-phase intervention (initial n=12, 4 dropouts): (1) "baseline"; (2) "VR" during which participants performed rotation exercises in VR with no manipulation of visual feedback; (3) "VR enhanced" during which identical exercises were performed but visual feedback overstated the range of motion being performed; (4) "follow-up." Primary outcomes were twice-daily measures of pain-free range of motion and pain intensity. During the baseline and follow-up phases, measures were taken but no intervention took place. RESULTS: No differences in primary outcomes were found between VR and baseline, VR enhanced and VR, or VR enhanced and follow-up. DISCUSSION: Our hypothesis, that neck exercises performed in VR with visual feedback of rotation amplified, would reduce persistent neck pain was not supported. Possible explanations and future directions are discussed.

Generalization of Pain-Related Fear Using a Left-Right Hand Judgment Conditioning Task.

Recent research suggests that the mere intention to perform a painful movement can elicit pain-related fear. Based on these findings, the present study aimed to determine whether imagining a movement that is associated with pain (CS+) can start to elicit conditioned pain-related fear as well and whether pain-related fear elicited by imagining a painful movement can spread towards novel, similar but distinct imagined movements. We proposed a new experimental paradigm that integrates the left-right hand judgment task (HJT) with a differential fear conditioning procedure. During Acquisition, one hand posture (CS+) was consistently followed by a painful electrocutaneous stimulus (pain-US) and another hand posture (CS-) was not. Participants were instructed to make left-right judgments, which involve mentally rotating their own hand to match the displayed hand postures (i.e., motor imagery). During Generalization, participants were presented with a series of novel hand postures with six grades of perceptual similarity to the CS+ (generalization stimuli; GSs). Finally, during Extinction, the CS+ hand posture was no longer reinforced. The results showed that (1) a painful hand posture triggers fear and increased US-expectancy as compared to a nonpainful hand posture, (2) this pain-related fear spreads to similar but distinct hand postures following a generalization gradient, and subsequently, (3) it can be successfully reduced during extinction. These effects were apparent in the verbal ratings, but not in the startle measures. Because of the lack of effect in the startle measures, we cannot draw firm conclusions about whether the "imagined movements" (i.e., motor imagery of the hand postures) gained associative strength rather than the hand posture pictures itself. From a clinical perspective, basic research into generalization of pain-related fear triggered by covert CSs such as intentions, imagined movements and movement-related cognitions might further our understanding of how pain and fear avoidance spread and persevere.

Spatial summation of pain in humans investigated using transcutaneous electrical stimulation.

UNLABELLED: Spatial summation of pain is well accepted but surprisingly understudied. Area-based summation refers to the increase in pain evoked by increasing the area of stimulation. Distance-based summation refers to the increase in pain evoked by increasing the distance between multiple stimuli. Although transcutaneous electrical stimulation has several advantages over other experimental pain paradigms, whether or not this modality evokes spatial summation remains unknown. We aimed to answer this question in order to lay the foundation for critical studies of spatial summation. Twenty-five healthy participants received stimuli on their forearm, and the primary outcome, pain intensity, was compared across 5 spatial configurations-1 with a single stimulus and 4 paired configurations at 0-, 5-, 10-, and 20-cm separations. Importantly, the potential confounder of a proximal-distal gradient in nociceptive sensitivity was removed in this study. Pain intensity was higher in response to the paired stimuli than in response to the single stimulus (P < .001), and the paired stimuli separated by 5, 10 and 20 cm, evoked greater pain than stimuli at a separation of 0 cm (P < .001), thus confirming both area- and distance-based summation, respectively. We conclude that transcutaneous electrical stimulation is appropriate for future investigations of spatial summation. PERSPECTIVE: Distance-based summation is likely implicated in some clinical pain. However, current understanding for spatial summation is limited. This study demonstrates that transcutaneous electrical stimulation is safe, feasible, and valid for future investigations of spatial summation and will allow critical questions to be answered.