Virtual Reality, Music, and Pain: Developing the Premise for an Interdisciplinary Approach to Pain Management

Emily Honzel; Sarah Murthi; Barbara Brawn-Cinani; Giancarlo Colloca; Craig Kier; Amitabh Varshney; Luana Colloca

Disclosures

Pain. 2019;160(9):1909-1919. 

In This Article

Virtual Reality and Pain

Neurobiological Bases of Immersive Virtual Reality and Their Relationship With Pain

There are several proposed mechanisms for how VR experiences may alleviate pain.[30,49,74,87] It has been suggested that VR engages pathways that would otherwise be devoted to pain signaling through distraction.[49,86] In this theory, VR creates a positive effect on cognitive variables to both enhance pain control[50] and moderate pain signaling pathways through memory, emotions, and other senses including haptic, aural, and visual.[20] It is also possible that VR distances patients from their current state through immersion. For example, patients with walking pain may be able to enter a reality where they are not physically moving their limbs but are able to virtually experience walking.[16] Efforts are under way to understand the mechanism through which VR functions have clinical relevance.[43] Researchers must discover whether the underlying mechanism is distraction,[23] in which case, salience is key; whether it acts through fundamentally regulating mood, emotions, and altering how we see and perceive the world around us, in which case, total immersion is paramount; or whether it requires active cognitive engagement, in which case, guided experiences may need to be explored.[43]

Despite the current paucity of VR equipment that is compatible with functional magnetic resonance imaging (fMRI) techniques, a few studies have reported that VR as compared to a no-VR condition decreases the neural activity in regions of interest (ROI) such as the anterior cingulate cortex, primary and secondary somatosensory cortices, insula, and thalamus in healthy participants when thermal painful stimulations are given.[30] A follow-up study indicated that the aforementioned ROIs are differently modulated by VR and pharmacological treatments. Healthy participants underwent a thermal painful stimulation in a within-subject design that included (1) control (no analgesia), (2) opioid (4 ng/mL hydromorphone administration), (3) immersive VR, and (4) combined opioid and VR.[31] The opioid alone reduced pain unpleasantness (Hedges' g = −0.367) and blood oxygen level–dependent activity in the insula and thalamus. Virtual reality alone reduced both worst pain intensity (Hedges' g = −0.367) along with neural activity in the insula, thalamus, and secondary somatosensory cortices. Interestingly, combining opioid and VR interventions resulted in a larger reduction of pain reports compared with opioid alone on all subjective pain measures (Hedges' g = −2.46). This finding supports the concept that multimodal combined pain therapeutics can be clinically relevant. As MRI-compatible technology improves, future studies with combined VR-MT should explore the mechanisms through which multimodal approaches modulate pain-related and other processes in patients suffering from pain.[31]

Acute Pain

Virtual reality pain management for acute pain has been frequently studied and reviewed in both healthy subjects[11,25,80,81] and pain patients, especially burn victims[26,37,44,53,75,79] and patients with phantom limb pain.[1,68,73] One pioneering study was conducted on 2 adolescents, showing that they were able to better tolerate painful procedures during burn dressing changes during a VR experience.[27] In the years since this study, Hoffman et al. have performed numerous studies with larger sample sizes examining VR interventions as an adjunctive treatment for burn pain.[5,52,53,78] For example, adult patients showed both improvement of pain function (eg, motion exercise ranges during physical therapy)[28] and pain reduction during wound care.[29] All patients reported significantly better outcomes with the immersive VR as compared to no VR.[28] Although the study was unblinded, the order of the condition was randomized and counterbalanced. Research that explores different VR features (eg, high-tech VR helmets,[32]) is aiming to further determine VR's impact on experimental pain.

A systematic review that assessed studies comparing VR with a control condition or an alternative intervention indicated that VR reduces experimental pain and acute clinical pain associated with burn injury care.[55] The review showed that VR works less with needle-related pain, and fully immersive VR-based tools were more likely to provide pain relief. Indovina et al.[35] analyzed VR interventions during painful medical procedures, including studies that looked at acute pain and other measures of distress, in varied patient populations. The authors, while confirming the validity of the VR interventions, called for the establishment of predictive factors that would encourage the development of personalized VR experiences.

Chronic Pain

As Indovina et al.[35] noted, studies considering VR interventions to treat chronic pain are "in (their) infancy." However, the numbers of such studies are increasing in recent years. Jones et al.[41] explored the efficacy of a 5-minute immersive VR environment (Cool!) as a pain intervention in 30 study participants with moderate chronic pain conditions (ie, cervical spine, lumbar spine, hip, shoulder, abdominal, thoracic pain, and diffuse pain from myalgia or connective tissue disease and neuropathy). During the VR treatment session, participants reported lowered pain by 60% and, after the session, lowered pain by 33% (Hedges' g = −0.741) as compared to their presession self-report of moderate pain.[41] In another chronic pain study, Jin et al. designed and tested the VR game Cryoslide in a randomized, controlled crossover study as an intervention to relieve "spikes" of pain and found a reduction of clinical pain compared with baseline and controls.[39] Keefe et al.[43] posited several ways in which VR could be used to treat specific chronic pain conditions, including altering pain-related movement patterns and integrating VR with behavioral interventions (eg, hypnosis, meditation, and exposure therapy). Future studies using immersive VR tools that are tailored to the etiology of pain disorders (eg, phantom pain[1]) are needed.

Technical Applications and Audio-based Interventions

A wide range of VR interventions have been developed. Well-established applications such as Cool! (DeepStream VR Inc, Seattle, WA, 2014) and Snow World (MultiGen-Paradigm.com, 2001) have provided a sense of immersion through visual and aural components. Other interventions are beginning to explore olfactory[19] and tactile[21] stimuli. The effectiveness of these interventions has been explored using a variety of subjective measures, including pain scales,[44] as well as objective measures such as blood-oxygen–dependent measurements of brain activity,[31] vital signs,[86] and measures of skin conductance.[84] While early VR interventional studies primarily used expensive equipment, commoditization has made lower-cost VR interventions more feasible.[15] Virtual reality hardware and software are evolving rapidly, and the viewing systems are becoming less expensive and more portable. At the same time, the library of digital content is rapidly increasing. This might facilitate the use of VR as an adjunct or alternative therapy for the treatment of distinct aspects of pain (sensory and affective components) across pain disorders.

Virtual reality interventions that are considered "higher tech" have been shown to increase the therapeutic effects of VR due to the increase of "presence," or the illusion of entering and being in the virtual world.[33] These higher tech interventions used sound effects, which indicate that incorporating auditory input for interventions may increase the sense of presence and therefore increase efficacy. A recent study directly examined the effect of adding aural input to a VR intervention in healthy subjects participating in a cold-pressor pain study.[40] Virtual reality including audio elicited higher pain tolerance as compared to an aural-only condition, a VR-only condition, and a control group (Hedges' g = 0.43). This suggests that the addition of sound may increase the attention-demanding nature of the experience, providing greater reduction of the perception of pain. The authors note that determining which kind of sounds is most effective in combination with the VR (context-relevant or distracting) may help describe the mechanisms through which VR therapies work.[40]

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