Anesth Analg 2007; 105:1526-1527
© 2007 International Anesthesia Research Society
doi: 10.1213/01.ane.0000295853.53423.44
EDITORIAL
Will Seeing Become Believing?
Spencer S. Liu, MD*, and
Emory N. Brown, MD, PhD
From the *Department of Anesthesiology, Hospital for Special Surgery and the Weill College of Medicine of Cornell University, New York, New York, and the Department of Anesthesia and Critical Care, Massachusetts General Hospital, Boston, MA, and the Department of Brain and Cognitive Sciences, Harvard-MIT, Division of Health Science and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts.
Address correspondence to Dr. Spencer S. Liu, Department of Anesthesiology, Hospital for Special Surgery, 535 East 70th St., New York, NY 10021. Address e-mail to liusp{at}hss.edu. No reprints will be available.
In this issue of Anesthesia & Analgesia, two pilot studies use functional imaging techniques to characterize regions of brain activity that are important for clinical and experimental pain processing (1,2). Both studies suggest that neuroanatomic correlates of subjective changes in pain perception can be identified. The studies are complementary, as Hoffman et al. (1) used experimental pain, whereas Buvanendran et al. (2) examined clinical postoperative pain. Experimental pain stimulation in many human and animal pain studies involves only a brief thermal stimulus, whereas postoperative pain is a more complex phenomenon involving mechanical and inflammatory-mediated activation of nociceptors for an extended time period. The extent to which brief experimental pain is an accurate model for postoperative pain is unclear, thus both studies are welcome.
Functional neuroimaging is a new and exciting field that has great potential to translate into clinical relevance. Both experimental and clinical evidence suggest different mechanisms for somatic, visceral, inflammatory, and neuropathic pain states (3,4). The neuroanatomic correlates of clinical postoperative pain identified by Buvanendran et al. (2) include some of those typically identified in experimental pain, such as the contralateral somatosensory cortex. However, in addition to the contralateral parietal region and the thalamus (the pulvinar and the medial dorsal nucleus), increased postoperative activation was seen in the contralateral putamen and the contralateral anterior cerebellar lobe. Activity in these two areas is associated with functions other than pain processing, such as movement coordination, various cognitive functions, and generalized avoidance and defensive behaviors.
Further work will therefore be needed before functional neuroimaging becomes useful in identifying specific brain areas and pathways that are involved in processing different mechanisms of pain. Once these specific areas and pathways are identified, then optimal therapies may be explored with this same technology. For example, functional neuroimaging with labeled analgesic molecules may allow targeting of specific individual or converging brain areas that may translate into more effective pharmacologic and nonpharmacologic analgesic therapy. This ability to specifically label and then measure functional effect of molecules for different receptors and brain areas may allow for rapid screening and evaluation of novel analgesic therapies.
Although currently there are technical difficulties, functional neuroimaging may become an important quantitative tool to determine the magnitude of effect of analgesic therapies. Currently, it is difficult to quantify and compare the clinical magnitude of effect of different analgesics. Clinical measures such as opioid sparing or changes in pain scores are often imprecise or clinically irrelevant. The ability of functional imaging to quantify the effects of different analgesics, both individually and as combinations, may allow more precise determination of optimal individual and combination drugs for different pain states. For example, Hoffman et al. (1) describe the therapeutic use of virtual reality and opioids for experimental pain. Functional imaging allows potential mapping of different brain areas for opioid analgesia and virtual reality. Furthermore, functional imaging begins the process of determining and clinically correlating the magnitude of effect of each therapy alone and in combination.
Virtual reality is a particularly interesting modality. Interest in nonpharmacologic analgesic therapies is increasing, in part because nonpharmacologic approaches might improve patient safety. The Anesthesia Patient Safety Foundation has recently released a position statement highlighting the potential risks of respiratory depression with systemic and central neuraxial opioid analgesia (5). Concurrently, the Institute for Healthcare Improvement has issued a statement that use of nonpharmacologic interventions may reduce adverse drug events from opioids (6). Virtual reality offers a nonpharmacologic, popular, and fun means to provide analgesia without the risks of ventilation depression. Video games are clearly an integral part of current culture with tremendous resources devoted to development of improved immersive and particularly interactive technology, such as the consistently sold out Nintendo Wi TM interactive game system. Thus the technology for virtual reality will only continue to improve in both quantity and quality. Functional imaging may allow more precise design of virtual reality as a pain therapy. Hoffman et al. (1) observed that not all typically associated brain representations of pain showed decreased activation when virtual reality was combined with opioid therapy. This suggests that the type of virtual reality distraction may be further optimized to be more effective at providing a distraction for pain perception. Such a design could make it significantly more effective clinically, and therefore suggests a way in which pain specialists may collaborate with cognitive neuroscientists to design more novel pain therapies.
Outside of the laboratory, virtual reality has already been used for clinical procedural pain therapy (1). This is only the surface of potential applications, as future uses to be studied include treatment of both acute postoperative and chronic pain states. For example, given the popularity of video games among children, virtual reality may be ideal for nonpharmacologic management of pediatric pain and procedures. Another use may be in the treatment of posttraumatic stress disorder and chronic pain. The Department of Veterans Affairs has reported estimated incidences of posttraumatic stress disorder after the Gulf War of 8%–16% and in up to 33% of treated veterans from the Iraq and Afghanistan theaters, especially in female veterans (7). Virtual reality and functional imaging offers a potential means to define mechanisms and may serve as a desensitization therapy for various stress disorders (8). Finally, acute and chronic pain is increasing in the active military, and chronic pain may be more prevalent in military than civilian cohorts (9). Most striking is that only 2% of personnel who suffered from chronic pain in the Iraq conflict were able to return to combat (10). Virtual reality may offer a means to also successfully treat both acute and chronic pain in any conflict theater and allow return to duty. Perhaps similar success in return to work and resumption of activities of daily living could also be accomplished in civilian chronic pain sufferers with the use of virtual reality.
The seminal studies by Hoffman et al. (1) and Buvanendran et al. (2) in this issue of Anesthesia & Analgesia demonstrate that "seeing" through functional neuroimaging has the potential to bring substantial benefits to pain research and clinical practice.
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Footnotes
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Accepted for publication September 13, 2007.
Financial disclosure: no external funding was provided.
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REFERENCES
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- Hoffman HG, Richards TL, Van Oostrom, Coda BA, Jensen MP, Blough DK, Sharar SR. Analgesic effects of opioids and immersive virtual reality distraction: evidence from subjective and functional brain imaging assessments. Anesth Analg 2007;105:1776–83[Abstract/Free Full Text]
- Buvanendran A, Ali A, Stoub TR, Berger RA, Kroin JS. Use of brain positron tomography to identify sites of postoperative pain processing with and without epidural analgesia. Anesth Analg 2007;105:1784–6[Abstract/Free Full Text]
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- Weinger MB. http://www.apsf.org/assets/Documents/winter2007.pdf. Accessed October 12, 2007
- http://www.ihi.org/IHI/Topics/PatientSafety/MedicationsSystem/Changes/IndividualChanges/Consider+Non-Pharmacological+Interventions+for+Pain+amd+Anxiety.htm. Accessed October 12, 2007
- Corbett S. The women’s war. The New York Times Magazine, March 18, 2007:41–55
- Huergo J. http://www.onr.navy.mil/media/article.asp?ID=86. Accessed October 12, 2007
- Reynolds K, Cosio-Lima L, Creedon J, Gregg R, Zigmont T Injury occurrence and risk factors in construction engineers and combat artillery soldiers. Mil Med 2002;167:971–7[Web of Science][Medline]
- Cohen SP, Griffith S, Larkin TM, Villena F, Larkin R. Presentation, diagnoses, mechanisms of injury, and treatment of soldiers injured in Operation Iraqi Freedom: and epidemiological study conducted at two military pain management centers. Anesth Analg 2005;101:1098–103[Abstract/Free Full Text]
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