Does Prism Adaptation Hold Promise for Pain Patients?

Pain management research goes far beyond identifying drug development and new uses for existing medication. One particularly interesting but neglected area of study involves prism adaptation, a non-invasive, non-medication procedure that sounds like something straight out of a science fiction novel.

Recently, we covered a new study showing that extended-release gabapentin may hold some promise for treating fibromyalgia—pretty big news on the medication treatment front. But pain management research goes far beyond identifying drug development and new uses for existing medication. One particularly interesting but neglected area of study involves prism adaptation (PA), a non-invasive, non-medication procedure that sounds like something straight out of a science fiction novel.

To this point, PA has mostly been used, with varying effectiveness, in patients suffering from neurological disorders. Chief among those disorders is unilateral neglect, in which, after some incidence of brain damage to one hemisphere of the brain, the patient’s frame of visual attention is biased toward one side of the brain. PA uses special prismatic goggles to displace the patient’s visual field left-to-right, or up-and-down. While wearing the goggles, the patient engages in a perceptual motor task such as pointing to a visual target directly in front of them. Over time, patients begin to detect—and, hopefully, correct—pointing errors by engaging the neglected side of their brain.

A recent paper in the European Journal of Pain reviewed the literature surrounding the use of PA to treat complex regional pain syndrome, a degenerative, chronic systemic disease often characterized by severe pain. CRPS is insidious; though it often starts in an arm or leg, in slightly more than a third of cases, it spreads throughout the body. The paper used PubMed to search for peer-reviewed articles on the use of PA to treat CRPS.

What did the research discover? Not much. Even in the case of its “wheelhouse” usage—for unilateral neglect—the research samples, while promising, have been too small to lead to much further research or a full-scale randomized, double-blind study. A 2012 review article in Nature Reviews Neurology lamented that “considerable investment in prism adaptation research has not yet touched the fundamentals needed for clinical implementation.”

For CRPS and other potential pain management targets, the progress is negligible. The authors of the study in the European Journal of Pain note that, “There is still no agreement as to whether CRPS patients really present neglect symptoms and, if they do, what it is that they neglect. Furthermore, there is insufficient data to determine whether PA exerts an effect on CRPS symptoms. Finally, it remains unknown whether neglect can be observed in other types of lateralized pain, or whether PA could be useful for these patients.” The authors conducted the review in the hope that additional research might be generated.

For now, the effectiveness of PA is still the stuff of science fiction.