As noted in a recent blog (Food Marketing Detectable on Functional MRI | gutsandgrowth), functional MRI is being studied for a number of applications. Now, more data has emerged that a “pain signature” can be identified with this technology (NEJM 2014; 368: 1388-97).
Using a series of experiments, the authors enrolled 114 healthy participants and ultimately identified an imaging signature that was associated with heat-induced pain and increased nonlinearly with increasing stimulus intensity. The first part of the study involved a machine-learning analyses after inducing physical pain by applying heat to the forearm of the participants. The sensitivity and specificity were 94% or more in discriminating painful heat from nonpainful warmth, pain anticipation, and pain recall. In the fourth part of the study, the authors showed that the signature response was reduced when an opiod analgesic (remifentanil) was administered.
Because this study enrolled otherwise healthy patients, the results cannot be extrapolated to other populations. Nevertheless, it is likely that other painful conditions will have unique functional MRI signatures.
Pain is not easy to ascertain and obtaining functional MRIs is not likely to have a role in the near future as a clinical tool. The concept of identifying a measurable pain biomarker though has been strengthened by this study.
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