February 5, 2016

Study Uncovers How Electromagnetic Fields Amplify Pain in Amputees

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A study published online January 13 in PLOS ONE provides scientific evidence that supports anecdotal stories of people with neuropathy and/or amputations who report aberrant sensations and neuropathic pain when they are around cellphone towers and other technology that produce radiofrequency electromagnetic fields (EMFs). Whether radiofrequency EMFs are capable of triggering post-neurotomy pain is a clinically important question, the researchers said, as about 20-30 percent of individuals with amputations endure chronic, debilitating pain associated with the formation of benign peripheral nerve tumors in their residual limbs, called amputation neuromas. The study was led by researchers at The University of Texas at Dallas (UT Dallas).

Photograph courtesy of UT Dallas.

“Our study provides evidence, for the first time, that subjects exposed to cellphone towers at low, regular levels can actually perceive pain,” said Mario Romero-Ortega, PhD, senior author of the study and an associate professor of bioengineering in the university’s School of Engineering and Computer Science. “Our study also points to a specific nerve pathway that may contribute to our main finding.”

Most of the research into the possible effects of cellphone towers on humans has been conducted on individuals with no diagnosed preexisting conditions. This is one of the first studies to look at the effects of EMFs in a nerve-injury model, said Romero-Ortega, who researches nerve regeneration and builds neural interfaces, technology that connects bionic or robotic devices to the peripheral nerve.

The team hypothesized that the formation of neuromas created an environment that may be sensitive to EMF-tissue interactions. To test this, the team randomly assigned 20 rats into two groups—one received a nerve injury that simulated amputation, and the other group received a sham treatment. Researchers then exposed the subjects to a radiofrequency electromagnetic antenna for ten minutes once per week for eight weeks. The antenna delivered a power density equal to that measured at 39 meters from a local cellphone tower, described as a power density that a person might encounter outside of occupational settings.

Researchers found that by the fourth week, 88 percent of the subjects in the nerve-injured group demonstrated a behavioral pain response, while only one subject in the sham group exhibited pain at a single time point, and that was during the first week. After growth of a neuroma and resection, the pain responses persisted.

“Many believe that a neuroma has to be present in order to evoke pain. Our model found that electromagnetic fields evoked pain that is perceived before neuroma formation; subjects felt pain almost immediately,” Romero-Ortega said. “My hope is that this study will highlight the importance of developing clinical options to prevent neuromas, instead of the current partially effective surgery alternatives for neuroma resection to treat pain.” Researchers also performed experiments at the cellular level to explain the behavioral response. That led them to explore the protein TRPV4, which is known to be a factor in heat sensitivity and the development of allodynia (the experience of pain from a non-painful stimulation of the skin), which some subjects displayed.

“It is highly likely that TRPV4 is a mediator in the pain response for these subjects,” Romero-Ortega said. “Our calcium imaging experiments were a good indicator that TRPV4 is worth further exploration.” He added that since the research produced pain responses similar to those in anecdotal reports and a specific human case, the results “are very likely” generalizable to humans.

Editor’s note: This story was adapted from materials provided by UT Dallas.

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