Chronic pain and tinnitus, the incessant ear ringing that affects up to 30 percent of the adult population, may share a common source, new research shows. The finding may bring millions of people who suffer from both conditions a step closer to finding relief.
A study published in Trends in Cognitive Sciences found the “phantom pain” in both disorders often begins as a response to an injury, but continues when a faulty “circuit breaker” in the brain is unable to properly process the pain or noise.
Josef Rauschecker, director of the Laboratory for Integrative Neuroscience and Cognition at GUMC and one of the study’s authors, said the discovery is good news for those affected by both conditions. As of now, neither have direct treatments.
“The next step is ‘how could this be used for finding a cure?’” he said. “That is of course the challenge, but we are hoping to make some progress in the next 5-10 years.”
Rauschecker said brain imaging studies of tinnitus patients showed the condition was related to higher cognitive and affective brain systems. Meanwhile, separate researchers discovered the same mechanism was involved in chronic pain. Neuroscientists at Georgetown University Medical Center and Germany’s Technische Universität München brought the research together for this paper, published in Trends in Cognitive Sciences.
“This is an amazingly rare occurrence of two fields independently coming to the same conclusion,” Rauschecker said.
In the study, researchers traced stimuli through the brain using MRI technology. They compared tinnitus patients with those who did not have tinnitus and found volume loss in the medial prefrontal cortex, an area that plays a role in the limbic system and functions as a “gate” or control area for noise and pain signals that is also associated with depression.
“We expected to find changes in the auditory system, but what really stood out was this significant volume loss in this part of the mPFC,” he said. “This is an area that also lights up when you play unpleasant noises, so it has to do with unpleasant sensations. It was not expected to see something there, but it fit well with previous findings.”
They found the ventromedial prefrontal cortex and the nucleus accumbens are part of a “gatekeeping” system that determines which sounds or other stimuli to admit. When the system is defective, affected patients can be subjected to constant stimuli and long-lasting disturbances.
The area is also associated with depression and anxiety, conditions often arise “in lockstep” with chronic pain. Because of this, the researchers are now looking to drugs that regulate that system, like dopamine and serotonin, to restore the gatekeeping role and eliminate the chronic pain, but more research is needed.
“These are disorders that affect us every day, and many millions have them but we won’t be able to cure them unless we understand how they work,” Rauschecker said.