Chronic Pain and Tinnitus Share a Brain Gateway

SEPTEMBER 29, 2015
Caitlyn Fitzpatrick
Have you ever wondered what that ringing “in the ears” sensation is all about? Well it appears that the brain region responsible for the phenomenon shares a gateway with chronic pain.

About one in five people have tinnitus, which causes them to hear sounds such as ringing or buzzing that aren’t there. Since previous research determined that not everyone with damaged cochlear nerves or cortical auditory circuits experience tinnitus, it was hypothesized that a higher-level cognitive system is involved. Researchers from Technical University of Munich (TUM) and Georgetown University (GU) took the investigation a step further and found evidence suggesting that tinnitus and chronic pain have a common central gatekeeping system. similar structural and functional systems.

“The article is a review article which summarizes results from different studies with different methods, subjects, and patients,” one of the authors Markus Ploner, MD, Heisenberg professor of human pain research at TUM, told MD Magazine.

The team analyzed multiple studies using a variety of strategies, including functional magnetic resonance imaging, diffusion tensor imaging, and voxel-based morphometry, among others. Each review consisted of groups of patients “large enough to allow reliable statistical inferences,” according to author Josef P. Rauschecker, PhD, DSc, a professor of neuroscience at GU.

Changes in the same brain circuit, like the ventromedial prefrontal cortex and nucleus accumbens, play a significant role in emotions and perceptual sensations. These regions also monitor the flow of information to the brain, which the authors say is controlled by dopamine and serotonin. The new evidence suggests that similar structural and functional characteristics in those brain regions could help explain both tinnitus and chronic pain. Which, to sum up, means that this region acts as a central gatekeeping system for both conditions, as described in Trends in Cognitive Sciences.

“The most surprising and insightful part of the study was that tinnitus and chronic pain share the same brain structures and, thus, brain mechanisms,” Rauschecker said.

One of the common characteristics observed in both patients with tinnitus and chronic pain was the significant loss of gray matter in the specified brain regions. Furthermore, compromised circuit function and neurological changes were witnessed as well, according to a news release.

“Both teams involved in this study will continue their research on tinnitus and chronic pain, respectively. The next steps could be to investigate the molecular mechanisms in the circuits involved, so we can ultimately develop more effective drug treatment,” Rauschecker continued.

While the findings are promising, the authors stress that there are still unanswered questions to investigate before clinical interventions can be employed. For example, they need to better understand the structure, function, and metabolism of the brain circuits.

“This could help for the early diagnosis and early and targets treatment of both disorders,” Ploner concluded. “This is an endeavor which cannot be accomplished by a single research group but needs concerted efforts of researchers from different background and disciplines.”

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