Why head and face pain hurts more than other types

Researchers have discovered evidence of why head and face pain causes more suffering than pain elsewhere in the body. It turns out that pain in the head, face, eyes, ears, and teeth is more than just physically uncomfortable, but is emotionally disruptive as well.

The scientists found that sensory nerves are wired directly from the head and face into one of the brain’s key emotional signaling centers. Other sensory neurons in the body are only connected to this hub indirectly.

Study senior author Fan Wang is a professor of Neurobiology and Cell Biology at Duke University.

“Usually doctors focus on treating the sensation of pain, but this shows the we really need to treat the emotional aspects of pain as well,” said Wang.

Pain signals from the head are carried through two groups of sensory neurons to the brain, and there is a possibility that these neurons are simply more sensitive to pain than other neurons in the body. However, this would not explain the elevated fear and emotional suffering that comes along with head-face pain, said Wang

“There has been this observation in human studies that pain in the head and face seems to activate the emotional system more extensively,” said Wang. “But the underlying mechanisms remained unclear.”

The research team set out to examine the neural circuitry underlying head-face pain and pain elsewhere in the body. To do this, they tracked brain activity in mice after irritating either a paw or the face.

The scientists found that injury to the face caused increased activity in the brain’s parabrachial nucleus (PBL), a region that is directly wired into the brain’s emotional centers. Next, the team used advanced technology to identify the neurons which caused this heightened PBL activity.

“It was a eureka moment because the body neurons only have this indirect pathway to the PBL, whereas the head and face neurons, in addition to this indirect pathway, also have a direct input,” said Wang. “This could explain why you have stronger activation in the amygdala and the brain’s emotional centers from head and face pain.”

Further testing revealed that activating this pathway triggered face pain, while suppressing the pathway reduced the face pain.

“We have the first biological explanation for why this type of pain can be so much more emotionally taxing than others,” said co-author Wolfgang Liedtke.

Liedtke explained that the findings of the study could lead to innovative treatments for devastating head and face pain.

“This will open the door toward not only a more profound understanding of chronic head and face pain, but also toward translating this insight into treatments that will benefit people,” said Liedtke.

The research is published in the journal Nature Neuroscience.

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By Chrissy Sexton, Earth.com Staff Writer