Pain from headaches can often feel overwhelming, and a new Duke study sheds light on why that may be the case.
By tracking neurological activity in mice after stimulating either a paw or the face, a team of Duke scientists has discovered that the trigeminal ganglion—a cluster of sensory neurons serving the head and face—is directly linked to the brain’s emotional processing pathways. On the other hand, they showed that dorsal root ganglia—clusters of sensory neurons serving all other regions of the body—are only indirectly linked to the brain’s emotional hub.
These results are consistent with the longtime observation that people generally report head and face pain to be more emotionally draining than pain located in other parts of the body, explained Fan Wang, professor of neurobiology and cell biology and senior author of the study.
Wang noted that although it has traditionally been accepted that the head and face ganglia neurons are more sensitive than the neurons transmitting pain from other bodily regions, there has until now never been an explanation for why a greater pain signal would translate into greater emotional suffering in patients.
She explained that in designing their study, she and her team studied the literature on comparable human experiments and found that when applying the same intensity of stimuli to the face and any other region of the body, a brain region called the amygdala was activated more in response to the former case.
“The amygdala processes emotions, so we figured ‘What the heck? Let’s look into this emotional aspect some more,'” Wang said.
Another component of the literature that originally caught Wang’s attention was the observation that the two diseases most commonly linked to suicide are trigeminal neuralgia and cluster headaches. She explained that if people afflicted with these conditions might find them so painful that they can no longer handle them, there may be more than just pain receptors at play in their suffering.
Their study provides a better understanding of basic brain biology and also emphasizes the necessity of addressing emotional suffering when treating head and face pain, Wang noted.
“I think people will receive [the finding] at least enthusiastically, even though it’s not immediately clear how [the finding] leads to the perfect therapy,” she said. “But at least there is a clear path, a mechanism that we can work on.”
Sure enough, Wang’s team is already conducting research to figure out how they can tap into the brain’s circuitry that can make pain feel less intense.
She noted that their general research interests in pain have been partially fueled by the current opioid crisis. Part of the reason the opioid epidemic has been so difficult to manage is the limited number of available alternative pain-suppressing drugs on the market, Wang explained.
The general effectiveness of opioids is overshadowed by their complementary, negative consequences on patients’ health, she added.
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“If we only took the good part of opioids—the part which mimics the brain’s endogenous suppressing system and which has no other side effects—then it would be fine," Wang said. "It’s just that there’s the bad part, too.”
Wang said that she and her team are determined to find nodes within the brain’s endogenous pain-suppressing system that can effectively quell painful sensations without the negative side effects of opioids or comparable painkillers.
“Once we find these nodes, then I think we’ll be in good shape to develop new therapies,” she said.
Junior Howard Huang, who is studying neuroscience and was not involved in the study, said that in his experience, he regularly hears more complaints from people who have headaches and are stressed than those relating to other pains people may have.
“If this study is better able to help doctors or scientists find better treatments for headaches or better understand why headaches occur, then it’s really cool they discovered that at Duke, because that’s a really amazing finding,” he said.