A groundbreaking study has uncovered new insights into the pain pathways associated with temporomandibular joint (TMJ) disorders. Using an innovative in vivo imaging tool to capture functional activity in mouse models of TMJ injury and inflammation, the discovery could pave the way for more effective treatments for the millions affected by TMJ-related facial pain.
A study published in the Pain journal on December 2024 revealed a research team led by Yu Shin Kim, PhD , associate professor in the Department of Oral and Maxillofacial Surgery in the School of Dentistry at The University of Texas Health Science Center at San Antonio (UT Health San Antonio), observed for the first time the simultaneous activity of over 3,000 trigeminal ganglion (TG) neurons, which are cells clustered at the base of the brain that transmit information about sensations to the face, mouth and head.
"With our novel imaging technique and tools, we can see each individual neuron's activity, pattern and dynamics as well as 3,000 neuronal populational ensemble, network pattern and activities in real time while we are giving different stimuli," said Kim.
TMJ disorders are the second most common musculoskeletal disorder in the United States, affecting 8% to 12% of Americans. Current treatments often fall short, prompting researchers to explore the intricate nerve and vessel network surrounding TMJ.
The research revealed how injury or misalignment of the TMJ triggers inflammation in the joint, which can spread to other connected nerve networks, causing chronic pain. This study also found that over 100 neurons fired simultaneously, shedding light on the specific neural pathways involved in TMJ pain.
Kim's team observed connections between TMJ disorders and other conditions like migraines and headaches. This aligns with previous findings that inflammation in TG neurons can contribute to pain spreading to nearby areas, including those related to migraines.
A key focus of the study was the potential for Calcitonin Gene-Related Peptide (CGRP) antagonists to alleviate TMJ pain. CGRP, a molecule involved in pain transmission and inflammation, is found in higher levels in patients with TMJ disorders. Kim's team discovered that reducing CGRP levels in the synovial fluid provided relief from both TMJ pain and hypersensitivity in the trigeminal ganglion neurons.
While no FDA-approved treatments currently exist specifically for TMJ disorders, this finding suggests that CGRP antagonists, already approved for treating migraines, could offer a promising solution for TMJ pain relief.
This research marks a significant step forward in understanding TMJ disorders and could lead to new, more effective treatments for this chronic pain condition and broader pain management strategies.
"This imaging technique and tool allows us to see pain at its source — down to the activity of individual neurons — offering unprecedented insights into how pain develops and spreads," said Kim. "Our hope is that this approach will not only advance treatments for TMJ disorders but also pave the way for understanding and managing various chronic pain conditions more effectively."
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