Serotonin and TMJ Pain
A low level of serotonin (S-5-HT) has been associated with fibromyalgia (FM) in previous studies, and some researchers believe may be a causative factor in chronic pain. The authors of this current study compared the levels of serotonin between chronic temporomandibular disorder (TMD) pain subjects, FM patients, and healthy controls to determine if there was a relationship.
The researchers worked with a sample of 20 patients for each group. In TMD patients they assessed orofacial pain during the last week and tenderness; in FM patients they assessed painful body regions and tenderness. Blood examinations and analysis of serotonin levels were tested for all groups, including the healthy controls.
The serotonin levels ranged:
- In TMD patients, between 14 and 299
- In FM patients, between 6 and 306
- In healthy controls, between 18 and 338
The authors concluded that there were no significant differences in the groups when looking at just serum levels of serotonin. However, there was an interesting finding when looking at the relationship between serum serotonin and tender points.
"The main result of our study is the finding of an association between low S-T-HT level and local allodynia of temporomandibular muscles in patients with chronic TMD of muscular origin. To our knowledge, this has not been reported previously. In the patients with localized myalgia there was a significant correlation between low S-5-HT and high TPI [tender point index] of temporomandibular muscles, which indicates that S-T-HT has a considerable influence on tenderness to digital palpation or local allodynia in this patient group. This remarkable finding indicates that central mechanisms are involved in the modulation of allodynia in chronic TMD of muscular origin. It also supports the theory that pathologic alterations of the antinociceptive system may lead to allodynia."
The authors also found that a lower serum serotonin level was found in fibromyalgia patients with a high number of painful body regions.
Most of the literature on trauma and TMD symptoms has focused on direct physical trauma to the TMJ joint; this study indicates that TMD symptoms may have a more systemic origin than just direct trauma.
Ernberg M, Hedenberg-Magnusson B, Alstergren P, Lundeberg T, et al. Pain, allodynia, and serum serotonin level in orofacial pain of muscular origin. Journal of Orofacial Pain 1999;13(1):56-62.