Impact of fibromyalgia phenotype in temporomandibular disorders

BACKGROUND Mounting evidence suggests that central nervous system amplification, similar to that seen in fibromyalgia (FM), contributes to the pain experience in a subset of patients with temporomandibular disorders (TMD). METHODS In this prospective observational study, patients with TMD completed the 2011 FM survey questionnaire, a surrogate measure of "centralized" pain. The influence of centralized pain on TMD pain, dysfunction, and disability was assessed dichotomously by determining the incidence of FM-positive cases in the sample and by using FM survey scores as a continuous measure of "fibromyalgia-ness" ("FM-ness"). RESULTS The patients meeting criteria for FM diagnosis (17 of 89) had significantly more disease burden on numerous measures. FM-ness was positively associated with pain at rest, negative mood, tenderness to palpation, perceived jaw functional limitation, and pain-related disability, and it was negatively associated with comfortable pain-free jaw opening. The impact of FM-ness on perceived jaw functional limitation and disability was mediated by levels of spontaneous, ongoing pain in the orofacial region. Importantly, this pattern of findings was still present even in those not meeting the criteria for FM diagnosis. CONCLUSION Together, these results imply that higher FM-ness increases TMD patient burden by amplifying spontaneous pain and further hampering painless jaw function, even in patients who do not meet criteria for FM diagnosis. These results are highly relevant for the clinical management of TMD, as they imply that targeting the central nervous system in the treatment of patients with TMD with evidence of pain centralization may help ameliorate both pain and jaw dysfunction.