The chronic pain of Temporomandibular Disorders (TMD) can be debilitating and interfere significantly with daily life.
Physical pain, whether from TMD or another condition, may also trigger emotional stress that can exacerbate symptoms, causing elevated anxiety that further increases pain, only to create a positive feedback loop of more pain leading to more stress and more pain. This process has been described as “somatic amplification,” and may contribute to the hypersensitivity to pain that characterizes a newly described nervous system syndrome known as the Central Sensitization Syndrome (CSS). The condition provides a clinical model that is being used to test a new hypotheses about TMD. CSS is also being used to tie TMD to conditions such as chronic fatigue syndrome, lower back pain, and irritable bowel syndrome which are known to occur in TMD patients at a far greater frequency than would be expected by mere coincidence alone.
CSS was first used to describe the development of pain and symptoms including sleep disorders, diminished mental acuity, forgetfulness, and bowel disorders in patients with CFS or fibromyalgia. It is now being applied to other chronic conditions where pain is a prominent symptom, such as irritable bowel syndrome and vulvodynia. The biological mechanisms that underlie CSS symptoms have not been identified.
A recent study drew 250 acute TMD patients from dental clinics published in the journal Pain Practice confirms the importance of CSS in mediating pain in some TMD patients. Using diagnostic criteria that classifies TMD patients into three categories: Group I muscle disorders, Group II disc displacements; and Group III bone deficiencies, the researchers found that the patients with the most CSS symptoms were drawn from Group I (muscle disorders) or were individuals with more than one TMD diagnostic category. In addition, individuals with more than one TMD diagnosis had more symptoms of fibromyalgia, CFS and female pelvic pain. Interestingly, patients classified in the other two TMD diagnostic subgroups do not appear to be as strongly influenced by CSS.
These findings provide a foundation for future studies by basic researchers and clinicians aiming to understand the causes of TMD and develop more effective methods for the management and treatment. Finally, this report clearly adds support to the emerging evidence indicating altered central nervous system functions in pain pathways in individuals with TMD muscle disorders and co-morbid pain conditions.
Source: Lorduy, K. M., Liegey-Dougall, A., Haggard, R., Sanders, C. N. and Gatchel, R. J. (2013), The Prevalence of Comorbid Symptoms of Central Sensitization Syndrome Among Three Different Groups of Temporomandibular Disorder Patients. Pain Practice. doi: 10.1111/papr.12029