When you move your jaws, the cartilaginous disc between the condyle and your skull bone acts as a shock absorber by sliding between the bony surfaces. In some people, however, the disc becomes displaced and can cause pain, which is generally accompanied by a clicking sound or limitation in jaw movement. Thus, disc displacement is one of the problems that can occur in patients with TMD. An interesting scientific question is what happens over time to the disc in TMD patients? And, how do the changes in patients’ discs compare in people with mild TMJ symptoms who do not seek treatment and individuals without any signs of TM disorders?
A recent study by Swedish investigators published in the December 2012 issue of the journal Radiology provides interesting clues to these questions. The investigators focused on 53 adults who were not TMD patients but who volunteered for a study using magnetic resonance imaging (MRI) of the jaw, and followed them over 15 years.
The surprising result the Swedish investigators found was that at the beginning approximately 90 percent of individuals with mild TMD symptoms (symptomatic volunteers) displayed TMJ disc displacement of a magnitude similar to that of patients seeking treatment. Moreover, nearly a third (30 percent) of individuals without any jaw pain or dysfunction (asymptomatic volunteers ) also showed evidence of disc displacement. Note: studies of low back pain show similar findings. Many low back pain patients show spinal disc derangements yet scans of people without back pain can show similar spinal disc abnormalities.
While the number of individuals in the Swedish study was small, a very high 94% remained available for follow-up after 15 years. What was noteworthy was the stability of disc position in both groups of volunteers: one asymptomatic volunteer and 3 symptomatic volunteers showed disc displacement progression. In contrast, studies of TMD patients receiving care tend to show a worsening of disc displacement and symptoms over time, perhaps due to more serious disease at the onse
Conclusions: The Swedish study sheds light on the course of TM disease. Patients who present with disc displacement tend to progress over years, whereas the disc position, in people with only mild or no symptoms remains stable over time. This has implications for clinical trials. Because the prevalence of disc displacement is common in the general population, care needs to be taken to distinguish symptomatic and asymptomatic individuals in a control group to validate trial results.
Source: Salé H, Bryndahl F, Isberg A., Temporomandibular Joints in Asymptomatic and Symptomatic Nonpatient Volunteers: A Prospective 15-year Follow-up Clinical and MR Imaging Study, Radiology. 2012 Dec 18.